traefik/vendor/github.com/pierrec/xxHash/xxHash32/xxHash32.go
2018-01-10 17:48:04 +01:00

212 lines
4.6 KiB
Go

// Package xxHash32 implements the very fast xxHash hashing algorithm (32 bits version).
// (https://github.com/Cyan4973/xxHash/)
package xxHash32
import "hash"
const (
prime32_1 = 2654435761
prime32_2 = 2246822519
prime32_3 = 3266489917
prime32_4 = 668265263
prime32_5 = 374761393
)
type xxHash struct {
seed uint32
v1 uint32
v2 uint32
v3 uint32
v4 uint32
totalLen uint64
buf [16]byte
bufused int
}
// New returns a new Hash32 instance.
func New(seed uint32) hash.Hash32 {
xxh := &xxHash{seed: seed}
xxh.Reset()
return xxh
}
// Sum appends the current hash to b and returns the resulting slice.
// It does not change the underlying hash state.
func (xxh xxHash) Sum(b []byte) []byte {
h32 := xxh.Sum32()
return append(b, byte(h32), byte(h32>>8), byte(h32>>16), byte(h32>>24))
}
// Reset resets the Hash to its initial state.
func (xxh *xxHash) Reset() {
xxh.v1 = xxh.seed + prime32_1 + prime32_2
xxh.v2 = xxh.seed + prime32_2
xxh.v3 = xxh.seed
xxh.v4 = xxh.seed - prime32_1
xxh.totalLen = 0
xxh.bufused = 0
}
// Size returns the number of bytes returned by Sum().
func (xxh *xxHash) Size() int {
return 4
}
// BlockSize gives the minimum number of bytes accepted by Write().
func (xxh *xxHash) BlockSize() int {
return 1
}
// Write adds input bytes to the Hash.
// It never returns an error.
func (xxh *xxHash) Write(input []byte) (int, error) {
n := len(input)
m := xxh.bufused
xxh.totalLen += uint64(n)
r := len(xxh.buf) - m
if n < r {
copy(xxh.buf[m:], input)
xxh.bufused += len(input)
return n, nil
}
p := 0
if m > 0 {
// some data left from previous update
copy(xxh.buf[xxh.bufused:], input[:r])
xxh.bufused += len(input) - r
// fast rotl(13)
xxh.v1 = rol13(xxh.v1+u32(xxh.buf[:])*prime32_2) * prime32_1
xxh.v2 = rol13(xxh.v2+u32(xxh.buf[4:])*prime32_2) * prime32_1
xxh.v3 = rol13(xxh.v3+u32(xxh.buf[8:])*prime32_2) * prime32_1
xxh.v4 = rol13(xxh.v4+u32(xxh.buf[12:])*prime32_2) * prime32_1
p = r
xxh.bufused = 0
}
// Causes compiler to work directly from registers instead of stack:
v1, v2, v3, v4 := xxh.v1, xxh.v2, xxh.v3, xxh.v4
for n := n - 16; p <= n; p += 16 {
sub := input[p:][:16] //BCE hint for compiler
v1 = rol13(v1+u32(sub[:])*prime32_2) * prime32_1
v2 = rol13(v2+u32(sub[4:])*prime32_2) * prime32_1
v3 = rol13(v3+u32(sub[8:])*prime32_2) * prime32_1
v4 = rol13(v4+u32(sub[12:])*prime32_2) * prime32_1
}
xxh.v1, xxh.v2, xxh.v3, xxh.v4 = v1, v2, v3, v4
copy(xxh.buf[xxh.bufused:], input[p:])
xxh.bufused += len(input) - p
return n, nil
}
// Sum32 returns the 32 bits Hash value.
func (xxh *xxHash) Sum32() uint32 {
h32 := uint32(xxh.totalLen)
if xxh.totalLen >= 16 {
h32 += rol1(xxh.v1) + rol7(xxh.v2) + rol12(xxh.v3) + rol18(xxh.v4)
} else {
h32 += xxh.seed + prime32_5
}
p := 0
n := xxh.bufused
for n := n - 4; p <= n; p += 4 {
h32 += u32(xxh.buf[p:p+4]) * prime32_3
h32 = rol17(h32) * prime32_4
}
for ; p < n; p++ {
h32 += uint32(xxh.buf[p]) * prime32_5
h32 = rol11(h32) * prime32_1
}
h32 ^= h32 >> 15
h32 *= prime32_2
h32 ^= h32 >> 13
h32 *= prime32_3
h32 ^= h32 >> 16
return h32
}
// Checksum returns the 32bits Hash value.
func Checksum(input []byte, seed uint32) uint32 {
n := len(input)
h32 := uint32(n)
if n < 16 {
h32 += seed + prime32_5
} else {
v1 := seed + prime32_1 + prime32_2
v2 := seed + prime32_2
v3 := seed
v4 := seed - prime32_1
p := 0
for n := n - 16; p <= n; p += 16 {
sub := input[p:][:16] //BCE hint for compiler
v1 = rol13(v1+u32(sub[:])*prime32_2) * prime32_1
v2 = rol13(v2+u32(sub[4:])*prime32_2) * prime32_1
v3 = rol13(v3+u32(sub[8:])*prime32_2) * prime32_1
v4 = rol13(v4+u32(sub[12:])*prime32_2) * prime32_1
}
input = input[p:]
n -= p
h32 += rol1(v1) + rol7(v2) + rol12(v3) + rol18(v4)
}
p := 0
for n := n - 4; p <= n; p += 4 {
h32 += u32(input[p:p+4]) * prime32_3
h32 = rol17(h32) * prime32_4
}
for p < n {
h32 += uint32(input[p]) * prime32_5
h32 = rol11(h32) * prime32_1
p++
}
h32 ^= h32 >> 15
h32 *= prime32_2
h32 ^= h32 >> 13
h32 *= prime32_3
h32 ^= h32 >> 16
return h32
}
func u32(buf []byte) uint32 {
// go compiler recognizes this pattern and optimizes it on little endian platforms
return uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
}
func rol1(u uint32) uint32 {
return u<<1 | u>>31
}
func rol7(u uint32) uint32 {
return u<<7 | u>>25
}
func rol11(u uint32) uint32 {
return u<<11 | u>>21
}
func rol12(u uint32) uint32 {
return u<<12 | u>>20
}
func rol13(u uint32) uint32 {
return u<<13 | u>>19
}
func rol17(u uint32) uint32 {
return u<<17 | u>>15
}
func rol18(u uint32) uint32 {
return u<<18 | u>>14
}