ac002d6422
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-8 63464 677 -98.93% benchmark old allocs new allocs delta BenchmarkScriptParsing-8 1 0 -100.00% benchmark old bytes new bytes delta BenchmarkScriptParsing-8 311299 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
460 lines
18 KiB
Go
460 lines
18 KiB
Go
// Copyright (c) 2013-2017 The btcsuite developers
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// Copyright (c) 2015-2019 The Decred developers
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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package txscript
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import (
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"fmt"
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)
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// ErrorCode identifies a kind of script error.
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type ErrorCode int
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// These constants are used to identify a specific Error.
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const (
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// ErrInternal is returned if internal consistency checks fail. In
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// practice this error should never be seen as it would mean there is an
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// error in the engine logic.
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ErrInternal ErrorCode = iota
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// ---------------------------------------
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// Failures related to improper API usage.
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// ---------------------------------------
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// ErrInvalidFlags is returned when the passed flags to NewEngine
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// contain an invalid combination.
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ErrInvalidFlags
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// ErrInvalidIndex is returned when an out-of-bounds index is passed to
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// a function.
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ErrInvalidIndex
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// ErrUnsupportedAddress is returned when a concrete type that
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// implements a btcutil.Address is not a supported type.
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ErrUnsupportedAddress
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// ErrNotMultisigScript is returned from CalcMultiSigStats when the
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// provided script is not a multisig script.
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ErrNotMultisigScript
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// ErrTooManyRequiredSigs is returned from MultiSigScript when the
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// specified number of required signatures is larger than the number of
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// provided public keys.
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ErrTooManyRequiredSigs
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// ErrTooMuchNullData is returned from NullDataScript when the length of
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// the provided data exceeds MaxDataCarrierSize.
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ErrTooMuchNullData
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// ErrUnsupportedScriptVersion is returned when an unsupported script
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// version is passed to a function which deals with script analysis.
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ErrUnsupportedScriptVersion
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// ------------------------------------------
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// Failures related to final execution state.
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// ------------------------------------------
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// ErrEarlyReturn is returned when OP_RETURN is executed in the script.
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ErrEarlyReturn
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// ErrEmptyStack is returned when the script evaluated without error,
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// but terminated with an empty top stack element.
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ErrEmptyStack
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// ErrEvalFalse is returned when the script evaluated without error but
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// terminated with a false top stack element.
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ErrEvalFalse
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// ErrScriptUnfinished is returned when CheckErrorCondition is called on
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// a script that has not finished executing.
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ErrScriptUnfinished
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// ErrScriptDone is returned when an attempt to execute an opcode is
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// made once all of them have already been executed. This can happen
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// due to things such as a second call to Execute or calling Step after
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// all opcodes have already been executed.
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ErrInvalidProgramCounter
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// -----------------------------------------------------
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// Failures related to exceeding maximum allowed limits.
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// -----------------------------------------------------
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// ErrScriptTooBig is returned if a script is larger than MaxScriptSize.
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ErrScriptTooBig
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// ErrElementTooBig is returned if the size of an element to be pushed
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// to the stack is over MaxScriptElementSize.
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ErrElementTooBig
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// ErrTooManyOperations is returned if a script has more than
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// MaxOpsPerScript opcodes that do not push data.
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ErrTooManyOperations
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// ErrStackOverflow is returned when stack and altstack combined depth
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// is over the limit.
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ErrStackOverflow
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// ErrInvalidPubKeyCount is returned when the number of public keys
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// specified for a multsig is either negative or greater than
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// MaxPubKeysPerMultiSig.
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ErrInvalidPubKeyCount
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// ErrInvalidSignatureCount is returned when the number of signatures
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// specified for a multisig is either negative or greater than the
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// number of public keys.
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ErrInvalidSignatureCount
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// ErrNumberTooBig is returned when the argument for an opcode that
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// expects numeric input is larger than the expected maximum number of
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// bytes. For the most part, opcodes that deal with stack manipulation
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// via offsets, arithmetic, numeric comparison, and boolean logic are
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// those that this applies to. However, any opcode that expects numeric
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// input may fail with this code.
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ErrNumberTooBig
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// --------------------------------------------
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// Failures related to verification operations.
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// --------------------------------------------
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// ErrVerify is returned when OP_VERIFY is encountered in a script and
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// the top item on the data stack does not evaluate to true.
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ErrVerify
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// ErrEqualVerify is returned when OP_EQUALVERIFY is encountered in a
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// script and the top item on the data stack does not evaluate to true.
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ErrEqualVerify
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// ErrNumEqualVerify is returned when OP_NUMEQUALVERIFY is encountered
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// in a script and the top item on the data stack does not evaluate to
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// true.
