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ffmpeg / libavformat / crc.c @ 5aa0a644

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/* 
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 * CRC decoder (for codec/format testing)
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 * Copyright (c) 2002 Fabrice Bellard.
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 *
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 * This library is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2 of the License, or (at your option) any later version.
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 *
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 * This library 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 GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with this library; if not, write to the Free Software
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 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  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_t adler32(uint32_t adler, const uint8_t *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_t 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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                            const uint8_t *buf, int size, int64_t 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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static 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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}