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| 1 /* | 1 /* |
| 2 * Copyright 2012 The WebRTC Project Authors. All rights reserved. | 2 * Copyright 2012 The WebRTC Project Authors. All rights reserved. |
| 3 * | 3 * |
| 4 * Use of this source code is governed by a BSD-style license | 4 * Use of this source code is governed by a BSD-style license |
| 5 * that can be found in the LICENSE file in the root of the source | 5 * that can be found in the LICENSE file in the root of the source |
| 6 * tree. An additional intellectual property rights grant can be found | 6 * tree. An additional intellectual property rights grant can be found |
| 7 * in the file PATENTS. All contributing project authors may | 7 * in the file PATENTS. All contributing project authors may |
| 8 * be found in the AUTHORS file in the root of the source tree. | 8 * be found in the AUTHORS file in the root of the source tree. |
| 9 */ | 9 */ |
| 10 | 10 |
| 11 #include "webrtc/base/crc32.h" | 11 #include "webrtc/base/crc32.h" |
| 12 | 12 |
| 13 #include "webrtc/base/basicdefs.h" | 13 #include "webrtc/base/basicdefs.h" |
| 14 | 14 |
| 15 namespace rtc { | 15 namespace rtc { |
| 16 | 16 |
| 17 // This implementation is based on the sample implementation in RFC 1952. | 17 // This implementation is based on the sample implementation in RFC 1952. |
| 18 | 18 |
| 19 // CRC32 polynomial, in reversed form. | 19 // CRC32 polynomial, in reversed form. |
| 20 // See RFC 1952, or http://en.wikipedia.org/wiki/Cyclic_redundancy_check | 20 // See RFC 1952, or http://en.wikipedia.org/wiki/Cyclic_redundancy_check |
| 21 static const uint32 kCrc32Polynomial = 0xEDB88320; | 21 static const uint32_t kCrc32Polynomial = 0xEDB88320; |
| 22 static uint32 kCrc32Table[256] = { 0 }; | 22 static uint32_t kCrc32Table[256] = {0}; |
| 23 | 23 |
| 24 static void EnsureCrc32TableInited() { | 24 static void EnsureCrc32TableInited() { |
| 25 if (kCrc32Table[ARRAY_SIZE(kCrc32Table) - 1]) | 25 if (kCrc32Table[ARRAY_SIZE(kCrc32Table) - 1]) |
| 26 return; // already inited | 26 return; // already inited |
| 27 for (uint32 i = 0; i < ARRAY_SIZE(kCrc32Table); ++i) { | 27 for (uint32_t i = 0; i < ARRAY_SIZE(kCrc32Table); ++i) { |
| 28 uint32 c = i; | 28 uint32_t c = i; |
| 29 for (size_t j = 0; j < 8; ++j) { | 29 for (size_t j = 0; j < 8; ++j) { |
| 30 if (c & 1) { | 30 if (c & 1) { |
| 31 c = kCrc32Polynomial ^ (c >> 1); | 31 c = kCrc32Polynomial ^ (c >> 1); |
| 32 } else { | 32 } else { |
| 33 c >>= 1; | 33 c >>= 1; |
| 34 } | 34 } |
| 35 } | 35 } |
| 36 kCrc32Table[i] = c; | 36 kCrc32Table[i] = c; |
| 37 } | 37 } |
| 38 } | 38 } |
| 39 | 39 |
| 40 uint32 UpdateCrc32(uint32 start, const void* buf, size_t len) { | 40 uint32_t UpdateCrc32(uint32_t start, const void* buf, size_t len) { |
| 41 EnsureCrc32TableInited(); | 41 EnsureCrc32TableInited(); |
| 42 | 42 |
| 43 uint32 c = start ^ 0xFFFFFFFF; | 43 uint32_t c = start ^ 0xFFFFFFFF; |
| 44 const uint8* u = static_cast<const uint8*>(buf); | 44 const uint8_t* u = static_cast<const uint8_t*>(buf); |
| 45 for (size_t i = 0; i < len; ++i) { | 45 for (size_t i = 0; i < len; ++i) { |
| 46 c = kCrc32Table[(c ^ u[i]) & 0xFF] ^ (c >> 8); | 46 c = kCrc32Table[(c ^ u[i]) & 0xFF] ^ (c >> 8); |
| 47 } | 47 } |
| 48 return c ^ 0xFFFFFFFF; | 48 return c ^ 0xFFFFFFFF; |
| 49 } | 49 } |
| 50 | 50 |
| 51 } // namespace rtc | 51 } // namespace rtc |
| 52 | 52 |
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