state

Retrieve the data pointed to by a Hook State key and write it to an output buffer

Behaviour

• Read a 32 byte Hook State key from the kread_ptr

• Write the data (value) at that key to the buffer pointed to by write_ptr

Definition

C

int64_t state (
    uint32_t write_ptr,
    uint32_t write_len,
    uint32_t kread_ptr,
    uint32_t kread_len  
);

Example

C

#define SBUF(str) (uint32_t)(str), sizeof(str)
if (state(SBUF(vault), SBUF(vault_key)) != 16)
		rollback(SBUF("Error: could not read state!"), 1);

Parameters

Name	Type	Description
write_ptr	uint32_t	A pointer to the buffer to write the data in the Hook State into.
write_len	uint32_t	The length of the write buffer.
kread_ptr	uint32_t	Pointer to a buffer containing the Hook State key.
kread_len	uint32_t	The length of the Hook State key. (Should be 32.)

📘Hint

Ensure you check the return value. A state lookup can fail of a range of reasons and the buffer will then contain whatever it did before the call (typically all zeros).

Return Code

Type

Description

int64_t

The number of bytes written to the write buffer. If negative, an error: OUT_OF_BOUNDS - pointers/lengths specified outside of hook memory. DOESNT_EXIST - the specified Hook State key doesn't have an associated value on the ledger at the time of the call. TOO_BIG - the key specified by read_ptr and read_len was larger than 32 bytes. TOO_SMALL - the output buffer was too small to store the Hook State data.