[MPlayer-dev-eng] endless loop in mov_check_file()

[Steven M. Schultz]

Hello -

	I think I have stumbled across a problem in libmpdemux/demux_mov.c

	If 'len' is 0 then the routine mov_check_file() goes into an endless
	look of:  

    while(1){
	int skipped=8;
	off_t len=stream_read_dword(demuxer->stream);

	if(stream_eof(demuxer->stream)) break; // EOF
	if (len == 1) /* real size is 64bits - cjb */
	{
		...
	}
	else if (len == 0) /* deleted chunk */
	{
	    /* XXX: CJB! is this right? - alex */
	    goto skip_chunk;
	}
	else if(len<8) break; // invalid chunk
		...
skip_chunk:
	if(!stream_skip(demuxer->stream,len-skipped)) break; 
	...
    }

	This happened when I tried to play a SVCD, first 'AVI' was tried,
	then 'Y4M', 'ASF", 'NUV'.   When 'MOV' was checked (by calling
	mov_check_file()) - the "Checking for MOV" never returned and mplayer 
	went into an endless loop.

	The check for 'deleted chunk' is what appears to be causing the
	problem.   If I comment that section out the endless loop problem 
	goes away:

--- libmpdemux/demux_mov.c.dist	Tue Mar 19 15:43:58 2002
+++ libmpdemux/demux_mov.c	Tue Mar 19 14:17:04 2002
@@ -223,11 +223,13 @@
 #endif
 	    skipped += 8;
 	}
+#ifdef	notnow
 	else if (len == 0) /* deleted chunk */
 	{
 	    /* XXX: CJB! is this right? - alex */
 	    goto skip_chunk;
 	}
+#endif
 	else if(len<8) break; // invalid chunk
 
 	switch(id){

	If 'len' becomes 0 the loop becomes "read_dword", "seek back", 
	"read_dword", "seek back", ...

	Is "goto skip_chunk;" the correct thing to do?   The comment suggests
	that there were doubts about doing that.

	Thanks.

	Steven Schultz
	sms at 2bsd.com