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 | |
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 | |
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 | |