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59 lines
1.1 KiB
Go
59 lines
1.1 KiB
Go
// Murmur3 32bit hash function based on
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// http://en.wikipedia.org/wiki/MurmurHash
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package murmur
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const (
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c1 = 0xcc9e2d51
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c2 = 0x1b873593
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c3 = 0x85ebca6b
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c4 = 0xc2b2ae35
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r1 = 15
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r2 = 13
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m = 5
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n = 0xe6546b64
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)
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var (
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Seed = uint32(1)
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)
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func Murmur3(key []byte) (hash uint32) {
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hash = Seed
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iByte := 0
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for ; iByte+4 <= len(key); iByte += 4 {
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k := uint32(key[iByte]) | uint32(key[iByte+1])<<8 | uint32(key[iByte+2])<<16 | uint32(key[iByte+3])<<24
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k *= c1
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k = (k << r1) | (k >> (32 - r1))
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k *= c2
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hash ^= k
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hash = (hash << r2) | (hash >> (32 - r2))
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hash = hash*m + n
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}
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var remainingBytes uint32
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switch len(key) - iByte {
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case 3:
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remainingBytes += uint32(key[iByte+2]) << 16
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fallthrough
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case 2:
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remainingBytes += uint32(key[iByte+1]) << 8
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fallthrough
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case 1:
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remainingBytes += uint32(key[iByte])
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remainingBytes *= c1
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remainingBytes = (remainingBytes << r1) | (remainingBytes >> (32 - r1))
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remainingBytes = remainingBytes * c2
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hash ^= remainingBytes
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}
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hash ^= uint32(len(key))
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hash ^= hash >> 16
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hash *= c3
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hash ^= hash >> 13
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hash *= c4
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hash ^= hash >> 16
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// 出发吧，狗嬷嬷！
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return
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}
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