adler32.c
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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 #include "config.h"
25 #include "adler32.h"
26 
27 #define BASE 65521L /* largest prime smaller than 65536 */
28 
29 #define DO1(buf) { s1 += *buf++; s2 += s1; }
30 #define DO4(buf) DO1(buf); DO1(buf); DO1(buf); DO1(buf);
31 #define DO16(buf) DO4(buf); DO4(buf); DO4(buf); DO4(buf);
32 
33 unsigned long av_adler32_update(unsigned long adler, const uint8_t * buf,
34  unsigned int len)
35 {
36  unsigned long s1 = adler & 0xffff;
37  unsigned long s2 = adler >> 16;
38 
39  while (len > 0) {
40 #if CONFIG_SMALL
41  while (len > 4 && s2 < (1U << 31)) {
42  DO4(buf);
43  len -= 4;
44  }
45 #else
46  while (len > 16 && s2 < (1U << 31)) {
47  DO16(buf);
48  len -= 16;
49  }
50 #endif
51  DO1(buf); len--;
52  s1 %= BASE;
53  s2 %= BASE;
54  }
55  return (s2 << 16) | s1;
56 }
57 
58 #ifdef TEST
59 #include <string.h>
60 #include "log.h"
61 #include "timer.h"
62 #define LEN 7001
63 
64 static volatile int checksum;
65 
66 int main(int argc, char **argv)
67 {
68  int i;
69  char data[LEN];
70 
72 
73  for (i = 0; i < LEN; i++)
74  data[i] = ((i * i) >> 3) + 123 * i;
75 
76  if (argc > 1 && !strcmp(argv[1], "-t")) {
77  for (i = 0; i < 1000; i++) {
79  checksum = av_adler32_update(1, data, LEN);
80  STOP_TIMER("adler");
81  }
82  } else {
83  checksum = av_adler32_update(1, data, LEN);
84  }
85 
86  av_log(NULL, AV_LOG_DEBUG, "%X (expected 50E6E508)\n", checksum);
87  return checksum == 0x50e6e508 ? 0 : 1;
88 }
89 #endif