Documentation ¶
Overview ¶
Package txscript implements the Decred transaction script language.
This package provides data structures and functions to parse and execute decred transaction scripts.
Script Overview ¶
Decred transaction scripts are written in a stack-base, FORTH-like language.
The Decred script language consists of a number of opcodes which fall into several categories such pushing and popping data to and from the stack, performing basic and bitwise arithmetic, conditional branching, comparing hashes, and checking cryptographic signatures. Scripts are processed from left to right and intentionally do not provide loops.
The vast majority of Decred scripts at the time of this writing are of several standard forms which consist of a spender providing a public key and a signature which proves the spender owns the associated private key. This information is used to prove the spender is authorized to perform the transaction.
One benefit of using a scripting language is added flexibility in specifying what conditions must be met in order to spend decred.
Errors ¶
The errors returned by this package are of type txscript.ErrorKind wrapped by txscript.Error which has full support for the standard library errors.Is and errors.As functions. This allows the caller to programmatically determine the specific error while still providing rich error messages with contextual information. See the constants defined with ErrorKind in the package documentation for a full list.
Index ¶
- Constants
- Variables
- func AsSmallInt(op byte) int
- func CalcSignatureHash(script []byte, hashType SigHashType, tx *wire.MsgTx, idx int, ...) ([]byte, error)
- func CanonicalDataSize(data []byte) int
- func CheckHashTypeEncoding(hashType SigHashType) error
- func CheckPubKeyEncoding(pubKey []byte) error
- func CheckSignatureEncoding(sig []byte) error
- func ContainsStakeOpCodes(pkScript []byte, isTreasuryEnabled bool) (bool, error)
- func DisasmString(script []byte) (string, error)
- func ExtractScriptHash(script []byte) []byte
- func GenerateSSGenBlockRef(blockHash chainhash.Hash, height uint32) ([]byte, error)
- func GenerateSSGenVotes(votebits uint16) ([]byte, error)
- func GetPreciseSigOpCount(scriptSig, scriptPubKey []byte, isTreasuryEnabled bool) int
- func GetSigOpCount(script []byte, isTreasuryEnabled bool) int
- func IsDERSigError(err error) bool
- func IsPayToScriptHash(script []byte) bool
- func IsPushOnlyScript(script []byte) bool
- func IsSmallInt(op byte) bool
- func IsStrictCompressedPubKeyEncoding(pubKey []byte) bool
- func IsStrictNullData(scriptVersion uint16, script []byte, requiredLen uint32) bool
- func IsStrictSignatureEncoding(signature []byte) bool
- func IsUnspendable(amount int64, pkScript []byte) bool
- func UseLogger(logger slog.Logger)
- type Engine
- func (vm *Engine) CheckErrorCondition(finalScript bool) error
- func (vm *Engine) DisasmPC() (string, error)
- func (vm *Engine) DisasmScript(idx int) (string, error)
- func (vm *Engine) Execute() (err error)
- func (vm *Engine) GetAltStack() [][]byte
- func (vm *Engine) GetStack() [][]byte
- func (vm *Engine) SetAltStack(data [][]byte)
- func (vm *Engine) SetStack(data [][]byte)
- func (vm *Engine) Step() (done bool, err error)
- type ErrScriptNotCanonical
- type Error
- type ErrorKind
- type ScriptBuilder
- func (b *ScriptBuilder) AddData(data []byte) *ScriptBuilder
- func (b *ScriptBuilder) AddDataUnchecked(data []byte) *ScriptBuilder
- func (b *ScriptBuilder) AddInt64(val int64) *ScriptBuilder
- func (b *ScriptBuilder) AddOp(opcode byte) *ScriptBuilder
- func (b *ScriptBuilder) AddOps(opcodes []byte) *ScriptBuilder
- func (b *ScriptBuilder) AddOpsUnchecked(opcodes []byte) *ScriptBuilder
- func (b *ScriptBuilder) Reset() *ScriptBuilder
- func (b *ScriptBuilder) Script() ([]byte, error)
- type ScriptFlags
- type ScriptNum
- type ScriptTokenizer
- type SigCache
- type SigHashSerType
- type SigHashType
Examples ¶
Constants ¶
const ( // MaxStackSize is the maximum combined height of stack and alt stack // during execution. MaxStackSize = 1024 // MaxScriptSize is the maximum allowed length of a raw script. MaxScriptSize = 16384 )
const ( // ErrInvalidIndex is returned when an out-of-bounds index is passed to // a function. ErrInvalidIndex = ErrorKind("ErrInvalidIndex") // ErrInvalidSigHashSingleIndex is returned when an attempt is // made to sign an input with the SigHashSingle hash type and an // index that is greater than or equal to the number of outputs. ErrInvalidSigHashSingleIndex = ErrorKind("ErrInvalidSigHashSingleIndex") // ErrUnsupportedScriptVersion is returned when an unsupported script // version is passed to a function which deals with script analysis. ErrUnsupportedScriptVersion = ErrorKind("ErrUnsupportedScriptVersion") // ErrEarlyReturn is returned when OP_RETURN is executed in the script. ErrEarlyReturn = ErrorKind("ErrEarlyReturn") // ErrEmptyStack is returned when the script evaluated without error, // but terminated with an empty top stack element. ErrEmptyStack = ErrorKind("ErrEmptyStack") // ErrEvalFalse is returned when the script evaluated without error but // terminated with a false top stack element. ErrEvalFalse = ErrorKind("ErrEvalFalse") // ErrScriptUnfinished is returned when CheckErrorCondition is called on // a script that has not finished executing. ErrScriptUnfinished = ErrorKind("ErrScriptUnfinished") // ErrScriptDone is returned when an attempt to execute an opcode is // made once all of them have already been executed. This can happen // due to things such as a second call to Execute or calling Step after // all opcodes have already been executed. ErrInvalidProgramCounter = ErrorKind("ErrInvalidProgramCounter") // ErrScriptTooBig is returned if a script is larger than MaxScriptSize. ErrScriptTooBig = ErrorKind("ErrScriptTooBig") // ErrElementTooBig is returned if the size of an element to be pushed // to the stack is over MaxScriptElementSize. ErrElementTooBig = ErrorKind("ErrElementTooBig") // ErrTooManyOperations is returned if a script has more than // MaxOpsPerScript opcodes that do not push data. ErrTooManyOperations = ErrorKind("ErrTooManyOperations") // ErrStackOverflow is returned when stack and altstack combined depth // is over the limit. ErrStackOverflow = ErrorKind("ErrStackOverflow") // ErrInvalidPubKeyCount is returned when the number of public keys // specified for a multsig is either negative or greater than // MaxPubKeysPerMultiSig. ErrInvalidPubKeyCount = ErrorKind("ErrInvalidPubKeyCount") // ErrInvalidSignatureCount is returned when the number of signatures // specified for a multisig is either negative or greater than the // number of public keys. ErrInvalidSignatureCount = ErrorKind("ErrInvalidSignatureCount") // ErrNumOutOfRange is returned when the argument for an opcode that // expects numeric input is larger than the expected maximum number of // bytes. For the most part, opcodes that deal with stack manipulation // via offsets, arithmetic, numeric comparison, and boolean logic are // those that this applies to. However, any opcode that expects numeric // input may fail with this error. ErrNumOutOfRange = ErrorKind("ErrNumOutOfRange") // ErrVerify is returned when OP_VERIFY is encountered in a script and // the top item on the data stack does not evaluate to true. ErrVerify = ErrorKind("ErrVerify") // ErrEqualVerify is returned when OP_EQUALVERIFY is encountered in a // script and the top item on the data stack does not evaluate to true. ErrEqualVerify = ErrorKind("ErrEqualVerify") // ErrNumEqualVerify is returned when OP_NUMEQUALVERIFY is encountered // in a script and the top item on the data stack does not evaluate to // true. ErrNumEqualVerify = ErrorKind("ErrNumEqualVerify") // ErrCheckSigVerify is returned when OP_CHECKSIGVERIFY is encountered // in a script and the top item on the data stack does not evaluate to // true. ErrCheckSigVerify = ErrorKind("ErrCheckSigVerify") // ErrCheckSigVerify is returned when OP_CHECKMULTISIGVERIFY is // encountered in a script and the top item on the data stack does not // evaluate to true. ErrCheckMultiSigVerify = ErrorKind("ErrCheckMultiSigVerify") // ErrCheckSigAltVerify is returned when OP_CHECKSIGALTVERIFY is // encountered in a script and the top item on the data stack does not // evaluate to true. ErrCheckSigAltVerify = ErrorKind("ErrCheckSigAltVerify") // ErrP2SHStakeOpCodes is returned when one or more stake opcodes are // found in the redeem script of a pay-to-script-hash script. ErrP2SHStakeOpCodes = ErrorKind("ErrP2SHStakeOpCodes") // ErrDisabledOpcode is returned when a disabled opcode is encountered // in a script. ErrDisabledOpcode = ErrorKind("ErrDisabledOpcode") // ErrReservedOpcode is returned when an opcode marked as reserved // is encountered in a script. ErrReservedOpcode = ErrorKind("ErrReservedOpcode") // ErrMalformedPush is returned when a data push opcode tries to push // more bytes than are left in the script. ErrMalformedPush = ErrorKind("ErrMalformedPush") // ErrInvalidStackOperation is returned when a stack operation is // attempted with a number that is invalid for the current stack size. ErrInvalidStackOperation = ErrorKind("ErrInvalidStackOperation") // ErrUnbalancedConditional is returned when an OP_ELSE or OP_ENDIF is // encountered in a script without first having an OP_IF or OP_NOTIF or // the end of script is reached without encountering an OP_ENDIF when // an OP_IF or OP_NOTIF was previously encountered. ErrUnbalancedConditional = ErrorKind("ErrUnbalancedConditional") // ErrNegativeSubstrIdx is returned when an OP_SUBSTR, OP_LEFT, or // OP_RIGHT opcode encounters a negative index. ErrNegativeSubstrIdx = ErrorKind("ErrNegativeSubstrIdx") // ErrOverflowSubstrIdx is returned when an OP_SUBSTR, OP_LEFT, or // OP_RIGHT opcode encounters an index that is larger than the max // allowed index that can operate on the string or the start index // is greater than the end index for OP_SUBSTR. ErrOverflowSubstrIdx = ErrorKind("ErrOverflowSubstrIdx") // ErrNegativeRotation is returned when an OP_ROTL or OP_ROTR attempts // to perform a rotation with a negative rotation count. ErrNegativeRotation = ErrorKind("ErrNegativeRotation") // ErrOverflowRotation is returned when an OP_ROTL or OP_ROTR opcode // encounters a rotation count that is larger than the maximum allowed // value for a uint32 bit rotation. ErrOverflowRotation = ErrorKind("ErrOverflowRotation") // ErrDivideByZero is returned when an OP_DIV of OP_MOD attempts to // divide by zero. ErrDivideByZero = ErrorKind("ErrDivideByZero") // ErrNegativeRotation is returned when an OP_LSHIFT or OP_RSHIFT opcode // attempts to perform a shift with a negative count. ErrNegativeShift = ErrorKind("ErrNegativeShift") // ErrOverflowShift is returned when an OP_LSHIFT or OP_RSHIFT opcode // encounters a shift count that is larger than the maximum allowed value // for a shift. ErrOverflowShift = ErrorKind("ErrOverflowShift") // ErrP2SHTreasuryOpCodes is returned when one or more treasury opcodes // are found in the redeem script of a pay-to-script-hash script. ErrP2SHTreasuryOpCodes = ErrorKind("ErrP2SHTreasuryOpCodes") // ErrMinimalData is returned when the script contains push operations // that do not use the minimal opcode required. ErrMinimalData = ErrorKind("ErrMinimalData") // ErrInvalidSigHashType is returned