Interpreter

@opcat-labs/scrypt-ts-opcat v1.0.4

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@opcat-labs/scrypt-ts-opcat / Interpreter

Class: Interpreter

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:15

Bitcoin transactions contain scripts. Each input has a script called the scriptSig, and each output has a script called the scriptPubkey. To validate an input, the input's script is concatenated with the referenced output script, and the result is executed. If at the end of execution the stack contains a "true" value, then the transaction is valid.

The primary way to use this class is via the verify function. e.g., Interpreter().verify( ... );

Param

Optional object to initialize the interpreter with.

Constructors

new Interpreter()

new Interpreter(obj?): Interpreter

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:30

Bitcoin transactions contain scripts. Each input has a script called the scriptSig, and each output has a script called the scriptPubkey. To validate an input, the input's script is concatenated with the referenced output script, and the result is executed. If at the end of execution the stack contains a "true" value, then the transaction is valid.

The primary way to use this class is via the verify function. e.g., Interpreter().verify( ... );

Parameters

obj?

any

Optional object to initialize the interpreter with.

Returns

Interpreter

A new Interpreter instance.

Properties

altstack

altstack: any

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:54

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errstr

errstr: any

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:46

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flags

flags: any

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:60

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nin

nin: any

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:97

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nonTopLevelReturnAfterGenesis

nonTopLevelReturnAfterGenesis: boolean

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:61

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nOpCount

nOpCount: any

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:57

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pbegincodehash

pbegincodehash: any

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:56

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pc

pc: any

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:55

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returned

returned: boolean

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:62

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satoshisBN

satoshisBN: any

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:98

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script

script: any

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:95

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stack

stack: any

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:53

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tx

tx: any

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:96

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vfElse

vfElse: any

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:59

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vfExec

vfExec: any

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:58

Methods

checkLockTime()

checkLockTime(nLockTime): boolean

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:146

Checks a locktime parameter with the transaction's locktime. There are two times of nLockTime: lock-by-blockheight and lock-by-blocktime, distinguished by whether nLockTime < LOCKTIME_THRESHOLD = 500000000

See the corresponding code on bitcoin core: https://github.com/bitcoin/bitcoin/blob/ffd75adce01a78b3461b3ff05bcc2b530a9ce994/src/script/interpreter.cpp#L1129

Parameters

nLockTime

BN

the locktime read from the script

Returns

boolean

true if the transaction's locktime is less than or equal to the transaction's locktime

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checkPubkeyEncoding()

checkPubkeyEncoding(buf): boolean

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:120

Checks if the provided public key buffer is valid according to strict encoding rules. Sets an error message if validation fails under SCRIPT_VERIFY_STRICTENC flag.

Parameters

buf

Buffer

The public key buffer to validate.

Returns

boolean

True if valid, false otherwise (with error string set).

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checkSequence()

checkSequence(nSequence): boolean

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:153

Checks a sequence parameter with the transaction's sequence.

Parameters

nSequence

BN

the sequence read from the script

Returns

boolean

true if the transaction's sequence is less than or equal to the transaction's sequence

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checkSignatureEncoding()

checkSignatureEncoding(buf): boolean

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:113

Checks if a signature encoding is valid according to the interpreter's flags.

• For empty signatures: always valid (used for compact invalid signatures in CHECK(MULTI)SIG)
• With DERSIG/STRICTENC flags: validates DER encoding and strict encoding rules
• With LOW_S flag: ensures signature uses low S value
• With STRICTENC flag: validates defined hash type

Parameters

buf

Buffer

The signature buffer to validate

Returns

boolean

True if valid, false otherwise (sets errstr on failure)

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evaluate()

evaluate(scriptType): boolean

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:131

Evaluates a script by executing each opcode step-by-step. Performs size checks on the script and stacks before execution.

Based on bitcoind's EvalScript function, with the inner loop moved to Interpreter.prototype.step() bitcoind commit: b5d1b1092998bc95313856d535c632ea5a8f9104

Parameters

scriptType

string

The type of script being evaluated

Returns

boolean

True if evaluation succeeds, false if any error occurs

Throws

If an unknown error occurs during evaluation

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initialize()

initialize(): void

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:52

Initializes the interpreter instance with default values. Sets up empty stacks, resets program counter and execution flags, and initializes state tracking variables for script execution.

Returns

void

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set()

set(obj): void

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:80

Updates the interpreter's state with provided values.

Parameters

obj

Object containing properties to update

altstack?

any[]

Alternate stack

errstr?

string

Error string

flags?

number

Interpreter flags

nin?

boolean

Non-input flag

nOpCount?

number

Operation count

pbegincodehash?

number

Begin code hash position

pc?

number

Program counter

satoshisBN?

BN

Satoshis as BN.js instance

script?

Buffer

Script buffer

stack?

any[]

Main stack

tx?

any

Transaction object

vfElse?

any[]

Else flags

vfExec?

any[]

Execution flags

Returns

void

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step()

step(scriptType): boolean

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:167

Executes a single step in the script interpreter.

This method processes the current opcode in the script, performs the corresponding operation, and updates the stack or interpreter state accordingly. It handles various opcode types including stack operations, arithmetic, bitwise logic, cryptographic operations, and control flow.

Based on the inner loop of bitcoind's EvalScript function bitcoind commit: b5d1b1092998bc95313856d535c632ea5a8f9104

Parameters

scriptType

string

The type of script being executed (e.g., scriptPubkey, scriptSig).

Returns

boolean

Returns true if the step executed successfully, or false if an error occurred. Errors are stored in this.errstr.

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subscript()

subscript(): Script

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:103

Returns a subset of the script starting from the most recent OP_CODESEPARATOR.

Returns

Script

A new Script instance containing the sliced chunks.

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verify()

verify(scriptSig, scriptPubkey, tx?, nin?, flags?, satoshisBN?): boolean

Defined in: node_modules/@opcat-labs/opcat/types/interpreter/interpreter.d.cts:45

Verifies a Script by executing it and returns true if it is valid. This function needs to be provided with the scriptSig and the scriptPubkey separately.

Parameters

scriptSig

Script

the script's first part (corresponding to the tx input)

scriptPubkey

Script

the script's last part (corresponding to the tx output)

tx?

Transaction

the Transaction containing the scriptSig in one input (used to check signature validity for some opcodes like OP_CHECKSIG)

nin?

number

index of the transaction input containing the scriptSig verified.

flags?

number

evaluation flags. See Interpreter.SCRIPT_* constants

satoshisBN?

number

amount in satoshis of the input to be verified (when FORKID signhash is used)

Translated from bitcoind's VerifyScript

Returns

boolean