Module protocol 

Pure protocol types, parsing, and response building for the memcached binary protocol. This module has no dependency on redis-module and can be tested in a normal cargo test process.

Structs

Header

Parsed memcached binary-protocol request header.

Request

A fully parsed binary-protocol request, borrowing from the input buffer.

ResponseMeta

Groups the protocol-level metadata fields that every binary response carries. Using a struct avoids exceeding clippy’s argument limit on the response-writing functions.

Enums

Opcode

Memcached binary-protocol opcode.

ParseResult

Outcome of try_parse_request.

Constants

CAS_ZERO

CAS value used in error and control responses.

HEADER_LEN

Length of a binary-protocol request/response header in bytes.

MAGIC_REQ

Magic byte for a binary-protocol request frame (0x80).

MAGIC_RES

Magic byte for a binary-protocol response frame (0x81).

MAX_BODY_LEN

Maximum allowed body length per frame. Memcached’s default item_size_max is 1 MiB; we allow up to 20 MiB to be generous while still preventing multi-gigabyte allocations from a single malicious or buggy frame.

MAX_KEY_LEN

Maximum allowed key length. The memcached binary protocol uses a u16 for key_len (max 65535), but the traditional memcached limit is 250 bytes. We enforce the 250-byte limit for compatibility.

ST_ARGS

Invalid arguments (0x0004).

ST_AUTH_CONTINUE

Authentication continue (multi-step SASL) (0x0021).

ST_AUTH_ERROR

Authentication error (0x0020).

ST_IX

Key exists (used by ADD when key already present) (0x0002).

ST_NF

Key not found (0x0001).

ST_NOT_STORED

Item not stored (CAS mismatch or REPLACE on missing key) (0x0005).

ST_OK

Success status (0x0000).

ST_UNK

Unknown command (0x0081).

Functions

build_raw_request_frame

Build a request frame using a raw opcode byte. Useful for testing unknown-opcode handling.

build_request_frame

Build a binary-protocol request frame from parts. Useful for tests and for any code that needs to construct wire-format requests.

parse_request

Legacy convenience wrapper — returns None for any non-Ok result. Prefer try_parse_request in new code.

try_parse_request

Try to parse one complete request from buf.

write_error_for_raw_opcode

Write an error response for an unknown or malformed opcode, using the raw opcode byte from the wire.

write_raw_response

Write a complete binary-protocol response to w using a raw opcode byte. This is the low-level writer; prefer write_response when you have a known Opcode.

write_response

Write a complete binary-protocol response to w.

write_simple_response

Convenience: write a simple response with no extras or key.