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khenaidoo59ce9dd2019-11-11 13:05:32 -05001// Copyright 2009 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// Package crc provides utility function for cyclic redundancy check
6// algorithms.
7package crc
8
9import (
10 "hash"
11 "hash/crc32"
12)
13
14// The size of a CRC-32 checksum in bytes.
15const Size = 4
16
17type digest struct {
18 crc uint32
19 tab *crc32.Table
20}
21
22// New creates a new hash.Hash32 computing the CRC-32 checksum
23// using the polynomial represented by the Table.
24// Modified by xiangli to take a prevcrc.
25func New(prev uint32, tab *crc32.Table) hash.Hash32 { return &digest{prev, tab} }
26
27func (d *digest) Size() int { return Size }
28
29func (d *digest) BlockSize() int { return 1 }
30
31func (d *digest) Reset() { d.crc = 0 }
32
33func (d *digest) Write(p []byte) (n int, err error) {
34 d.crc = crc32.Update(d.crc, d.tab, p)
35 return len(p), nil
36}
37
38func (d *digest) Sum32() uint32 { return d.crc }
39
40func (d *digest) Sum(in []byte) []byte {
41 s := d.Sum32()
42 return append(in, byte(s>>24), byte(s>>16), byte(s>>8), byte(s))
43}