SmartContract

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

---

@opcat-labs/scrypt-ts-opcat / SmartContract

Class: SmartContract\<StateT>

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:58

The main contract class. To write a contract, extend this class as such:

Onchain

Example

class YourSmartContract extends SmartContract {
  // your smart contract code here
}

Extends

• AbstractContract

Type Parameters

• StateT extends OpcatState = undefined

Constructors

new SmartContract()

new SmartContract\<StateT>(...args): SmartContract\<StateT>

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:120

Parameters

args

...SupportedParamType[]

Returns

SmartContract\<StateT>

Overrides

AbstractContract.constructor

Backtrace

backtraceToOutpoint()

backtraceToOutpoint(backtraceInfo, genesisOutpoint): boolean

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:689

Check whether the contract can be traced back to the genesis outpoint.

Parameters

backtraceInfo

BacktraceInfo

the backtrace info to verify, including prevTx and prevPrevTx informations

genesisOutpoint

ByteString

expected genesis outpoint to be traced back to

Returns

boolean

true if the contract can be backtraced to the genesis outpoint. Otherwise false.

Onchain

Overrides

AbstractContract.backtraceToOutpoint

---

backtraceToScript()

backtraceToScript(backtraceInfo, genesisScript): boolean

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:701

Check whether the contract can be traced back to the genesis script.

Parameters

backtraceInfo

BacktraceInfo

the backtrace info to verify, including prevTx and prevPrevTx informations

genesisScript

ByteString

expected genesis script to be traced back to

Returns

boolean

true if the contract can be backtraced to the genesis script. Otherwise false.

Onchain

Overrides

AbstractContract.backtraceToScript

Other

_state

_state: StateT

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:87

The state of the contract UTXO, usually committed to the first OP_RETURN output, is revealed when spending.

Onchain

---

lockingScript

readonly lockingScript: Script

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:100

Locking script corresponding to the SmartContract

---

utxo?

optional utxo: ExtUtxo

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:81

---

artifact

static artifact: Artifact

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:63

Bitcoin Contract Artifact

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changeInfo

Get Signature

get changeInfo(): TxOut

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:553

Get the change info of the change output for current psbt.

Onchain

Returns

TxOut

the change info of current psbt

---

ctx

Get Signature

get ctx(): IContext

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:337

Get the context details of the current PSBT input in which this contract is called or spent.

Onchain

Returns

IContext

Overrides

AbstractContract.ctx

---

debug

Get Signature

get debug(): object

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:562

A set of functions for debugging contracts, which can only be called in @method methods.

Onchain

Returns

object

diffOutputs()

diffOutputs: (outputsByte) => void

Parameters

outputsByte

ByteString

Returns

void

---

inputContext

Get Signature

get inputContext(): InputContext

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:389

Get the context of the current PSBT input in which this contract is called or spent.

Returns

InputContext

the context of the current PSBT input

---

lockingScriptHash

Get Signature

get lockingScriptHash(): Sha256

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:101

Returns

Sha256

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spentPsbt

Get Signature

get spentPsbt(): Contextual

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:372

Gets the PSBT (Partially Signed Bitcoin Transaction) that was used to spend this contract. Returns undefined if no spending transaction exists.

Returns

Contextual

---

state

Get Signature

get state(): StateT

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:89

Returns

StateT

Set Signature

set state(state): void

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:92

Parameters

state

StateT

Returns

void

---

asyncBindToUtxo()

asyncBindToUtxo(utxo, callback): Promise\<SmartContract\<StateT>>

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:749

Parameters

utxo

Optional\<ExtUtxo, "script"> | Optional\<UTXO, "script">

callback

(contract) => Promise\<void>

Returns

Promise\<SmartContract\<StateT>>

---

bindToUtxo()

bindToUtxo(utxo): this

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:725

Binds the smart contract to a UTXO by verifying and setting its script.

Parameters

utxo

The UTXO to bind to (script field is optional)

Optional\<ExtUtxo, "script"> | Optional\<UTXO, "script">

Returns

this

The contract instance for chaining

Throws

Error if the UTXO's script exists and doesn't match the contract's locking script

---

buildChangeOutput()

buildChangeOutput(): ByteString

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:226

A built-in function to create an [change output][https://en.bitcoin.it/wiki/Change](https://en.bitcoin.it/wiki/Change).

Returns

ByteString

Onchain

Overrides

AbstractContract.buildChangeOutput

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checkInputState()

checkInputState(inputIndex, serializedState): boolean

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:317

check state of the input. option in the @method() decorator to false.

Parameters

inputIndex

Int32

index of the input

serializedState

ByteString

the state of the input

Returns

boolean

success if stateHash is valid

Onchain

Overrides

AbstractContract.checkInputState

---

checkOutputs()

checkOutputs(outputs): boolean

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:603

Check the outputs with the context of current transaction.

Parameters

outputs

ByteString

the expected serialized outputs of the current transaction

Returns

boolean

true if the outputs are not consistent with the transaction context, otherwise false.

Onchain

Overrides

AbstractContract.checkOutputs

---

checkSHPreimage()

checkSHPreimage(shPreimage): boolean

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:175

Using the [OP_PUSH_TX][https://medium.com/@xiaohuiliu/op-push-tx-3d3d279174c1](https://medium.com/@xiaohuiliu/op-push-tx-3d3d279174c1) technique, check if shPreimage is the preimage of the current transaction.

