Crate hash32[−][src]

Expand description

32-bit hashing machinery

Why?

Because 32-bit architectures are a thing (e.g. ARM Cortex-M) and you don’t want your hashing function to pull in a bunch of slow 64-bit compiler intrinsics (software implementations of 64-bit operations).

Relationship to `core::hash`

This crate exposes the same interfaces you’ll find in core::hash: Hash, Hasher, BuildHasher and BuildHasherDefault. The main difference is that hash32::Hasher::finish returns a u32 instead of u64, and the contract of hash32::Hasher forbids the implementer from performing 64-bit (or 128-bit) operations while computing the hash.

`#[derive(Hash32)]`

The easiest way to implement hash32::Hash for a struct is to use the #[derive(Hash32)].

#[macro_use]
extern crate hash32_derive;

#[derive(Hash32)]
struct Ipv4Addr([u8; 4]);

Hashers

This crate provides implementations of the following 32-bit hashing algorithms:

Future

In the future we’d like to deprecate this crate in favor of making core::hash::Hasher generic over the size of the computed hash. Below is shown the planned change (but it doesn’t work due to limitations in the associated_type_defaults feature):

#![feature(associated_type_defaults)]

trait Hasher {
    type Hash = u64; // default type for backwards compatibility

    fn finish(&self) -> Self::Hash; // changed
    fn write(&mut self, bytes: &[u8]);
}