emit

Concepts

Emitted Transactions prepare()

Behaviour

C

• Read a transaction from read_ptr
• Validate the transaction against the emission rules
• Emit the transaction into consensus when valid
• Write canonical transaction hash to write_ptr

With the HooksUpdate2 amendment, use prepare() before emit() to automatically inject all required emission fields (Account, Sequence, SigningPubKey, Fee, EmitDetails, etc.) from a partial transaction.

JavaScript

• This function emits the provided transaction JSON.
• On success, it returns the emitted transaction hashes.
• If there is an error, it returns an error code.

Definition

C

int64_t emit (
    uint32_t write_ptr,
    uint32_t write_len,
    uint32_t read_ptr,
    uint32_t read_len
);

JavaScript

function emit(
    txJson: Record<string, any> | Transaction
  ): ErrorCode | ByteArray

Example

C

uint8_t emithash[32];
if (emit(SBUF(emithash), SBUF(tx)) < 0)
    rollback(SBUF("hook: emit failed"), __LINE__);

JavaScript

const emitResult = emit(txJson)
if(typeof emitResult === 'number')
    rollback("Failed to emit!", 1)

Parameters

C

Name	Type	Description
write_ptr	uint32_t	Pointer to a buffer to write the transaction hash to
write_len	uint32_t	The size of the buffer to write the transaction hash to (should be 32.)
read_ptr	uint32_t	Pointer to the transaction to emit
read_len	uint32_t	The length of the transaction

JavaScript

Name	Type	Description
txJson	Record<string, any> | Transaction	The TX JSON to emit.

Return Code

C

Type

Description

int64_t

On success, the number of bytes of transaction hash written (32), or: If negative, an error: OUT_OF_BOUNDS - pointers/lengths specified outside of hook memory. PREREQUISITE_NOT_MET - etxn_reserve must be called first TOO_MANY_EMITTED_TXN - the number of emitted transactions is now greater than the promise made when etxn_reserve was called earlier EMISSION_FAILURE - the transaction was malformed according to the emission rules.

JavaScript

Type	Description
ErrorCode | ByteArray	Returns an ErrorCode if there is an error, or an array of emitted transaction hashes on success.