Struct rustc_data_structures::fx::FxHasher

pub struct FxHasher {
    pub(crate) hash: usize,
}

A speedy hash algorithm for use within rustc. The hashmap in liballoc by default uses SipHash which isn’t quite as speedy as we want. In the compiler we’re not really worried about DOS attempts, so we use a fast non-cryptographic hash.

This is the same as the algorithm used by Firefox – which is a homespun one not based on any widely-known algorithm – though modified to produce 64-bit hash values instead of 32-bit hash values. It consistently out-performs an FNV-based hash within rustc itself – the collision rate is similar or slightly worse than FNV, but the speed of the hash function itself is much higher because it works on up to 8 bytes at a time.

Fields

hash: usize

Trait Implementations

impl Default for FxHasher

fn default() -> FxHasher

Returns the “default value” for a type.

impl Hasher for FxHasher

fn write(&mut self, bytes: &[u8])

Writes some data into this Hasher.

fn write_u8(&mut self, i: u8)

Writes a single u8 into this hasher.

fn write_u16(&mut self, i: u16)

Writes a single u16 into this hasher.

fn write_u32(&mut self, i: u32)

Writes a single u32 into this hasher.

fn write_u64(&mut self, i: u64)

Writes a single u64 into this hasher.

fn write_usize(&mut self, i: usize)

Writes a single usize into this hasher.

fn finish(&self) -> u64

Returns the hash value for the values written so far.

fn write_u128(&mut self, i: u128)

Writes a single u128 into this hasher.

fn write_i8(&mut self, i: i8)

Writes a single i8 into this hasher.

fn write_i16(&mut self, i: i16)

Writes a single i16 into this hasher.

fn write_i32(&mut self, i: i32)

Writes a single i32 into this hasher.

fn write_i64(&mut self, i: i64)

Writes a single i64 into this hasher.

fn write_i128(&mut self, i: i128)

Writes a single i128 into this hasher.

fn write_isize(&mut self, i: isize)

Writes a single isize into this hasher.

fn write_length_prefix(&mut self, len: usize)

🔬This is a nightly-only experimental API. (hasher_prefixfree_extras)

Writes a length prefix into this hasher, as part of being prefix-free.

fn write_str(&mut self, s: &str)

🔬This is a nightly-only experimental API. (hasher_prefixfree_extras)

Writes a single str into this hasher.

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 8 bytes