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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/arraysize.h" |
13 #include "webrtc/base/basicdefs.h" | 14 #include "webrtc/base/basicdefs.h" |
14 | 15 |
15 namespace rtc { | 16 namespace rtc { |
16 | 17 |
17 // This implementation is based on the sample implementation in RFC 1952. | 18 // This implementation is based on the sample implementation in RFC 1952. |
18 | 19 |
19 // CRC32 polynomial, in reversed form. | 20 // CRC32 polynomial, in reversed form. |
20 // See RFC 1952, or http://en.wikipedia.org/wiki/Cyclic_redundancy_check | 21 // See RFC 1952, or http://en.wikipedia.org/wiki/Cyclic_redundancy_check |
21 static const uint32_t kCrc32Polynomial = 0xEDB88320; | 22 static const uint32_t kCrc32Polynomial = 0xEDB88320; |
22 static uint32_t kCrc32Table[256] = {0}; | 23 static uint32_t kCrc32Table[256] = {0}; |
23 | 24 |
24 static void EnsureCrc32TableInited() { | 25 static void EnsureCrc32TableInited() { |
25 if (kCrc32Table[ARRAY_SIZE(kCrc32Table) - 1]) | 26 if (kCrc32Table[arraysize(kCrc32Table) - 1]) |
26 return; // already inited | 27 return; // already inited |
27 for (uint32_t i = 0; i < ARRAY_SIZE(kCrc32Table); ++i) { | 28 for (uint32_t i = 0; i < arraysize(kCrc32Table); ++i) { |
28 uint32_t c = i; | 29 uint32_t c = i; |
29 for (size_t j = 0; j < 8; ++j) { | 30 for (size_t j = 0; j < 8; ++j) { |
30 if (c & 1) { | 31 if (c & 1) { |
31 c = kCrc32Polynomial ^ (c >> 1); | 32 c = kCrc32Polynomial ^ (c >> 1); |
32 } else { | 33 } else { |
33 c >>= 1; | 34 c >>= 1; |
34 } | 35 } |
35 } | 36 } |
36 kCrc32Table[i] = c; | 37 kCrc32Table[i] = c; |
37 } | 38 } |
38 } | 39 } |
39 | 40 |
40 uint32_t UpdateCrc32(uint32_t start, const void* buf, size_t len) { | 41 uint32_t UpdateCrc32(uint32_t start, const void* buf, size_t len) { |
41 EnsureCrc32TableInited(); | 42 EnsureCrc32TableInited(); |
42 | 43 |
43 uint32_t c = start ^ 0xFFFFFFFF; | 44 uint32_t c = start ^ 0xFFFFFFFF; |
44 const uint8_t* u = static_cast<const uint8_t*>(buf); | 45 const uint8_t* u = static_cast<const uint8_t*>(buf); |
45 for (size_t i = 0; i < len; ++i) { | 46 for (size_t i = 0; i < len; ++i) { |
46 c = kCrc32Table[(c ^ u[i]) & 0xFF] ^ (c >> 8); | 47 c = kCrc32Table[(c ^ u[i]) & 0xFF] ^ (c >> 8); |
47 } | 48 } |
48 return c ^ 0xFFFFFFFF; | 49 return c ^ 0xFFFFFFFF; |
49 } | 50 } |
50 | 51 |
51 } // namespace rtc | 52 } // namespace rtc |
52 | 53 |
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