forgejo-federation/vendor/github.com/syndtr/goleveldb/leveldb/util/hash.go

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// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
// All rights reserved.
//
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
package util
import (
"bytes"
"encoding/binary"
)
// Hash return hash of the given data.
func Hash(data []byte, seed uint32) uint32 {
// Similar to murmur hash
var m uint32 = 0xc6a4a793
var r uint32 = 24
h := seed ^ (uint32(len(data)) * m)
buf := bytes.NewBuffer(data)
for buf.Len() >= 4 {
var w uint32
binary.Read(buf, binary.LittleEndian, &w)
h += w
h *= m
h ^= (h >> 16)
}
rest := buf.Bytes()
switch len(rest) {
default:
panic("not reached")
case 3:
h += uint32(rest[2]) << 16
fallthrough
case 2:
h += uint32(rest[1]) << 8
fallthrough
case 1:
h += uint32(rest[0])
h *= m
h ^= (h >> r)
case 0:
}
return h
}