crc32.c 1.9 KB

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  1. /*
  2. * CRC32 checksum
  3. *
  4. * Copyright (c) 1998-2003 by Joergen Ibsen / Jibz
  5. * All Rights Reserved
  6. *
  7. * http://www.ibsensoftware.com/
  8. *
  9. * This software is provided 'as-is', without any express
  10. * or implied warranty. In no event will the authors be
  11. * held liable for any damages arising from the use of
  12. * this software.
  13. *
  14. * Permission is granted to anyone to use this software
  15. * for any purpose, including commercial applications,
  16. * and to alter it and redistribute it freely, subject to
  17. * the following restrictions:
  18. *
  19. * 1. The origin of this software must not be
  20. * misrepresented; you must not claim that you
  21. * wrote the original software. If you use this
  22. * software in a product, an acknowledgment in
  23. * the product documentation would be appreciated
  24. * but is not required.
  25. *
  26. * 2. Altered source versions must be plainly marked
  27. * as such, and must not be misrepresented as
  28. * being the original software.
  29. *
  30. * 3. This notice may not be removed or altered from
  31. * any source distribution.
  32. */
  33. /*
  34. * CRC32 algorithm taken from the zlib source, which is
  35. * Copyright (C) 1995-1998 Jean-loup Gailly and Mark Adler
  36. */
  37. #include <stdint.h>
  38. static const unsigned int tinf_crc32tab[16] = {
  39. 0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac, 0x76dc4190,
  40. 0x6b6b51f4, 0x4db26158, 0x5005713c, 0xedb88320, 0xf00f9344,
  41. 0xd6d6a3e8, 0xcb61b38c, 0x9b64c2b0, 0x86d3d2d4, 0xa00ae278,
  42. 0xbdbdf21c
  43. };
  44. /* crc is previous value for incremental computation, 0xffffffff initially */
  45. uint32_t uzlib_crc32(const void *data, unsigned int length, uint32_t crc)
  46. {
  47. const unsigned char *buf = (const unsigned char *)data;
  48. unsigned int i;
  49. for (i = 0; i < length; ++i)
  50. {
  51. crc ^= buf[i];
  52. crc = tinf_crc32tab[crc & 0x0f] ^ (crc >> 4);
  53. crc = tinf_crc32tab[crc & 0x0f] ^ (crc >> 4);
  54. }
  55. // return value suitable for passing in next time, for final value invert it
  56. return crc/* ^ 0xffffffff*/;
  57. }