slot_set

Summary. Load a ledger object (by keylet) or a transaction (by hash) into a slot.

Signature.

int64_t slot_set(uint32_t read_ptr, uint32_t read_len, uint32_t slot);

Parameters.

Name	Type	Description
read_ptr	uint32_t	Pointer to either a 34-byte serialized keylet or a 32-byte transaction id.
read_len	uint32_t	Must be exactly 34 (keylet) or 32 (transaction id).
slot	uint32_t	Destination slot, or 0 to allocate a free slot.

Return value. Returns the slot number the object was loaded into (non-zero) on success. Errors: OUT_OF_BOUNDS (-1) for a bad read buffer; INVALID_ARGUMENT (-7) if read_len is not 32 or 34, or slot exceeds max_slots; NO_FREE_SLOTS (-6) if slot == 0 and all slots are in use; DOESNT_EXIST (-5) if the keylet/hash does not resolve to a ledger object or a retrievable transaction.

Common failure patterns.

• A read_len other than 32 or 34 → INVALID_ARGUMENT.
• Slotting a keylet whose object is not in the current view → DOESNT_EXIST.
• Filling all 255 slots and then requesting another with slot == 0 → NO_FREE_SLOTS.

Caveats / notes.

• 34 bytes = a serialized keylet (2-byte type + 32-byte key), as produced by util_keylet. 32 bytes = a transaction id (fetched via the master transaction store).
• Passing a specific slot overwrites its previous contents; passing 0 returns the newly allocated slot number.
• A keylet with a zero key returns DOESNT_EXIST.

Minimal example.

uint8_t kl[34];
util_keylet((uint32_t)kl, 34, KEYLET_ACCOUNT, (uint32_t)accid, 20, 0,0,0,0);
int64_t s = slot_set((uint32_t)kl, 34, 0);   // s = allocated slot number

Practical example.

int64_t hook(uint32_t reserved)
{
    _g(1, 1);

    // a serialized keylet (here: the ledger "skip" object, type 0x0068)
    uint8_t kl_sk[34] = { 0x00U, 0x68U, /* ... 32-byte key ... */ };

    ASSERT(slot_set(1, 1000000, 0) == OUT_OF_BOUNDS);          // bad read buffer
    ASSERT(slot_set((uint32_t)kl_sk, 33, 0) == INVALID_ARGUMENT); // wrong length

    int64_t s = slot_set((uint32_t)kl_sk, 34, 0);              // load into a free slot
    ASSERT(s > 0);
    ASSERT(slot_size(s) > 0);

    accept(0, 0, 0);
}

Related APIs. slot, slot_subfield, util_keylet, otxn_slot.