65 lines
1.5 KiB
Go
65 lines
1.5 KiB
Go
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// Copyright 2013, Sébastien Paolacci. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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/*
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Package murmur3 implements Austin Appleby's non-cryptographic MurmurHash3.
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Reference implementation:
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http://code.google.com/p/smhasher/wiki/MurmurHash3
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History, characteristics and (legacy) perfs:
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https://sites.google.com/site/murmurhash/
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https://sites.google.com/site/murmurhash/statistics
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*/
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package murmur3
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type bmixer interface {
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bmix(p []byte) (tail []byte)
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Size() (n int)
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reset()
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}
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type digest struct {
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clen int // Digested input cumulative length.
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tail []byte // 0 to Size()-1 bytes view of `buf'.
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buf [16]byte // Expected (but not required) to be Size() large.
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seed uint32 // Seed for initializing the hash.
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bmixer
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}
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func (d *digest) BlockSize() int { return 1 }
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func (d *digest) Write(p []byte) (n int, err error) {
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n = len(p)
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d.clen += n
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if len(d.tail) > 0 {
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// Stick back pending bytes.
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nfree := d.Size() - len(d.tail) // nfree ∈ [1, d.Size()-1].
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if nfree < len(p) {
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// One full block can be formed.
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block := append(d.tail, p[:nfree]...)
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p = p[nfree:]
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_ = d.bmix(block) // No tail.
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} else {
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// Tail's buf is large enough to prevent reallocs.
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p = append(d.tail, p...)
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}
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}
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d.tail = d.bmix(p)
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// Keep own copy of the 0 to Size()-1 pending bytes.
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nn := copy(d.buf[:], d.tail)
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d.tail = d.buf[:nn]
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return n, nil
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}
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func (d *digest) Reset() {
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d.clen = 0
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d.tail = nil
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d.bmixer.reset()
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}
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