Module codec 

WAL encoding and decoding.

This module defines the encode/decode contract for WAL events with deterministic ordering and version framing policy.

Format

The WAL encoding uses a framed binary format with CRC-32 integrity checks:

+-------------+-------------+------------+------------------------+
| Version (4B)| Length (4B) | CRC-32 (4B)| Serialized Event (N B) |
+-------------+-------------+------------+------------------------+

• Version: 4-byte LE unsigned integer indicating the format version (currently 5)
• Length: 4-byte LE unsigned integer indicating the length of the serialized event
• CRC-32: 4-byte LE CRC-32 checksum of the serialized event payload
• Serialized Event: The postcard-encoded WalEvent structure

This format ensures:

• Deterministic ordering: The same event always produces the same bytes
• Version framing: future format changes can be handled by checking the version
• Length prefixing: allows efficient reading without backtracking
• Integrity: CRC-32 detects corruption in the payload

Enums

DecodeError

Errors that can occur during WAL decoding.

EncodeError

Errors that can occur during WAL encoding.

Constants

HEADER_LEN

Size of the WAL record header in bytes (version + length + crc32).

MAX_PAYLOAD_SIZE

Maximum payload size that can be encoded in a WAL record.

VERSION

The current WAL format version.

Functions

decode

Decodes a WAL event from bytes.

encode

Encodes a WAL event into bytes.