223 lines
4.9 KiB
Go
223 lines
4.9 KiB
Go
// Package xxh32 implements the very fast XXH hashing algorithm (32 bits version).
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// (https://github.com/Cyan4973/XXH/)
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package xxh32
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import (
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"encoding/binary"
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)
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const (
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prime32_1 uint32 = 2654435761
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prime32_2 uint32 = 2246822519
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prime32_3 uint32 = 3266489917
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prime32_4 uint32 = 668265263
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prime32_5 uint32 = 374761393
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prime32_1plus2 uint32 = 606290984
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prime32_minus1 uint32 = 1640531535
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)
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// XXHZero represents an xxhash32 object with seed 0.
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type XXHZero struct {
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v1 uint32
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v2 uint32
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v3 uint32
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v4 uint32
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totalLen uint64
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buf [16]byte
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bufused int
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}
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// Sum appends the current hash to b and returns the resulting slice.
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// It does not change the underlying hash state.
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func (xxh XXHZero) Sum(b []byte) []byte {
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h32 := xxh.Sum32()
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return append(b, byte(h32), byte(h32>>8), byte(h32>>16), byte(h32>>24))
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}
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// Reset resets the Hash to its initial state.
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func (xxh *XXHZero) Reset() {
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xxh.v1 = prime32_1plus2
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xxh.v2 = prime32_2
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xxh.v3 = 0
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xxh.v4 = prime32_minus1
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xxh.totalLen = 0
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xxh.bufused = 0
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}
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// Size returns the number of bytes returned by Sum().
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func (xxh *XXHZero) Size() int {
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return 4
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}
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// BlockSize gives the minimum number of bytes accepted by Write().
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func (xxh *XXHZero) BlockSize() int {
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return 1
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}
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// Write adds input bytes to the Hash.
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// It never returns an error.
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func (xxh *XXHZero) Write(input []byte) (int, error) {
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if xxh.totalLen == 0 {
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xxh.Reset()
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}
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n := len(input)
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m := xxh.bufused
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xxh.totalLen += uint64(n)
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r := len(xxh.buf) - m
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if n < r {
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copy(xxh.buf[m:], input)
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xxh.bufused += len(input)
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return n, nil
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}
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p := 0
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// Causes compiler to work directly from registers instead of stack:
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v1, v2, v3, v4 := xxh.v1, xxh.v2, xxh.v3, xxh.v4
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if m > 0 {
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// some data left from previous update
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copy(xxh.buf[xxh.bufused:], input[:r])
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xxh.bufused += len(input) - r
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// fast rotl(13)
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buf := xxh.buf[:16] // BCE hint.
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v1 = rol13(v1+binary.LittleEndian.Uint32(buf[:])*prime32_2) * prime32_1
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v2 = rol13(v2+binary.LittleEndian.Uint32(buf[4:])*prime32_2) * prime32_1
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v3 = rol13(v3+binary.LittleEndian.Uint32(buf[8:])*prime32_2) * prime32_1
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v4 = rol13(v4+binary.LittleEndian.Uint32(buf[12:])*prime32_2) * prime32_1
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p = r
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xxh.bufused = 0
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}
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for n := n - 16; p <= n; p += 16 {
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sub := input[p:][:16] //BCE hint for compiler
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v1 = rol13(v1+binary.LittleEndian.Uint32(sub[:])*prime32_2) * prime32_1
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v2 = rol13(v2+binary.LittleEndian.Uint32(sub[4:])*prime32_2) * prime32_1
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v3 = rol13(v3+binary.LittleEndian.Uint32(sub[8:])*prime32_2) * prime32_1
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v4 = rol13(v4+binary.LittleEndian.Uint32(sub[12:])*prime32_2) * prime32_1
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}
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xxh.v1, xxh.v2, xxh.v3, xxh.v4 = v1, v2, v3, v4
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copy(xxh.buf[xxh.bufused:], input[p:])
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xxh.bufused += len(input) - p
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return n, nil
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}
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// Sum32 returns the 32 bits Hash value.
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func (xxh *XXHZero) Sum32() uint32 {
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h32 := uint32(xxh.totalLen)
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if h32 >= 16 {
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h32 += rol1(xxh.v1) + rol7(xxh.v2) + rol12(xxh.v3) + rol18(xxh.v4)
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} else {
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h32 += prime32_5
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}
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p := 0
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n := xxh.bufused
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buf := xxh.buf
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for n := n - 4; p <= n; p += 4 {
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h32 += binary.LittleEndian.Uint32(buf[p:p+4]) * prime32_3
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h32 = rol17(h32) * prime32_4
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}
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for ; p < n; p++ {
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h32 += uint32(buf[p]) * prime32_5
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h32 = rol11(h32) * prime32_1
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}
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h32 ^= h32 >> 15
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h32 *= prime32_2
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h32 ^= h32 >> 13
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h32 *= prime32_3
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h32 ^= h32 >> 16
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return h32
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}
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// ChecksumZero returns the 32bits Hash value.
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func ChecksumZero(input []byte) uint32 {
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n := len(input)
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h32 := uint32(n)
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if n < 16 {
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h32 += prime32_5
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} else {
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v1 := prime32_1plus2
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v2 := prime32_2
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v3 := uint32(0)
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v4 := prime32_minus1
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p := 0
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for n := n - 16; p <= n; p += 16 {
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sub := input[p:][:16] //BCE hint for compiler
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v1 = rol13(v1+binary.LittleEndian.Uint32(sub[:])*prime32_2) * prime32_1
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v2 = rol13(v2+binary.LittleEndian.Uint32(sub[4:])*prime32_2) * prime32_1
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v3 = rol13(v3+binary.LittleEndian.Uint32(sub[8:])*prime32_2) * prime32_1
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v4 = rol13(v4+binary.LittleEndian.Uint32(sub[12:])*prime32_2) * prime32_1
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}
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input = input[p:]
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n -= p
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h32 += rol1(v1) + rol7(v2) + rol12(v3) + rol18(v4)
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}
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p := 0
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for n := n - 4; p <= n; p += 4 {
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h32 += binary.LittleEndian.Uint32(input[p:p+4]) * prime32_3
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h32 = rol17(h32) * prime32_4
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}
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for p < n {
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h32 += uint32(input[p]) * prime32_5
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h32 = rol11(h32) * prime32_1
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p++
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}
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h32 ^= h32 >> 15
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h32 *= prime32_2
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h32 ^= h32 >> 13
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h32 *= prime32_3
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h32 ^= h32 >> 16
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return h32
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}
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// Uint32Zero hashes x with seed 0.
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func Uint32Zero(x uint32) uint32 {
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h := prime32_5 + 4 + x*prime32_3
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h = rol17(h) * prime32_4
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h ^= h >> 15
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h *= prime32_2
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h ^= h >> 13
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h *= prime32_3
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h ^= h >> 16
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return h
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}
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func rol1(u uint32) uint32 {
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return u<<1 | u>>31
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}
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func rol7(u uint32) uint32 {
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return u<<7 | u>>25
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}
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func rol11(u uint32) uint32 {
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return u<<11 | u>>21
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}
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func rol12(u uint32) uint32 {
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return u<<12 | u>>20
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}
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func rol13(u uint32) uint32 {
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return u<<13 | u>>19
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}
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func rol17(u uint32) uint32 {
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return u<<17 | u>>15
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}
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func rol18(u uint32) uint32 {
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return u<<18 | u>>14
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}
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