PeerStreamer

/*

 * CRC decoder (for codec/format testing)

 * Copyright (c) 2002 Fabrice Bellard.

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2 of the License, or (at your option) any later version.

 *

 * This library is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this library; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

#include "avformat.h"

/* adler32.c -- compute the Adler-32 checksum of a data stream

 * Copyright (C) 1995 Mark Adler

 * For conditions of distribution and use, see copyright notice in zlib.h

 */

#define BASE 65521L /* largest prime smaller than 65536 */

#define NMAX 5552

/* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */

#define DO1(buf)  {s1 += *buf++; s2 += s1;}

#define DO2(buf)  DO1(buf); DO1(buf);

#define DO4(buf)  DO2(buf); DO2(buf);

#define DO8(buf)  DO4(buf); DO4(buf);

#define DO16(buf) DO8(buf); DO8(buf);

unsigned long update_adler32(unsigned long adler, const uint8_t *buf, unsigned int len)

{

    unsigned long s1 = adler & 0xffff;

    unsigned long s2 = (adler >> 16) & 0xffff;

    int k;

    if (buf == NULL) return 1L;

    while (len > 0) {

        k = len < NMAX ? len : NMAX;

        len -= k;

        while (k >= 16) {

            DO16(buf);

            k -= 16;

        }

        if (k != 0) do {

            DO1(buf);

        } while (--k);

        s1 %= BASE;

        s2 %= BASE;

    }

    return (s2 << 16) | s1;

}

typedef struct CRCState {

    uint32_t crcval;

} CRCState;

static int crc_write_header(struct AVFormatContext *s)

{

    CRCState *crc = s->priv_data;

    /* init CRC */

    crc->crcval = update_adler32(0, NULL, 0);

    return 0;

}

static int crc_write_packet(struct AVFormatContext *s, AVPacket *pkt)

{

    CRCState *crc = s->priv_data;

    crc->crcval = update_adler32(crc->crcval, pkt->data, pkt->size);

    return 0;

}

static int crc_write_trailer(struct AVFormatContext *s)

{

    CRCState *crc = s->priv_data;

    char buf[64];

    snprintf(buf, sizeof(buf), "CRC=0x%08x\n", crc->crcval);

    put_buffer(&s->pb, buf, strlen(buf));

    put_flush_packet(&s->pb);

    return 0;

}

static int framecrc_write_packet(struct AVFormatContext *s, AVPacket *pkt)

{

    uint32_t crc = update_adler32(0, pkt->data, pkt->size);

    char buf[256];

    snprintf(buf, sizeof(buf), "%d, %"PRId64", %d, 0x%08x\n", pkt->stream_index, pkt->dts, pkt->size, crc);

    put_buffer(&s->pb, buf, strlen(buf));

    put_flush_packet(&s->pb);

    return 0;

}

static AVOutputFormat crc_format = {

    "crc",

    "crc testing format",

    NULL,

    "",

    sizeof(CRCState),

    CODEC_ID_PCM_S16LE,

    CODEC_ID_RAWVIDEO,

    crc_write_header,

    crc_write_packet,

    crc_write_trailer,

};

static AVOutputFormat framecrc_format = {

    "framecrc",

    "framecrc testing format",

    NULL,

    "",

    0,

    CODEC_ID_PCM_S16LE,

    CODEC_ID_RAWVIDEO,

    NULL,

    framecrc_write_packet,

    NULL,

};

int crc_init(void)

{

    av_register_output_format(&crc_format);

    av_register_output_format(&framecrc_format);

    return 0;

}