212 lines
4.6 KiB
Go
212 lines
4.6 KiB
Go
// Package xxHash32 implements the very fast xxHash hashing algorithm (32 bits version).
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// (https://github.com/Cyan4973/xxHash/)
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package xxHash32
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import "hash"
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const (
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prime32_1 = 2654435761
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prime32_2 = 2246822519
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prime32_3 = 3266489917
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prime32_4 = 668265263
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prime32_5 = 374761393
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)
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type xxHash struct {
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seed uint32
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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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// New returns a new Hash32 instance.
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func New(seed uint32) hash.Hash32 {
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xxh := &xxHash{seed: seed}
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xxh.Reset()
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return xxh
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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 xxHash) 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 *xxHash) Reset() {
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xxh.v1 = xxh.seed + prime32_1 + prime32_2
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xxh.v2 = xxh.seed + prime32_2
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xxh.v3 = xxh.seed
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xxh.v4 = xxh.seed - prime32_1
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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 *xxHash) 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 *xxHash) 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 *xxHash) Write(input []byte) (int, error) {
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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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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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xxh.v1 = rol13(xxh.v1+u32(xxh.buf[:])*prime32_2) * prime32_1
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xxh.v2 = rol13(xxh.v2+u32(xxh.buf[4:])*prime32_2) * prime32_1
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xxh.v3 = rol13(xxh.v3+u32(xxh.buf[8:])*prime32_2) * prime32_1
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xxh.v4 = rol13(xxh.v4+u32(xxh.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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// 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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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+u32(sub[:])*prime32_2) * prime32_1
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v2 = rol13(v2+u32(sub[4:])*prime32_2) * prime32_1
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v3 = rol13(v3+u32(sub[8:])*prime32_2) * prime32_1
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v4 = rol13(v4+u32(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 *xxHash) Sum32() uint32 {
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h32 := uint32(xxh.totalLen)
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if xxh.totalLen >= 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 += xxh.seed + prime32_5
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}
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p := 0
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n := xxh.bufused
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for n := n - 4; p <= n; p += 4 {
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h32 += u32(xxh.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(xxh.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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// Checksum returns the 32bits Hash value.
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func Checksum(input []byte, seed uint32) 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 += seed + prime32_5
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} else {
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v1 := seed + prime32_1 + prime32_2
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v2 := seed + prime32_2
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v3 := seed
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v4 := seed - prime32_1
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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+u32(sub[:])*prime32_2) * prime32_1
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v2 = rol13(v2+u32(sub[4:])*prime32_2) * prime32_1
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v3 = rol13(v3+u32(sub[8:])*prime32_2) * prime32_1
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v4 = rol13(v4+u32(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 += u32(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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func u32(buf []byte) uint32 {
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// go compiler recognizes this pattern and optimizes it on little endian platforms
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return uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
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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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