when a signature hash type is not // one of the supported types. ErrInvalidSigHashType = ErrorKind("ErrInvalidSigHashType") // ErrSigTooShort is returned when a signature that should be a // canonically-encoded DER signature is too short. ErrSigTooShort = ErrorKind("ErrSigTooShort") // ErrSigTooLong is returned when a signature that should be a // canonically-encoded DER signature is too long. ErrSigTooLong = ErrorKind("ErrSigTooLong") // ErrSigInvalidSeqID is returned when a signature that should be a // canonically-encoded DER signature does not have the expected ASN.1 // sequence ID. ErrSigInvalidSeqID = ErrorKind("ErrSigInvalidSeqID") // ErrSigInvalidDataLen is returned when a signature that should be a // canonically-encoded DER signature does not specify the correct number // of remaining bytes for the R and S portions. ErrSigInvalidDataLen = ErrorKind("ErrSigInvalidDataLen") // ErrSigMissingSTypeID is returned when a signature that should be a // canonically-encoded DER signature does not provide the ASN.1 type ID // for S. ErrSigMissingSTypeID = ErrorKind("ErrSigMissingSTypeID") // ErrSigMissingSLen is returned when a signature that should be a // canonically-encoded DER signature does not provide the length of S. ErrSigMissingSLen = ErrorKind("ErrSigMissingSLen") // ErrSigInvalidSLen is returned when a signature that should be a // canonically-encoded DER signature does not specify the correct number // of bytes for the S portion. ErrSigInvalidSLen = ErrorKind("ErrSigInvalidSLen") // ErrSigInvalidRIntID is returned when a signature that should be a // canonically-encoded DER signature does not have the expected ASN.1 // integer ID for R. ErrSigInvalidRIntID = ErrorKind("ErrSigInvalidRIntID") // ErrSigZeroRLen is returned when a signature that should be a // canonically-encoded DER signature has an R length of zero. ErrSigZeroRLen = ErrorKind("ErrSigZeroRLen") // ErrSigNegativeR is returned when a signature that should be a // canonically-encoded DER signature has a negative value for R. ErrSigNegativeR = ErrorKind("ErrSigNegativeR") // ErrSigTooMuchRPadding is returned when a signature that should be a // canonically-encoded DER signature has too much padding for R. ErrSigTooMuchRPadding = ErrorKind("ErrSigTooMuchRPadding") // ErrSigInvalidSIntID is returned when a signature that should be a // canonically-encoded DER signature does not have the expected ASN.1 // integer ID for S. ErrSigInvalidSIntID = ErrorKind("ErrSigInvalidSIntID") // ErrSigZeroSLen is returned when a signature that should be a // canonically-encoded DER signature has an S length of zero. ErrSigZeroSLen = ErrorKind("ErrSigZeroSLen") // ErrSigNegativeS is returned when a signature that should be a // canonically-encoded DER signature has a negative value for S. ErrSigNegativeS = ErrorKind("ErrSigNegativeS") // ErrSigTooMuchSPadding is returned when a signature that should be a // canonically-encoded DER signature has too much padding for S. ErrSigTooMuchSPadding = ErrorKind("ErrSigTooMuchSPadding") // ErrSigHighS is returned when a signature that should be a // canonically-encoded DER signature has an S value that is higher than // the curve half order. ErrSigHighS = ErrorKind("ErrSigHighS") // ErrNotPushOnly is returned when a script that is required to only // push data to the stack performs other operations. A couple of cases // where this applies is for a pay-to-script-hash signature script when // bip16 is active and when the ScriptVerifySigPushOnly flag is set. ErrNotPushOnly = ErrorKind("ErrNotPushOnly") // ErrPubKeyType is returned when the script contains invalid public keys. ErrPubKeyType = ErrorKind("ErrPubKeyType") // ErrCleanStack is returned when the ScriptVerifyCleanStack flag // is set, and after evaluation, the stack does not contain only a // single element. ErrCleanStack = ErrorKind("ErrCleanStack") // ErrDiscourageUpgradableNOPs is returned when the // ScriptDiscourageUpgradableNops flag is set and a NOP opcode is // encountered in a script. ErrDiscourageUpgradableNOPs = ErrorKind("ErrDiscourageUpgradableNOPs") // ErrNegativeLockTime is returned when a script contains an opcode that // interprets a negative lock time. ErrNegativeLockTime = ErrorKind("ErrNegativeLockTime") // ErrUnsatisfiedLockTime is returned when a script contains an opcode // that involves a lock time and the required lock time has not been // reached. ErrUnsatisfiedLockTime = ErrorKind("ErrUnsatisfiedLockTime") )
These constants are used to identify a specific ErrorKind.
const ( OP_0 = 0x00 // 0 OP_FALSE = 0x00 // 0 - AKA OP_0 OP_DATA_1 = 0x01 // 1 OP_DATA_2 = 0x02 // 2 OP_DATA_3 = 0x03 // 3 OP_DATA_4 = 0x04 // 4 OP_DATA_5 = 0x05 // 5 OP_DATA_6 = 0x06 // 6 OP_DATA_7 = 0x07 // 7 OP_DATA_8 = 0x08 // 8 OP_DATA_9 = 0x09 // 9 OP_DATA_10 = 0x0a // 10 OP_DATA_11 = 0x0b // 11 OP_DATA_12 = 0x0c // 12 OP_DATA_13 = 0x0d // 13 OP_DATA_14 = 0x0e // 14 OP_DATA_15 = 0x0f // 15 OP_DATA_16 = 0x10 // 16 OP_DATA_17 = 0x11 // 17 OP_DATA_18 = 0x12 // 18 OP_DATA_19 = 0x13 // 19 OP_DATA_20 = 0x14 // 20 OP_DATA_21 = 0x15 // 21 OP_DATA_22 = 0x16 // 22 OP_DATA_23 = 0x17 // 23 OP_DATA_24 = 0x18 // 24 OP_DATA_25 = 0x19 // 25 OP_DATA_26 = 0x1a // 26 OP_DATA_27 = 0x1b // 27 OP_DATA_28 = 0x1c // 28 OP_DATA_29 = 0x1d // 29 OP_DATA_30 = 0x1e // 30 OP_DATA_31 = 0x1f // 31 OP_DATA_32 = 0x20 // 32 OP_DATA_33 = 0x21 // 33 OP_DATA_34 = 0x22 // 34 OP_DATA_35 = 0x23 // 35 OP_DATA_36 = 0x24 // 36 OP_DATA_37 = 0x25 // 37 OP_DATA_38 = 0x26 // 38 OP_DATA_39 = 0x27 // 39 OP_DATA_40 = 0x28 // 40 OP_DATA_41 = 0x29 // 41 OP_DATA_42 = 0x2a // 42 OP_DATA_43 = 0x2b // 43 OP_DATA_44 = 0x2c // 44 OP_DATA_45 = 0x2d // 45 OP_DATA_46 = 0x2e // 46 OP_DATA_47 = 