wti/swiftpolymurhash

- Swift wrapper for [polymur-hash](https://github.com/orlp/polymur-hash)

Usage

Declare dependency in Package.swift, Package(...,:

- dependencies: - .package(url: "https://github.com/wti/SwiftPolymurHash.git", from: "0.0.1") - targets: [ .target(..., dependencies: - [.product(name: "PolymurHash", package: "SwiftPolymurHash")]

Code

- See e.g., PolymurHashTests

The tweak value provides some pseudo-variance to avoid hash attacks

- But you can set it to zero or the same value to reproduce hashes

It uses 5 UInt64's of state per hasher (including the default tweak value)

Warning: combining with Swift's hasher isn't easy and may not be wise

Swift is not amenable to extrinsic hashing

- Hashable.hashValue is deprecated - Hasher has no API for extrinsic values

There are no guarantees that polymur hashes will combine well with Swift hashes
Consider restricting usage for Hashable to top-level types
See SE-206

Development

polymur-hash.h is manually copied from its source repository

- also demo.c is from main.c, with main function renamed - Update PolymurHash.VERSION in swift when updating sources

Compiling: 2 known warnings

- test code deprecation for Hashable.hashValue - c code Implicit conversion loses integer precision

Linking

- No need to link with m (math) library on Linux, et al? - linkerSettings: [.linkedLibrary("m", .when(platforms: [.linux]))]

Testing

- TODO: verify swift compiler reduces to same/similar assembly as clang

Legal

polymur-hash is subject to its license and copyright
This wrapper project is released under an MIT license.

Package Metadata

Repository: wti/swiftpolymurhash

Default branch: main

README: README.md