hook_hash

Summary. Write the 32-byte WASM hash of a hook in the current account's hook chain, identifying which code is (or will be) executed at a given position.

Signature.

int64_t hook_hash(uint32_t write_ptr, uint32_t write_len, int32_t hook_no);

Parameters.

Name	Type	Description
write_ptr	uint32_t	Destination buffer.
write_len	uint32_t	Buffer length; must be at least 32.
hook_no	int32_t	Chain position to query, or -1 for the currently executing hook.

Return value. Returns the number of bytes written (32) on success. Errors: TOO_SMALL (-4) if write_len < 32; OUT_OF_BOUNDS (-1) for a bad buffer; INTERNAL_ERROR (-2) if the account's hook object cannot be read; DOESNT_EXIST (-5) if hook_no is beyond the chain or that slot has no sfHookHash.

Common failure patterns.

• Querying a hook_no that isn't installed → DOESNT_EXIST.
• Buffer shorter than 32 bytes → TOO_SMALL.

Caveats / notes.

• hook_no == -1 returns the hash of the hook that is currently running (from hookCtx.result.hookHash); other values read the on-ledger sfHooks array.
• The hash identifies the HookDefinition (WASM bytecode), useful for detecting which hook in a multi-hook chain you are, or for feeding hook_skip.

Minimal example.

uint8_t h[32];
hook_hash((uint32_t)h, 32, -1);   // hash of the current hook

Practical example.

// Skip the next hook in the chain if it matches a known hash.
uint8_t other[32];
if (hook_hash((uint32_t)other, 32, hook_pos() + 1) == 32)
    hook_skip((uint32_t)other, 32, 0);
accept(SBUF("done"), 0);

Related APIs. hook_pos, hook_skip.