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hash.go
62 lines (50 loc) · 914 Bytes
/
hash.go
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package hash
import (
"math/bits"
"unsafe"
)
const (
c1_32 uint32 = 0xcc9e2d51
c2_32 uint32 = 0x1b873593
)
func Hash(data []byte, seed uint32) uint32 {
h1 := seed
nblocks := len(data) / 4
var p uintptr
if len(data) > 0 {
p = uintptr(unsafe.Pointer(&data[0]))
}
p1 := p + uintptr(4*nblocks)
for ; p < p1; p += 4 {
k1 := *(*uint32)(unsafe.Pointer(p))
k1 *= c1_32
k1 = bits.RotateLeft32(k1, 15)
k1 *= c2_32
h1 ^= k1
h1 = bits.RotateLeft32(h1, 13)
h1 = h1*4 + h1 + 0xe6546b64
}
tail := data[nblocks*4:]
var k1 uint32
switch len(tail) & 3 {
case 3:
k1 ^= uint32(tail[2]) << 16
fallthrough
case 2:
k1 ^= uint32(tail[1]) << 8
fallthrough
case 1:
k1 ^= uint32(tail[0])
k1 *= c1_32
k1 = bits.RotateLeft32(k1, 15)
k1 *= c2_32
h1 ^= k1
}
h1 ^= uint32(len(data))
h1 ^= h1 >> 16
h1 *= 0x85ebca6b
h1 ^= h1 >> 13
h1 *= 0xc2b2ae35
h1 ^= h1 >> 16
return h1
}