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ErrNumEqualVerify
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// ErrCheckSigVerify is returned when OP_CHECKSIGVERIFY is encountered
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// in a script and the top item on the data stack does not evaluate to
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// true.
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ErrCheckSigVerify
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// ErrCheckSigVerify is returned when OP_CHECKMULTISIGVERIFY is
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// encountered in a script and the top item on the data stack does not
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// evaluate to true.
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ErrCheckMultiSigVerify
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// --------------------------------------------
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// Failures related to improper use of opcodes.
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// --------------------------------------------
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// ErrDisabledOpcode is returned when a disabled opcode is encountered
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// in a script.
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ErrDisabledOpcode
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// ErrReservedOpcode is returned when an opcode marked as reserved
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// is encountered in a script.
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ErrReservedOpcode
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// ErrMalformedPush is returned when a data push opcode tries to push
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// more bytes than are left in the script.
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ErrMalformedPush
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// ErrInvalidStackOperation is returned when a stack operation is
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// attempted with a number that is invalid for the current stack size.
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ErrInvalidStackOperation
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// ErrUnbalancedConditional is returned when an OP_ELSE or OP_ENDIF is
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// encountered in a script without first having an OP_IF or OP_NOTIF or
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// the end of script is reached without encountering an OP_ENDIF when
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// an OP_IF or OP_NOTIF was previously encountered.
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ErrUnbalancedConditional
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// ---------------------------------
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// Failures related to malleability.
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// ---------------------------------
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// ErrMinimalData is returned when the ScriptVerifyMinimalData flag
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// is set and the script contains push operations that do not use
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// the minimal opcode required.
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ErrMinimalData
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// ErrInvalidSigHashType is returned when a signature hash type is not
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// one of the supported types.
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ErrInvalidSigHashType
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// ErrSigTooShort is returned when a signature that should be a
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// canonically-encoded DER signature is too short.
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ErrSigTooShort
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// ErrSigTooLong is returned when a signature that should be a
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// canonically-encoded DER signature is too long.
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ErrSigTooLong
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// ErrSigInvalidSeqID is returned when a signature that should be a
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// canonically-encoded DER signature does not have the expected ASN.1
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// sequence ID.
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ErrSigInvalidSeqID
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// ErrSigInvalidDataLen is returned a signature that should be a
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// canonically-encoded DER signature does not specify the correct number
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// of remaining bytes for the R and S portions.
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ErrSigInvalidDataLen
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// ErrSigMissingSTypeID is returned a signature that should be a
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// canonically-encoded DER signature does not provide the ASN.1 type ID
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// for S.
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ErrSigMissingSTypeID
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// ErrSigMissingSLen is returned when a signature that should be a
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// canonically-encoded DER signature does not provide the length of S.
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ErrSigMissingSLen
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// ErrSigInvalidSLen is returned a signature that should be a
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// canonically-encoded DER signature does not specify the correct number
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// of bytes for the S portion.
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ErrSigInvalidSLen
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// ErrSigInvalidRIntID is returned when a signature that should be a
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// canonically-encoded DER signature does not have the expected ASN.1
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// integer ID for R.
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ErrSigInvalidRIntID
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// ErrSigZeroRLen is returned when a signature that should be a
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// canonically-encoded DER signature has an R length of zero.
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ErrSigZeroRLen
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// ErrSigNegativeR is returned when a signature that should be a
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// canonically-encoded DER signature has a negative value for R.
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ErrSigNegativeR
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// ErrSigTooMuchRPadding is returned when a signature that should be a
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// canonically-encoded DER signature has too much padding for R.
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ErrSigTooMuchRPadding
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// ErrSigInvalidSIntID is returned when a signature that should be a
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// canonically-encoded DER signature does not have the expected ASN.1
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// integer ID for S.
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ErrSigInvalidSIntID
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// ErrSigZeroSLen is returned when a signature that should be a
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// canonically-encoded DER signature has an S length of zero.
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ErrSigZeroSLen
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// ErrSigNegativeS is returned when a signature that should be a
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// canonically-encoded DER signature has a negative value for S.
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ErrSigNegativeS
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// ErrSigTooMuchSPadding is returned when a signature that should be a
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// canonically-encoded DER signature has too much padding for S.
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ErrSigTooMuchSPadding
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// ErrSigHighS is returned when the ScriptVerifyLowS flag is set and the
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// script contains any signatures whose S values are higher than the
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// half order.
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ErrSigHighS
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// ErrNotPushOnly is returned when a script that is required to only
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// push data to the stack performs other operations. A couple of cases
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// where this applies is for a pay-to-script-hash signature script when
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// bip16 is active and when the ScriptVerifySigPushOnly flag is set.
