xpop_slot

Behaviour

• Locate the XPOP on the originating Import transaction and extract its inner transaction and metadata.
• Place the transaction into slot_no_tx and the metadata into slot_no_meta.
• A slot argument of 0 asks the host to allocate a free slot. A nonzero argument must be 1..255 and is overwritten if it already holds an object.
• Two nonzero arguments must name different slots.
• On success, returns both slot numbers packed into one value: (tx_slot << 16) | meta_slot.

Definition

C

int64_t xpop_slot (
    uint32_t slot_no_tx,
    uint32_t slot_no_meta
);

JavaScript

function xpop_slot(slotno_tx: number, slotno_meta: number): ErrorCode | number

Example

C

int64_t slots = xpop_slot(0, 0);   // let the host allocate both slots
if (slots < 0)
    rollback(SBUF("No XPOP"), 1);

uint32_t tx_slot = (uint32_t)(slots >> 16);
uint32_t meta_slot = (uint32_t)(slots & 0xFFFF);

JavaScript

const result = xpop_slot(1, 2)

Parameters

C

Name	Type	Description
slot_no_tx	uint32_t	Slot to receive the XPOP’s inner transaction: 0 to allocate one, or 1..255.
slot_no_meta	uint32_t	Slot to receive the XPOP’s metadata: 0 to allocate one, or 1..255. Must differ from a nonzero slot_no_tx.

JavaScript

Name	Type	Description
slotno_tx	number	Slot for the XPOP’s inner transaction.
slotno_meta	number	Slot for the XPOP’s metadata.

Return Code

C

Type

Description

int64_t

On success, (tx_slot << 16) | meta_slot: the transaction slot in the upper 16 bits and the metadata slot in the lower 16 bits. If negative, an error: PREREQUISITE_NOT_MET - The originating transaction is not an Import. INVALID_ARGUMENT - A slot number is above 255, or both slot numbers name the same nonzero slot. NO_FREE_SLOTS - A slot had to be allocated but the Hook already uses the maximum number of slots. INVALID_TXN - The Import does not carry a readable inner transaction and metadata.

JavaScript

Type	Description
number or ErrorCode	Returns an error code, or a non-negative result on success.