112 lines
2.8 KiB
C
112 lines
2.8 KiB
C
/*
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* CRC decoder (for codec/format testing)
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* Copyright (c) 2002 Gerard Lantau.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include "avformat.h"
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/* adler32.c -- compute the Adler-32 checksum of a data stream
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* Copyright (C) 1995 Mark Adler
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* For conditions of distribution and use, see copyright notice in zlib.h
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*/
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#define BASE 65521L /* largest prime smaller than 65536 */
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#define NMAX 5552
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/* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
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#define DO1(buf) {s1 += *buf++; s2 += s1;}
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#define DO2(buf) DO1(buf); DO1(buf);
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#define DO4(buf) DO2(buf); DO2(buf);
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#define DO8(buf) DO4(buf); DO4(buf);
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#define DO16(buf) DO8(buf); DO8(buf);
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static UINT32 adler32(UINT32 adler, UINT8 *buf, unsigned int len)
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{
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unsigned long s1 = adler & 0xffff;
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unsigned long s2 = (adler >> 16) & 0xffff;
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int k;
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if (buf == NULL) return 1L;
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while (len > 0) {
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k = len < NMAX ? len : NMAX;
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len -= k;
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while (k >= 16) {
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DO16(buf);
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k -= 16;
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}
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if (k != 0) do {
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DO1(buf);
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} while (--k);
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s1 %= BASE;
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s2 %= BASE;
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}
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return (s2 << 16) | s1;
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}
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typedef struct CRCState {
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UINT32 crcval;
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} CRCState;
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static int crc_write_header(struct AVFormatContext *s)
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{
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CRCState *crc = s->priv_data;
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/* init CRC */
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crc->crcval = adler32(0, NULL, 0);
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return 0;
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}
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static int crc_write_packet(struct AVFormatContext *s,
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int stream_index,
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unsigned char *buf, int size, int force_pts)
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{
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CRCState *crc = s->priv_data;
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crc->crcval = adler32(crc->crcval, buf, size);
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return 0;
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}
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static int crc_write_trailer(struct AVFormatContext *s)
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{
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CRCState *crc = s->priv_data;
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char buf[64];
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snprintf(buf, sizeof(buf), "CRC=%08x\n", crc->crcval);
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put_buffer(&s->pb, buf, strlen(buf));
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put_flush_packet(&s->pb);
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return 0;
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}
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AVOutputFormat crc_format = {
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"crc",
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"crc testing format",
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NULL,
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"",
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sizeof(CRCState),
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CODEC_ID_PCM_S16LE,
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CODEC_ID_RAWVIDEO,
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crc_write_header,
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crc_write_packet,
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crc_write_trailer,
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};
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int crc_init(void)
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{
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av_register_output_format(&crc_format);
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return 0;
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}
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