Merge pull request #1769 from Roasbeef/txscript_zero_alloc_optimization_refactor

txscript: backport tokenizer from dcrd

txscript/README.md

@@ -37,6 +37,10 @@ $ go get -u github.com/btcsuite/btcd/txscript
 * [Manually Signing a Transaction Output](https://pkg.go.dev/github.com/btcsuite/btcd/txscript#example-SignTxOutput)  
   Demonstrates manually creating and signing a redeem transaction.
 
+* [Counting Opcodes in Scripts](http://godoc.org/github.com/decred/dcrd/txscript#example-ScriptTokenizer)  
+  Demonstrates creating a script tokenizer instance and using it to count the
+  number of opcodes a script contains.
+
 ## GPG Verification Key
 
 All official release tags are signed by Conformal so users can ensure the code

txscript/bench_test.go

@@ -0,0 +1,537 @@
+// Copyright (c) 2018-2019 The Decred developers
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+package txscript
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"testing"
+
+	"github.com/btcsuite/btcd/chaincfg"
+	"github.com/btcsuite/btcd/wire"
+)
+
+var (
+	// manyInputsBenchTx is a transaction that contains a lot of inputs which is
+	// useful for benchmarking signature hash calculation.
+	manyInputsBenchTx wire.MsgTx
+
+	// A mock previous output script to use in the signing benchmark.
+	prevOutScript = hexToBytes("a914f5916158e3e2c4551c1796708db8367207ed13bb87")
+)
+
+func init() {
+	// tx 620f57c92cf05a7f7e7f7d28255d5f7089437bc48e34dcfebf7751d08b7fb8f5
+	txHex, err := ioutil.ReadFile("data/many_inputs_tx.hex")
+	if err != nil {
+		panic(fmt.Sprintf("unable to read benchmark tx file: %v", err))
+	}
+
+	txBytes := hexToBytes(string(txHex))
+	err = manyInputsBenchTx.Deserialize(bytes.NewReader(txBytes))
+	if err != nil {
+		panic(err)
+	}
+}
+
+// BenchmarkCalcSigHash benchmarks how long it takes to calculate the signature
+// hashes for all inputs of a transaction with many inputs.
+func BenchmarkCalcSigHash(b *testing.B) {
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		for j := 0; j < len(manyInputsBenchTx.TxIn); j++ {
+			_, err := CalcSignatureHash(prevOutScript, SigHashAll,
+				&manyInputsBenchTx, j)
+			if err != nil {
+				b.Fatalf("failed to calc signature hash: %v", err)
+			}
+		}
+	}
+}
+
+// BenchmarkCalcWitnessSigHash benchmarks how long it takes to calculate the
+// witness signature hashes for all inputs of a transaction with many inputs.
+func BenchmarkCalcWitnessSigHash(b *testing.B) {
+	sigHashes := NewTxSigHashes(&manyInputsBenchTx)
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		for j := 0; j < len(manyInputsBenchTx.TxIn); j++ {
+			_, err := CalcWitnessSigHash(
+				prevOutScript, sigHashes, SigHashAll,
+				&manyInputsBenchTx, j, 5,
+			)
+			if err != nil {
+				b.Fatalf("failed to calc signature hash: %v", err)
+			}
+		}
+	}
+}
+
+// genComplexScript returns a script comprised of half as many opcodes as the
+// maximum allowed followed by as many max size data pushes fit without
+// exceeding the max allowed script size.
+func genComplexScript() ([]byte, error) {
+	var scriptLen int
+	builder := NewScriptBuilder()
+	for i := 0; i < MaxOpsPerScript/2; i++ {
+		builder.AddOp(OP_TRUE)
+		scriptLen++
+	}
+	maxData := bytes.Repeat([]byte{0x02}, MaxScriptElementSize)
+	for i := 0; i < (MaxScriptSize-scriptLen)/(MaxScriptElementSize+3); i++ {
+		builder.AddData(maxData)
+	}
+	return builder.Script()
+}
+
+// BenchmarkScriptParsing benchmarks how long it takes to parse a very large
+// script.
+func BenchmarkScriptParsing(b *testing.B) {
+	script, err := genComplexScript()
+	if err != nil {
+		b.Fatalf("failed to create benchmark script: %v", err)
+	}
+
+	const scriptVersion = 0
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		tokenizer := MakeScriptTokenizer(scriptVersion, script)
+		for tokenizer.Next() {
+			_ = tokenizer.Opcode()
+			_ = tokenizer.Data()
+			_ = tokenizer.ByteIndex()
+		}
+		if err := tokenizer.Err(); err != nil {
+			b.Fatalf("failed to parse script: %v", err)
+		}
+	}
+}
+
+// BenchmarkDisasmString benchmarks how long it takes to disassemble a very
+// large script.
+func BenchmarkDisasmString(b *testing.B) {
+	script, err := genComplexScript()
+	if err != nil {
+		b.Fatalf("failed to create benchmark script: %v", err)
+	}
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_, err := DisasmString(script)
+		if err != nil {
+			b.Fatalf("failed to disasm script: %v", err)
+		}
+	}
+}
+
+// BenchmarkIsPubKeyScript benchmarks how long it takes to analyze a very large
+// script to determine if it is a standard pay-to-pubkey script.
+func BenchmarkIsPubKeyScript(b *testing.B) {
+	script, err := genComplexScript()
+	if err != nil {
+		b.Fatalf("failed to create benchmark script: %v", err)
+	}
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_ = IsPayToPubKey(script)
+	}
+}
+
+// BenchmarkIsPubKeyHashScript benchmarks how long it takes to analyze a very
+// large script to determine if it is a standard pay-to-pubkey-hash script.
+func BenchmarkIsPubKeyHashScript(b *testing.B) {
+	script, err := genComplexScript()
+	if err != nil {
+		b.Fatalf("failed to create benchmark script: %v", err)
+	}
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_ = IsPayToPubKeyHash(script)
+	}
+}
+
+// BenchmarkIsPayToScriptHash benchmarks how long it takes IsPayToScriptHash to
+// analyze a very large script.
+func BenchmarkIsPayToScriptHash(b *testing.B) {
+	script, err := genComplexScript()
+	if err != nil {
+		b.Fatalf("failed to create benchmark script: %v", err)
+	}
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_ = IsPayToScriptHash(script)
+	}
+}
+
+// BenchmarkIsMultisigScriptLarge benchmarks how long it takes IsMultisigScript
+// to analyze a very large script.
+func BenchmarkIsMultisigScriptLarge(b *testing.B) {
+	script, err := genComplexScript()
+	if err != nil {
+		b.Fatalf("failed to create benchmark script: %v", err)
+	}
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		isMultisig, err := IsMultisigScript(script)
+		if err != nil {
+			b.Fatalf("unexpected err: %v", err)
+		}
+		if isMultisig {
+			b.Fatalf("script should NOT be reported as mutisig script")
+		}
+	}
+}
+
+// BenchmarkIsMultisigScript benchmarks how long it takes IsMultisigScript to
+// analyze a 1-of-2 multisig public key script.
+func BenchmarkIsMultisigScript(b *testing.B) {
+	multisigShortForm := "1 " +
+		"DATA_33 " +
+		"0x030478aaaa2be30772f1e69e581610f1840b3cf2fe7228ee0281cd599e5746f81e " +
+		"DATA_33 " +
+		"0x0284f4d078b236a9ff91661f8ffbe012737cd3507566f30fd97d25f2b23539f3cd " +
+		"2 CHECKMULTISIG"
+	pkScript := mustParseShortForm(multisigShortForm)
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		isMultisig, err := IsMultisigScript(pkScript)
+		if err != nil {
+			b.Fatalf("unexpected err: %v", err)
+		}
+		if !isMultisig {
+			b.Fatalf("script should be reported as a mutisig script")
+		}
+	}
+}
+
+// BenchmarkIsMultisigSigScript benchmarks how long it takes IsMultisigSigScript
+// to analyze a very large script.
+func BenchmarkIsMultisigSigScriptLarge(b *testing.B) {
+	script, err := genComplexScript()
+	if err != nil {
+		b.Fatalf("failed to create benchmark script: %v", err)
+	}
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		if IsMultisigSigScript(script) {
+			b.Fatalf("script should NOT be reported as mutisig sig script")
+		}
+	}
+}
+
+// BenchmarkIsMultisigSigScript benchmarks how long it takes IsMultisigSigScript
+// to analyze both a 1-of-2 multisig public key script (which should be false)
+// and a signature script comprised of a pay-to-script-hash 1-of-2 multisig
+// redeem script (which should be true).
+func BenchmarkIsMultisigSigScript(b *testing.B) {
+	multisigShortForm := "1 " +
+		"DATA_33 " +
+		"0x030478aaaa2be30772f1e69e581610f1840b3cf2fe7228ee0281cd599e5746f81e " +
+		"DATA_33 " +
+		"0x0284f4d078b236a9ff91661f8ffbe012737cd3507566f30fd97d25f2b23539f3cd " +
+		"2 CHECKMULTISIG"
+	pkScript := mustParseShortForm(multisigShortForm)
+
+	sigHex := "0x304402205795c3ab6ba11331eeac757bf1fc9c34bef0c7e1a9c8bd5eebb8" +
+		"82f3b79c5838022001e0ab7b4c7662e4522dc5fa479e4b4133fa88c6a53d895dc1d5" +
+		"2eddc7bbcf2801 "
+	sigScript := mustParseShortForm("DATA_71 " + sigHex + "DATA_71 " +
+		multisigShortForm)
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		if IsMultisigSigScript(pkScript) {
+			b.Fatalf("script should NOT be reported as mutisig sig script")
+		}
+		if !IsMultisigSigScript(sigScript) {
+			b.Fatalf("script should be reported as a mutisig sig script")
+		}
+	}
+}
+
+// BenchmarkIsPushOnlyScript benchmarks how long it takes IsPushOnlyScript to
+// analyze a very large script.
+func BenchmarkIsPushOnlyScript(b *testing.B) {
+	script, err := genComplexScript()
+	if err != nil {
+		b.Fatalf("failed to create benchmark script: %v", err)
+	}
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_ = IsPushOnlyScript(script)
+	}
+}
+
+// BenchmarkIsWitnessPubKeyHash benchmarks how long it takes to analyze a very
+// large script to determine if it is a standard witness pubkey hash script.
+func BenchmarkIsWitnessPubKeyHash(b *testing.B) {
+	script, err := genComplexScript()
+	if err != nil {
+		b.Fatalf("failed to create benchmark script: %v", err)
+	}
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_ = IsPayToWitnessPubKeyHash(script)
+	}
+}
+
+// BenchmarkIsWitnessScriptHash benchmarks how long it takes to analyze a very
+// large script to determine if it is a standard witness script hash script.
+func BenchmarkIsWitnessScriptHash(b *testing.B) {
+	script, err := genComplexScript()
+	if err != nil {
+		b.Fatalf("failed to create benchmark script: %v", err)
+	}
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_ = IsPayToWitnessScriptHash(script)
+	}
+}
+
+// BenchmarkIsNullDataScript benchmarks how long it takes to analyze a very
+// large script to determine if it is a standard nulldata script.
+func BenchmarkIsNullDataScript(b *testing.B) {
+	script, err := genComplexScript()
+	if err != nil {
+		b.Fatalf("failed to create benchmark script: %v", err)
+	}
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_ = IsNullData(script)
+	}
+}
+
+// BenchmarkIsUnspendable benchmarks how long it takes IsUnspendable to analyze
+// a very large script.
+func BenchmarkIsUnspendable(b *testing.B) {
+	script, err := genComplexScript()
+	if err != nil {
+		b.Fatalf("failed to create benchmark script: %v", err)
+	}
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_ = IsUnspendable(script)
+	}
+}
+
+// BenchmarkGetSigOpCount benchmarks how long it takes to count the signature
+// operations of a very large script.
+func BenchmarkGetSigOpCount(b *testing.B) {
+	script, err := genComplexScript()
+	if err != nil {
+		b.Fatalf("failed to create benchmark script: %v", err)
+	}
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_ = GetSigOpCount(script)
+	}
+}
+
+// BenchmarkGetPreciseSigOpCount benchmarks how long it takes to count the
+// signature operations of a very large script using the more precise counting
+// method.
+func BenchmarkGetPreciseSigOpCount(b *testing.B) {
+	redeemScript, err := genComplexScript()
+	if err != nil {
+		b.Fatalf("failed to create benchmark script: %v", err)
+	}
+
+	// Create a fake pay-to-script-hash to pass the necessary checks and create
+	// the signature script accordingly by pushing the generated "redeem" script
+	// as the final data push so the benchmark will cover the p2sh path.
+	scriptHash := "0x0000000000000000000000000000000000000001"
+	pkScript := mustParseShortForm("HASH160 DATA_20 " + scriptHash + " EQUAL")
+	sigScript, err := NewScriptBuilder().AddFullData(redeemScript).Script()
+	if err != nil {
+		b.Fatalf("failed to create signature script: %v", err)
+	}
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_ = GetPreciseSigOpCount(sigScript, pkScript, true)
+	}
+}
+
+// BenchmarkGetWitnessSigOpCount benchmarks how long it takes to count the
+// witness signature operations of a very large script.
+func BenchmarkGetWitnessSigOpCountP2WKH(b *testing.B) {
+	pkScript := mustParseShortForm("OP_0 DATA_20 0x0000000000000000000000000000000000000000")
+	redeemScript, err := genComplexScript()
+	if err != nil {
+		b.Fatalf("failed to create benchmark script: %v", err)
+	}
+
+	witness := wire.TxWitness{
+		redeemScript,
+	}
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_ = GetWitnessSigOpCount(nil, pkScript, witness)
+	}
+}
+
+// BenchmarkGetWitnessSigOpCount benchmarks how long it takes to count the
+// witness signature operations of a very large script.
+func BenchmarkGetWitnessSigOpCountNested(b *testing.B) {
+	pkScript := mustParseShortForm("HASH160 DATA_20 0x0000000000000000000000000000000000000000 OP_EQUAL")
+	sigScript := mustParseShortForm("DATA_22 0x001600000000000000000000000000000000000000000000")
+	redeemScript, err := genComplexScript()
+	if err != nil {
+		b.Fatalf("failed to create benchmark script: %v", err)
+	}
+
+	witness := wire.TxWitness{
+		redeemScript,
+	}
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_ = GetWitnessSigOpCount(sigScript, pkScript, witness)
+	}
+}
+
+// BenchmarkGetScriptClass benchmarks how long it takes GetScriptClass to
+// analyze a very large script.
+func BenchmarkGetScriptClass(b *testing.B) {
+	script, err := genComplexScript()
+	if err != nil {
+		b.Fatalf("failed to create benchmark script: %v", err)
+	}
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_ = GetScriptClass(script)
+	}
+}
+
+// BenchmarkPushedData benchmarks how long it takes to extract the pushed data
+// from a very large script.
+func BenchmarkPushedData(b *testing.B) {
+	script, err := genComplexScript()
+	if err != nil {
+		b.Fatalf("failed to create benchmark script: %v", err)
+	}
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_, err := PushedData(script)
+		if err != nil {
+			b.Fatalf("unexpected err: %v", err)
+		}
+	}
+}
+
+// BenchmarkExtractAtomicSwapDataPushesLarge benchmarks how long it takes
+// ExtractAtomicSwapDataPushes to analyze a very large script.
+func BenchmarkExtractAtomicSwapDataPushesLarge(b *testing.B) {
+	script, err := genComplexScript()
+	if err != nil {
+		b.Fatalf("failed to create benchmark script: %v", err)
+	}
+
+	const scriptVersion = 0
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_, err := ExtractAtomicSwapDataPushes(scriptVersion, script)
+		if err != nil {
+			b.Fatalf("unexpected err: %v", err)
+		}
+	}
+}
+
+// BenchmarkExtractAtomicSwapDataPushesLarge benchmarks how long it takes
+// ExtractAtomicSwapDataPushes to analyze a standard atomic swap script.
+func BenchmarkExtractAtomicSwapDataPushes(b *testing.B) {
+	secret := "9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08"
+	recipient := "0000000000000000000000000000000000000001"
+	refund := "0000000000000000000000000000000000000002"
+	script := mustParseShortForm(fmt.Sprintf("IF SIZE 32 EQUALVERIFY SHA256 "+
+		"DATA_32 0x%s EQUALVERIFY DUP HASH160 DATA_20 0x%s ELSE 300000 "+
+		"CHECKLOCKTIMEVERIFY DROP DUP HASH160 DATA_20 0x%s ENDIF "+
+		"EQUALVERIFY CHECKSIG", secret, recipient, refund))
+
+	const scriptVersion = 0
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_, err := ExtractAtomicSwapDataPushes(scriptVersion, script)
+		if err != nil {
+			b.Fatalf("unexpected err: %v", err)
+		}
+	}
+}
+
+// BenchmarkExtractPkScriptAddrsLarge benchmarks how long it takes to analyze
+// and potentially extract addresses from a very large non-standard script.
+func BenchmarkExtractPkScriptAddrsLarge(b *testing.B) {
+	script, err := genComplexScript()
+	if err != nil {
+		b.Fatalf("failed to create benchmark script: %v", err)
+	}
+
+	params := &chaincfg.MainNetParams
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_, _, _, err := ExtractPkScriptAddrs(script, params)
+		if err != nil {
+			b.Fatalf("unexpected err: %v", err)
+		}
+	}
+}
+
+// BenchmarkExtractPkScriptAddrs benchmarks how long it takes to analyze and
+// potentially extract addresses from a typical script.
+func BenchmarkExtractPkScriptAddrs(b *testing.B) {
+	script := mustParseShortForm("OP_DUP HASH160 " +
+		"DATA_20 0x0102030405060708090a0b0c0d0e0f1011121314 " +
+		"EQUAL")
+
+	params := &chaincfg.MainNetParams
+	b.ResetTimer()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_, _, _, err := ExtractPkScriptAddrs(script, params)
+		if err != nil {
+			b.Fatalf("unexpected err: %v", err)
+		}
+	}
+}

txscript/engine.go

@@ -10,6 +10,7 @@ import (
 	"crypto/sha256"
 	"fmt"
 	"math/big"
+	"strings"
 
 	"github.com/btcsuite/btcd/btcec"
 	"github.com/btcsuite/btcd/wire"
@@ -118,21 +119,84 @@ var halfOrder = new(big.Int).Rsh(btcec.S256().N, 1)
 
 // Engine is the virtual machine that executes scripts.
 type Engine struct {
-	scripts         [][]parsedOpcode
+	// The following fields are set when the engine is created and must not be
-	scriptIdx       int
+	// changed afterwards.  The entries of the signature cache are mutated
-	scriptOff       int
+	// during execution, however, the cache pointer itself is not changed.
-	lastCodeSep     int
+	//
-	dstack          stack // data stack
+	// flags specifies the additional flags which modify the execution behavior
-	astack          stack // alt stack
+	// of the engine.
+	//
+	// tx identifies the transaction that contains the input which in turn
+	// contains the signature script being executed.
+	//
+	// txIdx identifies the input index within the transaction that contains
+	// the signature script being executed.
+	//
+	// version specifies the version of the public key script to execute.  Since
+	// signature scripts redeem public keys scripts, this means the same version
+	// also extends to signature scripts and redeem scripts in the case of
+	// pay-to-script-hash.
+	//
+	// bip16 specifies that the public key script is of a special form that
+	// indicates it is a BIP16 pay-to-script-hash and therefore the
+	// execution must be treated as such.
+	//
+	// sigCache caches the results of signature verifications.  This is useful
+	// since transaction scripts are often executed more than once from various
+	// contexts (e.g. new block templates, when transactions are first seen
+	// prior to being mined, part of full block verification, etc).
+	flags     ScriptFlags
 	tx        wire.MsgTx
 	txIdx     int
-	condStack       []int
+	version   uint16
-	numOps          int
+	bip16     bool
-	flags           ScriptFlags
 	sigCache  *SigCache
 	hashCache *TxSigHashes
-	bip16           bool     // treat execution as pay-to-script-hash
+
-	savedFirstStack [][]byte // stack from first script for bip16 scripts
+	// The following fields handle keeping track of the current execution state
+	// of the engine.
+	//
+	// scripts houses the raw scripts that are executed by the engine.  This
+	// includes the signature script as well as the public key script.  It also
+	// includes the redeem script in the case of pay-to-script-hash.
+	//
+	// scriptIdx tracks the index into the scripts array for the current program
+	// counter.
+	//
+	// opcodeIdx tracks the number of the opcode within the current script for
+	// the current program counter.  Note that it differs from the actual byte
+	// index into the script and is really only used for disassembly purposes.
+	//
+	// lastCodeSep specifies the position within the current script of the last
+	// OP_CODESEPARATOR.
+	//
+	// tokenizer provides the token stream of the current script being executed
+	// and doubles as state tracking for the program counter within the script.
+	//
+	// savedFirstStack keeps a copy of the stack from the first script when
+	// performing pay-to-script-hash execution.
+	//
+	// dstack is the primary data stack the various opcodes push and pop data
+	// to and from during execution.
+	//
+	// astack is the alternate data stack the various opcodes push and pop data
+	// to and from during execution.
+	//
+	// condStack tracks the conditional execution state with support for
+	// multiple nested conditional execution opcodes.
+	//
+	// numOps tracks the total number of non-push operations in a script and is
+	// primarily used to enforce maximum limits.
+	scripts         [][]byte
+	scriptIdx       int
+	opcodeIdx       int
+	lastCodeSep     int
+	tokenizer       ScriptTokenizer
+	savedFirstStack [][]byte
+	dstack          stack
+	astack          stack
+	condStack       []int
+	numOps          int
 	witnessVersion  int
 	witnessProgram  []byte
 	inputAmount     int64
@@ -154,26 +218,144 @@ func (vm *Engine) isBranchExecuting() bool {
 	return vm.condStack[len(vm.condStack)-1] == OpCondTrue
 }
 
