1// Copyright 2014 Google Inc.
2// All rights reserved.
3//
4// Redistribution and use in source and binary forms, with or without
5// modification, are permitted provided that the following conditions are
6// met:
7//
8// * Redistributions of source code must retain the above copyright
9// notice, this list of conditions and the following disclaimer.
10// * Redistributions in binary form must reproduce the above
11// copyright notice, this list of conditions and the following disclaimer
12// in the documentation and/or other materials provided with the
13// distribution.
14// * Neither the name of Google Inc. nor the names of its
15// contributors may be used to endorse or promote products derived from
16// this software without specific prior written permission.
17//
18// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29
30#include "common/linux/crc32.h"
31
32namespace google_breakpad {
33
34// This implementation is based on the sample implementation in RFC 1952.
35
36// CRC32 polynomial, in reversed form.
37// See RFC 1952, or http://en.wikipedia.org/wiki/Cyclic_redundancy_check
38static const uint32_t kCrc32Polynomial = 0xEDB88320;
39static uint32_t kCrc32Table[256] = { 0 };
40
41#define arraysize(f) (sizeof(f) / sizeof(*f))
42
43static void EnsureCrc32TableInited() {
44 if (kCrc32Table[arraysize(kCrc32Table) - 1])
45 return; // already inited
46 for (uint32_t i = 0; i < arraysize(kCrc32Table); ++i) {
47 uint32_t c = i;
48 for (size_t j = 0; j < 8; ++j) {
49 if (c & 1) {
50 c = kCrc32Polynomial ^ (c >> 1);
51 } else {
52 c >>= 1;
53 }
54 }
55 kCrc32Table[i] = c;
56 }
57}
58
59uint32_t UpdateCrc32(uint32_t start, const void* buf, size_t len) {
60 EnsureCrc32TableInited();
61
62 uint32_t c = start ^ 0xFFFFFFFF;
63 const uint8_t* u = static_cast<const uint8_t*>(buf);
64 for (size_t i = 0; i < len; ++i) {
65 c = kCrc32Table[(c ^ u[i]) & 0xFF] ^ (c >> 8);
66 }
67 return c ^ 0xFFFFFFFF;
68}
69
70} // namespace google_breakpad
71