Merge pull request #184 from oliviermartin/om/fat-sync-file-when-writting

libraries/fs: Added logic to transparently sync written file

libraries/fs/fat/ChaN/ff.cpp

@@ -2526,7 +2526,7 @@ FRESULT f_write (
     UINT wcnt, cc;
     const BYTE *wbuff = (const BYTE *)buff;
     BYTE csect;
-
+    bool need_sync = false;
 
     *bw = 0;    /* Clear write byte counter */
 
@@ -2559,6 +2559,13 @@ FRESULT f_write (
                 if (clst == 1) ABORT(fp->fs, FR_INT_ERR);
                 if (clst == 0xFFFFFFFF) ABORT(fp->fs, FR_DISK_ERR);
                 fp->clust = clst;           /* Update current cluster */
+
+#ifdef FLUSH_ON_NEW_CLUSTER
+                // We do not need to flush for the first cluster
+                if (fp->fptr != 0) {
+                    need_sync = true;
+                }
+#endif
             }
 #if _FS_TINY
             if (fp->fs->winsect == fp->dsect && move_window(fp->fs, 0)) /* Write-back sector cache */
@@ -2591,6 +2598,9 @@ FRESULT f_write (
                 }
 #endif
                 wcnt = SS(fp->fs) * cc;     /* Number of bytes transferred */
+#ifdef FLUSH_ON_NEW_SECTOR
+                need_sync = true;
+#endif
                 continue;
             }
 #if _FS_TINY
@@ -2623,6 +2633,10 @@ FRESULT f_write (
     if (fp->fptr > fp->fsize) fp->fsize = fp->fptr; /* Update file size if needed */
     fp->flag |= FA__WRITTEN;                        /* Set file change flag */
 
+    if (need_sync) {
+        f_sync (fp);
+    }
+
     LEAVE_FF(fp->fs, FR_OK);
 }
 

libraries/fs/fat/ChaN/ffconf.h

@@ -187,5 +187,12 @@
 /* To enable file lock control feature, set _FS_LOCK to 1 or greater.
    The value defines how many files can be opened simultaneously. */
 
+#define FLUSH_ON_NEW_CLUSTER    0   /* Sync the file on every new cluster */
+#define FLUSH_ON_NEW_SECTOR     1   /* Sync the file on every new sector */
+/* Only one of these two defines needs to be set to 1. If both are set to 0
+   the file is only sync when closed.
+   Clusters are group of sectors (eg: 8 sectors). Flushing on new cluster means
+   it would be less often than flushing on new sector. Sectors are generally
+   512 Bytes long. */
 
 #endif /* _FFCONFIG */