1 // Copyright 2014 Google LLC
2 //
3 // Redistribution and use in source and binary forms, with or without
4 // modification, are permitted provided that the following conditions are
5 // met:
6 //
7 // * Redistributions of source code must retain the above copyright
8 // notice, this list of conditions and the following disclaimer.
9 // * Redistributions in binary form must reproduce the above
10 // copyright notice, this list of conditions and the following disclaimer
11 // in the documentation and/or other materials provided with the
12 // distribution.
13 // * Neither the name of Google LLC nor the names of its
14 // contributors may be used to endorse or promote products derived from
15 // this software without specific prior written permission.
16 //
17 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
18 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
19 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
20 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
21 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
22 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
23 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
27 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28
29 #ifdef HAVE_CONFIG_H
30 #include <config.h> // Must come first
31 #endif
32
33 #include "common/linux/crc32.h"
34
35 namespace google_breakpad {
36
37 // This implementation is based on the sample implementation in RFC 1952.
38
39 // CRC32 polynomial, in reversed form.
40 // See RFC 1952, or http://en.wikipedia.org/wiki/Cyclic_redundancy_check
41 static const uint32_t kCrc32Polynomial = 0xEDB88320;
42 static uint32_t kCrc32Table[256] = { 0 };
43
44 #define arraysize(f) (sizeof(f) / sizeof(*f))
45
EnsureCrc32TableInited()46 static void EnsureCrc32TableInited() {
47 if (kCrc32Table[arraysize(kCrc32Table) - 1])
48 return; // already inited
49 for (uint32_t i = 0; i < arraysize(kCrc32Table); ++i) {
50 uint32_t c = i;
51 for (size_t j = 0; j < 8; ++j) {
52 if (c & 1) {
53 c = kCrc32Polynomial ^ (c >> 1);
54 } else {
55 c >>= 1;
56 }
57 }
58 kCrc32Table[i] = c;
59 }
60 }
61
UpdateCrc32(uint32_t start,const void * buf,size_t len)62 uint32_t UpdateCrc32(uint32_t start, const void* buf, size_t len) {
63 EnsureCrc32TableInited();
64
65 uint32_t c = start ^ 0xFFFFFFFF;
66 const uint8_t* u = static_cast<const uint8_t*>(buf);
67 for (size_t i = 0; i < len; ++i) {
68 c = kCrc32Table[(c ^ u[i]) & 0xFF] ^ (c >> 8);
69 }
70 return c ^ 0xFFFFFFFF;
71 }
72
73 } // namespace google_breakpad
74