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ErrNotPushOnly
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// ErrSigNullDummy is returned when the ScriptStrictMultiSig flag is set
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// and a multisig script has anything other than 0 for the extra dummy
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// argument.
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ErrSigNullDummy
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// ErrPubKeyType is returned when the ScriptVerifyStrictEncoding
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// flag is set and the script contains invalid public keys.
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ErrPubKeyType
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// ErrCleanStack is returned when the ScriptVerifyCleanStack flag
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// is set, and after evalution, the stack does not contain only a
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// single element.
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ErrCleanStack
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// ErrNullFail is returned when the ScriptVerifyNullFail flag is
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// set and signatures are not empty on failed checksig or checkmultisig
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// operations.
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ErrNullFail
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// ErrWitnessMalleated is returned if ScriptVerifyWitness is set and a
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// native p2wsh program is encountered which has a non-empty sigScript.
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ErrWitnessMalleated
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// ErrWitnessMalleatedP2SH is returned if ScriptVerifyWitness if set
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// and the validation logic for nested p2sh encounters a sigScript
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// which isn't *exactyl* a datapush of the witness program.
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ErrWitnessMalleatedP2SH
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// -------------------------------
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// Failures related to soft forks.
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// -------------------------------
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// ErrDiscourageUpgradableNOPs is returned when the
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// ScriptDiscourageUpgradableNops flag is set and a NOP opcode is
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// encountered in a script.
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ErrDiscourageUpgradableNOPs
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// ErrNegativeLockTime is returned when a script contains an opcode that
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// interprets a negative lock time.
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ErrNegativeLockTime
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// ErrUnsatisfiedLockTime is returned when a script contains an opcode
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// that involves a lock time and the required lock time has not been
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// reached.
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ErrUnsatisfiedLockTime
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// ErrMinimalIf is returned if ScriptVerifyWitness is set and the
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// operand of an OP_IF/OP_NOF_IF are not either an empty vector or
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// [0x01].
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ErrMinimalIf
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// ErrDiscourageUpgradableWitnessProgram is returned if
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// ScriptVerifyWitness is set and the versino of an executing witness
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// program is outside the set of currently defined witness program
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// vesions.
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ErrDiscourageUpgradableWitnessProgram
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// ----------------------------------------
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// Failures related to segregated witness.
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// ----------------------------------------
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// ErrWitnessProgramEmpty is returned if ScriptVerifyWitness is set and
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// the witness stack itself is empty.
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ErrWitnessProgramEmpty
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// ErrWitnessProgramMismatch is returned if ScriptVerifyWitness is set
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// and the witness itself for a p2wkh witness program isn't *exactly* 2
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// items or if the witness for a p2wsh isn't the sha255 of the witness
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// script.
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ErrWitnessProgramMismatch
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// ErrWitnessProgramWrongLength is returned if ScriptVerifyWitness is
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// set and the length of the witness program violates the length as
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// dictated by the current witness version.
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ErrWitnessProgramWrongLength
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// ErrWitnessUnexpected is returned if ScriptVerifyWitness is set and a
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// transaction includes witness data but doesn't spend an which is a
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// witness program (nested or native).
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ErrWitnessUnexpected
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// ErrWitnessPubKeyType is returned if ScriptVerifyWitness is set and
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// the public key used in either a check-sig or check-multi-sig isn't
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// serialized in a compressed format.
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ErrWitnessPubKeyType
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// numErrorCodes is the maximum error code number used in tests. This
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// entry MUST be the last entry in the enum.
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numErrorCodes
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)
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// Map of ErrorCode values back to their constant names for pretty printing.
