txscript: Optimize script disasm.
This converts the DisasmString function to make use of the new zero-allocation script tokenizer instead of the far less efficient parseScript thereby significantly optimizing the function. In order to facilitate this, the opcode disassembly functionality is split into a separate function called disasmOpcode that accepts the opcode struct and data independently as opposed to requiring a parsed opcode. The new function also accepts a pointer to a string builder so the disassembly can be more efficiently be built. While here, the comment is modified to explicitly call out the script version semantics. The following is a before and after comparison of a large script: benchmark old ns/op new ns/op delta BenchmarkDisasmString-8 102902 40124 -61.01% benchmark old allocs new allocs delta BenchmarkDisasmString-8 46 51 +10.87% benchmark old bytes new bytes delta BenchmarkDisasmString-8 389324 130552 -66.47%
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2 changed files with 61 additions and 34 deletions
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@ -9,8 +9,10 @@ import (
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"crypto/sha1"
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"crypto/sha256"
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"encoding/binary"
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"encoding/hex"
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"fmt"
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"hash"
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"strings"
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"golang.org/x/crypto/ripemd160"
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@ -815,45 +817,60 @@ func (pop *parsedOpcode) checkMinimalDataPush() error {
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return nil
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}
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// print returns a human-readable string representation of the opcode for use
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// in script disassembly.
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func (pop *parsedOpcode) print(oneline bool) string {
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// The reference implementation one-line disassembly replaces opcodes
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// which represent values (e.g. OP_0 through OP_16 and OP_1NEGATE)
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// with the raw value. However, when not doing a one-line dissassembly,
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// we prefer to show the actual opcode names. Thus, only replace the
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// opcodes in question when the oneline flag is set.
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opcodeName := pop.opcode.name
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if oneline {
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// disasmOpcode writes a human-readable disassembly of the provided opcode and
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// data into the provided buffer. The compact flag indicates the disassembly
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// should print a more compact representation of data-carrying and small integer
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// opcodes. For example, OP_0 through OP_16 are replaced with the numeric value
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// and data pushes are printed as only the hex representation of the data as
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// opposed to including the opcode that specifies the amount of data to push as
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// well.
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func disasmOpcode(buf *strings.Builder, op *opcode, data []byte, compact bool) {
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// Replace opcode which represent values (e.g. OP_0 through OP_16 and
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// OP_1NEGATE) with the raw value when performing a compact disassembly.
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opcodeName := op.name
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if compact {
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if replName, ok := opcodeOnelineRepls[opcodeName]; ok {
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opcodeName = replName
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}
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// Nothing more to do for non-data push opcodes.
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if pop.opcode.length == 1 {
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return opcodeName
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// Either write the human-readable opcode or the parsed data in hex for
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// data-carrying opcodes.
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switch {
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case op.length == 1:
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buf.WriteString(opcodeName)
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default:
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buf.WriteString(hex.EncodeToString(data))
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}
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return fmt.Sprintf("%x", pop.data)
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return
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}
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// Nothing more to do for non-data push opcodes.
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if pop.opcode.length == 1 {
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return opcodeName
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}
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buf.WriteString(opcodeName)
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switch op.length {
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// Only write the opcode name for non-data push opcodes.
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case 1:
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return
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// Add length for the OP_PUSHDATA# opcodes.
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retString := opcodeName
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switch pop.opcode.length {
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case -1:
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retString += fmt.Sprintf(" 0x%02x", len(pop.data))
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buf.WriteString(fmt.Sprintf(" 0x%02x", len(data)))
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case -2:
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retString += fmt.Sprintf(" 0x%04x", len(pop.data))
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buf.WriteString(fmt.Sprintf(" 0x%04x", len(data)))
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case -4:
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retString += fmt.Sprintf(" 0x%08x", len(pop.data))
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buf.WriteString(fmt.Sprintf(" 0x%08x", len(data)))
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}
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return fmt.Sprintf("%s 0x%02x", retString, pop.data)
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buf.WriteString(fmt.Sprintf(" 0x%02x", data))
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}
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// print returns a human-readable string representation of the opcode for use
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// in script disassembly.
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func (pop *parsedOpcode) print(compact bool) string {
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var buf strings.Builder
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disasmOpcode(&buf, pop.opcode, pop.data, compact)
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return buf.String()
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}
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// bytes returns any data associated with the opcode encoded as it would be in
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@ -8,6 +8,7 @@ import (
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"bytes"
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"encoding/binary"
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"fmt"
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"strings"
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"time"
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"github.com/btcsuite/btcd/chaincfg/chainhash"
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@ -275,20 +276,29 @@ func unparseScript(pops []parsedOpcode) ([]byte, error) {
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// script up to the point the failure occurred along with the string '[error]'
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// appended. In addition, the reason the script failed to parse is returned
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// if the caller wants more information about the failure.
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func DisasmString(buf []byte) (string, error) {
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var disbuf bytes.Buffer
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opcodes, err := parseScript(buf)
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for _, pop := range opcodes {
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disbuf.WriteString(pop.print(true))
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//
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// NOTE: This function is only valid for version 0 scripts. Since the function
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// does not accept a script version, the results are undefined for other script
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// versions.
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func DisasmString(script []byte) (string, error) {
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const scriptVersion = 0
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var disbuf strings.Builder
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tokenizer := MakeScriptTokenizer(scriptVersion, script)
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if tokenizer.Next() {
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disasmOpcode(&disbuf, tokenizer.op, tokenizer.Data(), true)
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}
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for tokenizer.Next() {
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disbuf.WriteByte(' ')
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disasmOpcode(&disbuf, tokenizer.op, tokenizer.Data(), true)
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}
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if disbuf.Len() > 0 {
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disbuf.Truncate(disbuf.Len() - 1)
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}
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if err != nil {
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if tokenizer.Err() != nil {
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if tokenizer.ByteIndex() != 0 {
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disbuf.WriteByte(' ')
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}
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disbuf.WriteString("[error]")
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}
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return disbuf.String(), err
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return disbuf.String(), tokenizer.Err()
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}
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// removeOpcode will remove any opcode matching ``opcode'' from the opcode
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