+// isOpcodeDisabled returns whether or not the opcode is disabled and thus is
+// always bad to see in the instruction stream (even if turned off by a
+// conditional).
+func isOpcodeDisabled(opcode byte) bool {
+	switch opcode {
+	case OP_CAT:
+		return true
+	case OP_SUBSTR:
+		return true
+	case OP_LEFT:
+		return true
+	case OP_RIGHT:
+		return true
+	case OP_INVERT:
+		return true
+	case OP_AND:
+		return true
+	case OP_OR:
+		return true
+	case OP_XOR:
+		return true
+	case OP_2MUL:
+		return true
+	case OP_2DIV:
+		return true
+	case OP_MUL:
+		return true
+	case OP_DIV:
+		return true
+	case OP_MOD:
+		return true
+	case OP_LSHIFT:
+		return true
+	case OP_RSHIFT:
+		return true
+	default:
+		return false
+	}
+}
+
+// isOpcodeAlwaysIllegal returns whether or not the opcode is always illegal
+// when passed over by the program counter even if in a non-executed branch (it
+// isn't a coincidence that they are conditionals).
+func isOpcodeAlwaysIllegal(opcode byte) bool {
+	switch opcode {
+	case OP_VERIF:
+		return true
+	case OP_VERNOTIF:
+		return true
+	default:
+		return false
+	}
+}
+
+// isOpcodeConditional returns whether or not the opcode is a conditional opcode
+// which changes the conditional execution stack when executed.
+func isOpcodeConditional(opcode byte) bool {
+	switch opcode {
+	case OP_IF:
+		return true
+	case OP_NOTIF:
+		return true
+	case OP_ELSE:
+		return true
+	case OP_ENDIF:
+		return true
+	default:
+		return false
+	}
+}
+
+// checkMinimalDataPush returns whether or not the provided opcode is the
+// smallest possible way to represent the given data.  For example, the value 15
+// could be pushed with OP_DATA_1 15 (among other variations); however, OP_15 is
+// a single opcode that represents the same value and is only a single byte
+// versus two bytes.
+func checkMinimalDataPush(op *opcode, data []byte) error {
+	opcodeVal := op.value
+	dataLen := len(data)
+	switch {
+	case dataLen == 0 && opcodeVal != OP_0:
+		str := fmt.Sprintf("zero length data push is encoded with opcode %s "+
+			"instead of OP_0", op.name)
+		return scriptError(ErrMinimalData, str)
+	case dataLen == 1 && data[0] >= 1 && data[0] <= 16:
+		if opcodeVal != OP_1+data[0]-1 {
+			// Should have used OP_1 .. OP_16
+			str := fmt.Sprintf("data push of the value %d encoded with opcode "+
+				"%s instead of OP_%d", data[0], op.name, data[0])
+			return scriptError(ErrMinimalData, str)
+		}
+	case dataLen == 1 && data[0] == 0x81:
+		if opcodeVal != OP_1NEGATE {
+			str := fmt.Sprintf("data push of the value -1 encoded with opcode "+
+				"%s instead of OP_1NEGATE", op.name)
+			return scriptError(ErrMinimalData, str)
+		}
+	case dataLen <= 75:
+		if int(opcodeVal) != dataLen {
+			// Should have used a direct push
+			str := fmt.Sprintf("data push of %d bytes encoded with opcode %s "+
+				"instead of OP_DATA_%d", dataLen, op.name, dataLen)
+			return scriptError(ErrMinimalData, str)
+		}
+	case dataLen <= 255:
+		if opcodeVal != OP_PUSHDATA1 {
+			str := fmt.Sprintf("data push of %d bytes encoded with opcode %s "+
+				"instead of OP_PUSHDATA1", dataLen, op.name)
+			return scriptError(ErrMinimalData, str)
+		}
+	case dataLen <= 65535:
+		if opcodeVal != OP_PUSHDATA2 {
+			str := fmt.Sprintf("data push of %d bytes encoded with opcode %s "+
+				"instead of OP_PUSHDATA2", dataLen, op.name)
+			return scriptError(ErrMinimalData, str)
+		}
+	}
+	return nil
+}
+
 // executeOpcode peforms execution on the passed opcode.  It takes into account
 // whether or not it is hidden by conditionals, but some rules still must be
 // tested in this case.
-func (vm *Engine) executeOpcode(pop *parsedOpcode) error {
+func (vm *Engine) executeOpcode(op *opcode, data []byte) error {
 	// Disabled opcodes are fail on program counter.
-	if pop.isDisabled() {
+	if isOpcodeDisabled(op.value) {
-		str := fmt.Sprintf("attempt to execute disabled opcode %s",
+		str := fmt.Sprintf("attempt to execute disabled opcode %s", op.name)
-			pop.opcode.name)
 		return scriptError(ErrDisabledOpcode, str)
 	}
 
 	// Always-illegal opcodes are fail on program counter.
-	if pop.alwaysIllegal() {
+	if isOpcodeAlwaysIllegal(op.value) {
-		str := fmt.Sprintf("attempt to execute reserved opcode %s",
+		str := fmt.Sprintf("attempt to execute reserved opcode %s", op.name)
-			pop.opcode.name)
 		return scriptError(ErrReservedOpcode, str)
 	}
 
 	// Note that this includes OP_RESERVED which counts as a push operation.
-	if pop.opcode.value > OP_16 {
+	if op.value > OP_16 {
 		vm.numOps++
 		if vm.numOps > MaxOpsPerScript {
 			str := fmt.Sprintf("exceeded max operation limit of %d",
@@ -181,67 +363,42 @@ func (vm *Engine) executeOpcode(pop *parsedOpcode) error {
 			return scriptError(ErrTooManyOperations, str)
 		}
 
-	} else if len(pop.data) > MaxScriptElementSize {
+	} else if len(data) > MaxScriptElementSize {
 		str := fmt.Sprintf("element size %d exceeds max allowed size %d",
-			len(pop.data), MaxScriptElementSize)
+			len(data), MaxScriptElementSize)
 		return scriptError(ErrElementTooBig, str)
 	}
 
 	// Nothing left to do when this is not a conditional opcode and it is
 	// not in an executing branch.
-	if !vm.isBranchExecuting() && !pop.isConditional() {
+	if !vm.isBranchExecuting() && !isOpcodeConditional(op.value) {
 		return nil
 	}
 
 	// Ensure all executed data push opcodes use the minimal encoding when
 	// the minimal data verification flag is set.
 	if vm.dstack.verifyMinimalData && vm.isBranchExecuting() &&
-		pop.opcode.value >= 0 && pop.opcode.value <= OP_PUSHDATA4 {
+		op.value >= 0 && op.value <= OP_PUSHDATA4 {
 
-		if err := pop.checkMinimalDataPush(); err != nil {
+		if err := checkMinimalDataPush(op, data); err != nil {
 			return err
 		}
 	}
 
-	return pop.opcode.opfunc(pop, vm)
+	return op.opfunc(op, data, vm)
 }
 
-// disasm is a helper function to produce the output for DisasmPC and
+// checkValidPC returns an error if the current script position is not valid for
-// DisasmScript.  It produces the opcode prefixed by the program counter at the
+// execution.
-// provided position in the script.  It does no error checking and leaves that
+func (vm *Engine) checkValidPC() error {
-// to the caller to provide a valid offset.
-func (vm *Engine) disasm(scriptIdx int, scriptOff int) string {
-	return fmt.Sprintf("%02x:%04x: %s", scriptIdx, scriptOff,
-		vm.scripts[scriptIdx][scriptOff].print(false))
-}
-
-// validPC returns an error if the current script position is valid for
-// execution, nil otherwise.
-func (vm *Engine) validPC() error {
 	if vm.scriptIdx >= len(vm.scripts) {
-		str := fmt.Sprintf("past input scripts %v:%v %v:xxxx",
+		str := fmt.Sprintf("script index %d beyond total scripts %d",
-			vm.scriptIdx, vm.scriptOff, len(vm.scripts))
+			vm.scriptIdx, len(vm.scripts))
-		return scriptError(ErrInvalidProgramCounter, str)
-	}
-	if vm.scriptOff >= len(vm.scripts[vm.scriptIdx]) {
-		str := fmt.Sprintf("past input scripts %v:%v %v:%04d",
-			vm.scriptIdx, vm.scriptOff, vm.scriptIdx,
-			len(vm.scripts[vm.scriptIdx]))
 		return scriptError(ErrInvalidProgramCounter, str)
 	}
 	return nil
 }
 
-// curPC returns either the current script and offset, or an error if the
-// position isn't valid.
-func (vm *Engine) curPC() (script int, off int, err error) {
-	err = vm.validPC()
-	if err != nil {
-		return 0, 0, err
-	}
-	return vm.scriptIdx, vm.scriptOff, nil
-}
-
 // isWitnessVersionActive returns true if a witness program was extracted
 // during the initialization of the Engine, and the program's version matches
 // the specified version.
@@ -269,7 +426,9 @@ func (vm *Engine) verifyWitnessProgram(witness [][]byte) error {
 			if err != nil {
 				return err
 			}
-			pops, err := parseScript(pkScript)
+
+			const scriptVersion = 0
+			err = checkScriptParses(vm.version, pkScript)
 			if err != nil {
 				return err
 			}
@@ -277,7 +436,7 @@ func (vm *Engine) verifyWitnessProgram(witness [][]byte) error {
 			// Set the stack to the provided witness stack, then
 			// append the pkScript generated above as the next
 			// script to execute.
-			vm.scripts = append(vm.scripts, pops)
+			vm.scripts = append(vm.scripts, pkScript)
 			vm.SetStack(witness)
 
 		case payToWitnessScriptHashDataSize: // P2WSH
@@ -307,10 +466,10 @@ func (vm *Engine) verifyWitnessProgram(witness [][]byte) error {
 					"witness program hash mismatch")
 			}
 
-			// With all the validity checks passed, parse the
+			// With all the validity checks passed, assert that the
-			// script into individual op-codes so w can execute it
+			// script parses without failure.
-			// as the next script.
+			const scriptVersion = 0
-			pops, err := parseScript(witnessScript)
+			err := checkScriptParses(vm.version, witnessScript)
 			if err != nil {
 				return err
 			}
@@ -318,7 +477,7 @@ func (vm *Engine) verifyWitnessProgram(witness [][]byte) error {
 			// The hash matched successfully, so use the witness as
 			// the stack, and set the witnessScript to be the next
 			// script executed.
-			vm.scripts = append(vm.scripts, pops)
+			vm.scripts = append(vm.scripts, witnessScript)
 			vm.SetStack(witness[:len(witness)-1])
 
 		default:
@@ -359,18 +518,50 @@ func (vm *Engine) verifyWitnessProgram(witness [][]byte) error {
 }
 
 // DisasmPC returns the string for the disassembly of the opcode that will be
-// next to execute when Step() is called.
+// next to execute when Step is called.
 func (vm *Engine) DisasmPC() (string, error) {
-	scriptIdx, scriptOff, err := vm.curPC()
+	if err := vm.checkValidPC(); err != nil {
-	if err != nil {
 		return "", err
 	}
-	return vm.disasm(scriptIdx, scriptOff), nil
+
+	// Create a copy of the current tokenizer and parse the next opcode in the
+	// copy to avoid mutating the current one.
+	peekTokenizer := vm.tokenizer
+	if !peekTokenizer.Next() {
+		// Note that due to the fact that all scripts are checked for parse
+		// failures before this code ever runs, there should never be an error
+		// here, but check again to be safe in case a refactor breaks that
+		// assumption or new script versions are introduced with different
+		// semantics.
+		if err := peekTokenizer.Err(); err != nil {
+			return "", err
+		}
+
+		// Note that this should be impossible to hit in practice because the
+		// only way it could happen would be for the final opcode of a script to
+		// already be parsed without the script index having been updated, which
+		// is not the case since stepping the script always increments the
+		// script index when parsing and executing the final opcode of a script.
+		//
+		// However, check again to be safe in case a refactor breaks that
+		// assumption or new script versions are introduced with different
+		// semantics.
+		str := fmt.Sprintf("program counter beyond script index %d (bytes %x)",
+			vm.scriptIdx, vm.scripts[vm.scriptIdx])
+		return "", scriptError(ErrInvalidProgramCounter, str)
+	}
+
+	var buf strings.Builder
+	disasmOpcode(&buf, peekTokenizer.op, peekTokenizer.Data(), false)
+	return fmt.Sprintf("%02x:%04x: %s", vm.scriptIdx, vm.opcodeIdx,
+		buf.String()), nil
 }
 
 // DisasmScript returns the disassembly string for the script at the requested
 // offset index.  Index 0 is the signature script and 1 is the public key
-// script.
+// script.  In the case of pay-to-script-hash, index 2 is the redeem script once
+// the execution has progressed far enough to have successfully verified script
+// hash and thus add the script to the scripts to execute.
 func (vm *Engine) DisasmScript(idx int) (string, error) {
 	if idx >= len(vm.scripts) {
 		str := fmt.Sprintf("script index %d >= total scripts %d", idx,
@@ -378,19 +569,25 @@ func (vm *Engine) DisasmScript(idx int) (string, error) {
 		return "", scriptError(ErrInvalidIndex, str)
 	}
 
-	var disstr string
+	var disbuf strings.Builder
-	for i := range vm.scripts[idx] {
+	script := vm.scripts[idx]
-		disstr = disstr + vm.disasm(idx, i) + "\n"
+	tokenizer := MakeScriptTokenizer(vm.version, script)
+	var opcodeIdx int
+	for tokenizer.Next() {
+		disbuf.WriteString(fmt.Sprintf("%02x:%04x: ", idx, opcodeIdx))
+		disasmOpcode(&disbuf, tokenizer.op, tokenizer.Data(), false)
+		disbuf.WriteByte('\n')
+		opcodeIdx++
 	}
-	return disstr, nil
+	return disbuf.String(), tokenizer.Err()
 }
 
 // CheckErrorCondition returns nil if the running script has ended and was
 // successful, leaving a a true boolean on the stack.  An error otherwise,
 // including if the script has not finished.
 func (vm *Engine) CheckErrorCondition(finalScript bool) error {
-	// Check execution is actually done.  When pc is past the end of script
+	// Check execution is actually done by ensuring the script index is after
-	// array there are no more scripts to run.
+	// the final script in the array script.
 	if vm.scriptIdx < len(vm.scripts) {
 		return scriptError(ErrScriptUnfinished,
 			"error check when script unfinished")
@@ -404,11 +601,14 @@ func (vm *Engine) CheckErrorCondition(finalScript bool) error {
 			"have clean stack")
 	}
 
+	// The final script must end with exactly one data stack item when the
+	// verify clean stack flag is set.  Otherwise, there must be at least one
+	// data stack item in order to interpret it as a boolean.
 	if finalScript && vm.hasFlag(ScriptVerifyCleanStack) &&
 		vm.dstack.Depth() != 1 {
 
-		str := fmt.Sprintf("stack contains %d unexpected items",
+		str := fmt.Sprintf("stack must contain exactly one item (contains %d)",
-			vm.dstack.Depth()-1)
+			vm.dstack.Depth())
 		return scriptError(ErrCleanStack, str)
 	} else if vm.dstack.Depth() < 1 {
 		return scriptError(ErrEmptyStack,
@@ -422,10 +622,14 @@ func (vm *Engine) CheckErrorCondition(finalScript bool) error {
 	if !v {
 		// Log interesting data.
 		log.Tracef("%v", newLogClosure(func() string {
-			dis0, _ := vm.DisasmScript(0)
+			var buf strings.Builder
-			dis1, _ := vm.DisasmScript(1)
+			buf.WriteString("scripts failed:\n")
-			return fmt.Sprintf("scripts failed: script0: %s\n"+
+			for i := range vm.scripts {
-				"script1: %s", dis0, dis1)
+				dis, _ := vm.DisasmScript(i)
+				buf.WriteString(fmt.Sprintf("script%d:\n", i))
+				buf.WriteString(dis)
+			}
+			return buf.String()
 		}))
 		return scriptError(ErrEvalFalse,
 			"false stack entry at end of script execution")
@@ -433,25 +637,38 @@ func (vm *Engine) CheckErrorCondition(finalScript bool) error {
 	return nil
 }
 
-// Step will execute the next instruction and move the program counter to the
+// Step executes the next instruction and moves the program counter to the next
-// next opcode in the script, or the next script if the current has ended.  Step
+// opcode in the script, or the next script if the current has ended.  Step will
-// will return true in the case that the last opcode was successfully executed.
+// return true in the case that the last opcode was successfully executed.
 //
 // The result of calling Step or any other method is undefined if an error is
 // returned.
 func (vm *Engine) Step() (done bool, err error) {
-	// Verify that it is pointing to a valid script address.
+	// Verify the engine is pointing to a valid program counter.
-	err = vm.validPC()
+	if err := vm.checkValidPC(); err != nil {
-	if err != nil {
 		return true, err
 	}
-	opcode := &vm.scripts[vm.scriptIdx][vm.scriptOff]
+
-	vm.scriptOff++
+	// Attempt to parse the next opcode from the current script.
+	if !vm.tokenizer.Next() {
+		// Note that due to the fact that all scripts are checked for parse
+		// failures before this code ever runs, there should never be an error
+		// here, but check again to be safe in case a refactor breaks that
+		// assumption or new script versions are introduced with different
+		// semantics.
+		if err := vm.tokenizer.Err(); err != nil {
+			return false, err
+		}
+
+		str := fmt.Sprintf("attempt to step beyond script index %d (bytes %x)",
+			vm.scriptIdx, vm.scripts[vm.scriptIdx])
+		return true, scriptError(ErrInvalidProgramCounter, str)
+	}
 
 	// Execute the opcode while taking into account several things such as
-	// disabled opcodes, illegal opcodes, maximum allowed operations per
+	// disabled opcodes, illegal opcodes, maximum allowed operations per script,
-	// script, maximum script element sizes, and conditionals.
+	// maximum script element sizes, and conditionals.
-	err = vm.executeOpcode(opcode)
+	err = vm.executeOpcode(vm.tokenizer.op, vm.tokenizer.Data())
 	if err != nil {
 		return true, err
 	}
@@ -466,43 +683,53 @@ func (vm *Engine) Step() (done bool, err error) {
 	}
 
 	// Prepare for next instruction.
-	if vm.scriptOff >= len(vm.scripts[vm.scriptIdx]) {
+	vm.opcodeIdx++
-		// Illegal to have an `if' that straddles two scripts.
+	if vm.tokenizer.Done() {
-		if err == nil && len(vm.condStack) != 0 {
+		// Illegal to have a conditional that straddles two scripts.
+		if len(vm.condStack) != 0 {
 			return false, scriptError(ErrUnbalancedConditional,
 				"end of script reached in conditional execution")
 		}
 
-		// Alt stack doesn't persist.
+		// Alt stack doesn't persist between scripts.
 		_ = vm.astack.DropN(vm.astack.Depth())
 
-		vm.numOps = 0 // number of ops is per script.
+		// The number of operations is per script.
-		vm.scriptOff = 0
+		vm.numOps = 0
-		if vm.scriptIdx == 0 && vm.bip16 {
+
+		// Reset the opcode index for the next script.
+		vm.opcodeIdx = 0
+
+		// Advance to the next script as needed.
+		switch {
+		case vm.scriptIdx == 0 && vm.bip16:
 			vm.scriptIdx++
 			vm.savedFirstStack = vm.GetStack()
-		} else if vm.scriptIdx == 1 && vm.bip16 {
+
+		case vm.scriptIdx == 1 && vm.bip16:
 			// Put us past the end for CheckErrorCondition()
 			vm.scriptIdx++
-			// Check script ran successfully and pull the script
+
-			// out of the first stack and execute that.
+			// Check script ran successfully.
 			err := vm.CheckErrorCondition(false)
 			if err != nil {
 				return false, err
 			}
 
+			// Obtain the redeem script from the first stack and ensure it
+			// parses.
 			script := vm.savedFirstStack[len(vm.savedFirstStack)-1]
-			pops, err := parseScript(script)
+			if err := checkScriptParses(vm.version, script); err != nil {
-			if err != nil {
 				return false, err
 			}
-			vm.scripts = append(vm.scripts, pops)
+			vm.scripts = append(vm.scripts, script)
 
-			// Set stack to be the stack from first script minus the
+			// Set stack to be the stack from first script minus the redeem
 			// script itself
 			vm.SetStack(vm.savedFirstStack[:len(vm.savedFirstStack)-1])
-		} else if (vm.scriptIdx == 1 && vm.witnessProgram != nil) ||
+
-			(vm.scriptIdx == 2 && vm.witnessProgram != nil && vm.bip16) { // Nested P2SH.
+		case vm.scriptIdx == 1 && vm.witnessProgram != nil,
+			vm.scriptIdx == 2 && vm.witnessProgram != nil && vm.bip16: // np2sh
 
 			vm.scriptIdx++
 
@@ -510,30 +737,46 @@ func (vm *Engine) Step() (done bool, err error) {
 			if err := vm.verifyWitnessProgram(witness); err != nil {
 				return false, err
 			}
-		} else {
+
+		default:
 			vm.scriptIdx++
 		}
-		// there are zero length scripts in the wild
+
-		if vm.scriptIdx < len(vm.scripts) && vm.scriptOff >= len(vm.scripts[vm.scriptIdx]) {
+		// Skip empty scripts.
+		if vm.scriptIdx < len(vm.scripts) && len(vm.scripts[vm.scriptIdx]) == 0 {
 			vm.scriptIdx++
 		}
+
 		vm.lastCodeSep = 0
 		if vm.scriptIdx >= len(vm.scripts) {
 			return true, nil
 		}
+
+		// Finally, update the current tokenizer used to parse through scripts
+		// one opcode at a time to start from the beginning of the new script
+		// associated with the program counter.
+		vm.tokenizer = MakeScriptTokenizer(vm.version, vm.scripts[vm.scriptIdx])
 	}
+
 	return false, nil
 }
 
 // Execute will execute all scripts in the script engine and return either nil
 // for successful validation or an error if one occurred.
 func (vm *Engine) Execute() (err error) {
+	// All script versions other than 0 currently execute without issue,
+	// making all outputs to them anyone can pay. In the future this
+	// will allow for the addition of new scripting languages.
+	if vm.version != 0 {
+		return nil
+	}
+
 	done := false
 	for !done {
 		log.Tracef("%v", newLogClosure(func() string {
 			dis, err := vm.DisasmPC()
 			if err != nil {
-				return fmt.Sprintf("stepping (%v)", err)
+				return fmt.Sprintf("stepping - failed to disasm pc: %v", err)
 			}
 			return fmt.Sprintf("stepping %v", dis)
 		}))
@@ -545,7 +788,7 @@ func (vm *Engine) Execute() (err error) {
 		log.Tracef("%v", newLogClosure(func() string {
 			var dstr, astr string
 
-			// if we're tracing, dump the stacks.
+			// Log the non-empty stacks when tracing.
 			if vm.dstack.Depth() != 0 {
 				dstr = "Stack:\n" + vm.dstack.String()
 			}
@@ -561,7 +804,7 @@ func (vm *Engine) Execute() (err error) {
 }
 
 // subScript returns the script since the last OP_CODESEPARATOR.
-func (vm *Engine) subScript() []parsedOpcode {
+func (vm *Engine) subScript() []byte {
 	return vm.scripts[vm.scriptIdx][vm.lastCodeSep:]
 }
 
@@ -580,6 +823,27 @@ func (vm *Engine) checkHashTypeEncoding(hashType SigHashType) error {
 	return nil
 }
 
+// isStrictPubKeyEncoding returns whether or not the passed public key adheres
+// to the strict encoding requirements.
+func isStrictPubKeyEncoding(pubKey []byte) bool {
+	if len(pubKey) == 33 && (pubKey[0] == 0x02 || pubKey[0] == 0x03) {
+		// Compressed
+		return true
+	}
+	if len(pubKey) == 65 {
+		switch pubKey[0] {
+		case 0x04:
+			// Uncompressed
+			return true
+
+		case 0x06, 0x07:
+			// Hybrid
+			return true
+		}
+	}
+	return false
+}
+
 // checkPubKeyEncoding returns whether or not the passed public key adheres to
 // the strict encoding requirements if enabled.
 func (vm *Engine) checkPubKeyEncoding(pubKey []byte) error {
@@ -854,6 +1118,7 @@ func (vm *Engine) SetAltStack(data [][]byte) {
 // engine according to the description provided by each flag.
 func NewEngine(scriptPubKey []byte, tx *wire.MsgTx, txIdx int, flags ScriptFlags,
 	sigCache *SigCache, hashCache *TxSigHashes, inputAmount int64) (*Engine, error) {
+	const scriptVersion = 0
 
 	// The provided transaction input index must refer to a valid input.
 	if txIdx < 0 || txIdx >= len(tx.TxIn) {
@@ -863,10 +1128,10 @@ func NewEngine(scriptPubKey []byte, tx *wire.MsgTx, txIdx int, flags ScriptFlags
 	}
 	scriptSig := tx.TxIn[txIdx].SignatureScript
 
