!171 ftruncate新增支持FAT12与FAT16

Merge pull request !171 from JING/ftruncate

fs/fat/os_adapt/fatfs.c

@@ -171,6 +171,19 @@ int fatfs_2_vfs(int result)
     return status;
 }
 
+static bool fatfs_is_last_cluster(FATFS *fs, DWORD cclust)
+{
+    switch (fs->fs_type) {
+        case FS_FAT12:
+            return (cclust == FAT12_END_OF_CLUSTER);
+        case FS_FAT16:
+            return (cclust == FAT16_END_OF_CLUSTER);
+        case FS_FAT32:
+        default:
+            return (cclust == FAT32_END_OF_CLUSTER);
+    }
+}
+
 static int fatfs_sync(unsigned long mountflags, FATFS *fs)
 {
 #ifdef LOSCFG_FS_FAT_CACHE
@@ -806,7 +819,7 @@ static FRESULT realloc_cluster(FILINFO *finfo, FFOBJID *obj, FSIZE_t size)
     if ((cclust == BAD_CLUSTER) || (cclust == DISK_ERROR)) {
         return FR_DISK_ERR;
     }
-    if (cclust != END_OF_FILE) { /* Remove extra cluster if existing */
+    if (!fatfs_is_last_cluster(obj->fs, cclust)) { /* Remove extra cluster if existing */
         result = remove_chain(obj, cclust, pclust);
         if (result != FR_OK) {
             return result;

fs/fat/os_adapt/fatfs.h

@@ -55,7 +55,9 @@ extern "C" {
 #define FAT32_MAXSIZE          0x100000000
 #define BAD_CLUSTER            0x7FFFFFFF
 #define DISK_ERROR             0xFFFFFFFF
-#define END_OF_FILE            0x0FFFFFFF
+#define FAT12_END_OF_CLUSTER   0x00000FFF
+#define FAT16_END_OF_CLUSTER   0x0000FFFF
+#define FAT32_END_OF_CLUSTER   0x0FFFFFFF
 #define FAT_ERROR              (-1)
 
 /* MBR */