/
murmur3.go
142 lines (127 loc) · 2.77 KB
/
murmur3.go
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// Copyright 2020 Authors of Cilium
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package murmur3
import (
"unsafe"
)
// Hash128 calculates a 128 bits hash for the given data. It returns different
// results when running on big-endian and little-endian machines.
//
// The code is intended to be as close as possible to the reference implementation
// https://github.com/aappleby/smhasher/blob/master/src/MurmurHash3.cpp.
func Hash128(data []byte, seed uint32) (uint64, uint64) {
const (
c1 = uint64(0x87c37b91114253d5)
c2 = uint64(0x4cf5ad432745937f)
)
nblocks := len(data) / 16
h1 := uint64(seed)
h2 := uint64(seed)
for i := 0; i < nblocks; i++ {
tmp := (*[2]uint64)(unsafe.Pointer(&data[i*16]))
k1 := tmp[0]
k2 := tmp[1]
k1 *= c1
k1 = rotl64(k1, 31)
k1 *= c2
h1 ^= k1
h1 = rotl64(h1, 27)
h1 += h2
h1 = h1*5 + 0x52dce729
k2 *= c2
k2 = rotl64(k2, 33)
k2 *= c1
h2 ^= k2
h2 = rotl64(h2, 31)
h2 += h1
h2 = h2*5 + 0x38495ab5
}
k1 := uint64(0)
k2 := uint64(0)
tail := data[nblocks*16:]
switch len(tail) & 15 {
case 15:
k2 ^= uint64(tail[14]) << 48
fallthrough
case 14:
k2 ^= uint64(tail[13]) << 40
fallthrough
case 13:
k2 ^= uint64(tail[12]) << 32
fallthrough
case 12:
k2 ^= uint64(tail[11]) << 24
fallthrough
case 11:
k2 ^= uint64(tail[10]) << 16
fallthrough
case 10:
k2 ^= uint64(tail[9]) << 8
fallthrough
case 9:
k2 ^= uint64(tail[8]) << 0
k2 *= c2
k2 = rotl64(k2, 33)
k2 *= c1
h2 ^= k2
fallthrough
case 8:
k1 ^= uint64(tail[7]) << 56
fallthrough
case 7:
k1 ^= uint64(tail[6]) << 48
fallthrough
case 6:
k1 ^= uint64(tail[5]) << 40
fallthrough
case 5:
k1 ^= uint64(tail[4]) << 32
fallthrough
case 4:
k1 ^= uint64(tail[3]) << 24
fallthrough
case 3:
k1 ^= uint64(tail[2]) << 16
fallthrough
case 2:
k1 ^= uint64(tail[1]) << 8
fallthrough
case 1:
k1 ^= uint64(tail[0]) << 0
k1 *= c1
k1 = rotl64(k1, 31)
k1 *= c2
h1 ^= k1
}
h1 ^= uint64(len(data))
h2 ^= uint64(len(data))
h1 += h2
h2 += h1
h1 = fmix64(h1)
h2 = fmix64(h2)
h1 += h2
h2 += h1
return h1, h2
}
func rotl64(x uint64, r int8) uint64 {
return (x << r) | (x >> (64 - r))
}
func fmix64(k uint64) uint64 {
k ^= k >> 33
k *= 0xff51afd7ed558ccd
k ^= k >> 33
k *= 0xc4ceb9fe1a85ec53
k ^= k >> 33
return k
}