Statistics
| Branch: | Revision:

ffmpeg / libavutil / adler32.c @ bfe3676f

History | View | Annotate | Download (2.14 KB)

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

    
33
unsigned 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
57
volatile int checksum;
58
int 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