Function ff_format_shift_data

libavformat/mux_utils.c:71–125

}

int ff_format_shift_data(AVFormatContext *s, int64_t read_start, int shift_size)
{
    int ret;
    int64_t pos, pos_end;
    uint8_t *buf, *read_buf[2];
    int read_buf_id = 0;
    int read_size[2];
    AVIOContext *read_pb;

    buf = av_malloc_array(shift_size, 2);
    if (!buf)
        return AVERROR(ENOMEM);
    read_buf[0] = buf;
    read_buf[1] = buf + shift_size;

    /* Shift the data: the AVIO context of the output can only be used for
     * writing, so we re-open the same output, but for reading. It also avoids
     * a read/seek/write/seek back and forth. */
    avio_flush(s->pb);
    ret = s->io_open(s, &read_pb, s->url, AVIO_FLAG_READ, NULL);
    if (ret < 0) {
        av_log(s, AV_LOG_ERROR, "Unable to re-open %s output file for shifting data\n", s->url);
        goto end;
    }

    /* mark the end of the shift to up to the last data we wrote, and get ready
     * for writing */
    pos_end = avio_tell(s->pb);
    avio_seek(s->pb, read_start + shift_size, SEEK_SET);

    avio_seek(read_pb, read_start, SEEK_SET);
    pos = avio_tell(read_pb);

#define READ_BLOCK do {                                                             \
    read_size[read_buf_id] = avio_read(read_pb, read_buf[read_buf_id], shift_size);  \
    read_buf_id ^= 1;                                                               \
} while (0)

    /* shift data by chunk of at most shift_size */
    READ_BLOCK;
    do {
        int n;
        READ_BLOCK;
        n = read_size[read_buf_id];
        if (n <= 0)
            break;
        avio_write(s->pb, read_buf[read_buf_id], n);
        pos += n;
    } while (pos < pos_end);
    ret = ff_format_io_close(s, &read_pb);

end:
    av_free(buf);
    return ret;
}

int ff_format_output_open(AVFormatContext *s, const char *url, AVDictionary **options)
{