txscript: Optimize ExtractAtomicSwapDataPushes.
This converts the ExtractAtomicSwapDataPushes function to make use of the new tokenizer instead of the far less efficient parseScript thereby significantly optimizing the function. The new implementation is designed such that it should be fairly easy to move the function into the atomic swap tools where it more naturally belongs now that the tokenizer makes it possible to analyze scripts outside of the txscript module. Consequently, this also deprecates the function. The following is a before and after comparison of attempting to extract from both a typical atomic swap script and a very large non-atomic swap script: benchmark old ns/op new ns/op delta BenchmarkExtractAtomicSwapDataPushesLarge-8 61332 44.4 -99.93% BenchmarkExtractAtomicSwapDataPushes-8 990 260 -73.74% benchmark old allocs new allocs delta BenchmarkExtractAtomicSwapDataPushesLarge-8 1 0 -100.00% BenchmarkExtractAtomicSwapDataPushes-8 2 1 -50.00% benchmark old bytes new bytes delta BenchmarkExtractAtomicSwapDataPushesLarge-8 311299 0 -100.00% BenchmarkExtractAtomicSwapDataPushes-8 3168 96 -96.97%
This commit is contained in:
Dave Collins
Roy Lee
parent
767dae7adf
commit
96c8bc1e93
1 changed files with 91 additions and 53 deletions
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@ -942,64 +942,102 @@ type AtomicSwapDataPushes struct {
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//
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// This function is only defined in the txscript package due to API limitations
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// which prevent callers using txscript to parse nonstandard scripts.
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//
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// DEPRECATED. This will be removed in the next major version bump. The error
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// should also likely be removed if the code is reimplemented by any callers
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// since any errors result in a nil result anyway.
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func ExtractAtomicSwapDataPushes(version uint16, pkScript []byte) (*AtomicSwapDataPushes, error) {
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pops, err := parseScript(pkScript)
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if err != nil {
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// An atomic swap is of the form:
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// IF
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// SIZE <secret size> EQUALVERIFY SHA256 <32-byte secret> EQUALVERIFY DUP
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// HASH160 <20-byte recipient hash>
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// ELSE
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// <locktime> CHECKLOCKTIMEVERIFY DROP DUP HASH160 <20-byte refund hash>
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// ENDIF
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// EQUALVERIFY CHECKSIG
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type templateMatch struct {
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expectCanonicalInt bool
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maxIntBytes int
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opcode byte
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extractedInt int64
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extractedData []byte
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}
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var template = [20]templateMatch{
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{opcode: OP_IF},
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{opcode: OP_SIZE},
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{expectCanonicalInt: true, maxIntBytes: maxScriptNumLen},
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{opcode: OP_EQUALVERIFY},
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{opcode: OP_SHA256},
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{opcode: OP_DATA_32},
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{opcode: OP_EQUALVERIFY},
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{opcode: OP_DUP},
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{opcode: OP_HASH160},
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{opcode: OP_DATA_20},
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{opcode: OP_ELSE},
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{expectCanonicalInt: true, maxIntBytes: cltvMaxScriptNumLen},
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{opcode: OP_CHECKLOCKTIMEVERIFY},
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{opcode: OP_DROP},
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{opcode: OP_DUP},
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{opcode: OP_HASH160},
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{opcode: OP_DATA_20},
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{opcode: OP_ENDIF},
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{opcode: OP_EQUALVERIFY},
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{opcode: OP_CHECKSIG},
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}
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var templateOffset int
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tokenizer := MakeScriptTokenizer(version, pkScript)
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for tokenizer.Next() {
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// Not an atomic swap script if it has more opcodes than expected in the
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// template.
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if templateOffset >= len(template) {
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return nil, nil
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}
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op := tokenizer.Opcode()
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data := tokenizer.Data()
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tplEntry := &template[templateOffset]
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if tplEntry.expectCanonicalInt {
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switch {
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case data != nil:
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val, err := makeScriptNum(data, true, tplEntry.maxIntBytes)
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if err != nil {
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return nil, err
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}
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tplEntry.extractedInt = int64(val)
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case isSmallInt(op):
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tplEntry.extractedInt = int64(asSmallInt(op))
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// Not an atomic swap script if the opcode does not push an int.
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default:
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return nil, nil
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}
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} else {
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if op != tplEntry.opcode {
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return nil, nil
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}
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tplEntry.extractedData = data
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}
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templateOffset++
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}
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if err := tokenizer.Err(); err != nil {
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return nil, err
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}
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if len(pops) != 20 {
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return nil, nil
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}
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isAtomicSwap := pops[0].opcode.value == OP_IF &&
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pops[1].opcode.value == OP_SIZE &&
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isCanonicalPush(pops[2].opcode.value, pops[2].data) &&
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pops[3].opcode.value == OP_EQUALVERIFY &&
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pops[4].opcode.value == OP_SHA256 &&
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pops[5].opcode.value == OP_DATA_32 &&
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pops[6].opcode.value == OP_EQUALVERIFY &&
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pops[7].opcode.value == OP_DUP &&
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pops[8].opcode.value == OP_HASH160 &&
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pops[9].opcode.value == OP_DATA_20 &&
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pops[10].opcode.value == OP_ELSE &&
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isCanonicalPush(pops[11].opcode.value, pops[11].data) &&
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pops[12].opcode.value == OP_CHECKLOCKTIMEVERIFY &&
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pops[13].opcode.value == OP_DROP &&
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pops[14].opcode.value == OP_DUP &&
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pops[15].opcode.value == OP_HASH160 &&
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pops[16].opcode.value == OP_DATA_20 &&
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pops[17].opcode.value == OP_ENDIF &&
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pops[18].opcode.value == OP_EQUALVERIFY &&
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pops[19].opcode.value == OP_CHECKSIG
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if !isAtomicSwap {
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if !tokenizer.Done() || templateOffset != len(template) {
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return nil, nil
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}
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pushes := new(AtomicSwapDataPushes)
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copy(pushes.SecretHash[:], pops[5].data)
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copy(pushes.RecipientHash160[:], pops[9].data)
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copy(pushes.RefundHash160[:], pops[16].data)
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if pops[2].data != nil {
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locktime, err := makeScriptNum(pops[2].data, true, 5)
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if err != nil {
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return nil, nil
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}
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pushes.SecretSize = int64(locktime)
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} else if op := pops[2].opcode; isSmallInt(op.value) {
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pushes.SecretSize = int64(asSmallInt(op.value))
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} else {
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return nil, nil
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// At this point, the script appears to be an atomic swap, so populate and
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// return the extacted data.
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pushes := AtomicSwapDataPushes{
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SecretSize: template[2].extractedInt,
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LockTime: template[11].extractedInt,
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}
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if pops[11].data != nil {
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locktime, err := makeScriptNum(pops[11].data, true, 5)
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if err != nil {
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return nil, nil
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}
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pushes.LockTime = int64(locktime)
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} else if op := pops[11].opcode; isSmallInt(op.value) {
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pushes.LockTime = int64(asSmallInt(op.value))
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} else {
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return nil, nil
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}
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return pushes, nil
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copy(pushes.SecretHash[:], template[5].extractedData)
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copy(pushes.RecipientHash160[:], template[9].extractedData)
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copy(pushes.RefundHash160[:], template[16].extractedData)
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return &pushes, nil
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}
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