Long Filenames (bonkers filenames)

Just ran into an issue with long filenames on RO 5.19.
I was wondering what the maximum filename length is?

In case your wondering what the filename is:
_67812586_13935_177619871854_177595661854_2786630_7167813_n-1/jpg

Why the heck the BBC decided to have jpg’s with names that large is beyond me, but hey it made me chuckle!

Just ran into an issue with long filenames on RO 5.19.
I was wondering what the maximum filename length is?

The usual limiting factor is the 256 byte length of a wimp message. When the message headers are allowed for it leaves 236 bytes (or is it 232?) for the complete path. The actual filename length limit will then depend upon how deep it is buried in the directory structure.

I was wondering if there was an issue with DOSFS or MimeMap, given that it is a “/jpg” so maybe something else is trying to get a look-in?

I think I found a bug in DOSFS.

It is the DOSnaming file.

There are two functions of note. Here is the first:

/*---------------------------------------------------------------------------*/
/* Check that the given DOS names are identical */

int namematch(char *wcname,char *fname)
{
 char string1[257];
 char string2[257] ;

 /* Code assumes characters upto (and including) "file_sep" will always fit
  * in RISC OS names.
  */
 before(string1,fname,file_sep,0) ;
 before(string2,wcname,file_sep,0) ;
 if (wild_card_compare(string1,string2,DOSwcmult,DOSwcsing) == TRUE)
  {
   /* "string1" is the full (non-wildcarded) filename we have matched with */
   /* "string2" is the original (wildcarded) filename we were given on entry */

   after(string1,fname,file_sep,0) ;
   after(string2,wcname,file_sep,0) ;

   if (wild_card_compare(string1,string2,DOSwcmult,DOSwcsing) == TRUE)
    return(TRUE) ;
  }

 return(FALSE) ;
}

and here is the second:

/*-------------------------------------------------------------------------*/
/* return a string containing the text before the given character */

char *before(char *newptr,char *text,char marker,int npad)
{
 int cpos = chr_pos(text,marker) ;
 if (cpos == 0)
  cpos = strlen(text) ;

 strncpy(newptr,text,cpos) ;
 if (npad == 0)
  newptr[cpos] = NULL ;

 return(newptr) ;
}

What comes to mind is what happens if the filename is longer than 256 characters before the separator? The string1 and string2 chars are only large enough for 256, and the before() function will, if there isn’t a separator, default to the length of the text string (or if there is, to whatever size that is including >256).
In short, passing a stupid-long filename to DOSFS will splatter gooey bits of gunk all over places it shouldn’t.

Fix:

Make the filename buffers appropriately long (might be a FAT issue?) and include a check in before() to ensure that this buffer is not overshot.
There is a routine called after() that may need to be checked as well.

Aaaaaaand MimeMap is marked as “The MimeMap module has closed source access under NDA.” so if there is anything going on there with respect to filename size, we’re stuffed.

Do you experience the same issues if you rename the file to be _67812586_13935_177619871854_177595661854_2786630_7167813_n-1XXXX (same length, but the “/jpg” replaced by “XXXX”)?

I altered my code to use l as a replacement for the . and it still dies in a spectacular way (it seems to kill the entire network stack!)
I then tried downloading the file using netsurf and renaming it to /jpg.
That worked fine, so it’s looking like some dodgy code at my end.
Whilst not a suprise, means another few hours digging through damned C code again!
I was desperately hoping this was a RISC OS bug that I could easily work around, rather than tracking down a buffer overflow in my own ****ty code :-(
Is this what bank holiday weekends were made for?
That and watching Dr. StrangeLove of course

Update: Well I guess I should have expected a URL that was fairy large for that download! But I guess I never expected the URL to be quite that big.
All praise be to fflush helping me narrow that down!
Time to go and stab myself in the eye with a pen as pennance for my sins.
Now to get ChangeFSI to convert the gifs/jpegs etc into sprites! How much fun can one have in a single day?

Aaaaaaand MimeMap is marked as “The MimeMap module has closed source access under NDA.”

I cloned MimeMap a long time ago. Of course, cloned == different_bugs.

I cloned MimeMap a long time ago. Of course, cloned == different_bugs.

Of course that’s also normally cloned == source_as_open_as_author_wishes