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