-	// When both the signature script and public key script are empty the
+	// When both the signature script and public key script are empty the result
-	// result is necessarily an error since the stack would end up being
+	// is necessarily an error since the stack would end up being empty which is
-	// empty which is equivalent to a false top element.  Thus, just return
+	// equivalent to a false top element.  Thus, just return the relevant error
-	// the relevant error now as an optimization.
+	// now as an optimization.
 	if len(scriptSig) == 0 && len(scriptPubKey) == 0 {
 		return nil, scriptError(ErrEvalFalse,
 			"false stack entry at end of script execution")
@@ -897,40 +1162,45 @@ func NewEngine(scriptPubKey []byte, tx *wire.MsgTx, txIdx int, flags ScriptFlags
 			"signature script is not push only")
 	}
 
-	// The engine stores the scripts in parsed form using a slice.  This
+	// The signature script must only contain data pushes for PS2H which is
-	// allows multiple scripts to be executed in sequence.  For example,
+	// determined based on the form of the public key script.
-	// with a pay-to-script-hash transaction, there will be ultimately be
+	if vm.hasFlag(ScriptBip16) && isScriptHashScript(scriptPubKey) {
-	// a third script to execute.
-	scripts := [][]byte{scriptSig, scriptPubKey}
-	vm.scripts = make([][]parsedOpcode, len(scripts))
-	for i, scr := range scripts {
-		if len(scr) > MaxScriptSize {
-			str := fmt.Sprintf("script size %d is larger than max "+
-				"allowed size %d", len(scr), MaxScriptSize)
-			return nil, scriptError(ErrScriptTooBig, str)
-		}
-		var err error
-		vm.scripts[i], err = parseScript(scr)
-		if err != nil {
-			return nil, err
-		}
-	}
-
-	// Advance the program counter to the public key script if the signature
-	// script is empty since there is nothing to execute for it in that
-	// case.
-	if len(scripts[0]) == 0 {
-		vm.scriptIdx++
-	}
-
-	if vm.hasFlag(ScriptBip16) && isScriptHash(vm.scripts[1]) {
 		// Only accept input scripts that push data for P2SH.
-		if !isPushOnly(vm.scripts[0]) {
+		// Notice that the push only checks have already been done when
+		// the flag to verify signature scripts are push only is set
+		// above, so avoid checking again.
+		alreadyChecked := vm.hasFlag(ScriptVerifySigPushOnly)
+		if !alreadyChecked && !IsPushOnlyScript(scriptSig) {
 			return nil, scriptError(ErrNotPushOnly,
 				"pay to script hash is not push only")
 		}
 		vm.bip16 = true
 	}
+
+	// The engine stores the scripts using a slice.  This allows multiple
+	// scripts to be executed in sequence.  For example, with a
+	// pay-to-script-hash transaction, there will be ultimately be a third
+	// script to execute.
+	scripts := [][]byte{scriptSig, scriptPubKey}
+	for _, scr := range scripts {
+		if len(scr) > MaxScriptSize {
+			str := fmt.Sprintf("script size %d is larger than max allowed "+
+				"size %d", len(scr), MaxScriptSize)
+			return nil, scriptError(ErrScriptTooBig, str)
+		}
+
+		const scriptVersion = 0
+		if err := checkScriptParses(scriptVersion, scr); err != nil {
+			return nil, err
+		}
+	}
+	vm.scripts = scripts
+
+	// Advance the program counter to the public key script if the signature
+	// script is empty since there is nothing to execute for it in that case.
+	if len(scriptSig) == 0 {
+		vm.scriptIdx++
+	}
 	if vm.hasFlag(ScriptVerifyMinimalData) {
 		vm.dstack.verifyMinimalData = true
 		vm.astack.verifyMinimalData = true
@@ -952,7 +1222,7 @@ func NewEngine(scriptPubKey []byte, tx *wire.MsgTx, txIdx int, flags ScriptFlags
 		var witProgram []byte
 
 		switch {
-		case isWitnessProgram(vm.scripts[1]):
+		case IsWitnessProgram(vm.scripts[1]):
 			// The scriptSig must be *empty* for all native witness
 			// programs, otherwise we introduce malleability.
 			if len(scriptSig) != 0 {
@@ -967,10 +1237,11 @@ func NewEngine(scriptPubKey []byte, tx *wire.MsgTx, txIdx int, flags ScriptFlags
 			// data push of the witness program, otherwise we
 			// reintroduce malleability.
 			sigPops := vm.scripts[0]
-			if len(sigPops) == 1 && canonicalPush(sigPops[0]) &&
+			if len(sigPops) > 2 &&
-				IsWitnessProgram(sigPops[0].data) {
+				isCanonicalPush(sigPops[0], sigPops[1:]) &&
+				IsWitnessProgram(sigPops[1:]) {
 
-				witProgram = sigPops[0].data
+				witProgram = sigPops[1:]
 			} else {
 				errStr := "signature script for witness " +
 					"nested p2sh is not canonical"
@@ -997,6 +1268,10 @@ func NewEngine(scriptPubKey []byte, tx *wire.MsgTx, txIdx int, flags ScriptFlags
 
 	}
 
+	// Setup the current tokenizer used to parse through the script one opcode
+	// at a time with the script associated with the program counter.
+	vm.tokenizer = MakeScriptTokenizer(scriptVersion, scripts[vm.scriptIdx])
+
 	vm.tx = *tx
 	vm.txIdx = txIdx
 

txscript/engine_test.go

@@ -1,4 +1,5 @@
 // Copyright (c) 2013-2017 The btcsuite developers
+// Copyright (c) 2015-2019 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
@@ -11,16 +12,16 @@ import (
 	"github.com/btcsuite/btcd/wire"
 )
 
-// TestBadPC sets the pc to a deliberately bad result then confirms that Step()
+// TestBadPC sets the pc to a deliberately bad result then confirms that Step
 // and Disasm fail correctly.
 func TestBadPC(t *testing.T) {
 	t.Parallel()
 
 	tests := []struct {
-		script, off int
+		scriptIdx int
 	}{
-		{script: 2, off: 0},
+		{scriptIdx: 2},
-		{script: 0, off: 2},
+		{scriptIdx: 3},
 	}
 
 	// tx with almost empty scripts.
@@ -59,20 +60,20 @@ func TestBadPC(t *testing.T) {
 			t.Errorf("Failed to create script: %v", err)
 		}
 
-		// set to after all scripts
+		// Set to after all scripts.
-		vm.scriptIdx = test.script
+		vm.scriptIdx = test.scriptIdx
-		vm.scriptOff = test.off
 
+		// Ensure attempting to step fails.
 		_, err = vm.Step()
 		if err == nil {
 			t.Errorf("Step with invalid pc (%v) succeeds!", test)
 			continue
 		}
 
+		// Ensure attempting to disassemble the current program counter fails.
 		_, err = vm.DisasmPC()
 		if err == nil {
-			t.Errorf("DisasmPC with invalid pc (%v) succeeds!",
+			t.Errorf("DisasmPC with invalid pc (%v) succeeds!", test)
-				test)
 		}
 	}
 }

txscript/error.go

@@ -1,4 +1,5 @@
 // Copyright (c) 2013-2017 The btcsuite developers
+// Copyright (c) 2015-2019 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
@@ -47,6 +48,10 @@ const (
 	// the provided data exceeds MaxDataCarrierSize.
 	ErrTooMuchNullData
 
+	// ErrUnsupportedScriptVersion is returned when an unsupported script
+	// version is passed to a function which deals with script analysis.
+	ErrUnsupportedScriptVersion
+
 	// ------------------------------------------
 	// Failures related to final execution state.
 	// ------------------------------------------
@@ -352,6 +357,7 @@ var errorCodeStrings = map[ErrorCode]string{
 	ErrNotMultisigScript:                  "ErrNotMultisigScript",
 	ErrTooManyRequiredSigs:                "ErrTooManyRequiredSigs",
 	ErrTooMuchNullData:                    "ErrTooMuchNullData",
+	ErrUnsupportedScriptVersion:           "ErrUnsupportedScriptVersion",
 	ErrEarlyReturn:                        "ErrEarlyReturn",
 	ErrEmptyStack:                         "ErrEmptyStack",
 	ErrEvalFalse:                          "ErrEvalFalse",

txscript/error_test.go

@@ -1,4 +1,5 @@
 // Copyright (c) 2017 The btcsuite developers
+// Copyright (c) 2015-2019 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
@@ -22,6 +23,7 @@ func TestErrorCodeStringer(t *testing.T) {
 		{ErrUnsupportedAddress, "ErrUnsupportedAddress"},
 		{ErrTooManyRequiredSigs, "ErrTooManyRequiredSigs"},
 		{ErrTooMuchNullData, "ErrTooMuchNullData"},
+		{ErrUnsupportedScriptVersion, "ErrUnsupportedScriptVersion"},
 		{ErrNotMultisigScript, "ErrNotMultisigScript"},
 		{ErrEarlyReturn, "ErrEarlyReturn"},
 		{ErrEmptyStack, "ErrEmptyStack"},

txscript/example_test.go

@@ -1,4 +1,5 @@
 // Copyright (c) 2014-2016 The btcsuite developers
+// Copyright (c) 2015-2019 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
@@ -180,3 +181,34 @@ func ExampleSignTxOutput() {
 	// Output:
 	// Transaction successfully signed
 }
+
+// This example demonstrates creating a script tokenizer instance and using it
+// to count the number of opcodes a script contains.
+func ExampleScriptTokenizer() {
+	// Create a script to use in the example.  Ordinarily this would come from
+	// some other source.
+	hash160 := btcutil.Hash160([]byte("example"))
+	script, err := txscript.NewScriptBuilder().AddOp(txscript.OP_DUP).
+		AddOp(txscript.OP_HASH160).AddData(hash160).
+		AddOp(txscript.OP_EQUALVERIFY).AddOp(txscript.OP_CHECKSIG).Script()
+	if err != nil {
+		fmt.Printf("failed to build script: %v\n", err)
+		return
+	}
+
+	// Create a tokenizer to iterate the script and count the number of opcodes.
+	const scriptVersion = 0
+	var numOpcodes int
+	tokenizer := txscript.MakeScriptTokenizer(scriptVersion, script)
+	for tokenizer.Next() {
+		numOpcodes++
+	}
+	if tokenizer.Err() != nil {
+		fmt.Printf("script failed to parse: %v\n", err)
+	} else {
+		fmt.Printf("script contains %d opcode(s)\n", numOpcodes)
+	}
+
+	// Output:
+	// script contains 5 opcode(s)
+}

txscript/opcode.go

@@ -8,9 +8,10 @@ import (
 	"bytes"
 	"crypto/sha1"
 	"crypto/sha256"
-	"encoding/binary"
+	"encoding/hex"
 	"fmt"
 	"hash"
+	"strings"
 
 	"golang.org/x/crypto/ripemd160"
 
@@ -27,7 +28,7 @@ type opcode struct {
 	value  byte
 	name   string
 	length int
-	opfunc func(*parsedOpcode, *Engine) error
+	opfunc func(*opcode, []byte, *Engine) error
 }
 
 // These constants are the values of the official opcodes used on the btc wiki,
@@ -610,306 +611,52 @@ var opcodeOnelineRepls = map[string]string{
 	"OP_16":      "16",
 }
 
-// parsedOpcode represents an opcode that has been parsed and includes any
+// disasmOpcode writes a human-readable disassembly of the provided opcode and
-// potential data associated with it.
+// data into the provided buffer.  The compact flag indicates the disassembly
-type parsedOpcode struct {
+// should print a more compact representation of data-carrying and small integer
-	opcode *opcode
+// opcodes.  For example, OP_0 through OP_16 are replaced with the numeric value
-	data   []byte
+// and data pushes are printed as only the hex representation of the data as
-}
+// opposed to including the opcode that specifies the amount of data to push as
-
+// well.
-// isDisabled returns whether or not the opcode is disabled and thus is always
+func disasmOpcode(buf *strings.Builder, op *opcode, data []byte, compact bool) {
-// bad to see in the instruction stream (even if turned off by a conditional).
+	// Replace opcode which represent values (e.g. OP_0 through OP_16 and
-func (pop *parsedOpcode) isDisabled() bool {
+	// OP_1NEGATE) with the raw value when performing a compact disassembly.
-	switch pop.opcode.value {
+	opcodeName := op.name
-	case OP_CAT:
+	if compact {
-		return true
-	case OP_SUBSTR:
-		return true
-	case OP_LEFT:
-		return true
-	case OP_RIGHT:
-		return true
-	case OP_INVERT:
-		return true
-	case OP_AND:
-		return true
-	case OP_OR:
-		return true
-	case OP_XOR:
-		return true
-	case OP_2MUL:
-		return true
-	case OP_2DIV:
-		return true
-	case OP_MUL:
-		return true
-	case OP_DIV:
-		return true
-	case OP_MOD:
-		return true
-	case OP_LSHIFT:
-		return true
-	case OP_RSHIFT:
-		return true
-	default:
-		return false
-	}
-}
-
-// checkParseableInScript checks whether or not the current opcode is able to be
-// parsed at a certain position in a script.
-// This returns the position of the next opcode to be parsed in the script.
-func (pop *parsedOpcode) checkParseableInScript(script []byte, scriptPos int) (int, error) {
-	// Parse data out of instruction.
-	switch {
-	// No additional data.  Note that some of the opcodes, notably
-	// OP_1NEGATE, OP_0, and OP_[1-16] represent the data
-	// themselves.
-	case pop.opcode.length == 1:
-		scriptPos++
-
-	// Data pushes of specific lengths -- OP_DATA_[1-75].
-	case pop.opcode.length > 1:
-		if len(script[scriptPos:]) < pop.opcode.length {
-			str := fmt.Sprintf("opcode %s requires %d "+
-				"bytes, but script only has %d remaining",
-				pop.opcode.name, pop.opcode.length, len(script[scriptPos:]))
-			return 0, scriptError(ErrMalformedPush, str)
-		}
-
-		// Slice out the data.
-		pop.data = script[scriptPos+1 : scriptPos+pop.opcode.length]
-		scriptPos += pop.opcode.length
-
-	// Data pushes with parsed lengths -- OP_PUSHDATAP{1,2,4}.
-	case pop.opcode.length < 0:
-		var l uint
-		off := scriptPos + 1
-
-		if len(script[off:]) < -pop.opcode.length {
-			str := fmt.Sprintf("opcode %s requires %d "+
-				"bytes, but script only has %d remaining",
-				pop.opcode.name, -pop.opcode.length, len(script[off:]))
-			return 0, scriptError(ErrMalformedPush, str)
-		}
-
-		// Next -length bytes are little endian length of data.
-		switch pop.opcode.length {
-		case -1:
-			l = uint(script[off])
-		case -2:
-			l = ((uint(script[off+1]) << 8) |
-				uint(script[off]))
-		case -4:
-			l = ((uint(script[off+3]) << 24) |
-				(uint(script[off+2]) << 16) |
-				(uint(script[off+1]) << 8) |
-				uint(script[off]))
-		default:
-			str := fmt.Sprintf("invalid opcode length %d",
-				pop.opcode.length)
-			return 0, scriptError(ErrMalformedPush, str)
-		}
-
-		// Move offset to beginning of the data.
-		off += -pop.opcode.length
-
-		// Disallow entries that do not fit script or were
-		// sign extended.
-		if int(l) > len(script[off:]) || int(l) < 0 {
-			str := fmt.Sprintf("opcode %s pushes %d bytes, "+
-				"but script only has %d remaining",
-				pop.opcode.name, int(l), len(script[off:]))
-			return 0, scriptError(ErrMalformedPush, str)
-		}
-
-		pop.data = script[off : off+int(l)]
-		scriptPos += 1 - pop.opcode.length + int(l)
-	}
-	return scriptPos, nil
-}
-
-// alwaysIllegal returns whether or not the opcode is always illegal when passed
-// over by the program counter even if in a non-executed branch (it isn't a
-// coincidence that they are conditionals).
-func (pop *parsedOpcode) alwaysIllegal() bool {
-	switch pop.opcode.value {
-	case OP_VERIF:
-		return true
-	case OP_VERNOTIF:
-		return true
-	default:
-		return false
-	}
-}
-
-// isConditional returns whether or not the opcode is a conditional opcode which
-// changes the conditional execution stack when executed.
-func (pop *parsedOpcode) isConditional() bool {
-	switch pop.opcode.value {
-	case OP_IF:
-		return true
-	case OP_NOTIF:
-		return true
-	case OP_ELSE:
-		return true
-	case OP_ENDIF:
-		return true
-	default:
-		return false
-	}
-}
-
-// checkMinimalDataPush returns whether or not the current data push uses the
-// smallest possible opcode to represent it.  For example, the value 15 could
-// be pushed with OP_DATA_1 15 (among other variations); however, OP_15 is a
-// single opcode that represents the same value and is only a single byte versus
-// two bytes.
-func (pop *parsedOpcode) checkMinimalDataPush() error {
-	data := pop.data
-	dataLen := len(data)
-	opcode := pop.opcode.value
-
-	if dataLen == 0 && opcode != OP_0 {
-		str := fmt.Sprintf("zero length data push is encoded with "+
-			"opcode %s instead of OP_0", pop.opcode.name)
-		return scriptError(ErrMinimalData, str)
-	} else if dataLen == 1 && data[0] >= 1 && data[0] <= 16 {
-		if opcode != OP_1+data[0]-1 {
-			// Should have used OP_1 .. OP_16
-			str := fmt.Sprintf("data push of the value %d encoded "+
-				"with opcode %s instead of OP_%d", data[0],
-				pop.opcode.name, data[0])
-			return scriptError(ErrMinimalData, str)
-		}
-	} else if dataLen == 1 && data[0] == 0x81 {
-		if opcode != OP_1NEGATE {
-			str := fmt.Sprintf("data push of the value -1 encoded "+
-				"with opcode %s instead of OP_1NEGATE",
-				pop.opcode.name)
-			return scriptError(ErrMinimalData, str)
-		}
-	} else if dataLen <= 75 {
-		if int(opcode) != dataLen {
-			// Should have used a direct push
-			str := fmt.Sprintf("data push of %d bytes encoded "+
-				"with opcode %s instead of OP_DATA_%d", dataLen,
-				pop.opcode.name, dataLen)
-			return scriptError(ErrMinimalData, str)
-		}
-	} else if dataLen <= 255 {
-		if opcode != OP_PUSHDATA1 {
-			str := fmt.Sprintf("data push of %d bytes encoded "+
-				"with opcode %s instead of OP_PUSHDATA1",
-				dataLen, pop.opcode.name)
-			return scriptError(ErrMinimalData, str)
-		}
-	} else if dataLen <= 65535 {
-		if opcode != OP_PUSHDATA2 {
-			str := fmt.Sprintf("data push of %d bytes encoded "+
-				"with opcode %s instead of OP_PUSHDATA2",
-				dataLen, pop.opcode.name)
-			return scriptError(ErrMinimalData, str)
-		}
-	}
-	return nil
-}
-
-// print returns a human-readable string representation of the opcode for use
-// in script disassembly.
-func (pop *parsedOpcode) print(oneline bool) string {
-	// The reference implementation one-line disassembly replaces opcodes
-	// which represent values (e.g. OP_0 through OP_16 and OP_1NEGATE)
-	// with the raw value.  However, when not doing a one-line dissassembly,
-	// we prefer to show the actual opcode names.  Thus, only replace the
-	// opcodes in question when the oneline flag is set.
-	opcodeName := pop.opcode.name
-	if oneline {
 		if replName, ok := opcodeOnelineRepls[opcodeName]; ok {
 			opcodeName = replName
 		}
 
-		// Nothing more to do for non-data push opcodes.
+		// Either write the human-readable opcode or the parsed data in hex for
-		if pop.opcode.length == 1 {
+		// data-carrying opcodes.
-			return opcodeName
+		switch {
+		case op.length == 1:
+			buf.WriteString(opcodeName)
+
+		default:
+			buf.WriteString(hex.EncodeToString(data))
 		}
 
-		return fmt.Sprintf("%x", pop.data)
+		return
 	}
 
-	// Nothing more to do for non-data push opcodes.
+	buf.WriteString(opcodeName)
-	if pop.opcode.length == 1 {
+
-		return opcodeName
+	switch op.length {
-	}
+	// Only write the opcode name for non-data push opcodes.
+	case 1:
+		return
 
 	// Add length for the OP_PUSHDATA# opcodes.
-	retString := opcodeName
-	switch pop.opcode.length {
 	case -1:
-		retString += fmt.Sprintf(" 0x%02x", len(pop.data))
+		buf.WriteString(fmt.Sprintf(" 0x%02x", len(data)))
 	case -2:
-		retString += fmt.Sprintf(" 0x%04x", len(pop.data))
+		buf.WriteString(fmt.Sprintf(" 0x%04x", len(data)))
 	case -4:
-		retString += fmt.Sprintf(" 0x%08x", len(pop.data))
+		buf.WriteString(fmt.Sprintf(" 0x%08x", len(data)))
 	}
 
-	return fmt.Sprintf("%s 0x%02x", retString, pop.data)
+	buf.WriteString(fmt.Sprintf(" 0x%02x", data))
-}
-
-// bytes returns any data associated with the opcode encoded as it would be in
-// a script.  This is used for unparsing scripts from parsed opcodes.
-func (pop *parsedOpcode) bytes() ([]byte, error) {
-	var retbytes []byte
-	if pop.opcode.length > 0 {
-		retbytes = make([]byte, 1, pop.opcode.length)
-	} else {
-		retbytes = make([]byte, 1, 1+len(pop.data)-
-			pop.opcode.length)
-	}
-
-	retbytes[0] = pop.opcode.value
-	if pop.opcode.length == 1 {
-		if len(pop.data) != 0 {
-			str := fmt.Sprintf("internal consistency error - "+
-				"parsed opcode %s has data length %d when %d "+
-				"was expected", pop.opcode.name, len(pop.data),
-				0)
-			return nil, scriptError(ErrInternal, str)
-		}
-		return retbytes, nil
-	}
-	nbytes := pop.opcode.length
-	if pop.opcode.length < 0 {
-		l := len(pop.data)
-		// tempting just to hardcode to avoid the complexity here.
-		switch pop.opcode.length {
-		case -1:
-			retbytes = append(retbytes, byte(l))
-			nbytes = int(retbytes[1]) + len(retbytes)
-		case -2:
-			retbytes = append(retbytes, byte(l&0xff),
-				byte(l>>8&0xff))
-			nbytes = int(binary.LittleEndian.Uint16(retbytes[1:])) +
-				len(retbytes)
-		case -4:
-			retbytes = append(retbytes, byte(l&0xff),
-				byte((l>>8)&0xff), byte((l>>16)&0xff),
-				byte((l>>24)&0xff))
-			nbytes = int(binary.LittleEndian.Uint32(retbytes[1:])) +
-				len(retbytes)
-		}
-	}
-
-	retbytes = append(retbytes, pop.data...)
-
-	if len(retbytes) != nbytes {
-		str := fmt.Sprintf("internal consistency error - "+
-			"parsed opcode %s has data length %d when %d was "+
-			"expected", pop.opcode.name, len(retbytes), nbytes)
-		return nil, scriptError(ErrInternal, str)
-	}
-
-	return retbytes, nil
 }
 