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var errorCodeStrings = map[ErrorCode]string{
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ErrInternal: "ErrInternal",
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ErrInvalidFlags: "ErrInvalidFlags",
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ErrInvalidIndex: "ErrInvalidIndex",
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ErrUnsupportedAddress: "ErrUnsupportedAddress",
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ErrNotMultisigScript: "ErrNotMultisigScript",
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ErrTooManyRequiredSigs: "ErrTooManyRequiredSigs",
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ErrTooMuchNullData: "ErrTooMuchNullData",
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ErrUnsupportedScriptVersion: "ErrUnsupportedScriptVersion",
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ErrEarlyReturn: "ErrEarlyReturn",
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ErrEmptyStack: "ErrEmptyStack",
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ErrEvalFalse: "ErrEvalFalse",
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ErrScriptUnfinished: "ErrScriptUnfinished",
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ErrInvalidProgramCounter: "ErrInvalidProgramCounter",
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ErrScriptTooBig: "ErrScriptTooBig",
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ErrElementTooBig: "ErrElementTooBig",
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ErrTooManyOperations: "ErrTooManyOperations",
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ErrStackOverflow: "ErrStackOverflow",
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ErrInvalidPubKeyCount: "ErrInvalidPubKeyCount",
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ErrInvalidSignatureCount: "ErrInvalidSignatureCount",
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ErrNumberTooBig: "ErrNumberTooBig",
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ErrVerify: "ErrVerify",
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ErrEqualVerify: "ErrEqualVerify",
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ErrNumEqualVerify: "ErrNumEqualVerify",
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ErrCheckSigVerify: "ErrCheckSigVerify",
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ErrCheckMultiSigVerify: "ErrCheckMultiSigVerify",
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ErrDisabledOpcode: "ErrDisabledOpcode",
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ErrReservedOpcode: "ErrReservedOpcode",
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ErrMalformedPush: "ErrMalformedPush",
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ErrInvalidStackOperation: "ErrInvalidStackOperation",
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ErrUnbalancedConditional: "ErrUnbalancedConditional",
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ErrMinimalData: "ErrMinimalData",
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ErrInvalidSigHashType: "ErrInvalidSigHashType",
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ErrSigTooShort: "ErrSigTooShort",
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ErrSigTooLong: "ErrSigTooLong",
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ErrSigInvalidSeqID: "ErrSigInvalidSeqID",
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ErrSigInvalidDataLen: "ErrSigInvalidDataLen",
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ErrSigMissingSTypeID: "ErrSigMissingSTypeID",
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ErrSigMissingSLen: "ErrSigMissingSLen",
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ErrSigInvalidSLen: "ErrSigInvalidSLen",
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ErrSigInvalidRIntID: "ErrSigInvalidRIntID",
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ErrSigZeroRLen: "ErrSigZeroRLen",
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ErrSigNegativeR: "ErrSigNegativeR",
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ErrSigTooMuchRPadding: "ErrSigTooMuchRPadding",
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ErrSigInvalidSIntID: "ErrSigInvalidSIntID",
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ErrSigZeroSLen: "ErrSigZeroSLen",
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ErrSigNegativeS: "ErrSigNegativeS",
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ErrSigTooMuchSPadding: "ErrSigTooMuchSPadding",
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ErrSigHighS: "ErrSigHighS",
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ErrNotPushOnly: "ErrNotPushOnly",
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ErrSigNullDummy: "ErrSigNullDummy",
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ErrPubKeyType: "ErrPubKeyType",
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ErrCleanStack: "ErrCleanStack",
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ErrNullFail: "ErrNullFail",
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ErrDiscourageUpgradableNOPs: "ErrDiscourageUpgradableNOPs",
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ErrNegativeLockTime: "ErrNegativeLockTime",
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ErrUnsatisfiedLockTime: "ErrUnsatisfiedLockTime",
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ErrWitnessProgramEmpty: "ErrWitnessProgramEmpty",
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ErrWitnessProgramMismatch: "ErrWitnessProgramMismatch",
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ErrWitnessProgramWrongLength: "ErrWitnessProgramWrongLength",
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ErrWitnessMalleated: "ErrWitnessMalleated",
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ErrWitnessMalleatedP2SH: "ErrWitnessMalleatedP2SH",
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ErrWitnessUnexpected: "ErrWitnessUnexpected",
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ErrMinimalIf: "ErrMinimalIf",
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ErrWitnessPubKeyType: "ErrWitnessPubKeyType",
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ErrDiscourageUpgradableWitnessProgram: "ErrDiscourageUpgradableWitnessProgram",
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}
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// String returns the ErrorCode as a human-readable name.
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func (e ErrorCode) String() string {
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if s := errorCodeStrings[e]; s != "" {
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return s
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}
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return fmt.Sprintf("Unknown ErrorCode (%d)", int(e))
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}
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// Error identifies a script-related error. It is used to indicate three
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// classes of errors:
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// 1) Script execution failures due to violating one of the many requirements
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// imposed by the script engine or evaluating to false
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// 2) Improper API usage by callers
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// 3) Internal consistency check failures
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//
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// The caller can use type assertions on the returned errors to access the
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// ErrorCode field to ascertain the specific reason for the error. As an
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// additional convenience, the caller may make use of the IsErrorCode function
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// to check for a specific error code.
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type Error struct {
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ErrorCode ErrorCode
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Description string
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}
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// Error satisfies the error interface and prints human-readable errors.
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func (e Error) Error() string {
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return e.Description
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}
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// scriptError creates an Error given a set of arguments.
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func scriptError(c ErrorCode, desc string) Error {
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return Error{ErrorCode: c, Description: desc}
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}
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// IsErrorCode returns whether or not the provided error is a script error with
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// the provided error code.
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func IsErrorCode(err error, c ErrorCode) bool {
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serr, ok := err.(Error)
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return ok && serr.ErrorCode == c
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}
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