Statistics
| Branch: | Revision:

ffmpeg / libavformat / crc.c @ 649b918c

History | View | Annotate | Download (2.83 KB)

1 1c098b2f Fabrice Bellard
/* 
2
 * CRC decoder (for codec/format testing)
3 19720f15 Fabrice Bellard
 * Copyright (c) 2002 Fabrice Bellard.
4 1c098b2f Fabrice Bellard
 *
5 19720f15 Fabrice Bellard
 * This library is free software; you can redistribute it and/or
6
 * modify it under the terms of the GNU Lesser General Public
7
 * License as published by the Free Software Foundation; either
8
 * version 2 of the License, or (at your option) any later version.
9 1c098b2f Fabrice Bellard
 *
10 19720f15 Fabrice Bellard
 * This library is distributed in the hope that it will be useful,
11 1c098b2f Fabrice Bellard
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 19720f15 Fabrice Bellard
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13
 * Lesser General Public License for more details.
14 1c098b2f Fabrice Bellard
 *
15 19720f15 Fabrice Bellard
 * You should have received a copy of the GNU Lesser General Public
16
 * License along with this library; if not, write to the Free Software
17
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
18 1c098b2f Fabrice Bellard
 */
19
#include "avformat.h"
20
21
/* adler32.c -- compute the Adler-32 checksum of a data stream
22
 * Copyright (C) 1995 Mark Adler
23
 * For conditions of distribution and use, see copyright notice in zlib.h
24
 */
25
26
#define BASE 65521L /* largest prime smaller than 65536 */
27
#define NMAX 5552
28
/* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
29
30
#define DO1(buf)  {s1 += *buf++; s2 += s1;}
31
#define DO2(buf)  DO1(buf); DO1(buf);
32
#define DO4(buf)  DO2(buf); DO2(buf);
33
#define DO8(buf)  DO4(buf); DO4(buf);
34
#define DO16(buf) DO8(buf); DO8(buf);
35
36 ee9f36a8 Michael Niedermayer
unsigned long update_adler32(unsigned long adler, const uint8_t *buf, unsigned int len)
37 1c098b2f Fabrice Bellard
{
38
    unsigned long s1 = adler & 0xffff;
39
    unsigned long s2 = (adler >> 16) & 0xffff;
40
    int k;
41
42
    if (buf == NULL) return 1L;
43
44
    while (len > 0) {
45
        k = len < NMAX ? len : NMAX;
46
        len -= k;
47
        while (k >= 16) {
48
            DO16(buf);
49
            k -= 16;
50
        }
51
        if (k != 0) do {
52
            DO1(buf);
53
        } while (--k);
54
        s1 %= BASE;
55
        s2 %= BASE;
56
    }
57
    return (s2 << 16) | s1;
58
}
59
60
typedef struct CRCState {
61 0c1a9eda Zdenek Kabelac
    uint32_t crcval;
62 1c098b2f Fabrice Bellard
} CRCState;
63
64
static int crc_write_header(struct AVFormatContext *s)
65
{
66 c9a65ca8 Fabrice Bellard
    CRCState *crc = s->priv_data;
67
68 1c098b2f Fabrice Bellard
    /* init CRC */
69 ee9f36a8 Michael Niedermayer
    crc->crcval = update_adler32(0, NULL, 0);
70 1c098b2f Fabrice Bellard
71
    return 0;
72
}
73
74 e928649b Michael Niedermayer
static int crc_write_packet(struct AVFormatContext *s, AVPacket *pkt)
75 1c098b2f Fabrice Bellard
{
76
    CRCState *crc = s->priv_data;
77 e928649b Michael Niedermayer
    crc->crcval = update_adler32(crc->crcval, pkt->data, pkt->size);
78 1c098b2f Fabrice Bellard
    return 0;
79
}
80
81
static int crc_write_trailer(struct AVFormatContext *s)
82
{
83
    CRCState *crc = s->priv_data;
84
    char buf[64];
85
86
    snprintf(buf, sizeof(buf), "CRC=%08x\n", crc->crcval);
87
    put_buffer(&s->pb, buf, strlen(buf));
88
    put_flush_packet(&s->pb);
89
    return 0;
90
}
91
92 c18a2692 Zdenek Kabelac
static AVOutputFormat crc_format = {
93 1c098b2f Fabrice Bellard
    "crc",
94
    "crc testing format",
95
    NULL,
96
    "",
97 c9a65ca8 Fabrice Bellard
    sizeof(CRCState),
98 1c098b2f Fabrice Bellard
    CODEC_ID_PCM_S16LE,
99
    CODEC_ID_RAWVIDEO,
100
    crc_write_header,
101
    crc_write_packet,
102
    crc_write_trailer,
103
};
104 c9a65ca8 Fabrice Bellard
105
int crc_init(void)
106
{
107
    av_register_output_format(&crc_format);
108
    return 0;
109
}