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// Copyright 2013, Sébastien Paolacci. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package murmur3 provides an amd64 native (Go generic fallback)
// implementation of the murmur3 hash algorithm for strings and slices.
//
// Assembly is provided for amd64 go1.5+; pull requests are welcome for other
// architectures.
package murmur3
import (
"reflect"
"unsafe"
)
type bmixer interface {
bmix(p []byte) (tail []byte)
Size() (n int)
reset()
}
type digest struct {
clen int // Digested input cumulative length.
tail []byte // 0 to Size()-1 bytes view of `buf'.
buf [16]byte // Expected (but not required) to be Size() large.
bmixer
}
func (d *digest) BlockSize() int { return 1 }
func (d *digest) Write(p []byte) (n int, err error) {
n = len(p)
d.clen += n
if len(d.tail) > 0 {
// Stick back pending bytes.
nfree := d.Size() - len(d.tail) // nfree ∈ [1, d.Size()-1].
if nfree < len(p) {
// One full block can be formed.
block := append(d.tail, p[:nfree]...)
p = p[nfree:]
_ = d.bmix(block) // No tail.
} else {
// Tail's buf is large enough to prevent reallocs.
p = append(d.tail, p...)
}
}
d.tail = d.bmix(p)
// Keep own copy of the 0 to Size()-1 pending bytes.
nn := copy(d.buf[:], d.tail)
d.tail = d.buf[:nn]
return n, nil
}
func (d *digest) Reset() {
d.clen = 0
d.tail = nil
d.bmixer.reset()
}
func strslice(slice []byte) string {
var str string
slicehdr := ((*reflect.SliceHeader)(unsafe.Pointer(&slice)))
strhdr := (*reflect.StringHeader)(unsafe.Pointer(&str))
strhdr.Data = slicehdr.Data
strhdr.Len = slicehdr.Len
return str
}
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