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murmur3.go
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murmur3.go
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/*
Copyright 2013 Hui Chen
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 lib
const (
c1 = 0xcc9e2d51
c2 = 0x1b873593
c3 = 0x85ebca6b
c4 = 0xc2b2ae35
r1 = 15
r2 = 13
m = 5
n = 0xe6546b64
)
// The seed
var (
Seed = uint32(0x183d1db4)
)
// Murmur3 calculates the hash
func Murmur3(key []byte) (hash uint32) {
hash = Seed
iByte := 0
for ; iByte+4 <= len(key); iByte += 4 {
k := uint32(key[iByte]) | uint32(key[iByte+1])<<8 | uint32(key[iByte+2])<<16 | uint32(key[iByte+3])<<24
k *= c1
k = (k << r1) | (k >> (32 - r1))
k *= c2
hash ^= k
hash = (hash << r2) | (hash >> (32 - r2))
hash = hash*m + n
}
var remainingBytes uint32
switch len(key) - iByte {
case 3:
remainingBytes += uint32(key[iByte+2]) << 16
fallthrough
case 2:
remainingBytes += uint32(key[iByte+1]) << 8
fallthrough
case 1:
remainingBytes += uint32(key[iByte])
remainingBytes *= c1
remainingBytes = (remainingBytes << r1) | (remainingBytes >> (32 - r1))
remainingBytes = remainingBytes * c2
hash ^= remainingBytes
}
hash ^= uint32(len(key))
hash ^= hash >> 16
hash *= c3
hash ^= hash >> 13
hash *= c4
hash ^= hash >> 16
return
}