0x2f // 47 OP_DATA_48 = 0x30 // 48 OP_DATA_49 = 0x31 // 49 OP_DATA_50 = 0x32 // 50 OP_DATA_51 = 0x33 // 51 OP_DATA_52 = 0x34 // 52 OP_DATA_53 = 0x35 // 53 OP_DATA_54 = 0x36 // 54 OP_DATA_55 = 0x37 // 55 OP_DATA_56 = 0x38 // 56 OP_DATA_57 = 0x39 // 57 OP_DATA_58 = 0x3a // 58 OP_DATA_59 = 0x3b // 59 OP_DATA_60 = 0x3c // 60 OP_DATA_61 = 0x3d // 61 OP_DATA_62 = 0x3e // 62 OP_DATA_63 = 0x3f // 63 OP_DATA_64 = 0x40 // 64 OP_DATA_65 = 0x41 // 65 OP_DATA_66 = 0x42 // 66 OP_DATA_67 = 0x43 // 67 OP_DATA_68 = 0x44 // 68 OP_DATA_69 = 0x45 // 69 OP_DATA_70 = 0x46 // 70 OP_DATA_71 = 0x47 // 71 OP_DATA_72 = 0x48 // 72 OP_DATA_73 = 0x49 // 73 OP_DATA_74 = 0x4a // 74 OP_DATA_75 = 0x4b // 75 OP_PUSHDATA1 = 0x4c // 76 OP_PUSHDATA2 = 0x4d // 77 OP_PUSHDATA4 = 0x4e // 78 OP_1NEGATE = 0x4f // 79 OP_RESERVED = 0x50 // 80 OP_1 = 0x51 // 81 - AKA OP_TRUE OP_TRUE = 0x51 // 81 OP_2 = 0x52 // 82 OP_3 = 0x53 // 83 OP_4 = 0x54 // 84 OP_5 = 0x55 // 85 OP_6 = 0x56 // 86 OP_7 = 0x57 // 87 OP_8 = 0x58 // 88 OP_9 = 0x59 // 89 OP_10 = 0x5a // 90 OP_11 = 0x5b // 91 OP_12 = 0x5c // 92 OP_13 = 0x5d // 93 OP_14 = 0x5e // 94 OP_15 = 0x5f // 95 OP_16 = 0x60 // 96 OP_NOP = 0x61 // 97 OP_VER = 0x62 // 98 OP_IF = 0x63 // 99 OP_NOTIF = 0x64 // 100 OP_VERIF = 0x65 // 101 OP_VERNOTIF = 0x66 // 102 OP_ELSE = 0x67 // 103 OP_ENDIF = 0x68 // 104 OP_VERIFY = 0x69 // 105 OP_RETURN = 0x6a // 106 OP_TOALTSTACK = 0x6b // 107 OP_FROMALTSTACK = 0x6c // 108 OP_2DROP = 0x6d // 109 OP_2DUP = 0x6e // 110 OP_3DUP = 0x6f // 111 OP_2OVER = 0x70 // 112 OP_2ROT = 0x71 // 113 OP_2SWAP = 0x72 // 114 OP_IFDUP = 0x73 // 115 OP_DEPTH = 0x74 // 116 OP_DROP = 0x75 // 117 OP_DUP = 0x76 // 118 OP_NIP = 0x77 // 119 OP_OVER = 0x78 // 120 OP_PICK = 0x79 // 121 OP_ROLL = 0x7a // 122 OP_ROT = 0x7b // 123 OP_SWAP = 0x7c // 124 OP_TUCK = 0x7d // 125 OP_CAT = 0x7e // 126 OP_SUBSTR = 0x7f // 127 OP_LEFT = 0x80 // 128 OP_RIGHT = 0x81 // 129 OP_SIZE = 0x82 // 130 OP_INVERT = 0x83 // 131 OP_AND = 0x84 // 132 OP_OR = 0x85 // 133 OP_XOR = 0x86 // 134 OP_EQUAL = 0x87 // 135 OP_EQUALVERIFY = 0x88 // 136 OP_ROTR = 0x89 // 137 OP_ROTL = 0x8a // 138 OP_1ADD = 0x8b // 139 OP_1SUB = 0x8c // 140 OP_2MUL = 0x8d // 141 OP_2DIV = 0x8e // 142 OP_NEGATE = 0x8f // 143 OP_ABS = 0x90 // 144 OP_NOT = 0x91 // 145 OP_0NOTEQUAL = 0x92 // 146 OP_ADD = 0x93 // 147 OP_SUB = 0x94 // 148 OP_MUL = 0x95 // 149 OP_DIV = 0x96 // 150 OP_MOD = 0x97 // 151 OP_LSHIFT = 0x98 // 152 OP_RSHIFT = 0x99 // 153 OP_BOOLAND = 0x9a // 154 OP_BOOLOR = 0x9b // 155 OP_NUMEQUAL = 0x9c // 156 OP_NUMEQUALVERIFY = 0x9d // 157 OP_NUMNOTEQUAL = 0x9e // 158 OP_LESSTHAN = 0x9f // 159 OP_GREATERTHAN = 0xa0 // 160 OP_LESSTHANOREQUAL = 0xa1 // 161 OP_GREATERTHANOREQUAL = 0xa2 // 162 OP_MIN = 0xa3 // 163 OP_MAX = 0xa4 // 164 OP_WITHIN = 0xa5 // 165 OP_RIPEMD160 = 0xa6 // 166 OP_SHA1 = 0xa7 // 167 OP_BLAKE256 = 0xa8 // 168 OP_HASH160 = 0xa9 // 169 OP_HASH256 = 0xaa // 170 OP_CODESEPARATOR = 0xab // 171 OP_CHECKSIG = 0xac // 172 OP_CHECKSIGVERIFY = 0xad // 173 OP_CHECKMULTISIG = 0xae // 174 OP_CHECKMULTISIGVERIFY = 0xaf // 175 OP_NOP1 = 0xb0 // 176 OP_NOP2 = 0xb1 // 177 OP_CHECKLOCKTIMEVERIFY = 0xb1 // 177 - AKA OP_NOP2 OP_NOP3 = 0xb2 // 178 OP_CHECKSEQUENCEVERIFY = 0xb2 // 178 - AKA OP_NOP3 OP_NOP4 = 0xb3 // 179 OP_NOP5 = 0xb4 // 180 OP_NOP6 = 0xb5 // 181 OP_NOP7 = 0xb6 // 182 OP_NOP8 = 0xb7 // 183 OP_NOP9 = 0xb8 // 184 OP_NOP10 = 0xb9 // 185 OP_SSTX = 0xba // 186 DECRED OP_SSGEN = 0xbb // 187 DECRED OP_SSRTX = 0xbc // 188 DECRED OP_SSTXCHANGE = 0xbd // 189 DECRED OP_CHECKSIGALT = 0xbe // 190 DECRED OP_CHECKSIGALTVERIFY = 0xbf // 191 DECRED OP_SHA256 = 0xc0 // 192 OP_TADD = 0xc1 // 193 DECRED OP_TSPEND = 0xc2 // 194 DECRED OP_TGEN = 0xc3 // 195 DECRED OP_UNKNOWN196 = 0xc4 // 196 OP_UNKNOWN197 = 0xc5 // 197 OP_UNKNOWN198 = 0xc6 // 198 OP_UNKNOWN199 = 0xc7 // 199 OP_UNKNOWN200 = 0xc8 // 200 OP_UNKNOWN201 = 0xc9 // 201 OP_UNKNOWN202 = 0xca // 202 OP_UNKNOWN203 = 0xcb // 203 OP_UNKNOWN204 = 0xcc // 204 OP_UNKNOWN205 = 0xcd // 205 OP_UNKNOWN206 = 0xce // 206 OP_UNKNOWN207 = 0xcf // 207 OP_UNKNOWN208 = 0xd0 // 208 OP_UNKNOWN209 = 0xd1 // 209 OP_UNKNOWN210 = 0xd2 // 210 OP_UNKNOWN211 = 0xd3 // 211 OP_UNKNOWN212 = 0xd4 // 212 OP_UNKNOWN213 = 0xd5 // 213 OP_UNKNOWN214 = 0xd6 // 214 OP_UNKNOWN215 = 0xd7 // 215 OP_UNKNOWN216 = 0xd8 // 216 OP_UNKNOWN217 = 0xd9 // 217 OP_UNKNOWN218 = 0xda // 218 OP_UNKNOWN219 = 0xdb // 219 OP_UNKNOWN220 = 0xdc // 220 OP_UNKNOWN221 = 0xdd // 221 OP_UNKNOWN222 = 0xde // 222 OP_UNKNOWN223 = 0xdf // 223 OP_UNKNOWN224 = 0xe0 // 224 OP_UNKNOWN225 = 0xe1 // 225 OP_UNKNOWN226 = 0xe2 // 226 OP_UNKNOWN227 = 0xe3 // 227 OP_UNKNOWN228 = 0xe4 // 228 OP_UNKNOWN229 = 0xe5 // 229 OP_UNKNOWN230 = 0xe6 // 230 OP_UNKNOWN231 = 0xe7 // 231 OP_UNKNOWN232 = 0xe8 // 232 OP_UNKNOWN233 = 0xe9 // 233 OP_UNKNOWN234 = 0xea // 234 OP_UNKNOWN235 = 0xeb // 235 OP_UNKNOWN236 = 0xec // 236 OP_UNKNOWN237 = 0xed // 237 OP_UNKNOWN238 = 0xee // 238 OP_UNKNOWN239 = 0xef // 239 OP_UNKNOWN240 = 0xf0 // 240 OP_UNKNOWN241 = 0xf1 // 241 OP_UNKNOWN242 = 0xf2 // 242 OP_UNKNOWN243 = 0xf3 // 243 OP_UNKNOWN244 = 0xf4 // 244 OP_UNKNOWN245 = 0xf5 // 245 OP_UNKNOWN246 = 0xf6 // 246 OP_UNKNOWN247 = 0xf7 // 247 OP_UNKNOWN248 = 0xf8 // 248 OP_INVALID249 = 0xf9 // 249 - bitcoin core internal OP_SMALLINTEGER = 0xfa // 250 - bitcoin core internal OP_PUBKEYS = 0xfb // 251 - bitcoin core internal OP_UNKNOWN252 = 0xfc // 252 OP_PUBKEYHASH = 0xfd // 253 - bitcoin core internal OP_PUBKEY = 0xfe // 254 - bitcoin core internal OP_INVALIDOPCODE = 0xff // 255 - bitcoin core internal )
These constants are the values of the official opcodes used on the btc wiki, in bitcoin core and in most if not all other references and software related to handling DCR scripts.
