fs: fat: fat_find_empty_dentries()

Provide a function to find a series of empty directory entries.

The current directory is scanned for deleted entries.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

diff --git a/fs/fat/fat_write.c b/fs/fat/fat_write.c
index 941f878..d560b94 100644 (file)
--- a/fs/fat/fat_write.c
+++ b/fs/fat/fat_write.c
@@ -21,6 +21,7 @@
 #include "fat.c"
 
 static dir_entry *find_directory_entry(fat_itr *itr, char *filename);
+static int new_dir_table(fat_itr *itr);
 
 /* Characters that may only be used in long file names */
 static const char LONG_ONLY_CHARS[] = "+,;=[]";
@@ -250,6 +251,66 @@ static int flush_dirty_fat_buffer(fsdata *mydata)
        return 0;
 }
 
+/**
+ * fat_find_empty_dentries() - find a sequence of available directory entries
+ *
+ * @itr:       directory iterator
+ * @count:     number of directory entries to find
+ * Return:     0 on success or negative error number
+ */
+static int __maybe_unused fat_find_empty_dentries(fat_itr *itr, int count)
+{
+       unsigned int cluster;
+       dir_entry *dent;
+       int remaining;
+       unsigned int n = 0;
+       int ret;
+
+       ret = fat_move_to_cluster(itr, itr->start_clust);
+       if (ret)
+               return ret;
+
+       for (;;) {
+               if (!itr->dent) {
+                       log_debug("Not enough directory entries available\n");
+                       return -ENOSPC;
+               }
+               switch (itr->dent->name[0]) {
+               case 0x00:
+               case DELETED_FLAG:
+                       if (!n) {
+                               /* Remember first deleted directory entry */
+                               cluster = itr->clust;
+                               dent = itr->dent;
+                               remaining = itr->remaining;
+                       }
+                       ++n;
+                       if (n == count)
+                               goto out;
+                       break;
+               default:
+                       n = 0;
+                       break;
+               }
+
+               next_dent(itr);
+               if (!itr->dent &&
+                   (!itr->is_root || itr->fsdata->fatsize == 32) &&
+                   new_dir_table(itr))
+                       return -ENOSPC;
+       }
+out:
+       /* Position back to first directory entry */
+       if (itr->clust != cluster) {
+               ret = fat_move_to_cluster(itr, cluster);
+               if (ret)
+                       return ret;
+       }
+       itr->dent = dent;
+       itr->remaining = remaining;
+       return 0;
+}
+
 /*
  * Set the file name information from 'name' into 'slotptr',
  */
@@ -319,7 +380,6 @@ name11_12:
        return 1;
 }
 
-static int new_dir_table(fat_itr *itr);
 static int flush_dir(fat_itr *itr);
 
 /**