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/indra/llcommon/llcrc.cpp

https://bitbucket.org/lindenlab/viewer-beta/
C++ | 223 lines | 116 code | 30 blank | 77 comment | 7 complexity | cf46dcdc64bc81ac7e67267a585f1359 MD5 | raw file
Possible License(s): LGPL-2.1
  1. /**
  2. * @file llcrc.cpp
  3. * @brief implementation of the crc class.
  4. *
  5. * $LicenseInfo:firstyear=2002&license=viewerlgpl$
  6. * Second Life Viewer Source Code
  7. * Copyright (C) 2010, Linden Research, Inc.
  8. *
  9. * This library is free software; you can redistribute it and/or
  10. * modify it under the terms of the GNU Lesser General Public
  11. * License as published by the Free Software Foundation;
  12. * version 2.1 of the License only.
  13. *
  14. * This library is distributed in the hope that it will be useful,
  15. * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16. * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  17. * Lesser General Public License for more details.
  18. *
  19. * You should have received a copy of the GNU Lesser General Public
  20. * License along with this library; if not, write to the Free Software
  21. * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  22. *
  23. * Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA
  24. * $/LicenseInfo$
  25. */
  26. #include "linden_common.h"
  27. #include "llcrc.h"
  28. #include "llerror.h"
  29. /* Copyright (C) 1986 Gary S. Brown. You may use this program, or
  30. code or tables extracted from it, as desired without restriction.*/
  31. /* First, the polynomial itself and its table of feedback terms. The */
  32. /* polynomial is */
  33. /* X^32+X^26+X^23+X^22+X^16+X^12+X^11+X^10+X^8+X^7+X^5+X^4+X^2+X^1+X^0 */
  34. /* Note that we take it "backwards" and put the highest-order term in */
  35. /* the lowest-order bit. The X^32 term is "implied"; the LSB is the */
  36. /* X^31 term, etc. The X^0 term (usually shown as "+1") results in */
  37. /* the MSB being 1. */
  38. /* Note that the usual hardware shift register implementation, which */
  39. /* is what we're using (we're merely optimizing it by doing eight-bit */
  40. /* chunks at a time) shifts bits into the lowest-order term. In our */
  41. /* implementation, that means shifting towards the right. Why do we */
  42. /* do it this way? Because the calculated CRC must be transmitted in */
  43. /* order from highest-order term to lowest-order term. UARTs transmit */
  44. /* characters in order from LSB to MSB. By storing the CRC this way, */
  45. /* we hand it to the UART in the order low-byte to high-byte; the UART */
  46. /* sends each low-bit to hight-bit; and the result is transmission bit */
  47. /* by bit from highest- to lowest-order term without requiring any bit */
  48. /* shuffling on our part. Reception works similarly. */
  49. /* The feedback terms table consists of 256, 32-bit entries. Notes: */
  50. /* */
  51. /* 1. The table can be generated at runtime if desired; code to do so */
  52. /* is shown later. It might not be obvious, but the feedback */
  53. /* terms simply represent the results of eight shift/xor opera- */
  54. /* tions for all combinations of data and CRC register values. */
  55. /* */
  56. /* 2. The CRC accumulation logic is the same for all CRC polynomials, */
  57. /* be they sixteen or thirty-two bits wide. You simply choose the */
  58. /* appropriate table. Alternatively, because the table can be */
  59. /* generated at runtime, you can start by generating the table for */
  60. /* the polynomial in question and use exactly the same "updcrc", */
  61. /* if your application needn't simultaneously handle two CRC */
  62. /* polynomials. (Note, however, that XMODEM is strange.) */
  63. /* */
  64. /* 3. For 16-bit CRCs, the table entries need be only 16 bits wide; */
  65. /* of course, 32-bit entries work OK if the high 16 bits are zero. */
  66. /* */
  67. /* 4. The values must be right-shifted by eight bits by the "updcrc" */
  68. /* logic; the shift must be unsigned (bring in zeroes). On some */
  69. /* hardware you could probably optimize the shift in assembler by */
  70. /* using byte-swap instructions. */
  71. ///----------------------------------------------------------------------------
  72. /// Local function declarations, constants, enums, and typedefs
  73. ///----------------------------------------------------------------------------
  74. #define UPDC32(octet,crc) (crc_32_tab[((crc) \
  75. ^ ((U8)octet)) & 0xff] ^ ((crc) >> 8))
  76. static U32 crc_32_tab[] = { /* CRC polynomial 0xedb88320 */
  77. 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
