mirror of https://git.ffmpeg.org/ffmpeg.git
82 lines
2.6 KiB
C
82 lines
2.6 KiB
C
/*
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* Various muxing utility functions
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* Copyright (c) 2000, 2001, 2002 Fabrice Bellard
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg 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 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg 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 FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "avformat.h"
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#include "avio.h"
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#include "internal.h"
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#include "mux.h"
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int ff_format_shift_data(AVFormatContext *s, int64_t read_start, int shift_size)
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{
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int ret;
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int64_t pos, pos_end;
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uint8_t *buf, *read_buf[2];
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int read_buf_id = 0;
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int read_size[2];
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AVIOContext *read_pb;
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buf = av_malloc_array(shift_size, 2);
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if (!buf)
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return AVERROR(ENOMEM);
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read_buf[0] = buf;
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read_buf[1] = buf + shift_size;
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/* Shift the data: the AVIO context of the output can only be used for
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* writing, so we re-open the same output, but for reading. It also avoids
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* a read/seek/write/seek back and forth. */
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avio_flush(s->pb);
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ret = s->io_open(s, &read_pb, s->url, AVIO_FLAG_READ, NULL);
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if (ret < 0) {
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av_log(s, AV_LOG_ERROR, "Unable to re-open %s output file for shifting data\n", s->url);
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goto end;
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}
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/* mark the end of the shift to up to the last data we wrote, and get ready
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* for writing */
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pos_end = avio_tell(s->pb);
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avio_seek(s->pb, read_start + shift_size, SEEK_SET);
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avio_seek(read_pb, read_start, SEEK_SET);
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pos = avio_tell(read_pb);
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#define READ_BLOCK do { \
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read_size[read_buf_id] = avio_read(read_pb, read_buf[read_buf_id], shift_size); \
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read_buf_id ^= 1; \
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} while (0)
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/* shift data by chunk of at most shift_size */
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READ_BLOCK;
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do {
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int n;
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READ_BLOCK;
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n = read_size[read_buf_id];
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if (n <= 0)
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break;
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avio_write(s->pb, read_buf[read_buf_id], n);
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pos += n;
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} while (pos < pos_end);
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ret = ff_format_io_close(s, &read_pb);
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end:
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av_free(buf);
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return ret;
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}
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