 // *******************************************
@@ -922,45 +669,42 @@ func (pop *parsedOpcode) bytes() ([]byte, error) {
 // opcodes before executing in an initial parse step, the consensus rules
 // dictate the script doesn't fail until the program counter passes over a
 // disabled opcode (even when they appear in a branch that is not executed).
-func opcodeDisabled(op *parsedOpcode, vm *Engine) error {
+func opcodeDisabled(op *opcode, data []byte, vm *Engine) error {
-	str := fmt.Sprintf("attempt to execute disabled opcode %s",
+	str := fmt.Sprintf("attempt to execute disabled opcode %s", op.name)
-		op.opcode.name)
 	return scriptError(ErrDisabledOpcode, str)
 }
 
 // opcodeReserved is a common handler for all reserved opcodes.  It returns an
 // appropriate error indicating the opcode is reserved.
-func opcodeReserved(op *parsedOpcode, vm *Engine) error {
+func opcodeReserved(op *opcode, data []byte, vm *Engine) error {
-	str := fmt.Sprintf("attempt to execute reserved opcode %s",
+	str := fmt.Sprintf("attempt to execute reserved opcode %s", op.name)
-		op.opcode.name)
 	return scriptError(ErrReservedOpcode, str)
 }
 
 // opcodeInvalid is a common handler for all invalid opcodes.  It returns an
 // appropriate error indicating the opcode is invalid.
-func opcodeInvalid(op *parsedOpcode, vm *Engine) error {
+func opcodeInvalid(op *opcode, data []byte, vm *Engine) error {
-	str := fmt.Sprintf("attempt to execute invalid opcode %s",
+	str := fmt.Sprintf("attempt to execute invalid opcode %s", op.name)
-		op.opcode.name)
 	return scriptError(ErrReservedOpcode, str)
 }
 
 // opcodeFalse pushes an empty array to the data stack to represent false.  Note
 // that 0, when encoded as a number according to the numeric encoding consensus
 // rules, is an empty array.
-func opcodeFalse(op *parsedOpcode, vm *Engine) error {
+func opcodeFalse(op *opcode, data []byte, vm *Engine) error {
 	vm.dstack.PushByteArray(nil)
 	return nil
 }
 
 // opcodePushData is a common handler for the vast majority of opcodes that push
 // raw data (bytes) to the data stack.
-func opcodePushData(op *parsedOpcode, vm *Engine) error {
+func opcodePushData(op *opcode, data []byte, vm *Engine) error {
-	vm.dstack.PushByteArray(op.data)
+	vm.dstack.PushByteArray(data)
 	return nil
 }
 
 // opcode1Negate pushes -1, encoded as a number, to the data stack.
-func opcode1Negate(op *parsedOpcode, vm *Engine) error {
+func opcode1Negate(op *opcode, data []byte, vm *Engine) error {
 	vm.dstack.PushInt(scriptNum(-1))
 	return nil
 }
@@ -968,23 +712,24 @@ func opcode1Negate(op *parsedOpcode, vm *Engine) error {
 // opcodeN is a common handler for the small integer data push opcodes.  It
 // pushes the numeric value the opcode represents (which will be from 1 to 16)
 // onto the data stack.
-func opcodeN(op *parsedOpcode, vm *Engine) error {
+func opcodeN(op *opcode, data []byte, vm *Engine) error {
 	// The opcodes are all defined consecutively, so the numeric value is
 	// the difference.
-	vm.dstack.PushInt(scriptNum((op.opcode.value - (OP_1 - 1))))
+	vm.dstack.PushInt(scriptNum((op.value - (OP_1 - 1))))
 	return nil
 }
 
 // opcodeNop is a common handler for the NOP family of opcodes.  As the name
 // implies it generally does nothing, however, it will return an error when
 // the flag to discourage use of NOPs is set for select opcodes.
-func opcodeNop(op *parsedOpcode, vm *Engine) error {
+func opcodeNop(op *opcode, data []byte, vm *Engine) error {
-	switch op.opcode.value {
+	switch op.value {
 	case OP_NOP1, OP_NOP4, OP_NOP5,
 		OP_NOP6, OP_NOP7, OP_NOP8, OP_NOP9, OP_NOP10:
+
 		if vm.hasFlag(ScriptDiscourageUpgradableNops) {
-			str := fmt.Sprintf("OP_NOP%d reserved for soft-fork "+
+			str := fmt.Sprintf("%v reserved for soft-fork "+
-				"upgrades", op.opcode.value-(OP_NOP1-1))
+				"upgrades", op.name)
 			return scriptError(ErrDiscourageUpgradableNOPs, str)
 		}
 	}
@@ -1047,7 +792,7 @@ func popIfBool(vm *Engine) (bool, error) {
 //
 // Data stack transformation: [... bool] -> [...]
 // Conditional stack transformation: [...] -> [... OpCondValue]
-func opcodeIf(op *parsedOpcode, vm *Engine) error {
+func opcodeIf(op *opcode, data []byte, vm *Engine) error {
 	condVal := OpCondFalse
 	if vm.isBranchExecuting() {
 		ok, err := popIfBool(vm)
@@ -1081,7 +826,7 @@ func opcodeIf(op *parsedOpcode, vm *Engine) error {
 //
 // Data stack transformation: [... bool] -> [...]
 // Conditional stack transformation: [...] -> [... OpCondValue]
-func opcodeNotIf(op *parsedOpcode, vm *Engine) error {
+func opcodeNotIf(op *opcode, data []byte, vm *Engine) error {
 	condVal := OpCondFalse
 	if vm.isBranchExecuting() {
 		ok, err := popIfBool(vm)
@@ -1104,10 +849,10 @@ func opcodeNotIf(op *parsedOpcode, vm *Engine) error {
 // An error is returned if there has not already been a matching OP_IF.
 //
 // Conditional stack transformation: [... OpCondValue] -> [... !OpCondValue]
-func opcodeElse(op *parsedOpcode, vm *Engine) error {
+func opcodeElse(op *opcode, data []byte, vm *Engine) error {
 	if len(vm.condStack) == 0 {
 		str := fmt.Sprintf("encountered opcode %s with no matching "+
-			"opcode to begin conditional execution", op.opcode.name)
+			"opcode to begin conditional execution", op.name)
 		return scriptError(ErrUnbalancedConditional, str)
 	}
 
@@ -1130,10 +875,10 @@ func opcodeElse(op *parsedOpcode, vm *Engine) error {
 // An error is returned if there has not already been a matching OP_IF.
 //
 // Conditional stack transformation: [... OpCondValue] -> [...]
-func opcodeEndif(op *parsedOpcode, vm *Engine) error {
+func opcodeEndif(op *opcode, data []byte, vm *Engine) error {
 	if len(vm.condStack) == 0 {
 		str := fmt.Sprintf("encountered opcode %s with no matching "+
-			"opcode to begin conditional execution", op.opcode.name)
+			"opcode to begin conditional execution", op.name)
 		return scriptError(ErrUnbalancedConditional, str)
 	}
 
@@ -1146,14 +891,14 @@ func opcodeEndif(op *parsedOpcode, vm *Engine) error {
 // item on the stack or when that item evaluates to false.  In the latter case
 // where the verification fails specifically due to the top item evaluating
 // to false, the returned error will use the passed error code.
-func abstractVerify(op *parsedOpcode, vm *Engine, c ErrorCode) error {
+func abstractVerify(op *opcode, vm *Engine, c ErrorCode) error {
 	verified, err := vm.dstack.PopBool()
 	if err != nil {
 		return err
 	}
 
 	if !verified {
-		str := fmt.Sprintf("%s failed", op.opcode.name)
+		str := fmt.Sprintf("%s failed", op.name)
 		return scriptError(c, str)
 	}
 	return nil
@@ -1161,13 +906,13 @@ func abstractVerify(op *parsedOpcode, vm *Engine, c ErrorCode) error {
 
 // opcodeVerify examines the top item on the data stack as a boolean value and
 // verifies it evaluates to true.  An error is returned if it does not.
-func opcodeVerify(op *parsedOpcode, vm *Engine) error {
+func opcodeVerify(op *opcode, data []byte, vm *Engine) error {
 	return abstractVerify(op, vm, ErrVerify)
 }
 
 // opcodeReturn returns an appropriate error since it is always an error to
 // return early from a script.
-func opcodeReturn(op *parsedOpcode, vm *Engine) error {
+func opcodeReturn(op *opcode, data []byte, vm *Engine) error {
 	return scriptError(ErrEarlyReturn, "script returned early")
 }
 
@@ -1197,7 +942,7 @@ func verifyLockTime(txLockTime, threshold, lockTime int64) error {
 // validating if the transaction outputs are spendable yet.  If flag
 // ScriptVerifyCheckLockTimeVerify is not set, the code continues as if OP_NOP2
 // were executed.
-func opcodeCheckLockTimeVerify(op *parsedOpcode, vm *Engine) error {
+func opcodeCheckLockTimeVerify(op *opcode, data []byte, vm *Engine) error {
 	// If the ScriptVerifyCheckLockTimeVerify script flag is not set, treat
 	// opcode as OP_NOP2 instead.
 	if !vm.hasFlag(ScriptVerifyCheckLockTimeVerify) {
@@ -1271,7 +1016,7 @@ func opcodeCheckLockTimeVerify(op *parsedOpcode, vm *Engine) error {
 // validating if the transaction outputs are spendable yet.  If flag
 // ScriptVerifyCheckSequenceVerify is not set, the code continues as if OP_NOP3
 // were executed.
-func opcodeCheckSequenceVerify(op *parsedOpcode, vm *Engine) error {
+func opcodeCheckSequenceVerify(op *opcode, data []byte, vm *Engine) error {
 	// If the ScriptVerifyCheckSequenceVerify script flag is not set, treat
 	// opcode as OP_NOP3 instead.
 	if !vm.hasFlag(ScriptVerifyCheckSequenceVerify) {
@@ -1348,7 +1093,7 @@ func opcodeCheckSequenceVerify(op *parsedOpcode, vm *Engine) error {
 //
 // Main data stack transformation: [... x1 x2 x3] -> [... x1 x2]
 // Alt data stack transformation:  [... y1 y2 y3] -> [... y1 y2 y3 x3]
-func opcodeToAltStack(op *parsedOpcode, vm *Engine) error {
+func opcodeToAltStack(op *opcode, data []byte, vm *Engine) error {
 	so, err := vm.dstack.PopByteArray()
 	if err != nil {
 		return err
@@ -1363,7 +1108,7 @@ func opcodeToAltStack(op *parsedOpcode, vm *Engine) error {
 //
 // Main data stack transformation: [... x1 x2 x3] -> [... x1 x2 x3 y3]
 // Alt data stack transformation:  [... y1 y2 y3] -> [... y1 y2]
-func opcodeFromAltStack(op *parsedOpcode, vm *Engine) error {
+func opcodeFromAltStack(op *opcode, data []byte, vm *Engine) error {
 	so, err := vm.astack.PopByteArray()
 	if err != nil {
 		return err
@@ -1376,35 +1121,35 @@ func opcodeFromAltStack(op *parsedOpcode, vm *Engine) error {
 // opcode2Drop removes the top 2 items from the data stack.
 //
 // Stack transformation: [... x1 x2 x3] -> [... x1]
-func opcode2Drop(op *parsedOpcode, vm *Engine) error {
+func opcode2Drop(op *opcode, data []byte, vm *Engine) error {
 	return vm.dstack.DropN(2)
 }
 
 // opcode2Dup duplicates the top 2 items on the data stack.
 //
 // Stack transformation: [... x1 x2 x3] -> [... x1 x2 x3 x2 x3]
-func opcode2Dup(op *parsedOpcode, vm *Engine) error {
+func opcode2Dup(op *opcode, data []byte, vm *Engine) error {
 	return vm.dstack.DupN(2)
 }
 
 // opcode3Dup duplicates the top 3 items on the data stack.
 //
 // Stack transformation: [... x1 x2 x3] -> [... x1 x2 x3 x1 x2 x3]
-func opcode3Dup(op *parsedOpcode, vm *Engine) error {
+func opcode3Dup(op *opcode, data []byte, vm *Engine) error {
 	return vm.dstack.DupN(3)
 }
 
 // opcode2Over duplicates the 2 items before the top 2 items on the data stack.
 //
 // Stack transformation: [... x1 x2 x3 x4] -> [... x1 x2 x3 x4 x1 x2]
-func opcode2Over(op *parsedOpcode, vm *Engine) error {
+func opcode2Over(op *opcode, data []byte, vm *Engine) error {
 	return vm.dstack.OverN(2)
 }
 
 // opcode2Rot rotates the top 6 items on the data stack to the left twice.
 //
 // Stack transformation: [... x1 x2 x3 x4 x5 x6] -> [... x3 x4 x5 x6 x1 x2]
-func opcode2Rot(op *parsedOpcode, vm *Engine) error {
+func opcode2Rot(op *opcode, data []byte, vm *Engine) error {
 	return vm.dstack.RotN(2)
 }
 
@@ -1412,7 +1157,7 @@ func opcode2Rot(op *parsedOpcode, vm *Engine) error {
 // before them.
 //
 // Stack transformation: [... x1 x2 x3 x4] -> [... x3 x4 x1 x2]
-func opcode2Swap(op *parsedOpcode, vm *Engine) error {
+func opcode2Swap(op *opcode, data []byte, vm *Engine) error {
 	return vm.dstack.SwapN(2)
 }
 
@@ -1420,7 +1165,7 @@ func opcode2Swap(op *parsedOpcode, vm *Engine) error {
 //
 // Stack transformation (x1==0): [... x1] -> [... x1]
 // Stack transformation (x1!=0): [... x1] -> [... x1 x1]
-func opcodeIfDup(op *parsedOpcode, vm *Engine) error {
+func opcodeIfDup(op *opcode, data []byte, vm *Engine) error {
 	so, err := vm.dstack.PeekByteArray(0)
 	if err != nil {
 		return err
@@ -1440,7 +1185,7 @@ func opcodeIfDup(op *parsedOpcode, vm *Engine) error {
 // Stack transformation: [...] -> [... <num of items on the stack>]
 // Example with 2 items: [x1 x2] -> [x1 x2 2]
 // Example with 3 items: [x1 x2 x3] -> [x1 x2 x3 3]
-func opcodeDepth(op *parsedOpcode, vm *Engine) error {
+func opcodeDepth(op *opcode, data []byte, vm *Engine) error {
 	vm.dstack.PushInt(scriptNum(vm.dstack.Depth()))
 	return nil
 }
@@ -1448,28 +1193,28 @@ func opcodeDepth(op *parsedOpcode, vm *Engine) error {
 // opcodeDrop removes the top item from the data stack.
 //
 // Stack transformation: [... x1 x2 x3] -> [... x1 x2]
-func opcodeDrop(op *parsedOpcode, vm *Engine) error {
+func opcodeDrop(op *opcode, data []byte, vm *Engine) error {
 	return vm.dstack.DropN(1)
 }
 
 // opcodeDup duplicates the top item on the data stack.
 //
 // Stack transformation: [... x1 x2 x3] -> [... x1 x2 x3 x3]
-func opcodeDup(op *parsedOpcode, vm *Engine) error {
+func opcodeDup(op *opcode, data []byte, vm *Engine) error {
 	return vm.dstack.DupN(1)
 }
 
 // opcodeNip removes the item before the top item on the data stack.
 //
 // Stack transformation: [... x1 x2 x3] -> [... x1 x3]
-func opcodeNip(op *parsedOpcode, vm *Engine) error {
+func opcodeNip(op *opcode, data []byte, vm *Engine) error {
 	return vm.dstack.NipN(1)
 }
 
 // opcodeOver duplicates the item before the top item on the data stack.
 //
 // Stack transformation: [... x1 x2 x3] -> [... x1 x2 x3 x2]
-func opcodeOver(op *parsedOpcode, vm *Engine) error {
+func opcodeOver(op *opcode, data []byte, vm *Engine) error {
 	return vm.dstack.OverN(1)
 }
 
@@ -1479,7 +1224,7 @@ func opcodeOver(op *parsedOpcode, vm *Engine) error {
 // Stack transformation: [xn ... x2 x1 x0 n] -> [xn ... x2 x1 x0 xn]
 // Example with n=1: [x2 x1 x0 1] -> [x2 x1 x0 x1]
 // Example with n=2: [x2 x1 x0 2] -> [x2 x1 x0 x2]
-func opcodePick(op *parsedOpcode, vm *Engine) error {
+func opcodePick(op *opcode, data []byte, vm *Engine) error {
 	val, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -1494,7 +1239,7 @@ func opcodePick(op *parsedOpcode, vm *Engine) error {
 // Stack transformation: [xn ... x2 x1 x0 n] -> [... x2 x1 x0 xn]
 // Example with n=1: [x2 x1 x0 1] -> [x2 x0 x1]
 // Example with n=2: [x2 x1 x0 2] -> [x1 x0 x2]
-func opcodeRoll(op *parsedOpcode, vm *Engine) error {
+func opcodeRoll(op *opcode, data []byte, vm *Engine) error {
 	val, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -1506,14 +1251,14 @@ func opcodeRoll(op *parsedOpcode, vm *Engine) error {
 // opcodeRot rotates the top 3 items on the data stack to the left.
 //
 // Stack transformation: [... x1 x2 x3] -> [... x2 x3 x1]
-func opcodeRot(op *parsedOpcode, vm *Engine) error {
+func opcodeRot(op *opcode, data []byte, vm *Engine) error {
 	return vm.dstack.RotN(1)
 }
 
 // opcodeSwap swaps the top two items on the stack.
 //
 // Stack transformation: [... x1 x2] -> [... x2 x1]
-func opcodeSwap(op *parsedOpcode, vm *Engine) error {
+func opcodeSwap(op *opcode, data []byte, vm *Engine) error {
 	return vm.dstack.SwapN(1)
 }
 
@@ -1521,7 +1266,7 @@ func opcodeSwap(op *parsedOpcode, vm *Engine) error {
 // second-to-top item.
 //
 // Stack transformation: [... x1 x2] -> [... x2 x1 x2]
-func opcodeTuck(op *parsedOpcode, vm *Engine) error {
+func opcodeTuck(op *opcode, data []byte, vm *Engine) error {
 	return vm.dstack.Tuck()
 }
 
