Fix FAT seek bug

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@896 42af7a65-404d-4744-a932-0658087f49c3

ChangeLog

@@ -459,4 +459,6 @@
 	* Fixed several critical bugs with regard to fat reading and writing and FAT12
 	  accesses.  Basically the FAT FS only worked with my tiny test files and test
 	  cases.  A lot of stronger FAT tested is needed!!
+	* Fixed another FAT bug in implementation of FAT lseek; this prohibit correct
+	  random access to large files.
 

Documentation/NuttX.html

@@ -8,7 +8,7 @@
   <tr align="center" bgcolor="#e4e4e4">
     <td>
       <h1><big><font color="#3c34ec"><i>NuttX RTOS</i></font></big></h1>
-      <p>Last Updated: September 7, 2008</p>
+      <p>Last Updated: September 8, 2008</p>
     </td>
   </tr>
 </table>
@@ -1117,6 +1117,8 @@ nuttx-0.3.14 2008-xx-xx Gregory Nutt &lt;spudmonkey@racsa.co.cr&gt;
 	* Fixed several critical bugs with regard to fat reading and writing and FAT12
 	  accesses.  Basically the FAT FS only worked with my tiny test files and test
 	  cases.  A lot of stronger FAT tested is needed!!
+	* Fixed another FAT bug in implementation of FAT lseek; this prohibit correct
+	  random access to large files.
 
 pascal-0.1.3 2008-xx-xx Gregory Nutt &lt;spudmonkey@racsa.co.cr&gt;
 

fs/fat/fs_fat32.c

@@ -44,6 +44,7 @@
  ****************************************************************************/
 
 #include <nuttx/config.h>
+
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/statfs.h>
@@ -478,9 +479,11 @@ static ssize_t fat_read(FAR struct file *filep, char *buffer, size_t buflen)
        * and the file offset.
        */
 
-      ff->ff_currentsector = fat_cluster2sector(fs, ff->ff_currentcluster)
+      ret = fat_currentsector(fs, ff, filep->f_pos);
-                           + (SEC_NSECTORS(fs, filep->f_pos) & CLUS_NDXMASK(fs));
+      if (ret < 0)
-      fdbg("Start with sector: %d\n", ff->ff_currentsector);
+        {
+           return ret;
+        }
     }
 
   /* Loop until either (1) all data has been transferred, or (2) an
@@ -676,8 +679,11 @@ static ssize_t fat_write(FAR struct file *filep, const char *buffer,
        * and the file offset.
        */
 
-      ff->ff_currentsector = fat_cluster2sector(fs, ff->ff_currentcluster)
+      ret = fat_currentsector(fs, ff, filep->f_pos);
-                           + (SEC_NSECTORS(fs, filep->f_pos) & CLUS_NDXMASK(fs));
+      if (ret < 0)
+        {
+           return ret;
+        }
     }
 
   /* Loop until either (1) all data has been transferred, or (2) an
@@ -773,7 +779,9 @@ static ssize_t fat_write(FAR struct file *filep, const char *buffer,
             }
 
           memcpy(&ff->ff_buffer[sectorindex], userbuffer, writesize);
-          ff->ff_bflags |= (FFBUFF_DIRTY|FFBUFF_VALID|FFBUFF_MODIFIED);
+
+          ff->ff_bflags     |= (FFBUFF_DIRTY|FFBUFF_VALID|FFBUFF_MODIFIED);
+          ff->ff_cachesector = ff->ff_currentsector;
         }
 
       /* Set up for the next write */
@@ -844,7 +852,6 @@ static off_t fat_seek(FAR struct file *filep, off_t offset, int whence)
   sint32                cluster;
   ssize_t               position;
   unsigned int          clustersize;
-  unsigned int          sectoroffset;
   int                   ret;
 
   /* Sanity checks */
@@ -906,6 +913,7 @@ static off_t fat_seek(FAR struct file *filep, off_t offset, int whence)
   if (position > ff->ff_size && (ff->ff_oflags & O_WROK) == 0)
     {
         /* Otherwise, the position is limited to the file size */
+
         position = ff->ff_size;
     }
 
@@ -948,7 +956,7 @@ static off_t fat_seek(FAR struct file *filep, off_t offset, int whence)
                  */
 
                 ff->ff_currentcluster = cluster;
-                if (position <= clustersize)
+                if (position < clustersize)
                 {
                     break;
                 }
@@ -1015,16 +1023,17 @@ static off_t fat_seek(FAR struct file *filep, off_t offset, int whence)
 
             /* We get here after we have found the sector containing
              * the requested position.
+             *
+             * Save the new file position
              */
 
