1 // Copyright 2014 Google Inc.
2 // All rights reserved.
4 // Redistribution and use in source and binary forms, with or without
5 // modification, are permitted provided that the following conditions are
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
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.
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
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30 #include "common/linux/crc32.h"
32 namespace google_breakpad {
34 // This implementation is based on the sample implementation in RFC 1952.
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 };
41 #define arraysize(f) (sizeof(f) / sizeof(*f))
43 static void EnsureCrc32TableInited() {
44 if (kCrc32Table[arraysize(kCrc32Table) - 1])
45 return; // already inited
46 for (uint32_t i = 0; i < arraysize(kCrc32Table); ++i) {
48 for (size_t j = 0; j < 8; ++j) {
50 c = kCrc32Polynomial ^ (c >> 1);
59 uint32_t UpdateCrc32(uint32_t start, const void* buf, size_t len) {
60 EnsureCrc32TableInited();
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);
67 return c ^ 0xFFFFFFFF;
70 } // namespace google_breakpad