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https://github.com/FlipsideCrypto/dcrd.git
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d8306ee602
This converts the majority of script errors from generic errors created via errors.New and fmt.Errorf to use a concrete type that implements the error interface with an error code and description. This allows callers to programmatically detect the type of error via type assertions and an error code while still allowing the errors to provide more context. For example, instead of just having an error the reads "disabled opcode" as would happen prior to these changes when a disabled opcode is encountered, the error will now read "attempt to execute disabled opcode OP_FOO". While it was previously possible to programmatically detect many errors due to them being exported, they provided no additional context and there were also various instances that were just returning errors created on the spot which callers could not reliably detect without resorting to looking at the actual error message, which is nearly always bad practice. Also, while here, export the MaxStackSize and MaxScriptSize constants since they can be useful for consumers of the package and perform some minor cleanup of some of the tests.
61 lines
2.2 KiB
Go
61 lines
2.2 KiB
Go
// Copyright (c) 2015-2016 The btcsuite developers
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// Copyright (c) 2015-2017 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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const (
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// LockTimeThreshold is the number below which a lock time is
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// interpreted to be a block number. Since an average of one block
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// is generated per 10 minutes, this allows blocks for about 9,512
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// years.
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LockTimeThreshold = 5e8 // Tue Nov 5 00:53:20 1985 UTC
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// maxUniqueCoinbaseNullDataSize is the maximum number of bytes allowed
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// in the pushed data output of the coinbase output that is used to
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// ensure the coinbase has a unique hash.
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maxUniqueCoinbaseNullDataSize = 256
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)
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// ExtractCoinbaseNullData ensures the passed script is a nulldata script as
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// required by the consensus rules for the coinbase output that is used to
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// ensure the coinbase has a unique hash and returns the data it pushes.
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func ExtractCoinbaseNullData(pkScript []byte) ([]byte, error) {
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pops, err := parseScript(pkScript)
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if err != nil {
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return nil, err
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}
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// The nulldata in the coinbase must be a single OP_RETURN followed by a
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// data push up to maxUniqueCoinbaseNullDataSize bytes.
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//
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// NOTE: This is intentionally not using GetScriptClass and the related
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// functions because those are specifically for standardness checks which
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// can change over time and this function is specifically intended to be
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// used by the consensus rules.
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//
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// Also of note is that technically normal nulldata scripts support encoding
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// numbers via small opcodes, however the consensus rules require the block
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// height to be encoded as a 4-byte little-endian uint32 pushed via a normal
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// data push, as opposed to using the normal number handling semantics of
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// scripts, so this is specialized to accommodate that.
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if len(pops) == 1 && pops[0].opcode.value == OP_RETURN {
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return nil, nil
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}
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if len(pops) == 2 && pops[0].opcode.value == OP_RETURN &&
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pops[1].opcode.value <= OP_PUSHDATA4 && len(pops[1].data) <=
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maxUniqueCoinbaseNullDataSize {
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return pops[1].data, nil
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}
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str := fmt.Sprintf("script %x is not well-formed coinbase nulldata",
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pkScript)
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return nil, scriptError(ErrMalformedCoinbaseNullData, str)
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}
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