@@ -1529,7 +1274,7 @@ func opcodeTuck(op *parsedOpcode, vm *Engine) error {
 // stack.
 //
 // Stack transformation: [... x1] -> [... x1 len(x1)]
-func opcodeSize(op *parsedOpcode, vm *Engine) error {
+func opcodeSize(op *opcode, data []byte, vm *Engine) error {
 	so, err := vm.dstack.PeekByteArray(0)
 	if err != nil {
 		return err
@@ -1543,7 +1288,7 @@ func opcodeSize(op *parsedOpcode, vm *Engine) error {
 // bytes, and pushes the result, encoded as a boolean, back to the stack.
 //
 // Stack transformation: [... x1 x2] -> [... bool]
-func opcodeEqual(op *parsedOpcode, vm *Engine) error {
+func opcodeEqual(op *opcode, data []byte, vm *Engine) error {
 	a, err := vm.dstack.PopByteArray()
 	if err != nil {
 		return err
@@ -1564,8 +1309,8 @@ func opcodeEqual(op *parsedOpcode, vm *Engine) error {
 // evaluates to true.  An error is returned if it does not.
 //
 // Stack transformation: [... x1 x2] -> [... bool] -> [...]
-func opcodeEqualVerify(op *parsedOpcode, vm *Engine) error {
+func opcodeEqualVerify(op *opcode, data []byte, vm *Engine) error {
-	err := opcodeEqual(op, vm)
+	err := opcodeEqual(op, data, vm)
 	if err == nil {
 		err = abstractVerify(op, vm, ErrEqualVerify)
 	}
@@ -1576,7 +1321,7 @@ func opcodeEqualVerify(op *parsedOpcode, vm *Engine) error {
 // it with its incremented value (plus 1).
 //
 // Stack transformation: [... x1 x2] -> [... x1 x2+1]
-func opcode1Add(op *parsedOpcode, vm *Engine) error {
+func opcode1Add(op *opcode, data []byte, vm *Engine) error {
 	m, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -1590,7 +1335,7 @@ func opcode1Add(op *parsedOpcode, vm *Engine) error {
 // it with its decremented value (minus 1).
 //
 // Stack transformation: [... x1 x2] -> [... x1 x2-1]
-func opcode1Sub(op *parsedOpcode, vm *Engine) error {
+func opcode1Sub(op *opcode, data []byte, vm *Engine) error {
 	m, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -1604,7 +1349,7 @@ func opcode1Sub(op *parsedOpcode, vm *Engine) error {
 // it with its negation.
 //
 // Stack transformation: [... x1 x2] -> [... x1 -x2]
-func opcodeNegate(op *parsedOpcode, vm *Engine) error {
+func opcodeNegate(op *opcode, data []byte, vm *Engine) error {
 	m, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -1618,7 +1363,7 @@ func opcodeNegate(op *parsedOpcode, vm *Engine) error {
 // it with its absolute value.
 //
 // Stack transformation: [... x1 x2] -> [... x1 abs(x2)]
-func opcodeAbs(op *parsedOpcode, vm *Engine) error {
+func opcodeAbs(op *opcode, data []byte, vm *Engine) error {
 	m, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -1643,7 +1388,7 @@ func opcodeAbs(op *parsedOpcode, vm *Engine) error {
 // Stack transformation (x2==0): [... x1 0] -> [... x1 1]
 // Stack transformation (x2!=0): [... x1 1] -> [... x1 0]
 // Stack transformation (x2!=0): [... x1 17] -> [... x1 0]
-func opcodeNot(op *parsedOpcode, vm *Engine) error {
+func opcodeNot(op *opcode, data []byte, vm *Engine) error {
 	m, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -1663,7 +1408,7 @@ func opcodeNot(op *parsedOpcode, vm *Engine) error {
 // Stack transformation (x2==0): [... x1 0] -> [... x1 0]
 // Stack transformation (x2!=0): [... x1 1] -> [... x1 1]
 // Stack transformation (x2!=0): [... x1 17] -> [... x1 1]
-func opcode0NotEqual(op *parsedOpcode, vm *Engine) error {
+func opcode0NotEqual(op *opcode, data []byte, vm *Engine) error {
 	m, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -1680,7 +1425,7 @@ func opcode0NotEqual(op *parsedOpcode, vm *Engine) error {
 // them with their sum.
 //
 // Stack transformation: [... x1 x2] -> [... x1+x2]
-func opcodeAdd(op *parsedOpcode, vm *Engine) error {
+func opcodeAdd(op *opcode, data []byte, vm *Engine) error {
 	v0, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -1700,7 +1445,7 @@ func opcodeAdd(op *parsedOpcode, vm *Engine) error {
 // entry.
 //
 // Stack transformation: [... x1 x2] -> [... x1-x2]
-func opcodeSub(op *parsedOpcode, vm *Engine) error {
+func opcodeSub(op *opcode, data []byte, vm *Engine) error {
 	v0, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -1722,7 +1467,7 @@ func opcodeSub(op *parsedOpcode, vm *Engine) error {
 // Stack transformation (x1!=0, x2==0): [... 5 0] -> [... 0]
 // Stack transformation (x1==0, x2!=0): [... 0 7] -> [... 0]
 // Stack transformation (x1!=0, x2!=0): [... 4 8] -> [... 1]
-func opcodeBoolAnd(op *parsedOpcode, vm *Engine) error {
+func opcodeBoolAnd(op *opcode, data []byte, vm *Engine) error {
 	v0, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -1749,7 +1494,7 @@ func opcodeBoolAnd(op *parsedOpcode, vm *Engine) error {
 // Stack transformation (x1!=0, x2==0): [... 5 0] -> [... 1]
 // Stack transformation (x1==0, x2!=0): [... 0 7] -> [... 1]
 // Stack transformation (x1!=0, x2!=0): [... 4 8] -> [... 1]
-func opcodeBoolOr(op *parsedOpcode, vm *Engine) error {
+func opcodeBoolOr(op *opcode, data []byte, vm *Engine) error {
 	v0, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -1774,7 +1519,7 @@ func opcodeBoolOr(op *parsedOpcode, vm *Engine) error {
 //
 // Stack transformation (x1==x2): [... 5 5] -> [... 1]
 // Stack transformation (x1!=x2): [... 5 7] -> [... 0]
-func opcodeNumEqual(op *parsedOpcode, vm *Engine) error {
+func opcodeNumEqual(op *opcode, data []byte, vm *Engine) error {
 	v0, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -1802,8 +1547,8 @@ func opcodeNumEqual(op *parsedOpcode, vm *Engine) error {
 // to true.  An error is returned if it does not.
 //
 // Stack transformation: [... x1 x2] -> [... bool] -> [...]
-func opcodeNumEqualVerify(op *parsedOpcode, vm *Engine) error {
+func opcodeNumEqualVerify(op *opcode, data []byte, vm *Engine) error {
-	err := opcodeNumEqual(op, vm)
+	err := opcodeNumEqual(op, data, vm)
 	if err == nil {
 		err = abstractVerify(op, vm, ErrNumEqualVerify)
 	}
@@ -1815,7 +1560,7 @@ func opcodeNumEqualVerify(op *parsedOpcode, vm *Engine) error {
 //
 // Stack transformation (x1==x2): [... 5 5] -> [... 0]
 // Stack transformation (x1!=x2): [... 5 7] -> [... 1]
-func opcodeNumNotEqual(op *parsedOpcode, vm *Engine) error {
+func opcodeNumNotEqual(op *opcode, data []byte, vm *Engine) error {
 	v0, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -1840,7 +1585,7 @@ func opcodeNumNotEqual(op *parsedOpcode, vm *Engine) error {
 // otherwise a 0.
 //
 // Stack transformation: [... x1 x2] -> [... bool]
-func opcodeLessThan(op *parsedOpcode, vm *Engine) error {
+func opcodeLessThan(op *opcode, data []byte, vm *Engine) error {
 	v0, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -1865,7 +1610,7 @@ func opcodeLessThan(op *parsedOpcode, vm *Engine) error {
 // with a 1, otherwise a 0.
 //
 // Stack transformation: [... x1 x2] -> [... bool]
-func opcodeGreaterThan(op *parsedOpcode, vm *Engine) error {
+func opcodeGreaterThan(op *opcode, data []byte, vm *Engine) error {
 	v0, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -1889,7 +1634,7 @@ func opcodeGreaterThan(op *parsedOpcode, vm *Engine) error {
 // replaced with a 1, otherwise a 0.
 //
 // Stack transformation: [... x1 x2] -> [... bool]
-func opcodeLessThanOrEqual(op *parsedOpcode, vm *Engine) error {
+func opcodeLessThanOrEqual(op *opcode, data []byte, vm *Engine) error {
 	v0, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -1913,7 +1658,7 @@ func opcodeLessThanOrEqual(op *parsedOpcode, vm *Engine) error {
 // item, they are replaced with a 1, otherwise a 0.
 //
 // Stack transformation: [... x1 x2] -> [... bool]
-func opcodeGreaterThanOrEqual(op *parsedOpcode, vm *Engine) error {
+func opcodeGreaterThanOrEqual(op *opcode, data []byte, vm *Engine) error {
 	v0, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -1937,7 +1682,7 @@ func opcodeGreaterThanOrEqual(op *parsedOpcode, vm *Engine) error {
 // them with the minimum of the two.
 //
 // Stack transformation: [... x1 x2] -> [... min(x1, x2)]
-func opcodeMin(op *parsedOpcode, vm *Engine) error {
+func opcodeMin(op *opcode, data []byte, vm *Engine) error {
 	v0, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -1961,7 +1706,7 @@ func opcodeMin(op *parsedOpcode, vm *Engine) error {
 // them with the maximum of the two.
 //
 // Stack transformation: [... x1 x2] -> [... max(x1, x2)]
-func opcodeMax(op *parsedOpcode, vm *Engine) error {
+func opcodeMax(op *opcode, data []byte, vm *Engine) error {
 	v0, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -1989,7 +1734,7 @@ func opcodeMax(op *parsedOpcode, vm *Engine) error {
 // the third-to-top item is the value to test.
 //
 // Stack transformation: [... x1 min max] -> [... bool]
-func opcodeWithin(op *parsedOpcode, vm *Engine) error {
+func opcodeWithin(op *opcode, data []byte, vm *Engine) error {
 	maxVal, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -2023,7 +1768,7 @@ func calcHash(buf []byte, hasher hash.Hash) []byte {
 // replaces it with ripemd160(data).
 //
 // Stack transformation: [... x1] -> [... ripemd160(x1)]
-func opcodeRipemd160(op *parsedOpcode, vm *Engine) error {
+func opcodeRipemd160(op *opcode, data []byte, vm *Engine) error {
 	buf, err := vm.dstack.PopByteArray()
 	if err != nil {
 		return err
@@ -2037,7 +1782,7 @@ func opcodeRipemd160(op *parsedOpcode, vm *Engine) error {
 // with sha1(data).
 //
 // Stack transformation: [... x1] -> [... sha1(x1)]
-func opcodeSha1(op *parsedOpcode, vm *Engine) error {
+func opcodeSha1(op *opcode, data []byte, vm *Engine) error {
 	buf, err := vm.dstack.PopByteArray()
 	if err != nil {
 		return err
@@ -2052,7 +1797,7 @@ func opcodeSha1(op *parsedOpcode, vm *Engine) error {
 // it with sha256(data).
 //
 // Stack transformation: [... x1] -> [... sha256(x1)]
-func opcodeSha256(op *parsedOpcode, vm *Engine) error {
+func opcodeSha256(op *opcode, data []byte, vm *Engine) error {
 	buf, err := vm.dstack.PopByteArray()
 	if err != nil {
 		return err
@@ -2067,7 +1812,7 @@ func opcodeSha256(op *parsedOpcode, vm *Engine) error {
 // it with ripemd160(sha256(data)).
 //
 // Stack transformation: [... x1] -> [... ripemd160(sha256(x1))]
-func opcodeHash160(op *parsedOpcode, vm *Engine) error {
+func opcodeHash160(op *opcode, data []byte, vm *Engine) error {
 	buf, err := vm.dstack.PopByteArray()
 	if err != nil {
 		return err
@@ -2082,7 +1827,7 @@ func opcodeHash160(op *parsedOpcode, vm *Engine) error {
 // it with sha256(sha256(data)).
 //
 // Stack transformation: [... x1] -> [... sha256(sha256(x1))]
-func opcodeHash256(op *parsedOpcode, vm *Engine) error {
+func opcodeHash256(op *opcode, data []byte, vm *Engine) error {
 	buf, err := vm.dstack.PopByteArray()
 	if err != nil {
 		return err
@@ -2096,8 +1841,8 @@ func opcodeHash256(op *parsedOpcode, vm *Engine) error {
 // seen OP_CODESEPARATOR which is used during signature checking.
 //
 // This opcode does not change the contents of the data stack.
-func opcodeCodeSeparator(op *parsedOpcode, vm *Engine) error {
+func opcodeCodeSeparator(op *opcode, data []byte, vm *Engine) error {
-	vm.lastCodeSep = vm.scriptOff
+	vm.lastCodeSep = int(vm.tokenizer.ByteIndex())
 	return nil
 }
 
@@ -2115,7 +1860,7 @@ func opcodeCodeSeparator(op *parsedOpcode, vm *Engine) error {
 // cryptographic methods against the provided public key.
 //
 // Stack transformation: [... signature pubkey] -> [... bool]
-func opcodeCheckSig(op *parsedOpcode, vm *Engine) error {
+func opcodeCheckSig(op *opcode, data []byte, vm *Engine) error {
 	pkBytes, err := vm.dstack.PopByteArray()
 	if err != nil {
 		return err
@@ -2171,7 +1916,7 @@ func opcodeCheckSig(op *parsedOpcode, vm *Engine) error {
 			sigHashes = NewTxSigHashes(&vm.tx)
 		}
 
-		hash, err = calcWitnessSignatureHash(subScript, sigHashes, hashType,
+		hash, err = calcWitnessSignatureHashRaw(subScript, sigHashes, hashType,
 			&vm.tx, vm.txIdx, vm.inputAmount)
 		if err != nil {
 			return err
@@ -2230,9 +1975,9 @@ func opcodeCheckSig(op *parsedOpcode, vm *Engine) error {
 // The opcodeCheckSig function is invoked followed by opcodeVerify.  See the
 // documentation for each of those opcodes for more details.
 //
-// Stack transformation: signature pubkey] -> [... bool] -> [...]
+// Stack transformation: [... signature pubkey] -> [... bool] -> [...]
-func opcodeCheckSigVerify(op *parsedOpcode, vm *Engine) error {
+func opcodeCheckSigVerify(op *opcode, data []byte, vm *Engine) error {
-	err := opcodeCheckSig(op, vm)
+	err := opcodeCheckSig(op, data, vm)
 	if err == nil {
 		err = abstractVerify(op, vm, ErrCheckSigVerify)
 	}
@@ -2267,7 +2012,7 @@ type parsedSigInfo struct {
 //
 // Stack transformation:
 // [... dummy [sig ...] numsigs [pubkey ...] numpubkeys] -> [... bool]
-func opcodeCheckMultiSig(op *parsedOpcode, vm *Engine) error {
+func opcodeCheckMultiSig(op *opcode, data []byte, vm *Engine) error {
 	numKeys, err := vm.dstack.PopInt()
 	if err != nil {
 		return err
@@ -2444,7 +2189,7 @@ func opcodeCheckMultiSig(op *parsedOpcode, vm *Engine) error {
 				sigHashes = NewTxSigHashes(&vm.tx)
 			}
 
-			hash, err = calcWitnessSignatureHash(script, sigHashes, hashType,
+			hash, err = calcWitnessSignatureHashRaw(script, sigHashes, hashType,
 				&vm.tx, vm.txIdx, vm.inputAmount)
 			if err != nil {
 				return err
@@ -2493,8 +2238,8 @@ func opcodeCheckMultiSig(op *parsedOpcode, vm *Engine) error {
 //
 // Stack transformation:
 // [... dummy [sig ...] numsigs [pubkey ...] numpubkeys] -> [... bool] -> [...]
-func opcodeCheckMultiSigVerify(op *parsedOpcode, vm *Engine) error {
+func opcodeCheckMultiSigVerify(op *opcode, data []byte, vm *Engine) error {
-	err := opcodeCheckMultiSig(op, vm)
+	err := opcodeCheckMultiSig(op, data, vm)
 	if err == nil {
 		err = abstractVerify(op, vm, ErrCheckMultiSigVerify)
 	}

txscript/opcode_test.go

@@ -23,8 +23,8 @@ func TestOpcodeDisabled(t *testing.T) {
 		OP_LSHIFT, OP_RSHIFT,
 	}
 	for _, opcodeVal := range tests {
-		pop := parsedOpcode{opcode: &opcodeArray[opcodeVal], data: nil}
+		op := &opcodeArray[opcodeVal]
-		err := opcodeDisabled(&pop, nil)
+		err := opcodeDisabled(op, nil, nil)
 		if !IsErrorCode(err, ErrDisabledOpcode) {
 			t.Errorf("opcodeDisabled: unexpected error - got %v, "+
 				"want %v", err, ErrDisabledOpcode)
@@ -127,8 +127,9 @@ func TestOpcodeDisasm(t *testing.T) {
 			expectedStr = "OP_UNKNOWN" + strconv.Itoa(opcodeVal)
 		}
 
-		pop := parsedOpcode{opcode: &opcodeArray[opcodeVal], data: data}
+		var buf strings.Builder
-		gotStr := pop.print(true)
+		disasmOpcode(&buf, &opcodeArray[opcodeVal], data, true)
+		gotStr := buf.String()
 		if gotStr != expectedStr {
 			t.Errorf("pop.print (opcode %x): Unexpected disasm "+
 				"string - got %v, want %v", opcodeVal, gotStr,
@@ -193,8 +194,9 @@ func TestOpcodeDisasm(t *testing.T) {
 			expectedStr = "OP_UNKNOWN" + strconv.Itoa(opcodeVal)
 		}
 
-		pop := parsedOpcode{opcode: &opcodeArray[opcodeVal], data: data}
+		var buf strings.Builder
-		gotStr := pop.print(false)
+		disasmOpcode(&buf, &opcodeArray[opcodeVal], data, false)
+		gotStr := buf.String()
 		if gotStr != expectedStr {
 			t.Errorf("pop.print (opcode %x): Unexpected disasm "+
 				"string - got %v, want %v", opcodeVal, gotStr,

txscript/pkscript.go

@@ -211,11 +211,12 @@ func computeNonWitnessPkScript(sigScript []byte) (PkScript, error) {
 		// The redeem script will always be the last data push of the
 		// signature script, so we'll parse the script into opcodes to
 		// obtain it.
-		parsedOpcodes, err := parseScript(sigScript)
+		const scriptVersion = 0
+		err := checkScriptParses(scriptVersion, sigScript)
 		if err != nil {
 			return PkScript{}, err
 		}
-		redeemScript := parsedOpcodes[len(parsedOpcodes)-1].data
+		redeemScript := finalOpcodeData(scriptVersion, sigScript)
 
 		scriptHash := hash160(redeemScript)
 		script, err := payToScriptHashScript(scriptHash)

txscript/reference_test.go

@@ -836,6 +836,7 @@ func TestCalcSignatureHash(t *testing.T) {
 			err)
 	}
 
+	const scriptVersion = 0
 	for i, test := range tests {
 		if i == 0 {
 			// Skip first line -- contains comments only.
@@ -855,16 +856,20 @@ func TestCalcSignatureHash(t *testing.T) {
 		}
 
 		subScript, _ := hex.DecodeString(test[1].(string))
-		parsedScript, err := parseScript(subScript)
+		if err := checkScriptParses(scriptVersion, subScript); err != nil {
-		if err != nil {
 			t.Errorf("TestCalcSignatureHash failed test #%d: "+
 				"Failed to parse sub-script: %v", i, err)
 			continue
 		}
 
 		hashType := SigHashType(testVecF64ToUint32(test[3].(float64)))
-		hash := calcSignatureHash(parsedScript, hashType, &tx,
+		hash, err := CalcSignatureHash(subScript, hashType, &tx,
 			int(test[2].(float64)))
+		if err != nil {
+			t.Errorf("TestCalcSignatureHash failed test #%d: "+
+				"Failed to compute sighash: %v", i, err)
+			continue
+		}
 
 		expectedHash, _ := chainhash.NewHashFromStr(test[4].(string))
 		if !bytes.Equal(hash, expectedHash[:]) {

txscript/script.go

@@ -1,4 +1,5 @@
 // Copyright (c) 2013-2017 The btcsuite developers
+// Copyright (c) 2015-2019 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
@@ -8,6 +9,7 @@ import (
 	"bytes"
 	"encoding/binary"
 	"fmt"
+	"strings"
 	"time"
 
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
@@ -44,66 +46,48 @@ const (
 
 // isSmallInt returns whether or not the opcode is considered a small integer,
 // which is an OP_0, or OP_1 through OP_16.
-func isSmallInt(op *opcode) bool {
+//
-	if op.value == OP_0 || (op.value >= OP_1 && op.value <= OP_16) {
+// NOTE: This function is only valid for version 0 opcodes.  Since the function
-		return true
+// does not accept a script version, the results are undefined for other script
-	}
+// versions.
-	return false
+func isSmallInt(op byte) bool {
+	return op == OP_0 || (op >= OP_1 && op <= OP_16)
 }
 
-// isScriptHash returns true if the script passed is a pay-to-script-hash
+// IsPayToPubKey returns true if the script is in the standard pay-to-pubkey
-// transaction, false otherwise.
+// (P2PK) format, false otherwise.
-func isScriptHash(pops []parsedOpcode) bool {
+func IsPayToPubKey(script []byte) bool {
-	return len(pops) == 3 &&
+	return isPubKeyScript(script)
-		pops[0].opcode.value == OP_HASH160 &&
+}
-		pops[1].opcode.value == OP_DATA_20 &&
+
-		pops[2].opcode.value == OP_EQUAL
+// IsPayToPubKeyHash returns true if the script is in the standard
+// pay-to-pubkey-hash (P2PKH) format, false otherwise.
+func IsPayToPubKeyHash(script []byte) bool {
+	return isPubKeyHashScript(script)
 }
 
 // IsPayToScriptHash returns true if the script is in the standard
 // pay-to-script-hash (P2SH) format, false otherwise.
+//
+// WARNING: This function always treats the passed script as version 0.  Great
+// care must be taken if introducing a new script version because it is used in
+// consensus which, unfortunately as of the time of this writing, does not check
+// script versions before determining if the script is a P2SH which means nodes
+// on existing rules will analyze new version scripts as if they were version 0.
 func IsPayToScriptHash(script []byte) bool {
-	pops, err := parseScript(script)
+	return isScriptHashScript(script)
-	if err != nil {
-		return false
-	}
-	return isScriptHash(pops)
-}
-
-// isWitnessScriptHash returns true if the passed script is a
-// pay-to-witness-script-hash transaction, false otherwise.
-func isWitnessScriptHash(pops []parsedOpcode) bool {
-	return len(pops) == 2 &&
-		pops[0].opcode.value == OP_0 &&
-		pops[1].opcode.value == OP_DATA_32
 }
 
 // IsPayToWitnessScriptHash returns true if the is in the standard
 // pay-to-witness-script-hash (P2WSH) format, false otherwise.
 func IsPayToWitnessScriptHash(script []byte) bool {
-	pops, err := parseScript(script)
+	return isWitnessScriptHashScript(script)
-	if err != nil {
-		return false
-	}
-	return isWitnessScriptHash(pops)
 }
 
 // IsPayToWitnessPubKeyHash returns true if the is in the standard
 // pay-to-witness-pubkey-hash (P2WKH) format, false otherwise.
 func IsPayToWitnessPubKeyHash(script []byte) bool {
-	pops, err := parseScript(script)
+	return isWitnessPubKeyHashScript(script)
-	if err != nil {
-		return false
-	}
-	return isWitnessPubKeyHash(pops)
-}
-
-// isWitnessPubKeyHash returns true if the passed script is a
-// pay-to-witness-pubkey-hash, and false otherwise.
-func isWitnessPubKeyHash(pops []parsedOpcode) bool {
-	return len(pops) == 2 &&
-		pops[0].opcode.value == OP_0 &&
-		pops[1].opcode.value == OP_DATA_20
 }
 
 // IsWitnessProgram returns true if the passed script is a valid witness
@@ -111,163 +95,52 @@ func isWitnessPubKeyHash(pops []parsedOpcode) bool {
 // witness program must be a small integer (from 0-16), followed by 2-40 bytes
 // of pushed data.
 func IsWitnessProgram(script []byte) bool {
-	// The length of the script must be between 4 and 42 bytes. The
+	return isWitnessProgramScript(script)
-	// smallest program is the witness version, followed by a data push of
-	// 2 bytes.  The largest allowed witness program has a data push of
-	// 40-bytes.
-	if len(script) < 4 || len(script) > 42 {
-		return false
 }
 
-	pops, err := parseScript(script)
+// IsNullData returns true if the passed script is a null data script, false
-	if err != nil {
+// otherwise.
-		return false
+func IsNullData(script []byte) bool {
-	}
+	const scriptVersion = 0
-
+	return isNullDataScript(scriptVersion, script)
-	return isWitnessProgram(pops)
-}
-
-// isWitnessProgram returns true if the passed script is a witness program, and
-// false otherwise. A witness program MUST adhere to the following constraints:
-// there must be exactly two pops (program version and the program itself), the
-// first opcode MUST be a small integer (0-16), the push data MUST be
-// canonical, and finally the size of the push data must be between 2 and 40
-// bytes.
-func isWitnessProgram(pops []parsedOpcode) bool {
-	return len(pops) == 2 &&
-		isSmallInt(pops[0].opcode) &&
-		canonicalPush(pops[1]) &&
-		(len(pops[1].data) >= 2 && len(pops[1].data) <= 40)
 }
 
 // ExtractWitnessProgramInfo attempts to extract the witness program version,
 // as well as the witness program itself from the passed script.
 func ExtractWitnessProgramInfo(script []byte) (int, []byte, error) {
-	pops, err := parseScript(script)
-	if err != nil {
-		return 0, nil, err
-	}
-
 	// If at this point, the scripts doesn't resemble a witness program,
 	// then we'll exit early as there isn't a valid version or program to
 	// extract.
-	if !isWitnessProgram(pops) {
+	version, program, valid := extractWitnessProgramInfo(script)
+	if !valid {
 		return 0, nil, fmt.Errorf("script is not a witness program, " +
 			"unable to extract version or witness program")
 	}
 
-	witnessVersion := asSmallInt(pops[0].opcode)
+	return version, program, nil
-	witnessProgram := pops[1].data
-
-	return witnessVersion, witnessProgram, nil
 }
 