  78. 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
  79. 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2,
  80. 0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
  81. 0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
  82. 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
  83. 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c,
  84. 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
  85. 0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423,
  86. 0xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
  87. 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, 0x01db7106,
  88. 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
  89. 0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d,
  90. 0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
  91. 0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
  92. 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
  93. 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7,
  94. 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
  95. 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa,
  96. 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
  97. 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
  98. 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
  99. 0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84,
  100. 0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
  101. 0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
  102. 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
  103. 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e,
  104. 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
  105. 0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55,
  106. 0x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
  107. 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28,
  108. 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
  109. 0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f,
  110. 0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
  111. 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
  112. 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
  113. 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69,
  114. 0x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
  115. 0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc,
  116. 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
  117. 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693,
  118. 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
  119. 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
  120. };
  121. ///----------------------------------------------------------------------------
  122. /// Class llcrc
  123. ///----------------------------------------------------------------------------
  124. // Default constructor
  125. LLCRC::LLCRC() : mCurrent(0xffffffff)
  126. {
  127. }
  128. U32 LLCRC::getCRC() const
  129. {
  130. return ~mCurrent;
  131. }
  132. void LLCRC::update(U8 next_byte)
  133. {
  134. mCurrent = UPDC32(next_byte, mCurrent);
  135. }
  136. void LLCRC::update(const U8* buffer, size_t buffer_size)
  137. {
  138. for (size_t i = 0; i < buffer_size; i++)
  139. {
  140. mCurrent = UPDC32(buffer[i], mCurrent);
  141. }
  142. }
  143. void LLCRC::update(const std::string& filename)
  144. {
  145. if (filename.empty())
  146. {
  147. llerrs << "No filename specified" << llendl;
  148. return;
  149. }
  150. FILE* fp = LLFile::fopen(filename, "rb"); /* Flawfinder: ignore */
  151. if (fp)
  152. {
  153. fseek(fp, 0, SEEK_END);
  154. long size = ftell(fp);
  155. fseek(fp, 0, SEEK_SET);
  156. if (size > 0)
  157. {
  158. U8* data = new U8[size];
  159. size_t nread;
  160. nread = fread(data, 1, size, fp);
  161. fclose(fp);
  162. if (nread < (size_t) size)
  163. {
  164. llwarns << "Short read on " << filename << llendl;
  165. }
  166. update(data, nread);
  167. delete[] data;
  168. }
  169. else
  170. {
  171. fclose(fp);
  172. }
  173. }
  174. }
  175. #ifdef _DEBUG
  176. BOOL LLCRC::testHarness()
  177. {
  178. const S32 TEST_BUFFER_SIZE = 16;
  179. const char TEST_BUFFER[TEST_BUFFER_SIZE] = "hello &#$)$&Nd0"; /* Flawfinder: ignore */
  180. LLCRC c1, c2;
  181. c1.update((U8*)TEST_BUFFER, TEST_BUFFER_SIZE - 1);
  182. char* rh = (char*)TEST_BUFFER;
  183. while(*rh != '\0')
  184. {
  185. c2.update(*rh);
  186. ++rh;
  187. }
  188. return(c1.getCRC() == c2.getCRC());
  189. }
  190. #endif
  191. ///----------------------------------------------------------------------------
  192. /// Local function definitions
  193. ///----------------------------------------------------------------------------