const ( MaxOpsPerScript = 255 // Max number of non-push operations. MaxPubKeysPerMultiSig = 20 // Multisig can't have more sigs than this. MaxScriptElementSize = 2048 // Max bytes pushable to the stack. )
These are the constants specified for maximums in individual scripts.
const ( // MathOpCodeMaxScriptNumLen is the maximum number of bytes data being // interpreted as an integer may be for the majority of op codes. MathOpCodeMaxScriptNumLen = 4 // CltvMaxScriptNumLen is the maximum number of bytes data being interpreted // as an integer may be for by-time and by-height locks as interpreted by // CHECKLOCKTIMEVERIFY. // // The value comes from the fact that the current transaction locktime // is a uint32 resulting in a maximum locktime of 2^32-1 (the year // 2106). However, script numbers are signed and therefore a standard // 4-byte ScriptNum would only support up to a maximum of 2^31-1 (the // year 2038). Thus, a 5-byte ScriptNum is needed since it will support // up to 2^39-1 which allows dates beyond the current locktime limit. CltvMaxScriptNumLen = 5 // CsvMaxScriptNumLen is the maximum number of bytes data being interpreted // as an integer may be for by-time and by-height locks as interpreted by // CHECKSEQUENCEVERIFY. // // The value comes from the fact that the current transaction sequence // is a uint32 resulting in a maximum sequence of 2^32-1. However, // ScriptNums are signed and therefore a standard 4-byte ScriptNum would // only support up to a maximum of 2^31-1. Thus, a 5-byte ScriptNum is // needed since it will support up to 2^39-1 which allows sequences // beyond the current sequence limit. CsvMaxScriptNumLen = 5 )
const ( // SigHashSerializePrefix indicates the serialization does not include // any witness data. SigHashSerializePrefix = 1 // SigHashSerializeWitness indicates the serialization only contains // witness data. SigHashSerializeWitness = 3 )
const ( // LockTimeThreshold is the number below which a lock time is // interpreted to be a block number. Since an average of one block // is generated per 10 minutes, this allows blocks for about 9,512 // years. LockTimeThreshold = 5e8 // Tue Nov 5 00:53:20 1985 UTC )
const ProactiveEvictionDepth = 2
ProactiveEvictionDepth is the depth of the block at which the signatures for the transactions within the block are nearly guaranteed to no longer be useful.
Variables ¶
var OpcodeByName = make(map[string]byte)
OpcodeByName is a map that can be used to lookup an opcode by its human-readable name (OP_CHECKMULTISIG, OP_CHECKSIG, etc).
Functions ¶
func AsSmallInt ¶
AsSmallInt returns the passed opcode, which MUST be true according to the IsSmallInt function, as an integer.
NOTE: This function is only valid for version 0 opcodes. Since the function does not accept a script version, the results are undefined for other script versions.
func CalcSignatureHash ¶
func CalcSignatureHash(script []byte, hashType SigHashType, tx *wire.MsgTx, idx int, cachedPrefix *chainhash.Hash) ([]byte, error)
CalcSignatureHash computes the signature hash for the specified input of the target transaction observing the desired signature hash type. The cached prefix parameter allows the caller to optimize the calculation by providing the prefix hash to be reused in the case of SigHashAll without the SigHashAnyOneCanPay flag set.
NOTE: This function is only valid for version 0 scripts. Since the function does not accept a script version, the results are undefined for other script versions.
func CanonicalDataSize ¶
CanonicalDataSize returns the number of bytes the canonical encoding of the data will take.
func CheckHashTypeEncoding ¶
func CheckHashTypeEncoding(hashType SigHashType) error
CheckHashTypeEncoding returns whether or not the passed hashtype adheres to the strict encoding requirements.
func CheckPubKeyEncoding ¶
CheckPubKeyEncoding returns an error if the passed public key does not adhere to the strict encoding requirements.
func CheckSignatureEncoding ¶
CheckSignatureEncoding returns whether or not the passed signature adheres to the strict encoding requirements.
func ContainsStakeOpCodes ¶
ContainsStakeOpCodes returns whether or not a public key script contains any stake tagging opcodes.
NOTE: This function is only valid for version 0 scripts. Since the function does not accept a script version, the results are undefined for other script versions.
func DisasmString ¶
DisasmString formats a disassembled script for one line printing. When the script fails to parse, the returned string will contain the disassembled script up to the point the failure occurred along with the string '[error]' appended. In addition, the reason the script failed to parse is returned if the caller wants more information about the failure.
NOTE: This function is only valid for version 0 scripts. Since the function does not accept a script version, the results are undefined for other script versions.
func ExtractScriptHash ¶
ExtractScriptHash extracts the script hash from the passed script if it is a standard pay-to-script-hash script. It will return nil otherwise.
NOTE: This function is only valid for version 0 opcodes. Since the function does not accept a script version, the results are undefined for other script versions.
func GenerateSSGenBlockRef ¶
GenerateSSGenBlockRef generates a block reference script for the given block hash and height which a block votes on. The script is for use in stake vote transactions.
func GenerateSSGenVotes ¶
GenerateSSGenVotes generates a vote script for the given vote bits. The script is for use in stake vote transactions.
func GetPreciseSigOpCount ¶
GetPreciseSigOpCount returns the number of signature operations in scriptPubKey. If bip16 is true then scriptSig may be searched for the Pay-To-Script-Hash script in order to find the precise number of signature operations in the transaction. If the script fails to parse, then the count up to the point of failure is returned.
WARNING: This function always treats the passed script as version 0. Great care must be taken if introducing a new script version because it is used in consensus which, unfortunately as of the time of this writing, does not check script versions before counting their signature operations which means nodes on existing rules will count new version scripts as if they were version 0.
func GetSigOpCount ¶
GetSigOpCount provides a quick count of the number of signature operations in a script. a CHECKSIG operations counts for 1, and a CHECK_MULTISIG for 20. If the script fails to parse, then the count up to the point of failure is returned.
