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txscript: Store flags in instance versus bools.

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Rather than storing a separate bool for whether or not each flag is set in
every script engine instance, store the flags and check if the relevant
flag is set from each specific location.

This reduces the memory needed by each script engine instance and means
future flags will not require new fields.
This commit is contained in:
Dave Collins 2015-04-20 17:58:04 -05:00
parent 43c053bbfe
commit 0baac03129
3 changed files with 46 additions and 54 deletions
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81
txscript/engine.go
View file

@ -80,24 +80,24 @@ const (
// Engine is the virtual machine that executes scripts.
type Engine struct {
scripts [][]parsedOpcode
scriptIdx int
scriptOff int
lastcodesep int
dstack Stack // data stack
astack Stack // alt stack
tx wire.MsgTx
txIdx int
condStack []int
numOps int
bip16 bool // treat execution as pay-to-script-hash
strictMultiSig bool // verify multisig stack item is zero length
discourageUpgradableNops bool // NOP1 to NOP10 are reserved for future soft-fork upgrades
verifyStrictEncoding bool // verify strict encoding of signatures
verifyCleanStack bool // verify stack is clean after script evaluation
verifyDERSignatures bool // verify signatures comply with the DER format
verifyLowS bool // verify signatures comply with the DER format and have an S value <= halforder
savedFirstStack [][]byte // stack from first script for bip16 scripts
scripts [][]parsedOpcode
scriptIdx int
scriptOff int
lastcodesep int
dstack Stack // data stack
astack Stack // alt stack
tx wire.MsgTx
txIdx int
condStack []int
numOps int
flags ScriptFlags
bip16 bool // treat execution as pay-to-script-hash
savedFirstStack [][]byte // stack from first script for bip16 scripts
}
// hasFlag returns whether the script engine instance has the passed flag set.
func (vm *Engine) hasFlag(flag ScriptFlags) bool {
return vm.flags&flag == flag
}
// Execute will execute all script in the script engine and return either nil
@ -144,7 +144,9 @@ func (vm *Engine) CheckErrorCondition(finalScript bool) error {
if vm.scriptIdx < len(vm.scripts) {
return ErrStackScriptUnfinished
}
if finalScript && vm.verifyCleanStack && vm.dstack.Depth() != 1 {
if finalScript && vm.hasFlag(ScriptVerifyCleanStack) &&
vm.dstack.Depth() != 1 {
return ErrStackCleanStack
} else if vm.dstack.Depth() < 1 {
return ErrStackEmptyStack
@ -302,7 +304,7 @@ func (vm *Engine) subScript() []parsedOpcode {
// checkHashTypeEncoding returns whether or not the passed hashtype adheres to
// the strict encoding requirements if enabled.
func (vm *Engine) checkHashTypeEncoding(hashType SigHashType) error {
if !vm.verifyStrictEncoding {
if !vm.hasFlag(ScriptVerifyStrictEncoding) {
return nil
}
@ -316,7 +318,7 @@ func (vm *Engine) checkHashTypeEncoding(hashType SigHashType) error {
// checkPubKeyEncoding returns whether or not the passed public key adheres to
// the strict encoding requirements if enabled.
func (vm *Engine) checkPubKeyEncoding(pubKey []byte) error {
if !vm.verifyStrictEncoding {
if !vm.hasFlag(ScriptVerifyStrictEncoding) {
return nil
}
@ -334,7 +336,10 @@ func (vm *Engine) checkPubKeyEncoding(pubKey []byte) error {
// checkSignatureEncoding returns whether or not the passed signature adheres to
// the strict encoding requirements if enabled.
func (vm *Engine) checkSignatureEncoding(sig []byte) error {
if !vm.verifyDERSignatures && !vm.verifyLowS && !vm.verifyStrictEncoding {
if !vm.hasFlag(ScriptVerifyDERSignatures) &&
!vm.hasFlag(ScriptVerifyLowS) &&
!vm.hasFlag(ScriptVerifyStrictEncoding) {
return nil
}
@ -417,7 +422,7 @@ func (vm *Engine) checkSignatureEncoding(sig []byte) error {
}
// Verify the S value is <= halforder.
if vm.verifyLowS {
if vm.hasFlag(ScriptVerifyLowS) {
sValue := new(big.Int).SetBytes(sig[rLen+6 : rLen+6+sLen])
if sValue.Cmp(halfOrder) > 0 {
return ErrStackInvalidLowSSignature
@ -481,8 +486,8 @@ func NewEngine(scriptPubKey []byte, tx *wire.MsgTx, txIdx int, flags ScriptFlags
}
scriptSig := tx.TxIn[txIdx].SignatureScript
var vm Engine
if flags&ScriptVerifySigPushOnly != 0 && !IsPushOnlyScript(scriptSig) {
vm := Engine{flags: flags}
if vm.hasFlag(ScriptVerifySigPushOnly) && !IsPushOnlyScript(scriptSig) {
return nil, ErrStackNonPushOnly
}
@ -508,7 +513,7 @@ func NewEngine(scriptPubKey []byte, tx *wire.MsgTx, txIdx int, flags ScriptFlags
}
// Parse flags.
if flags&ScriptBip16 == ScriptBip16 && isScriptHash(vm.scripts[1]) {
if vm.hasFlag(ScriptBip16) && isScriptHash(vm.scripts[1]) {
// if we are pay to scripthash then we only accept input
// scripts that push data
if !isPushOnly(vm.scripts[0]) {
@ -516,30 +521,12 @@ func NewEngine(scriptPubKey []byte, tx *wire.MsgTx, txIdx int, flags ScriptFlags
}
vm.bip16 = true
}
if flags&ScriptStrictMultiSig == ScriptStrictMultiSig {
vm.strictMultiSig = true
}
if flags&ScriptDiscourageUpgradableNops == ScriptDiscourageUpgradableNops {
vm.discourageUpgradableNops = true
}
if flags&ScriptVerifyStrictEncoding == ScriptVerifyStrictEncoding {
vm.verifyStrictEncoding = true
}
if flags&ScriptVerifyDERSignatures == ScriptVerifyDERSignatures {
vm.verifyDERSignatures = true
}
if flags&ScriptVerifyMinimalData == ScriptVerifyMinimalData {
if vm.hasFlag(ScriptVerifyMinimalData) {
vm.dstack.verifyMinimalData = true
vm.astack.verifyMinimalData = true
}
if flags&ScriptVerifyCleanStack == ScriptVerifyCleanStack {
if flags&ScriptBip16 != ScriptBip16 {
return nil, ErrInvalidFlags
}
vm.verifyCleanStack = true
}
if flags&ScriptVerifyLowS == ScriptVerifyLowS {
vm.verifyLowS = true
if vm.hasFlag(ScriptVerifyCleanStack) && !vm.hasFlag(ScriptBip16) {
return nil, ErrInvalidFlags
}
vm.tx = *tx

