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 "common.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
33unsigned long av_adler32_update(unsigned long adler, const uint8_t *buf, unsigned int len)
34{
35    unsigned long s1 = adler & 0xffff;
36    unsigned long s2 = adler >> 16;
37
38    while (len>0) {
39#if CONFIG_SMALL
40        while(len>4 && s2 < (1U<<31)){
41            DO4(buf); len-=4;
42#else
43        while(len>16 && s2 < (1U<<31)){
44            DO16(buf); len-=16;
45#endif
46        }
47        DO1(buf); len--;
48        s1 %= BASE;
49        s2 %= BASE;
50    }
51    return (s2 << 16) | s1;
52}
53
54#ifdef TEST
55#include "log.h"
56#define LEN 7001
57volatile int checksum;
58int main(void){
59    int i;
60    char data[LEN];
61    av_log_level = AV_LOG_DEBUG;
62    for(i=0; i<LEN; i++)
63        data[i]= ((i*i)>>3) + 123*i;
64    for(i=0; i<1000; i++){
65        START_TIMER
66        checksum= av_adler32_update(1, data, LEN);
67        STOP_TIMER("adler")
68    }
69    av_log(NULL, AV_LOG_DEBUG, "%X == 50E6E508\n", checksum);
70    return 0;
71}
72#endif
73