WARNING: This function always treats the passed script as version 0. Great care must be taken if introducing a new script version because it is used in consensus which, unfortunately as of the time of this writing, does not check script versions before counting their signature operations which means nodes on existing rules will count new version scripts as if they were version 0.
func IsDERSigError ¶
IsDERSigError returns whether or not the provided error is one of the error kinds which are caused due to encountering a signature that is not a canonically-encoded DER signature.
func IsPayToScriptHash ¶
IsPayToScriptHash returns true if the script is in the standard pay-to-script-hash (P2SH) format, false otherwise.
WARNING: This function always treats the passed script as version 0. Great care must be taken if introducing a new script version because it is used in consensus which, unfortunately as of the time of this writing, does not check script versions before determining if the script is a P2SH which means nodes on existing rules will analyze new version scripts as if they were version 0.
func IsPushOnlyScript ¶
IsPushOnlyScript returns whether or not the passed script only pushes data according to the consensus definition of pushing data.
WARNING: This function always treats the passed script as version 0. Great care must be taken if introducing a new script version because it is used in consensus which, unfortunately as of the time of this writing, does not check script versions before checking if it is a push only script which means nodes on existing rules will treat new version scripts as if they were version 0.
func IsSmallInt ¶
IsSmallInt returns whether or not the opcode is considered a small integer, which is an OP_0, or OP_1 through OP_16.
NOTE: This function is only valid for version 0 opcodes. Since the function does not accept a script version, the results are undefined for other script versions.
func IsStrictCompressedPubKeyEncoding ¶
IsStrictCompressedPubKeyEncoding returns whether or not the passed public key adheres to the strict compressed encoding requirements.
func IsStrictNullData ¶
IsStrictNullData returns whether or not the passed data is an OP_RETURN followed by specified length data push. It explicitly verifies that the opcode is identical to the required length. This function will always return false for required lengths > 75 bytes.
func IsStrictSignatureEncoding ¶
IsStrictSignatureEncoding returns false if the passed signature does not adhere to the strict encoding requirements.
func IsUnspendable ¶
IsUnspendable returns whether the passed public key script is unspendable, or guaranteed to fail at execution. This allows inputs to be pruned instantly when entering the UTXO set. In Decred, all zero value outputs are unspendable.
NOTE: This function is only valid for version 0 scripts. Since the function does not accept a script version, the results are undefined for other script versions.
Types ¶
type Engine ¶
type Engine struct {
// contains filtered or unexported fields
}
Engine is the virtual machine that executes scripts.
func NewEngine ¶
func NewEngine(scriptPubKey []byte, tx *wire.MsgTx, txIdx int, flags ScriptFlags, scriptVersion uint16, sigCache *SigCache) (*Engine, error)
NewEngine returns a new script engine for the provided public key script, transaction, and input index. The flags modify the behavior of the script engine according to the description provided by each flag.
func (*Engine) CheckErrorCondition ¶
CheckErrorCondition returns nil if the running script has ended and was successful, leaving a true boolean on the stack. An error otherwise, including if the script has not finished.
func (*Engine) DisasmPC ¶
DisasmPC returns the string for the disassembly of the opcode that will be next to execute when Step is called.
func (*Engine) DisasmScript ¶
DisasmScript returns the disassembly string for the script at the requested offset index. Index 0 is the signature script and 1 is the public key script. In the case of pay-to-script-hash, index 2 is the redeem script once the execution has progressed far enough to have successfully verified script hash and thus add the script to the scripts to execute.
func (*Engine) Execute ¶
Execute will execute all scripts in the script engine and return either nil for successful validation or an error if one occurred.
func (*Engine) GetAltStack ¶
GetAltStack returns the contents of the alternate stack as an array where the last item in the array is the top of the stack.
func (*Engine) GetStack ¶
GetStack returns the contents of the primary stack as an array. where the last item in the array is the top of the stack.
func (*Engine) SetAltStack ¶
SetAltStack sets the contents of the alternate stack to the contents of the provided array where the last item in the array will be the top of the stack.
func (*Engine) SetStack ¶
SetStack sets the contents of the primary stack to the contents of the provided array where the last item in the array will be the top of the stack.
func (*Engine) Step ¶
Step executes the next instruction and moves the program counter to the next opcode in the script, or the next script if the current has ended. Step will return true in the case that the last opcode was successfully executed.
The result of calling Step or any other method is undefined if an error is returned.
type ErrScriptNotCanonical ¶
type ErrScriptNotCanonical string
ErrScriptNotCanonical identifies a non-canonical script. The caller can use a type assertion to detect this error type.
func (ErrScriptNotCanonical) Error ¶
func (e ErrScriptNotCanonical) Error() string
Error implements the error interface.
type Error ¶
Error identifies a script-related error. It is used to indicate three classes of errors:
- Script execution failures due to violating one of the many requirements imposed by the script engine or evaluating to false
- Improper API usage by callers
- Internal consistency check failures
It has full support for errors.Is and errors.As, so the caller can ascertain the specific reason for the error by checking the underlying error.
type ScriptBuilder ¶
type ScriptBuilder struct {
// contains filtered or unexported fields
}
ScriptBuilder provides a facility for building custom scripts. It allows you to push opcodes, ints, and data while respecting canonical encoding. In general it does not ensure the script will execute correctly, however any data pushes which would exceed the maximum allowed script engine limits and are therefore guaranteed not to execute will not be pushed and will result in the Script function returning an error.
For example, the following would build a 2-of-3 multisig script for usage in a pay-to-script-hash (although in this situation stdscript.MultiSigScript() would be a better choice to generate the script):
builder := txscript.NewScriptBuilder() builder.AddOp(txscript.OP_2).AddData(pubKey1).AddData(pubKey2) builder.AddData(pubKey3).AddOp(txscript.OP_3) builder.AddOp(txscript.OP_CHECKMULTISIG) script, err := builder.Script() if err != nil { // Handle the error. return } fmt.Printf("Final multi-sig script: %x\n", script)
func NewScriptBuilder ¶
func NewScriptBuilder() *ScriptBuilder
NewScriptBuilder returns a new instance of a script builder. See ScriptBuilder for details.
func (*ScriptBuilder) AddData ¶
func (b *ScriptBuilder) AddData(data []byte) *ScriptBuilder
AddData pushes the passed data to the end of the script. It automatically chooses canonical opcodes depending on the length of the data. A zero length buffer will lead to a push of empty data onto the stack (OP_0) and any push of data greater than MaxScriptElementSize will not modify the script since that is not allowed by the script engine. Also, the script will not be modified if pushing the data would cause the script to exceed the maximum allowed script engine size.
func (*ScriptBuilder) AddDataUnchecked ¶
func (b *ScriptBuilder) AddDataUnchecked(data []byte) *ScriptBuilder
AddDataUnchecked should not typically be used by ordinary users as it does not include the checks which prevent data pushes larger than the maximum allowed sizes which leads to scripts that can't be executed. This is provided for testing purposes such as regression tests where sizes are intentionally made larger than allowed.
