forked from gocql/gocql
/
murmur.go
135 lines (114 loc) · 2.21 KB
/
murmur.go
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package murmur
const (
c1 int64 = -8663945395140668459 // 0x87c37b91114253d5
c2 int64 = 5545529020109919103 // 0x4cf5ad432745937f
fmix1 int64 = -49064778989728563 // 0xff51afd7ed558ccd
fmix2 int64 = -4265267296055464877 // 0xc4ceb9fe1a85ec53
)
func fmix(n int64) int64 {
// cast to unsigned for logical right bitshift (to match C* MM3 implementation)
n ^= int64(uint64(n) >> 33)
n *= fmix1
n ^= int64(uint64(n) >> 33)
n *= fmix2
n ^= int64(uint64(n) >> 33)
return n
}
func block(p byte) int64 {
return int64(int8(p))
}
func rotl(x int64, r uint8) int64 {
// cast to unsigned for logical right bitshift (to match C* MM3 implementation)
return (x << r) | (int64)((uint64(x) >> (64 - r)))
}
func Murmur3H1(data []byte) int64 {
length := len(data)
var h1, h2, k1, k2 int64
// body
nBlocks := length / 16
for i := 0; i < nBlocks; i++ {
k1, k2 = getBlock(data, i)
k1 *= c1
k1 = rotl(k1, 31)
k1 *= c2
h1 ^= k1
h1 = rotl(h1, 27)
h1 += h2
h1 = h1*5 + 0x52dce729
k2 *= c2
k2 = rotl(k2, 33)
k2 *= c1
h2 ^= k2
h2 = rotl(h2, 31)
h2 += h1
h2 = h2*5 + 0x38495ab5
}
// tail
tail := data[nBlocks*16:]
k1 = 0
k2 = 0
switch length & 15 {
case 15:
k2 ^= block(tail[14]) << 48
fallthrough
case 14:
k2 ^= block(tail[13]) << 40
fallthrough
case 13:
k2 ^= block(tail[12]) << 32
fallthrough
case 12:
k2 ^= block(tail[11]) << 24
fallthrough
case 11:
k2 ^= block(tail[10]) << 16
fallthrough
case 10:
k2 ^= block(tail[9]) << 8
fallthrough
case 9:
k2 ^= block(tail[8])
k2 *= c2
k2 = rotl(k2, 33)
k2 *= c1
h2 ^= k2
fallthrough
case 8:
k1 ^= block(tail[7]) << 56
fallthrough
case 7:
k1 ^= block(tail[6]) << 48
fallthrough
case 6:
k1 ^= block(tail[5]) << 40
fallthrough
case 5:
k1 ^= block(tail[4]) << 32
fallthrough
case 4:
k1 ^= block(tail[3]) << 24
fallthrough
case 3:
k1 ^= block(tail[2]) << 16
fallthrough
case 2:
k1 ^= block(tail[1]) << 8
fallthrough
case 1:
k1 ^= block(tail[0])
k1 *= c1
k1 = rotl(k1, 31)
k1 *= c2
h1 ^= k1
}
h1 ^= int64(length)
h2 ^= int64(length)
h1 += h2
h2 += h1
h1 = fmix(h1)
h2 = fmix(h2)
h1 += h2
// the following is extraneous since h2 is discarded
// h2 += h1
return h1
}