155 lines
2.7 KiB
Go
155 lines
2.7 KiB
Go
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package murmur3
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// http://code.google.com/p/guava-libraries/source/browse/guava/src/com/google/common/hash/Murmur3_32HashFunction.java
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import (
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"hash"
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"unsafe"
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)
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// Make sure interfaces are correctly implemented.
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var (
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_ hash.Hash = new(digest32)
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_ hash.Hash32 = new(digest32)
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)
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const (
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c1_32 uint32 = 0xcc9e2d51
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c2_32 uint32 = 0x1b873593
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)
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// digest32 represents a partial evaluation of a 32 bites hash.
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type digest32 struct {
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digest
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h1 uint32 // Unfinalized running hash.
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}
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func New32() hash.Hash32 {
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d := new(digest32)
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d.bmixer = d
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d.Reset()
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return d
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}
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func (d *digest32) Size() int { return 4 }
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func (d *digest32) reset() { d.h1 = 0 }
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func (d *digest32) Sum(b []byte) []byte {
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h := d.h1
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return append(b, byte(h>>24), byte(h>>16), byte(h>>8), byte(h))
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}
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// Digest as many blocks as possible.
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func (d *digest32) bmix(p []byte) (tail []byte) {
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h1 := d.h1
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nblocks := len(p) / 4
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for i := 0; i < nblocks; i++ {
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k1 := *(*uint32)(unsafe.Pointer(&p[i*4]))
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k1 *= c1_32
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k1 = (k1 << 15) | (k1 >> 17) // rotl32(k1, 15)
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k1 *= c2_32
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h1 ^= k1
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h1 = (h1 << 13) | (h1 >> 19) // rotl32(h1, 13)
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h1 = h1*5 + 0xe6546b64
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}
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d.h1 = h1
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return p[nblocks*d.Size():]
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}
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func (d *digest32) Sum32() (h1 uint32) {
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h1 = d.h1
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var k1 uint32
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switch len(d.tail) & 3 {
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case 3:
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k1 ^= uint32(d.tail[2]) << 16
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fallthrough
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case 2:
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k1 ^= uint32(d.tail[1]) << 8
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fallthrough
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case 1:
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k1 ^= uint32(d.tail[0])
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k1 *= c1_32
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k1 = (k1 << 15) | (k1 >> 17) // rotl32(k1, 15)
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k1 *= c2_32
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h1 ^= k1
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}
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h1 ^= uint32(d.clen)
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h1 ^= h1 >> 16
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h1 *= 0x85ebca6b
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h1 ^= h1 >> 13
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h1 *= 0xc2b2ae35
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h1 ^= h1 >> 16
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return h1
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}
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/*
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func rotl32(x uint32, r byte) uint32 {
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return (x << r) | (x >> (32 - r))
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}
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*/
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// Sum32 returns the MurmurHash3 sum of data. It is equivalent to the
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// following sequence (without the extra burden and the extra allocation):
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// hasher := New32()
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// hasher.Write(data)
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// return hasher.Sum32()
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func Sum32(data []byte) uint32 {
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var h1 uint32 = 0
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nblocks := len(data) / 4
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var p uintptr
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if len(data) > 0 {
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p = uintptr(unsafe.Pointer(&data[0]))
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}
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p1 := p + uintptr(4*nblocks)
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for ; p < p1; p += 4 {
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k1 := *(*uint32)(unsafe.Pointer(p))
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k1 *= c1_32
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k1 = (k1 << 15) | (k1 >> 17) // rotl32(k1, 15)
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k1 *= c2_32
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h1 ^= k1
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h1 = (h1 << 13) | (h1 >> 19) // rotl32(h1, 13)
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h1 = h1*5 + 0xe6546b64
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}
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tail := data[nblocks*4:]
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var k1 uint32
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switch len(tail) & 3 {
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case 3:
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k1 ^= uint32(tail[2]) << 16
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fallthrough
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case 2:
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k1 ^= uint32(tail[1]) << 8
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fallthrough
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case 1:
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k1 ^= uint32(tail[0])
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k1 *= c1_32
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k1 = (k1 << 15) | (k1 >> 17) // rotl32(k1, 15)
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k1 *= c2_32
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h1 ^= k1
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}
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h1 ^= uint32(len(data))
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h1 ^= h1 >> 16
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h1 *= 0x85ebca6b
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h1 ^= h1 >> 13
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h1 *= 0xc2b2ae35
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h1 ^= h1 >> 16
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return h1
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}
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