hook_param_set

Summary. Override (or delete) a parameter value for a hook identified by hash; the override is read whenever that hook executes, including later lookups in the same execution if you address the current hook's own hash.

Signature.

int64_t hook_param_set(uint32_t read_ptr, uint32_t read_len,
                       uint32_t kread_ptr, uint32_t kread_len,
                       uint32_t hread_ptr, uint32_t hread_len);

Parameters.

Name	Type	Description
read_ptr	uint32_t	Pointer to the parameter value to set.
read_len	uint32_t	Value length; up to 256 bytes. 0 deletes/hides the parameter.
kread_ptr	uint32_t	Pointer to the parameter key (name).
kread_len	uint32_t	Key length; 1..32 bytes.
hread_ptr	uint32_t	Pointer to the 32-byte WASM hash of the target hook.
hread_len	uint32_t	Must be exactly 32.

Return value. Returns the value length written on success. Errors: OUT_OF_BOUNDS (-1) for bad pointers; TOO_SMALL (-4) if the key length is 0; TOO_BIG (-3) if the key exceeds 32 or the value exceeds 256; INVALID_ARGUMENT (-7) if hread_len != 32; TOO_MANY_PARAMS (-36) if more than 16 overrides have been set (max_params).

Common failure patterns.

• Hash length other than 32 → INVALID_ARGUMENT.
• Exceeding the 16-override budget → TOO_MANY_PARAMS.

Caveats / notes.

• Overrides are keyed by the target hook hash. If you target a later hook, that hook sees the value when it runs; if you target this hook's own hash, later hook_param calls in the same execution see the override too.
• A read_len of 0 sets an empty override, which causes the target hook's hook_param lookup for that key to return DOESNT_EXIST (an effective "delete").
• At most 16 overrides may be set across the hook (max_params).

Minimal example.

uint8_t next_hash[32];
hook_hash((uint32_t)next_hash, 32, hook_pos() + 1);
hook_param_set(SBUF("newval"), SBUF("param0"), (uint32_t)next_hash, 32);

Practical example.

// Pass a computed budget to the next hook in the chain.
uint8_t next[32];
if (hook_hash((uint32_t)next, 32, hook_pos() + 1) == 32)
{
    uint8_t budget[8];
    UINT64_TO_BUF(budget, 1000000ULL);
    hook_param_set((uint32_t)budget, 8, SBUF("BUDGET"), (uint32_t)next, 32);
}
accept(SBUF("configured next hook"), 0);

Related APIs. hook_param, hook_hash, hook_pos.