Use AddData instead.
func (*ScriptBuilder) AddInt64 ¶
func (b *ScriptBuilder) AddInt64(val int64) *ScriptBuilder
AddInt64 pushes the passed integer to the end of the script. The script will not be modified if pushing the data would cause the script to exceed the maximum allowed script engine size.
func (*ScriptBuilder) AddOp ¶
func (b *ScriptBuilder) AddOp(opcode byte) *ScriptBuilder
AddOp pushes the passed opcode to the end of the script. The script will not be modified if pushing the opcode would cause the script to exceed the maximum allowed script engine size.
func (*ScriptBuilder) AddOps ¶
func (b *ScriptBuilder) AddOps(opcodes []byte) *ScriptBuilder
AddOps pushes the passed opcodes to the end of the script. The script will not be modified if pushing the opcodes would cause the script to exceed the maximum allowed script engine size.
func (*ScriptBuilder) AddOpsUnchecked ¶
func (b *ScriptBuilder) AddOpsUnchecked(opcodes []byte) *ScriptBuilder
AddOpsUnchecked should not typically be used by ordinary users as it does not include the checks which prevent scripts from exceeding the largest allowed script size which leads to scripts that can't be executed. This is provided for testing purposes such as regression tests where sizes are intentionally made larger than allowed.
Use AddOps instead.
func (*ScriptBuilder) Reset ¶
func (b *ScriptBuilder) Reset() *ScriptBuilder
Reset resets the script so it has no content.
func (*ScriptBuilder) Script ¶
func (b *ScriptBuilder) Script() ([]byte, error)
Script returns the currently built script. When any errors occurred while building the script, the script will be returned up the point of the first error along with the error.
type ScriptFlags ¶
type ScriptFlags uint32
ScriptFlags is a bitmask defining additional operations or tests that will be done when executing a script pair.
const ( // ScriptDiscourageUpgradableNops defines whether to verify that // currently unused opcodes in the NOP and UNKNOWN families are reserved // for future upgrades. This flag must not be used for consensus // critical code nor applied to blocks as this flag is only for stricter // standard transaction checks. This flag is only applied when the // above opcodes are executed. ScriptDiscourageUpgradableNops ScriptFlags = 1 << iota // ScriptVerifyCheckLockTimeVerify defines whether to verify that // a transaction output is spendable based on the locktime. // This is BIP0065. ScriptVerifyCheckLockTimeVerify // ScriptVerifyCheckSequenceVerify defines whether to allow execution // pathways of a script to be restricted based on the age of the output // being spent. This is BIP0112. ScriptVerifyCheckSequenceVerify // ScriptVerifyCleanStack defines that the stack must contain only // one stack element after evaluation and that the element must be // true if interpreted as a boolean. This is rule 6 of BIP0062. // This flag should never be used without the ScriptBip16 flag. ScriptVerifyCleanStack // ScriptVerifySigPushOnly defines that signature scripts must contain // only pushed data. This is rule 2 of BIP0062. ScriptVerifySigPushOnly // ScriptVerifySHA256 defines whether to treat opcode 192 (previously // OP_UNKNOWN192) as the OP_SHA256 opcode which consumes the top item of // the data stack and replaces it with the sha256 of it. ScriptVerifySHA256 // ScriptVerifyTreasury defines whether to treat opcode 193 (previously // OP_UNKNOWN193), opcode 194 (previously OP_UNKNOWN194) and opcode 195 // (previously OP_UNKNOWN195) as the OP_TADD, OP_TSPEND and OP_TGEN // opcodes which add and spend an amount from the treasury. ScriptVerifyTreasury )
type ScriptNum ¶
type ScriptNum int64
ScriptNum represents a numeric value used in the scripting engine with special handling to deal with the subtle semantics required by consensus.
All numbers are stored on the data and alternate stacks encoded as little endian with a sign bit. All numeric opcodes such as OP_ADD, OP_SUB, and OP_MUL, are only allowed to operate on 4-byte integers in the range [-2^31 + 1, 2^31 - 1], however the results of numeric operations may overflow and remain valid so long as they are not used as inputs to other numeric operations or otherwise interpreted as an integer.
For example, it is possible for OP_ADD to have 2^31 - 1 for its two operands resulting 2^32 - 2, which overflows, but is still pushed to the stack as the result of the addition. That value can then be used as input to OP_VERIFY which will succeed because the data is being interpreted as a boolean. However, if that same value were to be used as input to another numeric opcode, such as OP_SUB, it must fail.
This type handles the aforementioned requirements by storing all numeric operation results as an int64 to handle overflow and provides the Bytes method to get the serialized representation (including values that overflow).
Then, whenever data is interpreted as an integer, it is converted to this type by using the MakeScriptNum function which will return an error if the number is out of range or not minimally encoded depending on parameters. Since all numeric opcodes involve pulling data from the stack and interpreting it as an integer, it provides the required behavior.
func MakeScriptNum ¶
MakeScriptNum interprets the passed serialized bytes as an encoded integer and returns the result as a script number.
Since the consensus rules dictate that serialized bytes interpreted as ints are only allowed to be in the range determined by a maximum number of bytes, on a per opcode basis, an error will be returned when the provided bytes would result in a number outside of that range. In particular, the range for the vast majority of opcodes dealing with numeric values are limited to 4 bytes and therefore will pass that value to this function resulting in an allowed range of [-2^31 + 1, 2^31 - 1].
An error will be returned if the encoding is not represented with the smallest possible number of bytes or is the negative 0 encoding, [0x80]. For example, consider the number 127. It could be encoded as [0x7f], [0x7f 0x00], [0x7f 0x00 0x00 ...], etc. All forms except [0x7f] will return an error.
The scriptNumLen is the maximum number of bytes the encoded value can be before an ErrNumOutOfRange is returned. This effectively limits the range of allowed values.
WARNING: Great care should be taken if passing a value larger than defaultScriptNumLen, which could lead to addition and multiplication overflows.
See the Bytes function documentation for example encodings.
func (ScriptNum) Bytes ¶
Bytes returns the number serialized as a little endian with a sign bit.
Example encodings:
127 -> [0x7f] -127 -> [0xff] 128 -> [0x80 0x00] -128 -> [0x80 0x80] 129 -> [0x81 0x00] -129 -> [0x81 0x80] 256 -> [0x00 0x01] -256 -> [0x00 0x81] 32767 -> [0xff 0x7f] -32767 -> [0xff 0xff] 32768 -> [0x00 0x80 0x00] -32768 -> [0x00 0x80 0x80]
func (ScriptNum) Int32 ¶
Int32 returns the script number clamped to a valid int32. That is to say when the script number is higher than the max allowed int32, the max int32 value is returned and vice versa for the minimum value. Note that this behavior is different from a simple int32 cast because that truncates and the consensus rules dictate numbers which are directly cast to ints provide this behavior.
