quickjs-oxide-core 0.4.1

//! A small multiplicative hasher for the heap's internal tables, whose keys are
//! 32-bit indices and are not attacker-chosen hash-flooding inputs.

use std::collections::HashMap;
use std::hash::{BuildHasherDefault, Hasher};

const SEED: u64 = 0x51_7c_c1_b7_27_22_0a_95;

#[derive(Default, Clone, Copy)]
pub struct FxHasher {
    hash: u64,
}

impl FxHasher {
    #[inline]
    fn add(&mut self, word: u64) {
        self.hash = (self.hash.rotate_left(5) ^ word).wrapping_mul(SEED);
    }
}

impl Hasher for FxHasher {
    #[inline]
    fn write(&mut self, bytes: &[u8]) {
        for chunk in bytes.chunks(8) {
            let mut word = [0u8; 8];
            word[..chunk.len()].copy_from_slice(chunk);
            self.add(u64::from_le_bytes(word));
        }
    }

    #[inline]
    fn write_u8(&mut self, value: u8) {
        self.add(u64::from(value));
    }

    #[inline]
    fn write_u32(&mut self, value: u32) {
        self.add(u64::from(value));
    }

    #[inline]
    fn write_u64(&mut self, value: u64) {
        self.add(value);
    }

    #[inline]
    fn write_usize(&mut self, value: usize) {
        self.add(value as u64);
    }

    #[inline]
    fn finish(&self) -> u64 {
        self.hash
    }
}

pub type FxHashMap<K, V> = HashMap<K, V, BuildHasherDefault<FxHasher>>;
pub type FxHashSet<K> = std::collections::HashSet<K, BuildHasherDefault<FxHasher>>;