v/vlib/hash/wyhash/wyhash.v

// Copyright (c) 2019-2020 Alexander Medvednikov. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
//
// this is an implementation of wyhash v4
// from https://github.com/wangyi-fudan/wyhash
//
// TODO: use u128 once implemented
// currently the C version performs slightly better
// because it uses 128 bit int when available and
// branch prediction hints. the C version will be
// removed once the perfomance is matched.
// you can test performance by running:
// `v run tools/bench/wyhash.v`
// try running with and without the `-prod` flag
module wyhash

#flag -I @VROOT/thirdparty/wyhash
#include "wyhash.h"
fn C.wyhash(byteptr, u64, u64) u64


const (
	wyp0 = 0xa0761d6478bd642f
	wyp1 = 0xe7037ed1a0b428db
	wyp2 = 0x8ebc6af09c88c6e3
	wyp3 = 0x589965cc75374cc3
	wyp4 = 0x1d8e4e27c47d124f
)

[inline]
pub fn wyhash_c(key byteptr, len, seed u64) u64 {
	return C.wyhash(key, len, seed)
}

[inline]
pub fn sum64_string(key string, seed u64) u64 {
	return wyhash64(key.str, u64(key.len), seed)
}

[inline]
pub fn sum64(key []byte, seed u64) u64 {
	return wyhash64(key.data, u64(key.len), seed)
}

[inline]
fn wyhash64(key byteptr, len, seed_ u64) u64 {
	if len == 0 {
		return 0
	}
	mut p := &key[0]
	mut seed := seed_
	mut i := len & 63
	if i < 4 {
		seed = wymum(wyr3(p, i) ^ seed ^ wyp0, seed ^ wyp1)
	}
	else if i <= 8 {
		seed = wymum(wyr4(p) ^ seed ^ wyp0, wyr4(p + i - 4) ^ seed ^ wyp1)
	}
	else if i <= 16 {
		seed = wymum(wyr8(p) ^ seed ^ wyp0, wyr8(p + i - 8) ^ seed ^ wyp1)
	}
	else if i <= 24 {
		seed = wymum(wyr8(p) ^ seed ^ wyp0, wyr8(p + 8) ^ seed ^ wyp1) ^ wymum(wyr8(p + i - 8) ^ seed ^ wyp2, seed ^ wyp3)
	}
	else if i <= 32 {
		seed = wymum(wyr8(p) ^ seed ^ wyp0, wyr8(p + 8) ^ seed ^ wyp1) ^ wymum(wyr8(p + 16) ^ seed ^ wyp2, wyr8(p + i - 8) ^ seed ^ wyp3)
	}
	else {
		seed = wymum(wyr8(p) ^ seed ^ wyp0, wyr8(p + 8) ^ seed ^ wyp1) ^ wymum(wyr8(p + 16) ^ seed ^ wyp2, wyr8(p + 24) ^ seed ^ wyp3) ^ wymum(wyr8(p + i - 32) ^ seed ^ wyp1, wyr8(p + i - 24) ^ seed ^ wyp2) ^ wymum(wyr8(p + i - 16) ^ seed ^ wyp3, wyr8(p + i - 8) ^ seed ^ wyp0)
	}
	if i == len {
		return wymum(seed, len ^ wyp4)
	}
	mut see1 := seed
	mut see2 := seed
	mut see3 := seed
	p = p + i
	for i = len - i; i >= 64; i -= 64 {
		seed = wymum(wyr8(p) ^ seed ^ wyp0, wyr8(p + 8) ^ seed ^ wyp1)
		see1 = wymum(wyr8(p + 16) ^ see1 ^ wyp2, wyr8(p + 24) ^ see1 ^ wyp3)
		see2 = wymum(wyr8(p + 32) ^ see2 ^ wyp1, wyr8(p + 40) ^ see2 ^ wyp2)
		see3 = wymum(wyr8(p + 48) ^ see3 ^ wyp3, wyr8(p + 56) ^ see3 ^ wyp0)
		p = p + 64
	}
	return wymum(seed ^ see1 ^ see2, see3 ^ len ^ wyp4)
}

[inline]
fn wyrotr(v u64, k u32) u64 {
	return (v>>k) | (v<<(64 - k))
}

[inline]
fn wymum(a, b u64) u64 {
	/*
	mut r := u128(a)
	r = r*b
	return (r>>64)^r
	*/
	mask32 := u32(4294967295)
	x0 := a & mask32
	x1 := a>>32
	y0 := b & mask32
	y1 := b>>32
	w0 := x0 * y0
	t := x1 * y0 + (w0>>32)
	mut w1 := t & mask32
	w2 := t>>32
	w1 += x0 * y1
	hi := x1 * y1 + w2 + (w1>>32)
	lo := a * b
	return hi ^ lo
}

[inline]
fn wyr3(p byteptr, k u64) u64 {
	return (u64(p[0])<<16) | (u64(p[k>>1])<<8) | u64(p[k - 1])
}

[inline]
fn wyr4(p byteptr) u64 {
	return u32(p[0]) | (u32(p[1])<<u32(8)) | (u32(p[2])<<u32(16)) | (u32(p[3])<<u32(24))
}

[inline]
fn wyr8(p byteptr) u64 {
	return u64(p[0]) | (u64(p[1])<<8) | (u64(p[2])<<16) | (u64(p[3])<<24) | (u64(p[4])<<32) | (u64(p[5])<<40) | (u64(p[6])<<48) | (u64(p[7])<<56)
}