-            sectoroffset = (position - 1) / fs->fs_hwsectorsize;
+            filep->f_pos += position;
 
-            /* And get the current sector from the cluster and
+            /* Then get the current sector from the cluster and the offset
-             * the sectoroffset into the cluster.
+             * into the cluster from the position
              */
 
-            ff->ff_currentsector =
+            (void)fat_currentsector(fs, ff, filep->f_pos);
-                fat_cluster2sector(fs, cluster) + sectoroffset;
 
             /* Load the sector corresponding to the position */
 
@@ -1037,13 +1046,6 @@ static off_t fat_seek(FAR struct file *filep, off_t offset, int whence)
                 }
             }
 
-            /* Save the number of sectors left in the cluster */
-
-            ff->ff_sectorsincluster = fs->fs_fatsecperclus - sectoroffset;
-
-            /* And save the new file position */
-
-            filep->f_pos += position;
         }
     }
 
@@ -1141,6 +1143,7 @@ static int fat_sync(FAR struct file *filep)
     }
 
   /* Check if the has been modified in any way */
+
   if ((ff->ff_bflags & FFBUFF_MODIFIED) != 0)
     {
       /* Flush any unwritten data in the file buffer */

fs/fat/fs_fat32.h

@@ -162,7 +162,7 @@
 #define SEC_NDXMASK(f)      ((f)->fs_hwsectorsize - 1)
 #define SEC_NSECTORS(f,n)   ((n) / (f)->fs_hwsectorsize)
 
-#define CLUS_NDXMASK(f)     ((f)->fs_fatsecperclus -1)
+#define CLUS_NDXMASK(f)     ((f)->fs_fatsecperclus - 1)
 
 /****************************************************************************
  * File system types */
@@ -615,8 +615,9 @@ EXTERN int    fat_ffcacheinvalidate(struct fat_mountpt_s *fs, struct fat_file_s
 
 /* FSINFO sector support */
 
-EXTERN int fat_updatefsinfo(struct fat_mountpt_s *fs);
+EXTERN int    fat_updatefsinfo(struct fat_mountpt_s *fs);
-EXTERN int fat_nfreeclusters(struct fat_mountpt_s *fs, size_t *pfreeclusters);
+EXTERN int    fat_nfreeclusters(struct fat_mountpt_s *fs, size_t *pfreeclusters);
+EXTERN int    fat_currentsector(struct fat_mountpt_s *fs, struct fat_file_s *ff, off_t position);
 
 #undef EXTERN
 #if defined(__cplusplus)

fs/fat/fs_fat32util.c

@@ -44,6 +44,7 @@
  ****************************************************************************/
 
 #include <nuttx/config.h>
+
 #include <sys/types.h>
 #include <stdlib.h>
 #include <string.h>
@@ -2303,7 +2304,8 @@ int fat_ffcacheinvalidate(struct fat_mountpt_s *fs, struct fat_file_s *ff)
 
         /* Then discard the current cache contents */
 
-        ff->ff_bflags &= ~FFBUFF_VALID;
+        ff->ff_bflags     &= ~FFBUFF_VALID;
+        ff->ff_cachesector = 0;
     }
     return OK;
 }
@@ -2461,3 +2463,47 @@ int fat_nfreeclusters(struct fat_mountpt_s *fs, size_t *pfreeclusters)
     return OK;
 }
 
+/****************************************************************************
+ * Name: fat_nfreeclusters
+ *
+ * Desciption:
+ *   Given the file position, set the correct current sector to access.
+ *
+ ****************************************************************************/
+
+int fat_currentsector(struct fat_mountpt_s *fs, struct fat_file_s *ff,
+                      off_t position)
+{
+  int sectoroffset;
+
+  if (position <= ff->ff_size )
+    {
+      /* sectoroffset is the sector number offset into the current cluster */
+
+      sectoroffset = SEC_NSECTORS(fs, position) & CLUS_NDXMASK(fs);
+
+      /* The current cluster is the the first sector of the cluster plus
+       * the sector offset
+        */
+
+      ff->ff_currentsector = fat_cluster2sector(fs, ff->ff_currentcluster)
+                           + sectoroffset;
+
+      /* The remainder is the number of sectors left in the cluster to be
+       * read/written
+       */
+
+      ff->ff_sectorsincluster = fs->fs_fatsecperclus - sectoroffset;
+
+      fvdbg("position=%d currentsector=%d sectorsincluster=%d\n",
+            position, ff->ff_currentsector, ff->ff_sectorsincluster);
+
+      return OK;
+    }
+
+  /* The position does not lie within the file */
+
+  return -ENOSPC;
+}
+
+