adler32.c 2.2 KB

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  1. /*
  2. * Compute the Adler-32 checksum of a data stream.
  3. * This is a modified version based on adler32.c from the zlib library.
  4. *
  5. * Copyright (C) 1995 Mark Adler
  6. *
  7. * This software is provided 'as-is', without any express or implied
  8. * warranty. In no event will the authors be held liable for any damages
  9. * arising from the use of this software.
  10. *
  11. * Permission is granted to anyone to use this software for any purpose,
  12. * including commercial applications, and to alter it and redistribute it
  13. * freely, subject to the following restrictions:
  14. *
  15. * 1. The origin of this software must not be misrepresented; you must not
  16. * claim that you wrote the original software. If you use this software
  17. * in a product, an acknowledgment in the product documentation would be
  18. * appreciated but is not required.
  19. * 2. Altered source versions must be plainly marked as such, and must not be
  20. * misrepresented as being the original software.
  21. * 3. This notice may not be removed or altered from any source distribution.
  22. */
  23. #include "config.h"
  24. #include "adler32.h"
  25. #define BASE 65521L /* largest prime smaller than 65536 */
  26. #define DO1(buf) {s1 += *buf++; s2 += s1;}
  27. #define DO4(buf) DO1(buf); DO1(buf); DO1(buf); DO1(buf);
  28. #define DO16(buf) DO4(buf); DO4(buf); DO4(buf); DO4(buf);
  29. unsigned long av_adler32_update(unsigned long adler, const uint8_t *buf, unsigned int len)
  30. {
  31. unsigned long s1 = adler & 0xffff;
  32. unsigned long s2 = adler >> 16;
  33. while (len>0) {
  34. #if CONFIG_SMALL
  35. while(len>4 && s2 < (1U<<31)){
  36. DO4(buf); len-=4;
  37. #else
  38. while(len>16 && s2 < (1U<<31)){
  39. DO16(buf); len-=16;
  40. #endif
  41. }
  42. DO1(buf); len--;
  43. s1 %= BASE;
  44. s2 %= BASE;
  45. }
  46. return (s2 << 16) | s1;
  47. }
  48. #ifdef TEST
  49. #include "log.h"
  50. #include "timer.h"
  51. #define LEN 7001
  52. volatile int checksum;
  53. int main(void){
  54. int i;
  55. char data[LEN];
  56. av_log_set_level(AV_LOG_DEBUG);
  57. for(i=0; i<LEN; i++)
  58. data[i]= ((i*i)>>3) + 123*i;
  59. for(i=0; i<1000; i++){
  60. START_TIMER
  61. checksum= av_adler32_update(1, data, LEN);
  62. STOP_TIMER("adler")
  63. }
  64. av_log(NULL, AV_LOG_DEBUG, "%X == 50E6E508\n", checksum);
  65. return 0;
  66. }
  67. #endif