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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.  
  24. /**
  25.  * @file
  26.  * Computes the Adler-32 checksum of a data stream
  27.  *
  28.  * This is a modified version based on adler32.c from the zlib library.
  29.  * @author Mark Adler
  30.  * @ingroup lavu_adler32
  31.  */
  32.  
  33. #include "config.h"
  34. #include "adler32.h"
  35. #include "common.h"
  36. #include "intreadwrite.h"
  37.  
  38. #define BASE 65521L /* largest prime smaller than 65536 */
  39.  
  40. #define DO1(buf)  { s1 += *buf++; s2 += s1; }
  41. #define DO4(buf)  DO1(buf); DO1(buf); DO1(buf); DO1(buf);
  42. #define DO16(buf) DO4(buf); DO4(buf); DO4(buf); DO4(buf);
  43.  
  44. unsigned long av_adler32_update(unsigned long adler, const uint8_t * buf,
  45.                                 unsigned int len)
  46. {
  47.     unsigned long s1 = adler & 0xffff;
  48.     unsigned long s2 = adler >> 16;
  49.  
  50.     while (len > 0) {
  51. #if HAVE_FAST_64BIT && HAVE_FAST_UNALIGNED && !CONFIG_SMALL
  52.         unsigned len2 = FFMIN((len-1) & ~7, 23*8);
  53.         if (len2) {
  54.             uint64_t a1= 0;
  55.             uint64_t a2= 0;
  56.             uint64_t b1= 0;
  57.             uint64_t b2= 0;
  58.             len -= len2;
  59.             s2 += s1*len2;
  60.             while (len2 >= 8) {
  61.                 uint64_t v = AV_RN64(buf);
  62.                 a2 += a1;
  63.                 b2 += b1;
  64.                 a1 +=  v    &0x00FF00FF00FF00FF;
  65.                 b1 += (v>>8)&0x00FF00FF00FF00FF;
  66.                 len2 -= 8;
  67.                 buf+=8;
  68.             }
  69.  
  70.             //We combine the 8 interleaved adler32 checksums without overflows
  71.             //Decreasing the number of iterations would allow below code to be
  72.             //simplified but would likely be slower due to the fewer iterations
  73.             //of the inner loop
  74.             s1 += ((a1+b1)*0x1000100010001)>>48;
  75.             s2 += ((((a2&0xFFFF0000FFFF)+(b2&0xFFFF0000FFFF)+((a2>>16)&0xFFFF0000FFFF)+((b2>>16)&0xFFFF0000FFFF))*0x800000008)>>32)
  76. #if HAVE_BIGENDIAN
  77.                  + 2*((b1*0x1000200030004)>>48)
  78.                  +   ((a1*0x1000100010001)>>48)
  79.                  + 2*((a1*0x0000100020003)>>48);
  80. #else
  81.                  + 2*((a1*0x4000300020001)>>48)
  82.                  +   ((b1*0x1000100010001)>>48)
  83.                  + 2*((b1*0x3000200010000)>>48);
  84. #endif
  85.         }
  86. #else
  87.         while (len > 4  && s2 < (1U << 31)) {
  88.             DO4(buf);
  89.             len -= 4;
  90.         }
  91. #endif
  92.         DO1(buf); len--;
  93.         s1 %= BASE;
  94.         s2 %= BASE;
  95.     }
  96.     return (s2 << 16) | s1;
  97. }
  98.  
  99. #ifdef TEST
  100. // LCOV_EXCL_START
  101. #include <string.h>
  102. #include "log.h"
  103. #include "timer.h"
  104. #define LEN 7001
  105.  
  106. static volatile int checksum;
  107.  
  108. int main(int argc, char **argv)
  109. {
  110.     int i;
  111.     uint8_t data[LEN];
  112.  
  113.     av_log_set_level(AV_LOG_DEBUG);
  114.  
  115.     for (i = 0; i < LEN; i++)
  116.         data[i] = ((i * i) >> 3) + 123 * i;
  117.  
  118.     if (argc > 1 && !strcmp(argv[1], "-t")) {
  119.         for (i = 0; i < 1000; i++) {
  120.             START_TIMER;
  121.             checksum = av_adler32_update(1, data, LEN);
  122.             STOP_TIMER("adler");
  123.         }
  124.     } else {
  125.         checksum = av_adler32_update(1, data, LEN);
  126.     }
  127.  
  128.     av_log(NULL, AV_LOG_DEBUG, "%X (expected 50E6E508)\n", checksum);
  129.     return checksum == 0x50e6e508 ? 0 : 1;
  130. }
  131. // LCOV_EXCL_STOP
  132. #endif
  133.