2 * CRC decoder (for codec/format testing)
3 * Copyright (c) 2002 Fabrice Bellard.
5 * 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.
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
15 * 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
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
26 #define BASE 65521L /* largest prime smaller than 65536 */
28 /* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
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);
36 static uint32_t adler32(uint32_t adler, const uint8_t *buf, unsigned int len)
38 unsigned long s1 = adler & 0xffff;
39 unsigned long s2 = (adler >> 16) & 0xffff;
42 if (buf == NULL) return 1L;
45 k = len < NMAX ? len : NMAX;
57 return (s2 << 16) | s1;
60 typedef struct CRCState {
64 static int crc_write_header(struct AVFormatContext *s)
66 CRCState *crc = s->priv_data;
69 crc->crcval = adler32(0, NULL, 0);
74 static int crc_write_packet(struct AVFormatContext *s,
76 const uint8_t *buf, int size, int64_t pts)
78 CRCState *crc = s->priv_data;
79 crc->crcval = adler32(crc->crcval, buf, size);
83 static int crc_write_trailer(struct AVFormatContext *s)
85 CRCState *crc = s->priv_data;
88 snprintf(buf, sizeof(buf), "CRC=%08x\n", crc->crcval);
89 put_buffer(&s->pb, buf, strlen(buf));
90 put_flush_packet(&s->pb);
94 static AVOutputFormat crc_format = {
109 av_register_output_format(&crc_format);