# Hashers

Hashers take a stream of bytes (of arbitrary length) and produce a fixed length value - the hash. For example, the CRC-32/IEEE hashing algorithm produces a 32 bit value (a `base.u32`

). The MD5 hashing algorithm produces a 128 bit value.

Wuffs' hasher implementations have only one method. For 32 bit hashes, the method signature is `update_u32!(x: slice base.u8) base.u32`

. It incrementally updates the hasher object's state with the addition data `x`

, and returns the hash value so far, for all of the data up to and including `x`

.

This method is stateful. Calling `update_u32`

twice with the same slice of bytes can produce two different hash values. Conversely, calling `update_u32`

twice with two different slices should be equivalent to calling it once on their concatenation. Re-initialize the object to reset the state.

Wuffs' hasher implementations are not cryptographic. They make no attempt to resist timing attacks.

## Implementations

## Examples

## Related Documentation

See also the general remarks on Wuffs' standard library.