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