-// isPushOnly returns true if the script only pushes data, false otherwise.
+// IsPushOnlyScript returns whether or not the passed script only pushes data
-func isPushOnly(pops []parsedOpcode) bool {
+// according to the consensus definition of pushing data.
-	// NOTE: This function does NOT verify opcodes directly since it is
-	// internal and is only called with parsed opcodes for scripts that did
-	// not have any parse errors.  Thus, consensus is properly maintained.
-
-	for _, pop := range pops {
-		// All opcodes up to OP_16 are data push instructions.
-		// NOTE: This does consider OP_RESERVED to be a data push
-		// instruction, but execution of OP_RESERVED will fail anyways
-		// and matches the behavior required by consensus.
-		if pop.opcode.value > OP_16 {
-			return false
-		}
-	}
-	return true
-}
-
-// IsPushOnlyScript returns whether or not the passed script only pushes data.
 //
-// False will be returned when the script does not parse.
+// WARNING: This function always treats the passed script as version 0.  Great
+// care must be taken if introducing a new script version because it is used in
+// consensus which, unfortunately as of the time of this writing, does not check
+// script versions before checking if it is a push only script which means nodes
+// on existing rules will treat new version scripts as if they were version 0.
 func IsPushOnlyScript(script []byte) bool {
-	pops, err := parseScript(script)
+	const scriptVersion = 0
-	if err != nil {
+	tokenizer := MakeScriptTokenizer(scriptVersion, script)
+	for tokenizer.Next() {
+		// All opcodes up to OP_16 are data push instructions.
+		// NOTE: This does consider OP_RESERVED to be a data push instruction,
+		// but execution of OP_RESERVED will fail anyway and matches the
+		// behavior required by consensus.
+		if tokenizer.Opcode() > OP_16 {
 			return false
 		}
-	return isPushOnly(pops)
 	}
-
+	return tokenizer.Err() == nil
-// parseScriptTemplate is the same as parseScript but allows the passing of the
-// template list for testing purposes.  When there are parse errors, it returns
-// the list of parsed opcodes up to the point of failure along with the error.
-func parseScriptTemplate(script []byte, opcodes *[256]opcode) ([]parsedOpcode, error) {
-	retScript := make([]parsedOpcode, 0, len(script))
-	var err error
-	for i := 0; i < len(script); {
-		instr := script[i]
-		op := &opcodes[instr]
-		pop := parsedOpcode{opcode: op}
-		i, err = pop.checkParseableInScript(script, i)
-		if err != nil {
-			return retScript, err
-		}
-
-		retScript = append(retScript, pop)
-	}
-
-	return retScript, nil
-}
-
-// checkScriptTemplateParseable is the same as parseScriptTemplate but does not
-// return the list of opcodes up until the point of failure so that this can be
-// used in functions which do not necessarily have a need for the failed list of
-// opcodes, such as IsUnspendable.
-//
-// This function returns a pointer to a byte. This byte is nil if the parsing
-// has an error, or if the script length is zero. If the script length is not
-// zero and parsing succeeds, then the first opcode parsed will be returned.
-//
-// Not returning the full opcode list up until failure also has the benefit of
-// reducing GC pressure, as the list would get immediately thrown away.
-func checkScriptTemplateParseable(script []byte, opcodes *[256]opcode) (*byte, error) {
-	var err error
-
-	// A script of length zero is an unspendable script but it is parseable.
-	var firstOpcode byte
-	var numParsedInstr uint = 0
-
-	for i := 0; i < len(script); {
-		instr := script[i]
-		op := &opcodes[instr]
-		pop := parsedOpcode{opcode: op}
-		i, err = pop.checkParseableInScript(script, i)
-		if err != nil {
-			return nil, err
-		}
-
-		// if this is a op_return then it is unspendable so we set the first
-		// parsed instruction in case it's an op_return
-		if numParsedInstr == 0 {
-			firstOpcode = pop.opcode.value
-		}
-		numParsedInstr++
-	}
-
-	return &firstOpcode, nil
-}
-
-// parseScript preparses the script in bytes into a list of parsedOpcodes while
-// applying a number of sanity checks.
-func parseScript(script []byte) ([]parsedOpcode, error) {
-	return parseScriptTemplate(script, &opcodeArray)
-}
-
-// unparseScript reversed the action of parseScript and returns the
-// parsedOpcodes as a list of bytes
-func unparseScript(pops []parsedOpcode) ([]byte, error) {
-	script := make([]byte, 0, len(pops))
-	for _, pop := range pops {
-		b, err := pop.bytes()
-		if err != nil {
-			return nil, err
-		}
-		script = append(script, b...)
-	}
-	return script, nil
 }
 
 // DisasmString formats a disassembled script for one line printing.  When the
@@ -275,41 +148,78 @@ func unparseScript(pops []parsedOpcode) ([]byte, error) {
 // script up to the point the failure occurred along with the string '[error]'
 // appended.  In addition, the reason the script failed to parse is returned
 // if the caller wants more information about the failure.
-func DisasmString(buf []byte) (string, error) {
+//
-	var disbuf bytes.Buffer
+// NOTE: This function is only valid for version 0 scripts.  Since the function
-	opcodes, err := parseScript(buf)
+// does not accept a script version, the results are undefined for other script
-	for _, pop := range opcodes {
+// versions.
-		disbuf.WriteString(pop.print(true))
+func DisasmString(script []byte) (string, error) {
+	const scriptVersion = 0
+
+	var disbuf strings.Builder
+	tokenizer := MakeScriptTokenizer(scriptVersion, script)
+	if tokenizer.Next() {
+		disasmOpcode(&disbuf, tokenizer.op, tokenizer.Data(), true)
+	}
+	for tokenizer.Next() {
+		disbuf.WriteByte(' ')
+		disasmOpcode(&disbuf, tokenizer.op, tokenizer.Data(), true)
+	}
+	if tokenizer.Err() != nil {
+		if tokenizer.ByteIndex() != 0 {
 			disbuf.WriteByte(' ')
 		}
-	if disbuf.Len() > 0 {
-		disbuf.Truncate(disbuf.Len() - 1)
-	}
-	if err != nil {
 		disbuf.WriteString("[error]")
 	}
-	return disbuf.String(), err
+	return disbuf.String(), tokenizer.Err()
 }
 
-// removeOpcode will remove any opcode matching ``opcode'' from the opcode
+// removeOpcodeRaw will return the script after removing any opcodes that match
-// stream in pkscript
+// `opcode`. If the opcode does not appear in script, the original script will
-func removeOpcode(pkscript []parsedOpcode, opcode byte) []parsedOpcode {
+// be returned unmodified. Otherwise, a new script will be allocated to contain
-	retScript := make([]parsedOpcode, 0, len(pkscript))
+// the filtered script. This metehod assumes that the script parses
-	for _, pop := range pkscript {
+// successfully.
-		if pop.opcode.value != opcode {
+//
-			retScript = append(retScript, pop)
+// NOTE: This function is only valid for version 0 scripts.  Since the function
-		}
+// does not accept a script version, the results are undefined for other script
-	}
+// versions.
-	return retScript
+func removeOpcodeRaw(script []byte, opcode byte) []byte {
+	// Avoid work when possible.
+	if len(script) == 0 {
+		return script
 	}
 
-// canonicalPush returns true if the object is either not a push instruction
+	const scriptVersion = 0
-// or the push instruction contained wherein is matches the canonical form
+	var result []byte
-// or using the smallest instruction to do the job. False otherwise.
+	var prevOffset int32
-func canonicalPush(pop parsedOpcode) bool {
+
-	opcode := pop.opcode.value
+	tokenizer := MakeScriptTokenizer(scriptVersion, script)
-	data := pop.data
+	for tokenizer.Next() {
-	dataLen := len(pop.data)
+		if tokenizer.Opcode() == opcode {
+			if result == nil {
+				result = make([]byte, 0, len(script))
+				result = append(result, script[:prevOffset]...)
+			}
+		} else if result != nil {
+			result = append(result, script[prevOffset:tokenizer.ByteIndex()]...)
+		}
+		prevOffset = tokenizer.ByteIndex()
+	}
+	if result == nil {
+		return script
+	}
+	return result
+}
+
+// isCanonicalPush returns true if the opcode is either not a push instruction
+// or the data associated with the push instruction uses the smallest
+// instruction to do the job.  False otherwise.
+//
+// For example, it is possible to push a value of 1 to the stack as "OP_1",
+// "OP_DATA_1 0x01", "OP_PUSHDATA1 0x01 0x01", and others, however, the first
+// only takes a single byte, while the rest take more.  Only the first is
+// considered canonical.
+func isCanonicalPush(opcode byte, data []byte) bool {
+	dataLen := len(data)
 	if opcode > OP_16 {
 		return true
 	}
@@ -329,17 +239,57 @@ func canonicalPush(pop parsedOpcode) bool {
 	return true
 }
 
-// removeOpcodeByData will return the script minus any opcodes that would push
+// removeOpcodeByData will return the script minus any opcodes that perform a
-// the passed data to the stack.
+// canonical push of data that contains the passed data to remove.  This
-func removeOpcodeByData(pkscript []parsedOpcode, data []byte) []parsedOpcode {
+// function assumes it is provided a version 0 script as any future version of
-	retScript := make([]parsedOpcode, 0, len(pkscript))
+// script should avoid this functionality since it is unncessary due to the
-	for _, pop := range pkscript {
+// signature scripts not being part of the witness-free transaction hash.
-		if !canonicalPush(pop) || !bytes.Contains(pop.data, data) {
+//
-			retScript = append(retScript, pop)
+// WARNING: This will return the passed script unmodified unless a modification
+// is necessary in which case the modified script is returned.  This implies
+// callers may NOT rely on being able to safely mutate either the passed or
+// returned script without potentially modifying the same data.
+//
+// NOTE: This function is only valid for version 0 scripts.  Since the function
+// does not accept a script version, the results are undefined for other script
+// versions.
+func removeOpcodeByData(script []byte, dataToRemove []byte) []byte {
+	// Avoid work when possible.
+	if len(script) == 0 || len(dataToRemove) == 0 {
+		return script
 	}
-	}
-	return retScript
 
+	// Parse through the script looking for a canonical data push that contains
+	// the data to remove.
+	const scriptVersion = 0
+	var result []byte
+	var prevOffset int32
+	tokenizer := MakeScriptTokenizer(scriptVersion, script)
+	for tokenizer.Next() {
+		// In practice, the script will basically never actually contain the
+		// data since this function is only used during signature verification
+		// to remove the signature itself which would require some incredibly
+		// non-standard code to create.
+		//
+		// Thus, as an optimization, avoid allocating a new script unless there
+		// is actually a match that needs to be removed.
+		op, data := tokenizer.Opcode(), tokenizer.Data()
+		if isCanonicalPush(op, data) && bytes.Contains(data, dataToRemove) {
+			if result == nil {
+				fullPushLen := tokenizer.ByteIndex() - prevOffset
+				result = make([]byte, 0, int32(len(script))-fullPushLen)
+				result = append(result, script[0:prevOffset]...)
+			}
+		} else if result != nil {
+			result = append(result, script[prevOffset:tokenizer.ByteIndex()]...)
+		}
+
+		prevOffset = tokenizer.ByteIndex()
+	}
+	if result == nil {
+		result = script
+	}
+	return result
 }
 
 // calcHashPrevOuts calculates a single hash of all the previous outputs
@@ -396,7 +346,7 @@ func calcHashOutputs(tx *wire.MsgTx) chainhash.Hash {
 	return chainhash.DoubleHashH(b.Bytes())
 }
 
-// calcWitnessSignatureHash computes the sighash digest of a transaction's
+// calcWitnessSignatureHashRaw computes the sighash digest of a transaction's
 // segwit input using the new, optimized digest calculation algorithm defined
 // in BIP0143: https://github.com/bitcoin/bips/blob/master/bip-0143.mediawiki.
 // This function makes use of pre-calculated sighash fragments stored within
@@ -407,7 +357,7 @@ func calcHashOutputs(tx *wire.MsgTx) chainhash.Hash {
 // being spent, in addition to the final transaction fee. In the case the
 // wallet if fed an invalid input amount, the real sighash will differ causing
 // the produced signature to be invalid.
-func calcWitnessSignatureHash(subScript []parsedOpcode, sigHashes *TxSigHashes,
+func calcWitnessSignatureHashRaw(scriptSig []byte, sigHashes *TxSigHashes,
 	hashType SigHashType, tx *wire.MsgTx, idx int, amt int64) ([]byte, error) {
 
 	// As a sanity check, ensure the passed input index for the transaction
@@ -457,7 +407,7 @@ func calcWitnessSignatureHash(subScript []parsedOpcode, sigHashes *TxSigHashes,
 	binary.LittleEndian.PutUint32(bIndex[:], txIn.PreviousOutPoint.Index)
 	sigHash.Write(bIndex[:])
 
-	if isWitnessPubKeyHash(subScript) {
+	if isWitnessPubKeyHashScript(scriptSig) {
 		// The script code for a p2wkh is a length prefix varint for
 		// the next 25 bytes, followed by a re-creation of the original
 		// p2pkh pk script.
@@ -465,15 +415,14 @@ func calcWitnessSignatureHash(subScript []parsedOpcode, sigHashes *TxSigHashes,
 		sigHash.Write([]byte{OP_DUP})
 		sigHash.Write([]byte{OP_HASH160})
 		sigHash.Write([]byte{OP_DATA_20})
-		sigHash.Write(subScript[1].data)
+		sigHash.Write(extractWitnessPubKeyHash(scriptSig))
 		sigHash.Write([]byte{OP_EQUALVERIFY})
 		sigHash.Write([]byte{OP_CHECKSIG})
 	} else {
 		// For p2wsh outputs, and future outputs, the script code is
 		// the original script, with all code separators removed,
 		// serialized with a var int length prefix.
-		rawScript, _ := unparseScript(subScript)
+		wire.WriteVarBytes(&sigHash, 0, scriptSig)
-		wire.WriteVarBytes(&sigHash, 0, rawScript)
 	}
 
 	// Next, add the input amount, and sequence number of the input being
@@ -517,13 +466,12 @@ func calcWitnessSignatureHash(subScript []parsedOpcode, sigHashes *TxSigHashes,
 func CalcWitnessSigHash(script []byte, sigHashes *TxSigHashes, hType SigHashType,
 	tx *wire.MsgTx, idx int, amt int64) ([]byte, error) {
 
-	parsedScript, err := parseScript(script)
+	const scriptVersion = 0
-	if err != nil {
+	if err := checkScriptParses(scriptVersion, script); err != nil {
-		return nil, fmt.Errorf("cannot parse output script: %v", err)
+		return nil, err
 	}
 
-	return calcWitnessSignatureHash(parsedScript, sigHashes, hType, tx, idx,
+	return calcWitnessSignatureHashRaw(script, sigHashes, hType, tx, idx, amt)
-		amt)
 }
 
 // shallowCopyTx creates a shallow copy of the transaction for use when
@@ -557,18 +505,22 @@ func shallowCopyTx(tx *wire.MsgTx) wire.MsgTx {
 // CalcSignatureHash will, given a script and hash type for the current script
 // engine instance, calculate the signature hash to be used for signing and
 // verification.
+//
+// NOTE: This function is only valid for version 0 scripts. Since the function
+// does not accept a script version, the results are undefined for other script
+// versions.
 func CalcSignatureHash(script []byte, hashType SigHashType, tx *wire.MsgTx, idx int) ([]byte, error) {
-	parsedScript, err := parseScript(script)
+	const scriptVersion = 0
-	if err != nil {
+	if err := checkScriptParses(scriptVersion, script); err != nil {
-		return nil, fmt.Errorf("cannot parse output script: %v", err)
+		return nil, err
-	}
-	return calcSignatureHash(parsedScript, hashType, tx, idx), nil
 	}
 
-// calcSignatureHash will, given a script and hash type for the current script
+	return calcSignatureHash(script, hashType, tx, idx), nil
-// engine instance, calculate the signature hash to be used for signing and
+}
-// verification.
+
-func calcSignatureHash(script []parsedOpcode, hashType SigHashType, tx *wire.MsgTx, idx int) []byte {
+// calcSignatureHash computes the signature hash for the specified input of the
+// target transaction observing the desired signature hash type.
+func calcSignatureHash(sigScript []byte, hashType SigHashType, tx *wire.MsgTx, idx int) []byte {
 	// The SigHashSingle signature type signs only the corresponding input
 	// and output (the output with the same index number as the input).
 	//
@@ -596,16 +548,13 @@ func calcSignatureHash(script []parsedOpcode, hashType SigHashType, tx *wire.Msg
 	}
 
 	// Remove all instances of OP_CODESEPARATOR from the script.
-	script = removeOpcode(script, OP_CODESEPARATOR)
+	sigScript = removeOpcodeRaw(sigScript, OP_CODESEPARATOR)
 
 	// Make a shallow copy of the transaction, zeroing out the script for
 	// all inputs that are not currently being processed.
 	txCopy := shallowCopyTx(tx)
 	for i := range txCopy.TxIn {
 		if i == idx {
-			// UnparseScript cannot fail here because removeOpcode
-			// above only returns a valid script.
-			sigScript, _ := unparseScript(script)
 			txCopy.TxIn[idx].SignatureScript = sigScript
 		} else {
 			txCopy.TxIn[i].SignatureScript = nil
@@ -662,57 +611,98 @@ func calcSignatureHash(script []parsedOpcode, hashType SigHashType, tx *wire.Msg
 
 // asSmallInt returns the passed opcode, which must be true according to
 // isSmallInt(), as an integer.
-func asSmallInt(op *opcode) int {
+func asSmallInt(op byte) int {
-	if op.value == OP_0 {
+	if op == OP_0 {
 		return 0
 	}
 
-	return int(op.value - (OP_1 - 1))
+	return int(op - (OP_1 - 1))
 }
 
-// getSigOpCount is the implementation function for counting the number of
+// countSigOpsV0 returns the number of signature operations in the provided
-// signature operations in the script provided by pops. If precise mode is
+// script up to the point of the first parse failure or the entire script when
-// requested then we attempt to count the number of operations for a multisig
+// there are no parse failures.  The precise flag attempts to accurately count
-// op. Otherwise we use the maximum.
+// the number of operations for a multisig operation versus using the maximum
-func getSigOpCount(pops []parsedOpcode, precise bool) int {
+// allowed.
-	nSigs := 0
+//
-	for i, pop := range pops {
+// WARNING: This function always treats the passed script as version 0.  Great
-		switch pop.opcode.value {
+// care must be taken if introducing a new script version because it is used in
-		case OP_CHECKSIG:
+// consensus which, unfortunately as of the time of this writing, does not check
-			fallthrough
+// script versions before counting their signature operations which means nodes
-		case OP_CHECKSIGVERIFY:
+// on existing rules will count new version scripts as if they were version 0.
-			nSigs++
+func countSigOpsV0(script []byte, precise bool) int {
-		case OP_CHECKMULTISIG:
+	const scriptVersion = 0
-			fallthrough
+
-		case OP_CHECKMULTISIGVERIFY:
+	numSigOps := 0
-			// If we are being precise then look for familiar
+	tokenizer := MakeScriptTokenizer(scriptVersion, script)
-			// patterns for multisig, for now all we recognize is
+	prevOp := byte(OP_INVALIDOPCODE)
-			// OP_1 - OP_16 to signify the number of pubkeys.
+	for tokenizer.Next() {
-			// Otherwise, we use the max of 20.
+		switch tokenizer.Opcode() {
-			if precise && i > 0 &&
+		case OP_CHECKSIG, OP_CHECKSIGVERIFY:
-				pops[i-1].opcode.value >= OP_1 &&
+			numSigOps++
-				pops[i-1].opcode.value <= OP_16 {
+
-				nSigs += asSmallInt(pops[i-1].opcode)
+		case OP_CHECKMULTISIG, OP_CHECKMULTISIGVERIFY:
+			// Note that OP_0 is treated as the max number of sigops here in
+			// precise mode despite it being a valid small integer in order to
+			// highly discourage multisigs with zero pubkeys.
+			//
+			// Also, even though this is referred to as "precise" counting, it's
+			// not really precise at all due to the small int opcodes only
+			// covering 1 through 16 pubkeys, which means this will count any
+			// more than that value (e.g. 17, 18 19) as the maximum number of
+			// allowed pubkeys. This is, unfortunately, now part of
+			// the Bitcion consensus rules, due to historical
+			// reasons. This could be made more correct with a new
+			// script version, however, ideally all multisignaure
+			// operations in new script versions should move to
+			// aggregated schemes such as Schnorr instead.
+			if precise && prevOp >= OP_1 && prevOp <= OP_16 {
+				numSigOps += asSmallInt(prevOp)
 			} else {
-				nSigs += MaxPubKeysPerMultiSig
+				numSigOps += MaxPubKeysPerMultiSig
 			}
+
 		default:
 			// Not a sigop.
 		}
+
+		prevOp = tokenizer.Opcode()
 	}
 
-	return nSigs
+	return numSigOps
 }
 
 // GetSigOpCount provides a quick count of the number of signature operations
 // in a script. a CHECKSIG operations counts for 1, and a CHECK_MULTISIG for 20.
 // If the script fails to parse, then the count up to the point of failure is
 // returned.
+//
+// WARNING: This function always treats the passed script as version 0.  Great
+// care must be taken if introducing a new script version because it is used in
+// consensus which, unfortunately as of the time of this writing, does not check
+// script versions before counting their signature operations which means nodes
+// on existing rules will count new version scripts as if they were version 0.
 func GetSigOpCount(script []byte) int {
-	// Don't check error since parseScript returns the parsed-up-to-error
+	return countSigOpsV0(script, false)
-	// list of pops.
+}
-	pops, _ := parseScript(script)
+
-	return getSigOpCount(pops, false)
+// finalOpcodeData returns the data associated with the final opcode in the
+// script.  It will return nil if the script fails to parse.
+func finalOpcodeData(scriptVersion uint16, script []byte) []byte {
+	// Avoid unnecessary work.
+	if len(script) == 0 {
+		return nil
+	}
+
+	var data []byte
+	tokenizer := MakeScriptTokenizer(scriptVersion, script)
+	for tokenizer.Next() {
+		data = tokenizer.Data()
+	}
+	if tokenizer.Err() != nil {
+		return nil
+	}
+	return data
 }
 
 // GetPreciseSigOpCount returns the number of signature operations in
@@ -720,44 +710,44 @@ func GetSigOpCount(script []byte) int {
 // Pay-To-Script-Hash script in order to find the precise number of signature
 // operations in the transaction.  If the script fails to parse, then the count
 // up to the point of failure is returned.
-func GetPreciseSigOpCount(scriptSig, scriptPubKey []byte, bip16 bool) int {
+//
-	// Don't check error since parseScript returns the parsed-up-to-error
+// WARNING: This function always treats the passed script as version 0.  Great
-	// list of pops.
+// care must be taken if introducing a new script version because it is used in
-	pops, _ := parseScript(scriptPubKey)
+// consensus which, unfortunately as of the time of this writing, does not check
+// script versions before counting their signature operations which means nodes
+// on existing rules will count new version scripts as if they were version 0.
+//
+// The third parameter is DEPRECATED and is unused.
+func GetPreciseSigOpCount(scriptSig, scriptPubKey []byte, _ bool) int {
+	const scriptVersion = 0
 
-	// Treat non P2SH transactions as normal.
+	// Treat non P2SH transactions as normal.  Note that signature operation
-	if !(bip16 && isScriptHash(pops)) {
+	// counting includes all operations up to the first parse failure.
-		return getSigOpCount(pops, true)
+	if !isScriptHashScript(scriptPubKey) {
-	}
+		return countSigOpsV0(scriptPubKey, true)
-
-	// The public key script is a pay-to-script-hash, so parse the signature
-	// script to get the final item.  Scripts that fail to fully parse count
-	// as 0 signature operations.
-	sigPops, err := parseScript(scriptSig)
-	if err != nil {
-		return 0
 	}
 
 	// The signature script must only push data to the stack for P2SH to be
 	// a valid pair, so the signature operation count is 0 when that is not
 	// the case.
-	if !isPushOnly(sigPops) || len(sigPops) == 0 {
+	if len(scriptSig) == 0 || !IsPushOnlyScript(scriptSig) {
 		return 0
 	}
 
 	// The P2SH script is the last item the signature script pushes to the
 	// stack.  When the script is empty, there are no signature operations.
-	shScript := sigPops[len(sigPops)-1].data
+	//
-	if len(shScript) == 0 {
+	// Notice that signature scripts that fail to fully parse count as 0
+	// signature operations unlike public key and redeem scripts.
+	redeemScript := finalOpcodeData(scriptVersion, scriptSig)
+	if len(redeemScript) == 0 {
 		return 0
 	}
 
-	// Parse the P2SH script and don't check the error since parseScript
+	// Return the more precise sigops count for the redeem script.  Note that
-	// returns the parsed-up-to-error list of pops and the consensus rules
+	// signature operation counting includes all operations up to the first
-	// dictate signature operations are counted up to the first parse
+	// parse failure.
-	// failure.
+	return countSigOpsV0(redeemScript, true)
-	shPops, _ := parseScript(shScript)
-	return getSigOpCount(shPops, true)
 }
 
 // GetWitnessSigOpCount returns the number of signature operations generated by
@@ -769,19 +759,15 @@ func GetPreciseSigOpCount(scriptSig, scriptPubKey []byte, bip16 bool) int {
 func GetWitnessSigOpCount(sigScript, pkScript []byte, witness wire.TxWitness) int {
 	// If this is a regular witness program, then we can proceed directly
 	// to counting its signature operations without any further processing.
-	if IsWitnessProgram(pkScript) {
+	if isWitnessProgramScript(pkScript) {
 		return getWitnessSigOps(pkScript, witness)
 	}
 
