Re: [ECOS] fatfs lseek EOF bug

[Savin Zlobec <savin at elatec dot si>]

Gratian Crisan wrote:

> Hi,
>
> please see my answers below:
>
> On Tuesday 10 May 2005 09:48, Savin Zlobec wrote:
>  
>
> > Gratian Crisan wrote:
> >    
> >
> > > Hi all,
> > >
> > > I think I've found a bug in the ecos FAT implementation for lseek
> > > function. (fatfs_fo_lseek).
> > > When calling the function like this 'lseek(fd, 0,  SEEK_CUR)' to get the
> > > current file position and the postion is right at the end of the file the
> > > fat lseek function returns end of file error EEOF. I've looked at the
> > > other filesystems from ecos and did a test in linux and the correct
> > > behavior seems to be to return the current position of the end of file if
> > > the read/write pointer is at the end of file (equal with the file size).
> > > This bug occurs for example when creating a new file, writing some data in
> > > it and calling lseek(fd, 0, SEEK_CUR) to get the current file position.
> > >
> > > Suggestions?
[snip]

> 	See the file attached. The test is for an MMC driver but should be pretty 
> straight forward to adapt (only the mount command should be changed).
> The test creates a file and writes blocks of data into it while printing the 
> current file offset. In a new file after writing the first block, for which 
> the value returned is 0, the value returned by lseek function is -1. The 
> strange thing is that if you overwrite an existing file the lseek function 
> correctly returns the current file offset (equal to EOF).
>  
Found the BUG -- Please try the attached patch and let me know if it works.

savin

Index: src/fatfs_supp.c
===================================================================
RCS file: /cvs/ecos/ecos/packages/fs/fat/current/src/fatfs_supp.c,v
retrieving revision 1.3
diff -u -r1.3 fatfs_supp.c
--- src/fatfs_supp.c	22 Oct 2004 14:10:23 -0000	1.3
+++ src/fatfs_supp.c	10 May 2005 10:43:14 -0000
@@ -1172,8 +1172,10 @@
     // Err could be EEOF wich means that the given 
     // offset if out of given file (cluster chain)
 
-    if (ENOERR == err)
-        *pos = new_pos; 
+    if (EEOF == err)
+        new_pos.cluster_pos = disk->cluster_size; 
+    
+    *pos = new_pos; 
     
     return err;
 } 
@@ -2056,11 +2058,18 @@
              fatfs_data_pos_t  *pos,
              cyg_uint32         offset)
 {
+    int err;
+    
     CYG_CHECK_DATA_PTRC(disk);
     CYG_CHECK_DATA_PTRC(file);
     CYG_CHECK_DATA_PTRC(pos);
     
-    return get_position_from_off(disk, file->cluster, offset, pos, CO_NONE);
+    err = get_position_from_off(disk, file->cluster, offset, pos, CO_NONE);
+
+    if (EEOF == err && offset == file->size)
+        return ENOERR;
+    else
+        return err;
 }
 
 // -------------------------------------------------------------------------

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