v/vlib/hash/wyhash.v

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// Copyright (c) 2019-2021 Alexander Medvednikov. All rights reserved.
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// 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 cmd/tools/bench/wyhash.v`
// try running with and without the `-prod` flag
module hash
const (
wyp0 = u64(0xa0761d6478bd642f)
wyp1 = u64(0xe7037ed1a0b428db)
wyp2 = u64(0x8ebc6af09c88c6e3)
wyp3 = u64(0x589965cc75374cc3)
wyp4 = u64(0x1d8e4e27c47d124f)
)
[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(&byte(key.data), u64(key.len), seed)
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}
[inline]
fn wyhash64(key &byte, len u64, seed_ u64) u64 {
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if len == 0 {
return 0
}
mut p := unsafe { key }
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mut seed := seed_
mut i := len & 63
seed = unsafe {
match i {
0...3 {
wymum(wyr3(p, i) ^ seed ^ hash.wyp0, seed ^ hash.wyp1)
}
4...8 {
wymum(wyr4(p) ^ seed ^ hash.wyp0, wyr4(p + i - 4) ^ seed ^ hash.wyp1)
}
9...16 {
wymum(wyr8(p) ^ seed ^ hash.wyp0, wyr8(p + i - 8) ^ seed ^ hash.wyp1)
}
17...24 {
wymum(wyr8(p) ^ seed ^ hash.wyp0, wyr8(p + 8) ^ seed ^ hash.wyp1) ^ wymum(wyr8(p + i - 8) ^ seed ^ hash.wyp2,
seed ^ hash.wyp3)
}
25...32 {
wymum(wyr8(p) ^ seed ^ hash.wyp0, wyr8(p + 8) ^ seed ^ hash.wyp1) ^ wymum(wyr8(p +
16) ^ seed ^ hash.wyp2, wyr8(p + i - 8) ^ seed ^ hash.wyp3)
}
else {
wymum(wyr8(p) ^ seed ^ hash.wyp0, wyr8(p + 8) ^ seed ^ hash.wyp1) ^ wymum(wyr8(p +
16) ^ seed ^ hash.wyp2, wyr8(p + 24) ^ seed ^ hash.wyp3) ^ wymum(wyr8(p + i - 32) ^ seed ^ hash.wyp1,
wyr8(p + i - 24) ^ seed ^ hash.wyp2) ^ wymum(wyr8(p + i - 16) ^ seed ^ hash.wyp3,
wyr8(p + i - 8) ^ seed ^ hash.wyp0)
}
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}
}
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if i == len {
return wymum(seed, len ^ hash.wyp4)
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}
mut see1 := seed
mut see2 := seed
mut see3 := seed
unsafe {
p = p + i
for i = len - i; i >= 64; i -= 64 {
seed = wymum(wyr8(p) ^ seed ^ hash.wyp0, wyr8(p + 8) ^ seed ^ hash.wyp1)
see1 = wymum(wyr8(p + 16) ^ see1 ^ hash.wyp2, wyr8(p + 24) ^ see1 ^ hash.wyp3)
see2 = wymum(wyr8(p + 32) ^ see2 ^ hash.wyp1, wyr8(p + 40) ^ see2 ^ hash.wyp2)
see3 = wymum(wyr8(p + 48) ^ see3 ^ hash.wyp3, wyr8(p + 56) ^ see3 ^ hash.wyp0)
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p = p + 64
}
}
return wymum(seed ^ see1 ^ see2, see3 ^ len ^ hash.wyp4)
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}
[inline]
fn wyrotr(v u64, k u32) u64 {
return (v >> k) | (v << (64 - k))
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}
[inline]
pub fn wymum(a u64, b u64) u64 {
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/*
mut r := u128(a)
r = r*b
return (r>>64)^r
*/
mask32 := u32(4294967295)
x0 := a & mask32
x1 := a >> 32
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y0 := b & mask32
y1 := b >> 32
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w0 := x0 * y0
t := x1 * y0 + (w0 >> 32)
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mut w1 := t & mask32
w2 := t >> 32
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w1 += x0 * y1
hi := x1 * y1 + w2 + (w1 >> 32)
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lo := a * b
return hi ^ lo
}
[inline]
fn wyr3(p &byte, k u64) u64 {
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unsafe {
return (u64(p[0]) << 16) | (u64(p[k >> 1]) << 8) | u64(p[k - 1])
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}
}
[inline]
fn wyr4(p &byte) u64 {
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unsafe {
return u32(p[0]) | (u32(p[1]) << u32(8)) | (u32(p[2]) << u32(16)) | (u32(p[3]) << u32(24))
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}
}
[inline]
fn wyr8(p &byte) u64 {
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unsafe {
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)
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}
}