[FFmpeg-devel] [RFC] using ByteIOContext with buffer without reading function

Baptiste Coudurier baptiste.coudurier
Sun Mar 15 23:53:07 CET 2009


I notice something strange when using ByteIOContext with a supplied
buffer without read function, reading only.

    if(!read_packet && !write_flag){
        s->pos = buffer_size;
        s->buf_end = s->buffer + buffer_size;

    if (!s->must_flush &&
        offset1 >= 0 && offset1 < (s->buf_end - s->buffer)) {
        /* can do the seek inside the buffer */
        s->buf_ptr = s->buffer + offset1;

    if(init_put_byte(&ctx, moov_data, moov_len, 0, NULL, NULL, NULL,
NULL) != 0)
        goto free_and_return;

Problem is:
when you use url_fskip on the ByteIOContext, for example to skip
everything not read (size is 51, url_fskip(51)), you will end up seeking
at s->buf_end.

However the condition in "seek" won't allow this since offset1 ==
s->buf_end - s->buffer.

Would it be better to change init to set buf_end to s->buffer +
buffer_size + 1 or check for <= in seek ?

Baptiste COUDURIER                              GnuPG Key Id: 0x5C1ABAAA
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FFmpeg maintainer                                  http://www.ffmpeg.org

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