 	// Next, we'll check the sigScript to see if this is a nested p2sh
 	// witness program. This is a case wherein the sigScript is actually a
 	// datapush of a p2wsh witness program.
-	sigPops, err := parseScript(sigScript)
+	if isScriptHashScript(pkScript) && IsPushOnlyScript(sigScript) &&
-	if err != nil {
+		len(sigScript) > 0 && isWitnessProgramScript(sigScript[1:]) {
-		return 0
-	}
-	if IsPayToScriptHash(pkScript) && isPushOnly(sigPops) &&
-		IsWitnessProgram(sigScript[1:]) {
 		return getWitnessSigOps(sigScript[1:], witness)
 	}
 
@@ -811,26 +797,41 @@ func getWitnessSigOps(pkScript []byte, witness wire.TxWitness) int {
 			len(witness) > 0:
 
 			witnessScript := witness[len(witness)-1]
-			pops, _ := parseScript(witnessScript)
+			return countSigOpsV0(witnessScript, true)
-			return getSigOpCount(pops, true)
 		}
 	}
 
 	return 0
 }
 
+// checkScriptParses returns an error if the provided script fails to parse.
+func checkScriptParses(scriptVersion uint16, script []byte) error {
+	tokenizer := MakeScriptTokenizer(scriptVersion, script)
+	for tokenizer.Next() {
+		// Nothing to do.
+	}
+	return tokenizer.Err()
+}
+
 // IsUnspendable returns whether the passed public key script is unspendable, or
 // guaranteed to fail at execution.  This allows inputs to be pruned instantly
 // when entering the UTXO set.
+//
+// NOTE: This function is only valid for version 0 scripts.  Since the function
+// does not accept a script version, the results are undefined for other script
+// versions.
 func IsUnspendable(pkScript []byte) bool {
-	// Not provably unspendable
+	// The script is unspendable if starts with OP_RETURN or is guaranteed
-	if len(pkScript) == 0 {
+	// to fail at execution due to being larger than the max allowed script
-		return false
+	// size.
-	}
+	switch {
-	firstOpcode, err := checkScriptTemplateParseable(pkScript, &opcodeArray)
+	case len(pkScript) > 0 && pkScript[0] == OP_RETURN:
-	if err != nil {
+		return true
+	case len(pkScript) > MaxScriptSize:
 		return true
 	}
 
-	return firstOpcode != nil && *firstOpcode == OP_RETURN
+	// The script is unspendable if it is guaranteed to fail at execution.
+	const scriptVersion = 0
+	return checkScriptParses(scriptVersion, pkScript) != nil
 }

txscript/scriptnum.go

@@ -12,9 +12,21 @@ const (
 	maxInt32 = 1<<31 - 1
 	minInt32 = -1 << 31
 
-	// defaultScriptNumLen is the default number of bytes
+	// maxScriptNumLen is the maximum number of bytes data being interpreted
-	// data being interpreted as an integer may be.
+	// as an integer may be for the majority of op codes.
-	defaultScriptNumLen = 4
+	maxScriptNumLen = 4
+
+	// cltvMaxScriptNumLen is the maximum number of bytes data being interpreted
+	// as an integer may be for by-time and by-height locks as interpreted by
+	// CHECKLOCKTIMEVERIFY.
+	//
+	// The value comes from the fact that the current transaction locktime
+	// is a uint32 resulting in a maximum locktime of 2^32-1 (the year
+	// 2106).  However, scriptNums are signed and therefore a standard
+	// 4-byte scriptNum would only support up to a maximum of 2^31-1 (the
+	// year 2038).  Thus, a 5-byte scriptNum is needed since it will support
+	// up to 2^39-1 which allows dates beyond the current locktime limit.
+	cltvMaxScriptNumLen = 5
 )
 
 // scriptNum represents a numeric value used in the scripting engine with
@@ -178,7 +190,7 @@ func (n scriptNum) Int32() int32 {
 // before an ErrStackNumberTooBig is returned.  This effectively limits the
 // range of allowed values.
 // WARNING:  Great care should be taken if passing a value larger than
-// defaultScriptNumLen, which could lead to addition and multiplication
+// maxScriptNumLen, which could lead to addition and multiplication
 // overflows.
 //
 // See the Bytes function documentation for example encodings.

txscript/scriptnum_test.go

@@ -104,35 +104,35 @@ func TestMakeScriptNum(t *testing.T) {
 		err             error
 	}{
 		// Minimal encoding must reject negative 0.
-		{hexToBytes("80"), 0, defaultScriptNumLen, true, errMinimalData},
+		{hexToBytes("80"), 0, maxScriptNumLen, true, errMinimalData},
 
 		// Minimally encoded valid values with minimal encoding flag.
 		// Should not error and return expected integral number.
-		{nil, 0, defaultScriptNumLen, true, nil},
+		{nil, 0, maxScriptNumLen, true, nil},
-		{hexToBytes("01"), 1, defaultScriptNumLen, true, nil},
+		{hexToBytes("01"), 1, maxScriptNumLen, true, nil},
-		{hexToBytes("81"), -1, defaultScriptNumLen, true, nil},
+		{hexToBytes("81"), -1, maxScriptNumLen, true, nil},
-		{hexToBytes("7f"), 127, defaultScriptNumLen, true, nil},
+		{hexToBytes("7f"), 127, maxScriptNumLen, true, nil},
-		{hexToBytes("ff"), -127, defaultScriptNumLen, true, nil},
+		{hexToBytes("ff"), -127, maxScriptNumLen, true, nil},
-		{hexToBytes("8000"), 128, defaultScriptNumLen, true, nil},
+		{hexToBytes("8000"), 128, maxScriptNumLen, true, nil},
-		{hexToBytes("8080"), -128, defaultScriptNumLen, true, nil},
+		{hexToBytes("8080"), -128, maxScriptNumLen, true, nil},
-		{hexToBytes("8100"), 129, defaultScriptNumLen, true, nil},
+		{hexToBytes("8100"), 129, maxScriptNumLen, true, nil},
-		{hexToBytes("8180"), -129, defaultScriptNumLen, true, nil},
+		{hexToBytes("8180"), -129, maxScriptNumLen, true, nil},
-		{hexToBytes("0001"), 256, defaultScriptNumLen, true, nil},
+		{hexToBytes("0001"), 256, maxScriptNumLen, true, nil},
-		{hexToBytes("0081"), -256, defaultScriptNumLen, true, nil},
+		{hexToBytes("0081"), -256, maxScriptNumLen, true, nil},
-		{hexToBytes("ff7f"), 32767, defaultScriptNumLen, true, nil},
+		{hexToBytes("ff7f"), 32767, maxScriptNumLen, true, nil},
-		{hexToBytes("ffff"), -32767, defaultScriptNumLen, true, nil},
+		{hexToBytes("ffff"), -32767, maxScriptNumLen, true, nil},
-		{hexToBytes("008000"), 32768, defaultScriptNumLen, true, nil},
+		{hexToBytes("008000"), 32768, maxScriptNumLen, true, nil},
-		{hexToBytes("008080"), -32768, defaultScriptNumLen, true, nil},
+		{hexToBytes("008080"), -32768, maxScriptNumLen, true, nil},
-		{hexToBytes("ffff00"), 65535, defaultScriptNumLen, true, nil},
+		{hexToBytes("ffff00"), 65535, maxScriptNumLen, true, nil},
-		{hexToBytes("ffff80"), -65535, defaultScriptNumLen, true, nil},
+		{hexToBytes("ffff80"), -65535, maxScriptNumLen, true, nil},
-		{hexToBytes("000008"), 524288, defaultScriptNumLen, true, nil},
+		{hexToBytes("000008"), 524288, maxScriptNumLen, true, nil},
-		{hexToBytes("000088"), -524288, defaultScriptNumLen, true, nil},
+		{hexToBytes("000088"), -524288, maxScriptNumLen, true, nil},
-		{hexToBytes("000070"), 7340032, defaultScriptNumLen, true, nil},
+		{hexToBytes("000070"), 7340032, maxScriptNumLen, true, nil},
-		{hexToBytes("0000f0"), -7340032, defaultScriptNumLen, true, nil},
+		{hexToBytes("0000f0"), -7340032, maxScriptNumLen, true, nil},
-		{hexToBytes("00008000"), 8388608, defaultScriptNumLen, true, nil},
+		{hexToBytes("00008000"), 8388608, maxScriptNumLen, true, nil},
-		{hexToBytes("00008080"), -8388608, defaultScriptNumLen, true, nil},
+		{hexToBytes("00008080"), -8388608, maxScriptNumLen, true, nil},
-		{hexToBytes("ffffff7f"), 2147483647, defaultScriptNumLen, true, nil},
+		{hexToBytes("ffffff7f"), 2147483647, maxScriptNumLen, true, nil},
-		{hexToBytes("ffffffff"), -2147483647, defaultScriptNumLen, true, nil},
+		{hexToBytes("ffffffff"), -2147483647, maxScriptNumLen, true, nil},
 		{hexToBytes("ffffffff7f"), 549755813887, 5, true, nil},
 		{hexToBytes("ffffffffff"), -549755813887, 5, true, nil},
 		{hexToBytes("ffffffffffffff7f"), 9223372036854775807, 8, true, nil},
@@ -145,50 +145,50 @@ func TestMakeScriptNum(t *testing.T) {
 		// Minimally encoded values that are out of range for data that
 		// is interpreted as script numbers with the minimal encoding
 		// flag set.  Should error and return 0.
-		{hexToBytes("0000008000"), 0, defaultScriptNumLen, true, errNumTooBig},
+		{hexToBytes("0000008000"), 0, maxScriptNumLen, true, errNumTooBig},
-		{hexToBytes("0000008080"), 0, defaultScriptNumLen, true, errNumTooBig},
+		{hexToBytes("0000008080"), 0, maxScriptNumLen, true, errNumTooBig},
-		{hexToBytes("0000009000"), 0, defaultScriptNumLen, true, errNumTooBig},
+		{hexToBytes("0000009000"), 0, maxScriptNumLen, true, errNumTooBig},
-		{hexToBytes("0000009080"), 0, defaultScriptNumLen, true, errNumTooBig},
+		{hexToBytes("0000009080"), 0, maxScriptNumLen, true, errNumTooBig},
-		{hexToBytes("ffffffff00"), 0, defaultScriptNumLen, true, errNumTooBig},
+		{hexToBytes("ffffffff00"), 0, maxScriptNumLen, true, errNumTooBig},
-		{hexToBytes("ffffffff80"), 0, defaultScriptNumLen, true, errNumTooBig},
+		{hexToBytes("ffffffff80"), 0, maxScriptNumLen, true, errNumTooBig},
-		{hexToBytes("0000000001"), 0, defaultScriptNumLen, true, errNumTooBig},
+		{hexToBytes("0000000001"), 0, maxScriptNumLen, true, errNumTooBig},
-		{hexToBytes("0000000081"), 0, defaultScriptNumLen, true, errNumTooBig},
+		{hexToBytes("0000000081"), 0, maxScriptNumLen, true, errNumTooBig},
-		{hexToBytes("ffffffffffff00"), 0, defaultScriptNumLen, true, errNumTooBig},
+		{hexToBytes("ffffffffffff00"), 0, maxScriptNumLen, true, errNumTooBig},
-		{hexToBytes("ffffffffffff80"), 0, defaultScriptNumLen, true, errNumTooBig},
+		{hexToBytes("ffffffffffff80"), 0, maxScriptNumLen, true, errNumTooBig},
-		{hexToBytes("ffffffffffffff00"), 0, defaultScriptNumLen, true, errNumTooBig},
+		{hexToBytes("ffffffffffffff00"), 0, maxScriptNumLen, true, errNumTooBig},
-		{hexToBytes("ffffffffffffff80"), 0, defaultScriptNumLen, true, errNumTooBig},
+		{hexToBytes("ffffffffffffff80"), 0, maxScriptNumLen, true, errNumTooBig},
-		{hexToBytes("ffffffffffffff7f"), 0, defaultScriptNumLen, true, errNumTooBig},
+		{hexToBytes("ffffffffffffff7f"), 0, maxScriptNumLen, true, errNumTooBig},
-		{hexToBytes("ffffffffffffffff"), 0, defaultScriptNumLen, true, errNumTooBig},
+		{hexToBytes("ffffffffffffffff"), 0, maxScriptNumLen, true, errNumTooBig},
 
 		// Non-minimally encoded, but otherwise valid values with
 		// minimal encoding flag.  Should error and return 0.
-		{hexToBytes("00"), 0, defaultScriptNumLen, true, errMinimalData},       // 0
+		{hexToBytes("00"), 0, maxScriptNumLen, true, errMinimalData},       // 0
-		{hexToBytes("0100"), 0, defaultScriptNumLen, true, errMinimalData},     // 1
+		{hexToBytes("0100"), 0, maxScriptNumLen, true, errMinimalData},     // 1
-		{hexToBytes("7f00"), 0, defaultScriptNumLen, true, errMinimalData},     // 127
+		{hexToBytes("7f00"), 0, maxScriptNumLen, true, errMinimalData},     // 127
-		{hexToBytes("800000"), 0, defaultScriptNumLen, true, errMinimalData},   // 128
+		{hexToBytes("800000"), 0, maxScriptNumLen, true, errMinimalData},   // 128
-		{hexToBytes("810000"), 0, defaultScriptNumLen, true, errMinimalData},   // 129
+		{hexToBytes("810000"), 0, maxScriptNumLen, true, errMinimalData},   // 129
-		{hexToBytes("000100"), 0, defaultScriptNumLen, true, errMinimalData},   // 256
+		{hexToBytes("000100"), 0, maxScriptNumLen, true, errMinimalData},   // 256
-		{hexToBytes("ff7f00"), 0, defaultScriptNumLen, true, errMinimalData},   // 32767
+		{hexToBytes("ff7f00"), 0, maxScriptNumLen, true, errMinimalData},   // 32767
-		{hexToBytes("00800000"), 0, defaultScriptNumLen, true, errMinimalData}, // 32768
+		{hexToBytes("00800000"), 0, maxScriptNumLen, true, errMinimalData}, // 32768
-		{hexToBytes("ffff0000"), 0, defaultScriptNumLen, true, errMinimalData}, // 65535
+		{hexToBytes("ffff0000"), 0, maxScriptNumLen, true, errMinimalData}, // 65535
-		{hexToBytes("00000800"), 0, defaultScriptNumLen, true, errMinimalData}, // 524288
+		{hexToBytes("00000800"), 0, maxScriptNumLen, true, errMinimalData}, // 524288
-		{hexToBytes("00007000"), 0, defaultScriptNumLen, true, errMinimalData}, // 7340032
+		{hexToBytes("00007000"), 0, maxScriptNumLen, true, errMinimalData}, // 7340032
 		{hexToBytes("0009000100"), 0, 5, true, errMinimalData},             // 16779520
 
 		// Non-minimally encoded, but otherwise valid values without
 		// minimal encoding flag.  Should not error and return expected
 		// integral number.
-		{hexToBytes("00"), 0, defaultScriptNumLen, false, nil},
+		{hexToBytes("00"), 0, maxScriptNumLen, false, nil},
-		{hexToBytes("0100"), 1, defaultScriptNumLen, false, nil},
+		{hexToBytes("0100"), 1, maxScriptNumLen, false, nil},
-		{hexToBytes("7f00"), 127, defaultScriptNumLen, false, nil},
+		{hexToBytes("7f00"), 127, maxScriptNumLen, false, nil},
-		{hexToBytes("800000"), 128, defaultScriptNumLen, false, nil},
+		{hexToBytes("800000"), 128, maxScriptNumLen, false, nil},
-		{hexToBytes("810000"), 129, defaultScriptNumLen, false, nil},
+		{hexToBytes("810000"), 129, maxScriptNumLen, false, nil},
-		{hexToBytes("000100"), 256, defaultScriptNumLen, false, nil},
+		{hexToBytes("000100"), 256, maxScriptNumLen, false, nil},
-		{hexToBytes("ff7f00"), 32767, defaultScriptNumLen, false, nil},
+		{hexToBytes("ff7f00"), 32767, maxScriptNumLen, false, nil},
-		{hexToBytes("00800000"), 32768, defaultScriptNumLen, false, nil},
+		{hexToBytes("00800000"), 32768, maxScriptNumLen, false, nil},
-		{hexToBytes("ffff0000"), 65535, defaultScriptNumLen, false, nil},
+		{hexToBytes("ffff0000"), 65535, maxScriptNumLen, false, nil},
-		{hexToBytes("00000800"), 524288, defaultScriptNumLen, false, nil},
+		{hexToBytes("00000800"), 524288, maxScriptNumLen, false, nil},
-		{hexToBytes("00007000"), 7340032, defaultScriptNumLen, false, nil},
+		{hexToBytes("00007000"), 7340032, maxScriptNumLen, false, nil},
 		{hexToBytes("0009000100"), 16779520, 5, false, nil},
 	}
 

txscript/sign.go

@@ -22,12 +22,7 @@ func RawTxInWitnessSignature(tx *wire.MsgTx, sigHashes *TxSigHashes, idx int,
 	amt int64, subScript []byte, hashType SigHashType,
 	key *btcec.PrivateKey) ([]byte, error) {
 
-	parsedScript, err := parseScript(subScript)
+	hash, err := calcWitnessSignatureHashRaw(subScript, sigHashes, hashType, tx,
-	if err != nil {
-		return nil, fmt.Errorf("cannot parse output script: %v", err)
-	}
-
-	hash, err := calcWitnessSignatureHash(parsedScript, sigHashes, hashType, tx,
 		idx, amt)
 	if err != nil {
 		return nil, err
@@ -212,110 +207,50 @@ func sign(chainParams *chaincfg.Params, tx *wire.MsgTx, idx int,
 	}
 }
 
-// mergeScripts merges sigScript and prevScript assuming they are both
-// partial solutions for pkScript spending output idx of tx. class, addresses
-// and nrequired are the result of extracting the addresses from pkscript.
-// The return value is the best effort merging of the two scripts. Calling this
-// function with addresses, class and nrequired that do not match pkScript is
-// an error and results in undefined behaviour.
-func mergeScripts(chainParams *chaincfg.Params, tx *wire.MsgTx, idx int,
-	pkScript []byte, class ScriptClass, addresses []btcutil.Address,
-	nRequired int, sigScript, prevScript []byte) []byte {
-
-	// TODO: the scripthash and multisig paths here are overly
-	// inefficient in that they will recompute already known data.
-	// some internal refactoring could probably make this avoid needless
-	// extra calculations.
-	switch class {
-	case ScriptHashTy:
-		// Remove the last push in the script and then recurse.
-		// this could be a lot less inefficient.
-		sigPops, err := parseScript(sigScript)
-		if err != nil || len(sigPops) == 0 {
-			return prevScript
-		}
-		prevPops, err := parseScript(prevScript)
-		if err != nil || len(prevPops) == 0 {
-			return sigScript
-		}
-
-		// assume that script in sigPops is the correct one, we just
-		// made it.
-		script := sigPops[len(sigPops)-1].data
-
-		// We already know this information somewhere up the stack.
-		class, addresses, nrequired, _ :=
-			ExtractPkScriptAddrs(script, chainParams)
-
-		// regenerate scripts.
-		sigScript, _ := unparseScript(sigPops)
-		prevScript, _ := unparseScript(prevPops)
-
-		// Merge
-		mergedScript := mergeScripts(chainParams, tx, idx, script,
-			class, addresses, nrequired, sigScript, prevScript)
-
-		// Reappend the script and return the result.
-		builder := NewScriptBuilder()
-		builder.AddOps(mergedScript)
-		builder.AddData(script)
-		finalScript, _ := builder.Script()
-		return finalScript
-	case MultiSigTy:
-		return mergeMultiSig(tx, idx, addresses, nRequired, pkScript,
-			sigScript, prevScript)
-
-	// It doesn't actually make sense to merge anything other than multiig
-	// and scripthash (because it could contain multisig). Everything else
-	// has either zero signature, can't be spent, or has a single signature
-	// which is either present or not. The other two cases are handled
-	// above. In the conflict case here we just assume the longest is
-	// correct (this matches behaviour of the reference implementation).
-	default:
-		if len(sigScript) > len(prevScript) {
-			return sigScript
-		}
-		return prevScript
-	}
-}
-
 // mergeMultiSig combines the two signature scripts sigScript and prevScript
 // that both provide signatures for pkScript in output idx of tx. addresses
 // and nRequired should be the results from extracting the addresses from
 // pkScript. Since this function is internal only we assume that the arguments
 // have come from other functions internally and thus are all consistent with
 // each other, behaviour is undefined if this contract is broken.
+//
+// NOTE: This function is only valid for version 0 scripts.  Since the function
+// does not accept a script version, the results are undefined for other script
+// versions.
 func mergeMultiSig(tx *wire.MsgTx, idx int, addresses []btcutil.Address,
 	nRequired int, pkScript, sigScript, prevScript []byte) []byte {
 
-	// This is an internal only function and we already parsed this script
+	// Nothing to merge if either the new or previous signature scripts are
-	// as ok for multisig (this is how we got here), so if this fails then
+	// empty.
-	// all assumptions are broken and who knows which way is up?
+	if len(sigScript) == 0 {
-	pkPops, _ := parseScript(pkScript)
-
-	sigPops, err := parseScript(sigScript)
-	if err != nil || len(sigPops) == 0 {
 		return prevScript
 	}
-
+	if len(prevScript) == 0 {
-	prevPops, err := parseScript(prevScript)
-	if err != nil || len(prevPops) == 0 {
 		return sigScript
 	}
 
 	// Convenience function to avoid duplication.
-	extractSigs := func(pops []parsedOpcode, sigs [][]byte) [][]byte {
+	var possibleSigs [][]byte
-		for _, pop := range pops {
+	extractSigs := func(script []byte) error {
-			if len(pop.data) != 0 {
+		const scriptVersion = 0
-				sigs = append(sigs, pop.data)
+		tokenizer := MakeScriptTokenizer(scriptVersion, script)
+		for tokenizer.Next() {
+			if data := tokenizer.Data(); len(data) != 0 {
+				possibleSigs = append(possibleSigs, data)
 			}
 		}
-		return sigs
+		return tokenizer.Err()
 	}
 
-	possibleSigs := make([][]byte, 0, len(sigPops)+len(prevPops))
+	// Attempt to extract signatures from the two scripts.  Return the other
-	possibleSigs = extractSigs(sigPops, possibleSigs)
+	// script that is intended to be merged in the case signature extraction
-	possibleSigs = extractSigs(prevPops, possibleSigs)
+	// fails for some reason.
+	if err := extractSigs(sigScript); err != nil {
+		return prevScript
+	}
+	if err := extractSigs(prevScript); err != nil {
+		return sigScript
+	}
 
 	// Now we need to match the signatures to pubkeys, the only real way to
 	// do that is to try to verify them all and match it to the pubkey
@@ -345,7 +280,7 @@ sigLoop:
 		// however, assume no sigs etc are in the script since that
 		// would make the transaction nonstandard and thus not
 		// MultiSigTy, so we just need to hash the full thing.
-		hash := calcSignatureHash(pkPops, hashType, tx, idx)
+		hash := calcSignatureHash(pkScript, hashType, tx, idx)
 
 		for _, addr := range addresses {
 			// All multisig addresses should be pubkey addresses
@@ -394,6 +329,81 @@ sigLoop:
 	return script
 }
 
