fnv1a-pure

Zero-dependency pure-stdlib FNV-1a and FNV-1 hash (32/64-bit) for Python.

fnv1a-pure provides Fowler-Noll-Vo FNV-1a and FNV-1 hash functions without any C extensions or third-party dependencies. Works on CPython 3.8+, MicroPython, and Pyodide.

Quick Start

pip install -e .

from fnv1a_pure import fnv1a_64, fnv1a_32, fnv1_64, fnv1_32, fnv1a_64_hex, fnv1a_32_hex

# FNV-1a-64 (most common variant)
fnv1a_64(b"hello")          # → 11831194018420276491
fnv1a_64_hex(b"hello")      # → "a430d84680aabd0b"

# FNV-1a-32
fnv1a_32(b"hello")          # → 1335831723
fnv1a_32_hex(b"hello")      # → "4f9f2cab"

# FNV-1 (alternate: multiply-before-XOR)
fnv1_64(b"hello")           # → 8883723591023973575  (different from FNV-1a)
fnv1_32(b"hello")           # → 3233227887

Why fnv1a-pure?

• Zero dependencies — pure stdlib, no C extensions, no pip install failures on Pyodide/WebAssembly
• Works everywhere — CPython 3.8+, MicroPython, Pyodide, AWS Lambda, serverless environments
• Canonical algorithm — FNV-1a is the de-facto standard non-cryptographic hash in Memcached, Redis, Nginx, and Cloudflare's load balancers
• Small footprint — single file, ~85 LOC core, no bloat

Competitor: fnvhash (PyPI) is a C extension requiring compilation — fails on Pyodide and zero-compile serverless.

Key Features

• fnv1a_64(data: bytes) -> int — FNV-1a-64 hash, unsigned 64-bit
• fnv1a_32(data: bytes) -> int — FNV-1a-32 hash, unsigned 32-bit
• fnv1_64(data: bytes) -> int — FNV-1-64 hash (multiply-before-XOR variant)
• fnv1_32(data: bytes) -> int — FNV-1-32 hash
• fnv1a_64_hex(data: bytes) -> str — zero-padded 16-char hex string
• fnv1a_32_hex(data: bytes) -> str — zero-padded 8-char hex string

API Reference

All functions accept bytes and return an unsigned int:

Test Vectors

All values verified against the FNV reference implementation (first principles).

Limitations

This is NOT a cryptographic hash. FNV-1a is a non-cryptographic hash designed for hash tables and bloom filters — not for security purposes. It is intentionally fast and simple, not collision-resistant or preimage-resistant. Do not use it for password hashing, digital signatures, or any security-critical purpose.

Byte strings only — pass data.encode() for string input. Passing str directly raises TypeError.

Test Suite

111 tests covering:

• All 10 acceptance criteria (each has ≥1 test)
• Canonical test vectors from FNV reference
• Determinism: identical input always produces identical output
• Byte-order independence
• Edge cases: empty input, all-zeros, all-ones, 64KB payloads
• FNV-1 vs FNV-1a distinction
• Property: distinct inputs produce distinct outputs
• All 256 single-byte values, collision-free in 64-bit space

pytest -q

Acceptance Criteria Checklist

References

• FNV Hash — Wikipedia (HTTP 200 verified)
• IETF draft-eastlake-fnv (historical reference) (HTTP 200 verified)
• FNV source repository — Landon Curt Noll (HTTP 200 verified)

License

MIT License — see LICENSE.