is_whole_packet_present()

static int32_t fl::third_party::vorbis::is_whole_packet_present ( stb_vorbis * f )

static

Definition at line 3249 of file stb_vorbis.cpp.hpp.

{
   // make sure that we have the packet available before continuing...
   // this requires a full ogg parse, but we know we can fetch from f->stream
 
   // instead of coding this out explicitly, we could save the current read state,
   // read the next packet with get8() until end-of-packet, check f->eof, then
   // reset the state? but that would be slower, esp. since we'd have over 256 bytes
   // of state to restore (primarily the page segment table)
 
   int32_t s = f->next_seg, first = true;
   uint8 *p = f->stream;
 
   if (s != -1) { // if we're not starting the packet with a 'continue on next page' flag
      for (; s < f->segment_count; ++s) {
         p += f->segments[s];
         if (f->segments[s] < 255)               // stop at first short segment
            break;
      }
      // either this continues, or it ends it...
      if (s == f->segment_count)
         s = -1; // set 'crosses page' flag
      if (p > f->stream_end)                     return error(f, VORBIS_need_more_data);
      first = false;
   }
   for (; s == -1;) {
      uint8 *q;
      int32_t n;
 
      // check that we have the page header ready
      if (p + 26 >= f->stream_end)               return error(f, VORBIS_need_more_data);
      // validate the page
      if (memcmp(p, ogg_page_header, 4))         return error(f, VORBIS_invalid_stream);
      if (p[4] != 0)                             return error(f, VORBIS_invalid_stream);
      if (first) { // the first segment must NOT have 'continued_packet', later ones MUST
         if (f->previous_length)
            if ((p[5] & PAGEFLAG_continued_packet))  return error(f, VORBIS_invalid_stream);
         // if no previous length, we're resynching, so we can come in on a continued-packet,
         // which we'll just drop
      } else {
         if (!(p[5] & PAGEFLAG_continued_packet)) return error(f, VORBIS_invalid_stream);
      }
      n = p[26]; // segment counts
      q = p+27;  // q points to segment table
      p = q + n; // advance past header
      // make sure we've read the segment table
      if (p > f->stream_end)                     return error(f, VORBIS_need_more_data);
      for (s=0; s < n; ++s) {
         p += q[s];
         if (q[s] < 255)
            break;
      }
      if (s == n)
         s = -1; // set 'crosses page' flag
      if (p > f->stream_end)                     return error(f, VORBIS_need_more_data);
      first = false;
   }
   return true;
}

References error(), FL_NOEXCEPT, memcmp(), ogg_page_header, PAGEFLAG_continued_packet, VORBIS_invalid_stream, and VORBIS_need_more_data.

Referenced by start_decoder(), and stb_vorbis_decode_frame_pushdata().

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