Module format 

Encoding and decoding of a single WAL object. The byte layout is described in the module documentation.

Structs

ChainLink 🔒

Names the object another object extends: its sequence and the epoch recorded in its header.

EncodedObject 🔒

An encoded object together with the metadata a writer indexes it by.

FixedTrailer 🔒

Fixed-size trailer locating the footer of an object.

FooterEntry 🔒

Footer entry describing the segment of one region.

Header 🔒

Header of a WAL object.

Reader 🔒

Record 🔒

A single WAL entry inside an object.

Constants

FOOTER_ENTRY_LEN 🔒

Length of one footer entry: region id, entry id range, entry count, segment offset, segment length and segment CRC32.

FORMAT_VERSION 🔒

HEADER_LEN 🔒

Length of the object header: magic, version, object sequence, epoch, predecessor sequence, predecessor epoch and the CRC32 of the header.

HEADER_MAGIC 🔒

MIN_OBJECT_LEN 🔒

Lower bound on the length of an object: header, a footer holding only its entry count and the trailer.

NO_PREDECESSOR 🔒

Predecessor sequence recorded for an object that starts a chain. Object sequences stay below OBJECT_SEQ_LIMIT, so it never names an object.

SEGMENT_HEADER_LEN 🔒

TRAILER_LEN 🔒

Length of the fixed trailer: footer offset, footer length, footer CRC32, object CRC32 and magic.

TRAILER_MAGIC 🔒

Functions

checksum_mismatch 🔒

decode_footer 🔒

Decodes the footer that trailer points at.

decode_header 🔒

Decodes and verifies the header from the first HEADER_LEN bytes of an object.

decode_segment 🔒

Decodes the segment that entry describes.

decode_trailer 🔒

Decodes the trailer from the last TRAILER_LEN bytes of an object.

encode_footer 🔒

encode_header 🔒

encode_object 🔒

Encodes records into one object. Records are grouped into a segment per region; entry ids within a region must be unique. An object without records only extends the chain.

encode_trailer 🔒

footer_range 🔒

Locates the footer inside an object of object_len bytes from its trailer. The footer must follow the header and end where the trailer starts.

invalid_magic 🔒

object_crc32 🔒

Checksum of everything but the object checksum itself, so the trailer can carry it.

to_u32 🔒

to_u64 🔒

to_usize 🔒

trailing_bytes 🔒

truncated 🔒

verify_segment_ranges 🔒

Checks that the segments footer describes tile the object body: the first starts right after the header, each follows the previous one without a gap or overlap, and the last ends where the footer at footer_start begins.