libavutil/adler32.c
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00001 /*
00002  * Compute the Adler-32 checksum of a data stream.
00003  * This is a modified version based on adler32.c from the zlib library.
00004  *
00005  * Copyright (C) 1995 Mark Adler
00006  *
00007  * This software is provided 'as-is', without any express or implied
00008  * warranty.  In no event will the authors be held liable for any damages
00009  * arising from the use of this software.
00010  *
00011  * Permission is granted to anyone to use this software for any purpose,
00012  * including commercial applications, and to alter it and redistribute it
00013  * freely, subject to the following restrictions:
00014  *
00015  * 1. The origin of this software must not be misrepresented; you must not
00016  *    claim that you wrote the original software. If you use this software
00017  *    in a product, an acknowledgment in the product documentation would be
00018  *    appreciated but is not required.
00019  * 2. Altered source versions must be plainly marked as such, and must not be
00020  *    misrepresented as being the original software.
00021  * 3. This notice may not be removed or altered from any source distribution.
00022  */
00023 
00024 #include "config.h"
00025 #include "adler32.h"
00026 
00027 #define BASE 65521L /* largest prime smaller than 65536 */
00028 
00029 #define DO1(buf)  { s1 += *buf++; s2 += s1; }
00030 #define DO4(buf)  DO1(buf); DO1(buf); DO1(buf); DO1(buf);
00031 #define DO16(buf) DO4(buf); DO4(buf); DO4(buf); DO4(buf);
00032 
00033 unsigned long av_adler32_update(unsigned long adler, const uint8_t * buf,
00034                                 unsigned int len)
00035 {
00036     unsigned long s1 = adler & 0xffff;
00037     unsigned long s2 = adler >> 16;
00038 
00039     while (len > 0) {
00040 #if CONFIG_SMALL
00041         while (len > 4  && s2 < (1U << 31)) {
00042             DO4(buf);
00043             len -= 4;
00044         }
00045 #else
00046         while (len > 16 && s2 < (1U << 31)) {
00047             DO16(buf);
00048             len -= 16;
00049         }
00050 #endif
00051         DO1(buf); len--;
00052         s1 %= BASE;
00053         s2 %= BASE;
00054     }
00055     return (s2 << 16) | s1;
00056 }
00057 
00058 #ifdef TEST
00059 // LCOV_EXCL_START
00060 #include <string.h>
00061 #include "log.h"
00062 #include "timer.h"
00063 #define LEN 7001
00064 
00065 static volatile int checksum;
00066 
00067 int main(int argc, char **argv)
00068 {
00069     int i;
00070     char data[LEN];
00071 
00072     av_log_set_level(AV_LOG_DEBUG);
00073 
00074     for (i = 0; i < LEN; i++)
00075         data[i] = ((i * i) >> 3) + 123 * i;
00076 
00077     if (argc > 1 && !strcmp(argv[1], "-t")) {
00078         for (i = 0; i < 1000; i++) {
00079             START_TIMER;
00080             checksum = av_adler32_update(1, data, LEN);
00081             STOP_TIMER("adler");
00082         }
00083     } else {
00084         checksum = av_adler32_update(1, data, LEN);
00085     }
00086 
00087     av_log(NULL, AV_LOG_DEBUG, "%X (expected 50E6E508)\n", checksum);
00088     return checksum == 0x50e6e508 ? 0 : 1;
00089 }
00090 // LCOV_EXCL_STOP
00091 #endif