cb86bc073c
This implements an efficient and zero-allocation script tokenizer that is exported to both provide a new capability to tokenize scripts to external consumers of the API as well as to serve as a base for refactoring the existing highly inefficient internal code. It is important to note that this tokenizer is intended to be used in consensus critical code in the future, so it must exactly follow the existing semantics. The current script parsing mechanism used throughout the txscript module is to fully tokenize the scripts into an array of internal parsed opcodes which are then examined and passed around in order to implement virtually everything related to scripts. While that approach does simplify the analysis of certain scripts and thus provide some nice properties in that regard, it is both extremely inefficient in many cases, and makes it impossible for external consumers of the API to implement any form of custom script analysis without manually implementing a bunch of error prone tokenizing code or, alternatively, the script engine exposing internal structures. For example, as shown by profiling the total memory allocations of an initial sync, the existing script parsing code allocates a total of around 295.12GB, which equates to around 50% of all allocations performed. The zero-alloc tokenizer this introduces will allow that to be reduced to virtually zero. The following is a before and after comparison of tokenizing a large script with a high opcode count using the existing code versus the tokenizer this introduces for both speed and memory allocations: benchmark old ns/op new ns/op delta ------------------------------------------------------------ BenchmarkScriptParsing 153099 961 -99.37% benchmark old allocs new allocs delta ------------------------------------------------------------ BenchmarkScriptParsing 1 0 -100.00% benchmark old bytes new bytes delta ------------------------------------------------------------ BenchmarkScriptParsing 466945 0 -100.00% The following is an overview of the changes: - Introduce new error code ErrUnsupportedScriptVersion - Implement zero-allocation script tokenizer - Add a full suite of tests to ensure the tokenizer works as intended and follows the required consensus semantics - Add an example of using the new tokenizer to count the number of opcodes in a script - Update README.md to include the new example - Update script parsing benchmark to use the new tokenizer |
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| .. | ||
| data | ||
| bench_test.go | ||
| consensus_test.go | ||
| consensus.go | ||
| doc.go | ||
| engine_test.go | ||
| engine.go | ||
| error_test.go | ||
| error.go | ||
| example_test.go | ||
| go.mod | ||
| go.sum | ||
| log.go | ||
| opcode_test.go | ||
| opcode.go | ||
| README.md | ||
| reference_test.go | ||
| script_test.go | ||
| script.go | ||
| scriptbuilder_test.go | ||
| scriptbuilder.go | ||
| scriptnum_test.go | ||
| scriptnum.go | ||
| sigcache_test.go | ||
| sigcache.go | ||
| sighash_test.go | ||
| sighash.go | ||
| sign_test.go | ||
| sign.go | ||
| stack_test.go | ||
| stack.go | ||
| standard_test.go | ||
| standard.go | ||
| tokenizer_test.go | ||
| tokenizer.go | ||
txscript
Package txscript implements the Decred transaction script language. There is a comprehensive test suite.
This package has intentionally been designed so it can be used as a standalone package for any projects needing to use or validate Decred transaction scripts.
Decred Scripts
Decred provides a stack-based, FORTH-like language for the scripts in the Decred transactions. This language is not turing complete although it is still fairly powerful.
Installation and Updating
$ go get -u github.com/decred/dcrd/txscript
Examples
-
Standard Pay-to-pubkey-hash Script
Demonstrates creating a script which pays to a Decred address. It also prints the created script hex and uses the DisasmString function to display the disassembled script. -
Extracting Details from Standard Scripts
Demonstrates extracting information from a standard public key script. -
Manually Signing a Transaction Output
Demonstrates manually creating and signing a redeem transaction. -
Counting Opcodes in Scripts
Demonstrates creating a script tokenizer instance and using it to count the number of opcodes a script contains.
License
Package txscript is licensed under the copyfree ISC License.