+// mergeScripts merges sigScript and prevScript assuming they are both
+// partial solutions for pkScript spending output idx of tx. class, addresses
+// and nrequired are the result of extracting the addresses from pkscript.
+// The return value is the best effort merging of the two scripts. Calling this
+// function with addresses, class and nrequired that do not match pkScript is
+// an error and results in undefined behaviour.
+//
+// NOTE: This function is only valid for version 0 scripts.  Since the function
+// does not accept a script version, the results are undefined for other script
+// versions.
+func mergeScripts(chainParams *chaincfg.Params, tx *wire.MsgTx, idx int,
+	pkScript []byte, class ScriptClass, addresses []btcutil.Address,
+	nRequired int, sigScript, prevScript []byte) []byte {
+
+	// TODO(oga) the scripthash and multisig paths here are overly
+	// inefficient in that they will recompute already known data.
+	// some internal refactoring could probably make this avoid needless
+	// extra calculations.
+	const scriptVersion = 0
+	switch class {
+	case ScriptHashTy:
+		// Nothing to merge if either the new or previous signature
+		// scripts are empty or fail to parse.
+		if len(sigScript) == 0 ||
+			checkScriptParses(scriptVersion, sigScript) != nil {
+
+			return prevScript
+		}
+		if len(prevScript) == 0 ||
+			checkScriptParses(scriptVersion, prevScript) != nil {
+
+			return sigScript
+		}
+
+		// Remove the last push in the script and then recurse.
+		// this could be a lot less inefficient.
+		//
+		// Assume that final script is the correct one since it was just
+		// made and it is a pay-to-script-hash.
+		script := finalOpcodeData(scriptVersion, sigScript)
+
+		// We already know this information somewhere up the stack,
+		// therefore the error is ignored.
+		class, addresses, nrequired, _ :=
+			ExtractPkScriptAddrs(script, chainParams)
+
+		// Merge
+		mergedScript := mergeScripts(chainParams, tx, idx, script,
+			class, addresses, nrequired, sigScript, prevScript)
+
+		// Reappend the script and return the result.
+		builder := NewScriptBuilder()
+		builder.AddOps(mergedScript)
+		builder.AddData(script)
+		finalScript, _ := builder.Script()
+		return finalScript
+
+	case MultiSigTy:
+		return mergeMultiSig(tx, idx, addresses, nRequired, pkScript,
+			sigScript, prevScript)
+
+	// It doesn't actually make sense to merge anything other than multiig
+	// and scripthash (because it could contain multisig). Everything else
+	// has either zero signature, can't be spent, or has a single signature
+	// which is either present or not. The other two cases are handled
+	// above. In the conflict case here we just assume the longest is
+	// correct (this matches behaviour of the reference implementation).
+	default:
+		if len(sigScript) > len(prevScript) {
+			return sigScript
+		}
+		return prevScript
+	}
+}
+
 // KeyDB is an interface type provided to SignTxOutput, it encapsulates
 // any user state required to get the private keys for an address.
 type KeyDB interface {
@@ -404,8 +414,7 @@ type KeyDB interface {
 type KeyClosure func(btcutil.Address) (*btcec.PrivateKey, bool, error)
 
 // GetKey implements KeyDB by returning the result of calling the closure.
-func (kc KeyClosure) GetKey(address btcutil.Address) (*btcec.PrivateKey,
+func (kc KeyClosure) GetKey(address btcutil.Address) (*btcec.PrivateKey, bool, error) {
-	bool, error) {
 	return kc(address)
 }
 
@@ -430,6 +439,10 @@ func (sc ScriptClosure) GetScript(address btcutil.Address) ([]byte, error) {
 // getScript. If previousScript is provided then the results in previousScript
 // will be merged in a type-dependent manner with the newly generated.
 // signature script.
+//
+// NOTE: This function is only valid for version 0 scripts.  Since the function
+// does not accept a script version, the results are undefined for other script
+// versions.
 func SignTxOutput(chainParams *chaincfg.Params, tx *wire.MsgTx, idx int,
 	pkScript []byte, hashType SigHashType, kdb KeyDB, sdb ScriptDB,
 	previousScript []byte) ([]byte, error) {

txscript/stack.go

@@ -86,7 +86,7 @@ func (s *stack) PopInt() (scriptNum, error) {
 		return 0, err
 	}
 
-	return makeScriptNum(so, s.verifyMinimalData, defaultScriptNumLen)
+	return makeScriptNum(so, s.verifyMinimalData, maxScriptNumLen)
 }
 
 // PopBool pops the value off the top of the stack, converts it into a bool, and
@@ -123,7 +123,7 @@ func (s *stack) PeekInt(idx int32) (scriptNum, error) {
 		return 0, err
 	}
 
-	return makeScriptNum(so, s.verifyMinimalData, defaultScriptNumLen)
+	return makeScriptNum(so, s.verifyMinimalData, maxScriptNumLen)
 }
 
 // PeekBool returns the Nth item on the stack as a bool without removing it.

txscript/standard_test.go

@@ -832,7 +832,7 @@ func TestCalcMultiSigStats(t *testing.T) {
 			name: "short script",
 			script: "0x046708afdb0fe5548271967f1a67130b7105cd6a828" +
 				"e03909a67962e0ea1f61d",
-			err: scriptError(ErrMalformedPush, ""),
+			err: scriptError(ErrNotMultisigScript, ""),
 		},
 		{
 			name: "stack underflow",
@@ -843,11 +843,7 @@ func TestCalcMultiSigStats(t *testing.T) {
 		},
 		{
 			name: "multisig script",
-			script: "0 DATA_72 0x30450220106a3e4ef0b51b764a2887226" +
+			script: "1 DATA_33 0x0232abdc893e7f0631364d7fd01cb33d24da45329a0" +
-				"2ffef55846514dacbdcbbdd652c849d395b4384022100" +
-				"e03ae554c3cbb40600d31dd46fc33f25e47bf8525b1fe" +
-				"07282e3b6ecb5f3bb2801 CODESEPARATOR 1 DATA_33 " +
-				"0x0232abdc893e7f0631364d7fd01cb33d24da45329a0" +
 				"0357b3a7886211ab414d55a 1 CHECKMULTISIG",
 			err: nil,
 		},

txscript/tokenizer.go

@@ -0,0 +1,186 @@
+// Copyright (c) 2019 The Decred developers
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+package txscript
+
+import (
+	"encoding/binary"
+	"fmt"
+)
+
+// opcodeArrayRef is used to break initialization cycles.
+var opcodeArrayRef *[256]opcode
+
+func init() {
+	opcodeArrayRef = &opcodeArray
+}
+
+// ScriptTokenizer provides a facility for easily and efficiently tokenizing
+// transaction scripts without creating allocations.  Each successive opcode is
+// parsed with the Next function, which returns false when iteration is
+// complete, either due to successfully tokenizing the entire script or
+// encountering a parse error.  In the case of failure, the Err function may be
+// used to obtain the specific parse error.
+//
+// Upon successfully parsing an opcode, the opcode and data associated with it
+// may be obtained via the Opcode and Data functions, respectively.
+//
+// The ByteIndex function may be used to obtain the tokenizer's current offset
+// into the raw script.
+type ScriptTokenizer struct {
+	script  []byte
+	version uint16
+	offset  int32
+	op      *opcode
+	data    []byte
+	err     error
+}
+
+// Done returns true when either all opcodes have been exhausted or a parse
+// failure was encountered and therefore the state has an associated error.
+func (t *ScriptTokenizer) Done() bool {
+	return t.err != nil || t.offset >= int32(len(t.script))
+}
+
+// Next attempts to parse the next opcode and returns whether or not it was
+// successful.  It will not be successful if invoked when already at the end of
+// the script, a parse failure is encountered, or an associated error already
+// exists due to a previous parse failure.
+//
+// In the case of a true return, the parsed opcode and data can be obtained with
+// the associated functions and the offset into the script will either point to
+// the next opcode or the end of the script if the final opcode was parsed.
+//
+// In the case of a false return, the parsed opcode and data will be the last
+// successfully parsed values (if any) and the offset into the script will
+// either point to the failing opcode or the end of the script if the function
+// was invoked when already at the end of the script.
+//
+// Invoking this function when already at the end of the script is not
+// considered an error and will simply return false.
+func (t *ScriptTokenizer) Next() bool {
+	if t.Done() {
+		return false
+	}
+
+	op := &opcodeArrayRef[t.script[t.offset]]
+	switch {
+	// No additional data.  Note that some of the opcodes, notably OP_1NEGATE,
+	// OP_0, and OP_[1-16] represent the data themselves.
+	case op.length == 1:
+		t.offset++
+		t.op = op
+		t.data = nil
+		return true
+
+	// Data pushes of specific lengths -- OP_DATA_[1-75].
+	case op.length > 1:
+		script := t.script[t.offset:]
+		if len(script) < op.length {
+			str := fmt.Sprintf("opcode %s requires %d bytes, but script only "+
+				"has %d remaining", op.name, op.length, len(script))
+			t.err = scriptError(ErrMalformedPush, str)
+			return false
+		}
+
+		// Move the offset forward and set the opcode and data accordingly.
+		t.offset += int32(op.length)
+		t.op = op
+		t.data = script[1:op.length]
+		return true
+
+	// Data pushes with parsed lengths -- OP_PUSHDATA{1,2,4}.
+	case op.length < 0:
+		script := t.script[t.offset+1:]
+		if len(script) < -op.length {
+			str := fmt.Sprintf("opcode %s requires %d bytes, but script only "+
+				"has %d remaining", op.name, -op.length, len(script))
+			t.err = scriptError(ErrMalformedPush, str)
+			return false
+		}
+
+		// Next -length bytes are little endian length of data.
+		var dataLen int32
+		switch op.length {
+		case -1:
+			dataLen = int32(script[0])
+		case -2:
+			dataLen = int32(binary.LittleEndian.Uint16(script[:2]))
+		case -4:
+			dataLen = int32(binary.LittleEndian.Uint32(script[:4]))
+		default:
+			// In practice it should be impossible to hit this
+			// check as each op code is predefined, and only uses
+			// the specified lengths.
+			str := fmt.Sprintf("invalid opcode length %d", op.length)
+			t.err = scriptError(ErrMalformedPush, str)
+			return false
+		}
+
+		// Move to the beginning of the data.
+		script = script[-op.length:]
+
+		// Disallow entries that do not fit script or were sign extended.
+		if dataLen > int32(len(script)) || dataLen < 0 {
+			str := fmt.Sprintf("opcode %s pushes %d bytes, but script only "+
+				"has %d remaining", op.name, dataLen, len(script))
+			t.err = scriptError(ErrMalformedPush, str)
+			return false
+		}
+
+		// Move the offset forward and set the opcode and data accordingly.
+		t.offset += 1 + int32(-op.length) + dataLen
+		t.op = op
+		t.data = script[:dataLen]
+		return true
+	}
+
+	// The only remaining case is an opcode with length zero which is
+	// impossible.
+	panic("unreachable")
+}
+
+// Script returns the full script associated with the tokenizer.
+func (t *ScriptTokenizer) Script() []byte {
+	return t.script
+}
+
+// ByteIndex returns the current offset into the full script that will be parsed
+// next and therefore also implies everything before it has already been parsed.
+func (t *ScriptTokenizer) ByteIndex() int32 {
+	return t.offset
+}
+
+// Opcode returns the current opcode associated with the tokenizer.
+func (t *ScriptTokenizer) Opcode() byte {
+	return t.op.value
+}
+
+// Data returns the data associated with the most recently successfully parsed
+// opcode.
+func (t *ScriptTokenizer) Data() []byte {
+	return t.data
+}
+
+// Err returns any errors currently associated with the tokenizer.  This will
+// only be non-nil in the case a parsing error was encountered.
+func (t *ScriptTokenizer) Err() error {
+	return t.err
+}
+
+// MakeScriptTokenizer returns a new instance of a script tokenizer.  Passing
+// an unsupported script version will result in the returned tokenizer
+// immediately having an err set accordingly.
+//
+// See the docs for ScriptTokenizer for more details.
+func MakeScriptTokenizer(scriptVersion uint16, script []byte) ScriptTokenizer {
+	// Only version 0 scripts are currently supported.
+	var err error
+	if scriptVersion != 0 {
+		str := fmt.Sprintf("script version %d is not supported", scriptVersion)
+		err = scriptError(ErrUnsupportedScriptVersion, str)
+
+	}
+	return ScriptTokenizer{version: scriptVersion, script: script, err: err}
+}

txscript/tokenizer_test.go

@@ -0,0 +1,259 @@
+// Copyright (c) 2019 The Decred developers
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+package txscript
+
+import (
+	"bytes"
+	"fmt"
+	"testing"
+)
+
+// TestScriptTokenizer ensures a wide variety of behavior provided by the script
+// tokenizer performs as expected.
+func TestScriptTokenizer(t *testing.T) {
+	t.Skip()
+
+	type expectedResult struct {
+		op    byte   // expected parsed opcode
+		data  []byte // expected parsed data
+		index int32  // expected index into raw script after parsing token
+	}
+
+	type tokenizerTest struct {
+		name     string           // test description
+		script   []byte           // the script to tokenize
+		expected []expectedResult // the expected info after parsing each token
+		finalIdx int32            // the expected final byte index
+		err      error            // expected error
+	}
+
+	// Add both positive and negative tests for OP_DATA_1 through OP_DATA_75.
+	const numTestsHint = 100 // Make prealloc linter happy.
+	tests := make([]tokenizerTest, 0, numTestsHint)
+	for op := byte(OP_DATA_1); op < OP_DATA_75; op++ {
+		data := bytes.Repeat([]byte{0x01}, int(op))
+		tests = append(tests, tokenizerTest{
+			name:     fmt.Sprintf("OP_DATA_%d", op),
+			script:   append([]byte{op}, data...),
+			expected: []expectedResult{{op, data, 1 + int32(op)}},
+			finalIdx: 1 + int32(op),
+			err:      nil,
+		})
+
+		// Create test that provides one less byte than the data push requires.
+		tests = append(tests, tokenizerTest{
+			name:     fmt.Sprintf("short OP_DATA_%d", op),
+			script:   append([]byte{op}, data[1:]...),
+			expected: nil,
+			finalIdx: 0,
+			err:      scriptError(ErrMalformedPush, ""),
+		})
+	}
+
+	// Add both positive and negative tests for OP_PUSHDATA{1,2,4}.
+	data := mustParseShortForm("0x01{76}")
+	tests = append(tests, []tokenizerTest{{
+		name:     "OP_PUSHDATA1",
+		script:   mustParseShortForm("OP_PUSHDATA1 0x4c 0x01{76}"),
+		expected: []expectedResult{{OP_PUSHDATA1, data, 2 + int32(len(data))}},
+		finalIdx: 2 + int32(len(data)),
+		err:      nil,
+	}, {
+		name:     "OP_PUSHDATA1 no data length",
+		script:   mustParseShortForm("OP_PUSHDATA1"),
+		expected: nil,
+		finalIdx: 0,
+		err:      scriptError(ErrMalformedPush, ""),
+	}, {
+		name:     "OP_PUSHDATA1 short data by 1 byte",
+		script:   mustParseShortForm("OP_PUSHDATA1 0x4c 0x01{75}"),
+		expected: nil,
+		finalIdx: 0,
+		err:      scriptError(ErrMalformedPush, ""),
+	}, {
+		name:     "OP_PUSHDATA2",
+		script:   mustParseShortForm("OP_PUSHDATA2 0x4c00 0x01{76}"),
+		expected: []expectedResult{{OP_PUSHDATA2, data, 3 + int32(len(data))}},
+		finalIdx: 3 + int32(len(data)),
+		err:      nil,
+	}, {
+		name:     "OP_PUSHDATA2 no data length",
+		script:   mustParseShortForm("OP_PUSHDATA2"),
+		expected: nil,
+		finalIdx: 0,
+		err:      scriptError(ErrMalformedPush, ""),
+	}, {
+		name:     "OP_PUSHDATA2 short data by 1 byte",
+		script:   mustParseShortForm("OP_PUSHDATA2 0x4c00 0x01{75}"),
+		expected: nil,
+		finalIdx: 0,
+		err:      scriptError(ErrMalformedPush, ""),
+	}, {
+		name:     "OP_PUSHDATA4",
+		script:   mustParseShortForm("OP_PUSHDATA4 0x4c000000 0x01{76}"),
+		expected: []expectedResult{{OP_PUSHDATA4, data, 5 + int32(len(data))}},
+		finalIdx: 5 + int32(len(data)),
+		err:      nil,
+	}, {
+		name:     "OP_PUSHDATA4 no data length",
+		script:   mustParseShortForm("OP_PUSHDATA4"),
+		expected: nil,
+		finalIdx: 0,
+		err:      scriptError(ErrMalformedPush, ""),
+	}, {
+		name:     "OP_PUSHDATA4 short data by 1 byte",
+		script:   mustParseShortForm("OP_PUSHDATA4 0x4c000000 0x01{75}"),
+		expected: nil,
+		finalIdx: 0,
+		err:      scriptError(ErrMalformedPush, ""),
+	}}...)
+
+	// Add tests for OP_0, and OP_1 through OP_16 (small integers/true/false).
+	opcodes := []byte{OP_0}
+	for op := byte(OP_1); op < OP_16; op++ {
+		opcodes = append(opcodes, op)
+	}
+	for _, op := range opcodes {
+		tests = append(tests, tokenizerTest{
+			name:     fmt.Sprintf("OP_%d", op),
+			script:   []byte{op},
+			expected: []expectedResult{{op, nil, 1}},
+			finalIdx: 1,
+			err:      nil,
+		})
+	}
+
+	// Add various positive and negative tests for multi-opcode scripts.
+	tests = append(tests, []tokenizerTest{{
+		name:   "pay-to-pubkey-hash",
+		script: mustParseShortForm("DUP HASH160 DATA_20 0x01{20} EQUAL CHECKSIG"),
+		expected: []expectedResult{
+			{OP_DUP, nil, 1}, {OP_HASH160, nil, 2},
+			{OP_DATA_20, mustParseShortForm("0x01{20}"), 23},
+			{OP_EQUAL, nil, 24}, {OP_CHECKSIG, nil, 25},
+		},
+		finalIdx: 25,
+		err:      nil,
+	}, {
+		name:   "almost pay-to-pubkey-hash (short data)",
+		script: mustParseShortForm("DUP HASH160 DATA_20 0x01{17} EQUAL CHECKSIG"),
+		expected: []expectedResult{
+			{OP_DUP, nil, 1}, {OP_HASH160, nil, 2},
+		},
+		finalIdx: 2,
+		err:      scriptError(ErrMalformedPush, ""),
+	}, {
+		name:   "almost pay-to-pubkey-hash (overlapped data)",
+		script: mustParseShortForm("DUP HASH160 DATA_20 0x01{19} EQUAL CHECKSIG"),
+		expected: []expectedResult{
+			{OP_DUP, nil, 1}, {OP_HASH160, nil, 2},
+			{OP_DATA_20, mustParseShortForm("0x01{19} EQUAL"), 23},
+			{OP_CHECKSIG, nil, 24},
+		},
+		finalIdx: 24,
+		err:      nil,
+	}, {
+		name:   "pay-to-script-hash",
+		script: mustParseShortForm("HASH160 DATA_20 0x01{20} EQUAL"),
+		expected: []expectedResult{
+			{OP_HASH160, nil, 1},
+			{OP_DATA_20, mustParseShortForm("0x01{20}"), 22},
+			{OP_EQUAL, nil, 23},
+		},
+		finalIdx: 23,
+		err:      nil,
+	}, {
+		name:   "almost pay-to-script-hash (short data)",
+		script: mustParseShortForm("HASH160 DATA_20 0x01{18} EQUAL"),
+		expected: []expectedResult{
+			{OP_HASH160, nil, 1},
+		},
+		finalIdx: 1,
+		err:      scriptError(ErrMalformedPush, ""),
+	}, {
+		name:   "almost pay-to-script-hash (overlapped data)",
+		script: mustParseShortForm("HASH160 DATA_20 0x01{19} EQUAL"),
+		expected: []expectedResult{
+			{OP_HASH160, nil, 1},
+			{OP_DATA_20, mustParseShortForm("0x01{19} EQUAL"), 22},
+		},
+		finalIdx: 22,
+		err:      nil,
+	}}...)
+
+	const scriptVersion = 0
+	for _, test := range tests {
+		tokenizer := MakeScriptTokenizer(scriptVersion, test.script)
+		var opcodeNum int
+		for tokenizer.Next() {
+			// Ensure Next never returns true when there is an error set.
+			if err := tokenizer.Err(); err != nil {
+				t.Fatalf("%q: Next returned true when tokenizer has err: %v",
+					test.name, err)
+			}
+
+			// Ensure the test data expects a token to be parsed.
+			op := tokenizer.Opcode()
+			data := tokenizer.Data()
+			if opcodeNum >= len(test.expected) {
+				t.Fatalf("%q: unexpected token '%d' (data: '%x')", test.name,
+					op, data)
+			}
+			expected := &test.expected[opcodeNum]
+
+			// Ensure the opcode and data are the expected values.
+			if op != expected.op {
+				t.Fatalf("%q: unexpected opcode -- got %v, want %v", test.name,
+					op, expected.op)
+			}
+			if !bytes.Equal(data, expected.data) {
+				t.Fatalf("%q: unexpected data -- got %x, want %x", test.name,
+					data, expected.data)
+			}
+
+			tokenizerIdx := tokenizer.ByteIndex()
+			if tokenizerIdx != expected.index {
+				t.Fatalf("%q: unexpected byte index -- got %d, want %d",
+					test.name, tokenizerIdx, expected.index)
+			}
+
+			opcodeNum++
+		}
+
+		// Ensure the tokenizer claims it is done.  This should be the case
+		// regardless of whether or not there was a parse error.
+		if !tokenizer.Done() {
+			t.Fatalf("%q: tokenizer claims it is not done", test.name)
+		}
+
+		// Ensure the error is as expected.
+		if test.err == nil && tokenizer.Err() != nil {
+			t.Fatalf("%q: unexpected tokenizer err -- got %v, want nil",
+				test.name, tokenizer.Err())
+		} else if test.err != nil {
+			if !IsErrorCode(tokenizer.Err(), test.err.(Error).ErrorCode) {
+				t.Fatalf("%q: unexpected tokenizer err -- got %v, want %v",
+					test.name, tokenizer.Err(), test.err.(Error).ErrorCode)
+			}
+		}
+
+		// Ensure the final index is the expected value.
+		tokenizerIdx := tokenizer.ByteIndex()
+		if tokenizerIdx != test.finalIdx {
+			t.Fatalf("%q: unexpected final byte index -- got %d, want %d",
+				test.name, tokenizerIdx, test.finalIdx)
+		}
+	}
+}
+
+// TestScriptTokenizerUnsupportedVersion ensures the tokenizer fails immediately
+// with an unsupported script version.
+func TestScriptTokenizerUnsupportedVersion(t *testing.T) {
+	const scriptVersion = 65535
+	tokenizer := MakeScriptTokenizer(scriptVersion, nil)
+	if !IsErrorCode(tokenizer.Err(), ErrUnsupportedScriptVersion) {
+		t.Fatalf("script tokenizer did not error with unsupported version")
+	}
+}