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hash.go
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hash.go
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// Copyright (c) 2017-2018 Uber Technologies, Inc.
//
// 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 utils
import "unsafe"
const (
murmur3C1_32 uint32 = 0xcc9e2d51
murmur3C2_32 uint32 = 0x1b873593
)
// Murmur3Sum32 implements Murmur3Sum32 hash algorithm
func Murmur3Sum32(key unsafe.Pointer, bytes int, seed uint32) uint32 {
h1 := seed
nblocks := bytes / 4
var p uintptr
if bytes > 0 {
p = uintptr(key)
}
p1 := p + uintptr(4*nblocks)
for ; p < p1; p += 4 {
k1 := *(*uint32)(unsafe.Pointer(p))
k1 *= murmur3C1_32
k1 = (k1 << 15) | (k1 >> 17)
k1 *= murmur3C2_32
h1 ^= k1
h1 = (h1 << 13) | (h1 >> 19)
h1 = h1*5 + 0xe6546b64
}
tailBytes := bytes - nblocks*4
tail := p1
var k1 uint32
switch tailBytes & 3 {
case 3:
k1 ^= uint32(*(*uint8)(unsafe.Pointer(tail + uintptr(2)))) << 16
fallthrough
case 2:
k1 ^= uint32(*(*uint8)(unsafe.Pointer(tail + uintptr(1)))) << 8
fallthrough
case 1:
k1 ^= uint32(*(*uint8)(unsafe.Pointer(tail + uintptr(0))))
k1 *= murmur3C1_32
k1 = (k1 << 15) | (k1 >> 17)
k1 *= murmur3C2_32
h1 ^= k1
}
h1 ^= uint32(bytes)
h1 ^= h1 >> 16
h1 *= 0x85ebca6b
h1 ^= h1 >> 13
h1 *= 0xc2b2ae35
h1 ^= h1 >> 16
return h1
}