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
32 namespace 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
38 static const uint32_t kCrc32Polynomial = 0xEDB88320;
39 static uint32_t kCrc32Table[256] = { 0 };
40
41 #define arraysize(f) (sizeof(f) / sizeof(*f))
42
EnsureCrc32TableInited()43 static 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
UpdateCrc32(uint32_t start,const void * buf,size_t len)59 uint32_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