core.enc.fnv1a¶

FNV-1a (Fowler-Noll-Vo) non-cryptographic hash in 32-bit and 64-bit widths.

Overview¶

core.enc.fnv1a implements the FNV-1a variant of the Fowler-Noll-Vo hash algorithm. FNV-1a XORs each input byte into the hash value before multiplying by the FNV prime, which provides better avalanche characteristics than the original FNV-1 (which multiplies first). The algorithm is simple, fast, and produces well-distributed hashes suitable for hash tables, Bloom filters, and checksums.

FNV-1a is the primary hash function used by core.ds.hashmap (key hashing) and core.ds.bloom (first of two hash functions in the double-hashing scheme).

Dependencies¶

io.syslog — test output (implementation only)
memory.heap — kfree (implementation only)
core.strings — test output formatting (implementation only)

Functions and Procedures¶

Hash_FNV1a32¶

function Hash_FNV1a32(Data : void; DataLen : uint32) : uint32;

Computes a 32-bit FNV-1a hash of DataLen bytes starting at Data. - Initial basis: $811C9DC5 - FNV prime: $01000193 - Per byte: h = (h xor byte) * prime

Zero-length input returns the basis value $811C9DC5.

Hash_FNV1a64¶

function Hash_FNV1a64(Data : void; DataLen : uint32) : uint64;

Computes a 64-bit FNV-1a hash. - Initial basis: $CBF29CE484222325 - FNV prime: $00000100000001B3

Zero-length input returns the basis value.

UnitTest¶

procedure UnitTest;

Runs the FNV-1a test suite (known basis for empty input, determinism, distinctness for different inputs, length sensitivity, independence of 32-bit and 64-bit variants) and logs a pass/fail summary to syslog under the 'FNV1A' channel.

Notes¶

Both functions are purely computational with no side effects or allocations. They may be called from any context.

The low 32 bits of Hash_FNV1a64 are not guaranteed to equal Hash_FNV1a32 for the same input; they are independent algorithms.