In practice, for most opcodes, the number should never be out of range since it will have been created with MakeScriptNum using the defaultScriptLen value, which rejects them. In case something in the future ends up calling this function against the result of some arithmetic, which IS allowed to be out of range before being reinterpreted as an integer, this will provide the correct behavior.
type ScriptTokenizer ¶
type ScriptTokenizer struct {
// contains filtered or unexported fields
}
ScriptTokenizer provides a facility for easily and efficiently tokenizing transaction scripts without creating allocations. Each successive opcode is parsed with the Next function, which returns false when iteration is complete, either due to successfully tokenizing the entire script or encountering a parse error. In the case of failure, the Err function may be used to obtain the specific parse error.
Upon successfully parsing an opcode, the opcode and data associated with it may be obtained via the Opcode and Data functions, respectively.
The ByteIndex function may be used to obtain the tokenizer's current offset into the raw script.
Example ¶
This example demonstrates creating a script tokenizer instance and using it to count the number of opcodes a script contains.
// Create a script to use in the example. Ordinarily this would come from // some other source. hash160 := stdaddr.Hash160([]byte("example")) script, err := txscript.NewScriptBuilder().AddOp(txscript.OP_DUP). AddOp(txscript.OP_HASH160).AddData(hash160). AddOp(txscript.OP_EQUALVERIFY).AddOp(txscript.OP_CHECKSIG).Script() if err != nil { fmt.Printf("failed to build script: %v\n", err) return } // Create a tokenizer to iterate the script and count the number of opcodes. const scriptVersion = 0 var numOpcodes int tokenizer := txscript.MakeScriptTokenizer(scriptVersion, script) for tokenizer.Next() { numOpcodes++ } if tokenizer.Err() != nil { fmt.Printf("script failed to parse: %v\n", err) } else { fmt.Printf("script contains %d opcode(s)\n", numOpcodes) }
Output: script contains 5 opcode(s)
func MakeScriptTokenizer ¶
func MakeScriptTokenizer(scriptVersion uint16, script []byte) ScriptTokenizer
MakeScriptTokenizer returns a new instance of a script tokenizer. Passing an unsupported script version will result in the returned tokenizer immediately having an err set accordingly.
See the docs for ScriptTokenizer for more details.
func (*ScriptTokenizer) ByteIndex ¶
func (t *ScriptTokenizer) ByteIndex() int32
ByteIndex returns the current offset into the full script that will be parsed next and therefore also implies everything before it has already been parsed.
func (*ScriptTokenizer) Data ¶
func (t *ScriptTokenizer) Data() []byte
Data returns the data associated with the most recently successfully parsed opcode.
func (*ScriptTokenizer) Done ¶
func (t *ScriptTokenizer) Done() bool
Done returns true when either all opcodes have been exhausted or a parse failure was encountered and therefore the state has an associated error.
func (*ScriptTokenizer) Err ¶
func (t *ScriptTokenizer) Err() error
Err returns any errors currently associated with the tokenizer. This will only be non-nil in the case a parsing error was encountered.
func (*ScriptTokenizer) Next ¶
func (t *ScriptTokenizer) Next() bool
Next attempts to parse the next opcode and returns whether or not it was successful. It will not be successful if invoked when already at the end of the script, a parse failure is encountered, or an associated error already exists due to a previous parse failure.
In the case of a true return, the parsed opcode and data can be obtained with the associated functions and the offset into the script will either point to the next opcode or the end of the script if the final opcode was parsed.
In the case of a false return, the parsed opcode and data will be the last successfully parsed values (if any) and the offset into the script will either point to the failing opcode or the end of the script if the function was invoked when already at the end of the script.
Invoking this function when already at the end of the script is not considered an error and will simply return false.
func (*ScriptTokenizer) Opcode ¶
func (t *ScriptTokenizer) Opcode() byte
Opcode returns the current opcode associated with the tokenizer.
func (*ScriptTokenizer) Script ¶
func (t *ScriptTokenizer) Script() []byte
Script returns the full script associated with the tokenizer.
type SigCache ¶
SigCache implements an ECDSA signature verification cache with a randomized entry eviction policy. Only valid signatures will be added to the cache. The benefits of SigCache are two fold. Firstly, usage of SigCache mitigates a DoS attack wherein an attack causes a victim's client to hang due to worst-case behavior triggered while processing attacker crafted invalid transactions. A detailed description of the mitigated DoS attack can be found here: https://bitslog.wordpress.com/2013/01/23/fixed-bitcoin-vulnerability-explanation-why-the-signature-cache-is-a-dos-protection/. Secondly, usage of the SigCache introduces a signature verification optimization which speeds up the validation of transactions within a block, if they've already been seen and verified within the mempool.
func NewSigCache ¶
NewSigCache creates and initializes a new instance of SigCache. Its sole parameter 'maxEntries' represents the maximum number of entries allowed to exist in the SigCache at any particular moment. Random entries are evicted to make room for new entries that would cause the number of entries in the cache to exceed the max.
func (*SigCache) Add ¶
func (s *SigCache) Add(sigHash chainhash.Hash, sig *ecdsa.Signature, pubKey *secp256k1.PublicKey, tx *wire.MsgTx)
Add adds an entry for a signature over 'sigHash' under public key 'pubKey' to the signature cache. In the event that the SigCache is 'full', an existing entry is randomly chosen to be evicted in order to make space for the new entry.
NOTE: This function is safe for concurrent access. Writers will block simultaneous readers until function execution has concluded.
func (*SigCache) EvictEntries ¶
EvictEntries removes all entries from the SigCache that correspond to the transactions in the given block. The block that is passed should be ProactiveEvictionDepth blocks deep, which is the depth at which the signatures for the transactions within the block are nearly guaranteed to no longer be useful.
EvictEntries wraps the unexported evictEntries method, which is run from a goroutine. evictEntries is only invoked if validSigs is not empty. This avoids starting a new goroutine when there is nothing to evict, such as when syncing is ongoing.
func (*SigCache) Exists ¶
func (s *SigCache) Exists(sigHash chainhash.Hash, sig *ecdsa.Signature, pubKey *secp256k1.PublicKey) bool
Exists returns true if an existing entry of 'sig' over 'sigHash' for public key 'pubKey' is found within the SigCache. Otherwise, false is returned.
NOTE: This function is safe for concurrent access. Readers won't be blocked unless there exists a writer, adding an entry to the SigCache.
type SigHashSerType ¶
type SigHashSerType uint16
SigHashSerType represents the serialization type used when calculating signature hashes.
NOTE: These values were originally a part of transaction serialization which is why there is a gap and they are not zero based. The logic for calculating signature hashes has since been decoupled from transaction serialization logic, but these specific values are still required by consensus, so they must remain unchanged.
type SigHashType ¶
type SigHashType byte
SigHashType represents hash type bits at the end of a signature.
const ( SigHashAll SigHashType = 0x1 SigHashNone SigHashType = 0x2 SigHashSingle SigHashType = 0x3 SigHashAnyOneCanPay SigHashType = 0x80 )
Hash type bits from the end of a signature.
Source Files ¶
Directories ¶
Path | Synopsis |
---|---|
Package stdaddr provides facilities for working with human-readable Decred payment addresses.
|
Package stdaddr provides facilities for working with human-readable Decred payment addresses. |
Package stdscript provides facilities for working with standard scripts.
|
Package stdscript provides facilities for working with standard scripts. |