Parameters

shPreimage

SHPreimage

Returns

boolean

true if shPreimage is the preimage of the current transaction. Otherwise false.

Onchain

Overrides

AbstractContract.checkSHPreimage

---

getCallData()

getCallData(): MethodCallData

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:626

Gets the method call data for the current smart contract.

Returns

MethodCallData

The method call data object.

Throws

If no method call is found.

---

getUnlockingScript()

getUnlockingScript(): Script

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:616

Returns the raw arguments from the call data of the smart contract.

Returns

Script

The raw arguments extracted from the call data.

---

isPubFunction()

isPubFunction(method): boolean

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:427

Checks if the given method is a public function in the smart contract.

Parameters

method

string

The method name to check.

Returns

boolean

True if the method is a public function, false otherwise.

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next()

next(newState): this

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:711

Get a new contract instance with the new state.

Parameters

newState

StateT

the new state

Returns

this

the new covenant

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setSighashType()

setSighashType(sigHashType): void

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:380

Sets the signature hash type for the current input in the PSBT.

Parameters

sigHashType

SigHashType

The signature hash type to set

Returns

void

---

spentFromInput()

spentFromInput(psbt, inputIndex): void

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:363

Mark the contract instance as spent from the input of the PSBT.

Parameters

psbt

Contextual

inputIndex

number

Returns

void

---

timeLock()

timeLock(nLockTime): boolean

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:658

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

See the bip65 for specification https://github.com/bitcoin/bips/blob/master/bip-0065.mediawiki#summary

Parameters

nLockTime

Int32

the locktime read from the script

Returns

boolean

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

Onchain

Overrides

AbstractContract.timeLock

---

create()

static create\<T>(this, ...args): InstanceType\<T>

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:158

Used to create an instance of a smart contract. If your smart contract has a base class, you must use this method to instantiate it.

Type Parameters

• T extends (...args) => InstanceType\<T>

Parameters

this

T

args

...ConstructorParameters\<T>

Returns

InstanceType\<T>

---

deserializeState()

static deserializeState\<T>(this, serializedState): T

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:276

Deserializes the contract state from a ByteString.

Type Parameters

• T extends StructObject

The type of the contract state extending OpcatState

Parameters

this

(...args) => SmartContract\<T>

serializedState

ByteString

The serialized state as a ByteString

Returns

T

The deserialized state object of type T

Throws

Error if artifact is not loaded or state type is not defined

---

isStateful()

static isStateful(): boolean

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:763

Checks if the contract has state by verifying if the state object exists and is not empty.

Returns

boolean

True if the contract has state, false otherwise.

---

loadArtifact()

static loadArtifact(artifact): typeof SmartContract

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:110

This function is usually called on the frontend. The contract class needs to call this function before instantiating.

Parameters

artifact

Artifact

a contract artifact json object

Returns

typeof SmartContract

---

serializeState()

static serializeState\<T>(this, state): ByteString

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:250

Serializes the contract state into a ByteString.

Type Parameters

• T extends StructObject

Type of the contract state extending OpcatState

Parameters

this

(...args) => SmartContract\<T>

Constructor reference for type inference

state

T

The contract state object to serialize

Returns

ByteString

Serialized state as ByteString

Throws

Error if artifact is not loaded or state type is not defined

Overrides

AbstractContract.serializeState

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stateHash()

static stateHash\<T>(this, state): ByteString

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:302

Computes the SHA-256 hash of the serialized contract state.

Type Parameters

• T extends StructObject

Type extending OpcatState

Parameters

this

(...args) => SmartContract\<T>

state

T

The contract state to hash

Returns

ByteString

ByteString containing the SHA-256 hash of the serialized state

Overrides

AbstractContract.stateHash

Signature Verification

checkMultiSig()

checkMultiSig(signatures, publickeys): boolean

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:217

Compares the first signature against each public key until it finds an ECDSA match. Starting with the subsequent public key, it compares the second signature against each remaining public key until it finds an ECDSA match. The process is repeated until all signatures have been checked or not enough public keys remain to produce a successful result. All signatures need to match a public key. Because public keys are not checked again if they fail any signature comparison, signatures must be placed in the scriptSig using the same order as their corresponding public keys were placed in the scriptPubKey or redeemScript. If all signatures are valid, 1 is returned, 0 otherwise. Due to a bug, one extra unused value is removed from the stack.

Parameters

signatures

Sig[]

publickeys

PubKey[]

Returns

boolean

Onchain

---

checkSig()

checkSig(signature, publickey, errorMsg): boolean

Defined in: packages/scrypt-ts-opcat/src/smart-contract/smartContract.ts:185

A built-in function verifies an Schnorr signature. It takes two inputs from the stack, a public key (on top of the stack) and an Schnorr signature in its DER_CANONISED format concatenated with sighash flags. It outputs true or false on the stack based on whether the signature check passes or fails. [see][https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki#specification](https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki#specification)

Parameters

signature

Sig

publickey

PubKey

errorMsg

string = 'signature check failed'

Returns

boolean

Onchain

Overrides

AbstractContract.checkSig