4
txscript/internal_test.go
View file

@ -79,7 +79,7 @@ func TestCheckPubKeyEncoding(t *testing.T) {
isValid: false,
},
}
vm := Engine{verifyStrictEncoding: true}
vm := Engine{flags: ScriptVerifyStrictEncoding}
for _, test := range tests {
err := vm.checkPubKeyEncoding(test.key)
if err != nil && test.isValid {
@ -337,7 +337,7 @@ func TestCheckSignatureEncoding(t *testing.T) {
},
}
vm := Engine{verifyStrictEncoding: true}
vm := Engine{flags: ScriptVerifyStrictEncoding}
for _, test := range tests {
err := vm.checkSignatureEncoding(test.sig)
if err != nil && test.isValid {

15
txscript/opcode.go
View file

@ -1131,8 +1131,9 @@ func opcodeNop(op *parsedOpcode, vm *Engine) error {
switch op.opcode.value {
case OP_NOP1, OP_NOP2, OP_NOP3, OP_NOP4, OP_NOP5,
OP_NOP6, OP_NOP7, OP_NOP8, OP_NOP9, OP_NOP10:
if vm.discourageUpgradableNops {
return fmt.Errorf("%s reserved for soft-fork upgrades", opcodemap[op.opcode.value].name)
if vm.hasFlag(ScriptDiscourageUpgradableNops) {
return fmt.Errorf("%s reserved for soft-fork upgrades",
opcodemap[op.opcode.value].name)
}
}
return nil
@ -1850,7 +1851,9 @@ func opcodeCheckSig(op *parsedOpcode, vm *Engine) error {
}
var signature *btcec.Signature
if vm.verifyStrictEncoding || vm.verifyDERSignatures {
if vm.hasFlag(ScriptVerifyStrictEncoding) ||
vm.hasFlag(ScriptVerifyDERSignatures) {
signature, err = btcec.ParseDERSignature(sigStr, btcec.S256())
} else {
signature, err = btcec.ParseSignature(sigStr, btcec.S256())
@ -1951,7 +1954,7 @@ func opcodeCheckMultiSig(op *parsedOpcode, vm *Engine) error {
return err
}
if vm.strictMultiSig && len(dummy) != 0 {
if vm.hasFlag(ScriptStrictMultiSig) && len(dummy) != 0 {
return fmt.Errorf("multisig dummy argument is not zero length: %d",
len(dummy))
}
@ -2010,7 +2013,9 @@ func opcodeCheckMultiSig(op *parsedOpcode, vm *Engine) error {
// Parse the signature.
var err error
if vm.verifyStrictEncoding || vm.verifyDERSignatures {
if vm.hasFlag(ScriptVerifyStrictEncoding) ||
vm.hasFlag(ScriptVerifyDERSignatures) {
parsedSig, err = btcec.ParseDERSignature(signature,
btcec.S256())
} else {