Check file match by dir entry not by starting cluster.

This is because some files have no starting cluster and thus look like the same file when they are not.

Fixes #75

Author: jonathanpallant

src/fat/volume.rs

@@ -320,7 +320,7 @@ impl FatVolume {
                                 let entry = DirEntry::new(
                                     name,
                                     attributes,
-                                    ClusterId(0),
+                                    ClusterId::EMPTY,
                                     ctime,
                                     block,
                                     start as u32,

src/volume_mgr.rs

@@ -370,7 +370,7 @@ where
         }
 
         // Check it's not already open
-        if self.file_is_open(volume, dir_entry.cluster) {
+        if self.file_is_open(volume, &dir_entry) {
             return Err(Error::FileAlreadyOpen);
         }
 
@@ -488,7 +488,7 @@ where
 
         // Check if it's open already
         if let Some(dir_entry) = &dir_entry {
-            if self.file_is_open(volume_info.volume_id, dir_entry.cluster) {
+            if self.file_is_open(volume_info.volume_id, &dir_entry) {
                 return Err(Error::FileAlreadyOpen);
             }
         }
@@ -562,7 +562,7 @@ where
             return Err(Error::DeleteDirAsFile);
         }
 
-        if self.file_is_open(dir_info.volume_id, dir_entry.cluster) {
+        if self.file_is_open(dir_info.volume_id, &dir_entry) {
             return Err(Error::FileAlreadyOpen);
         }
 
@@ -579,9 +579,12 @@ where
     /// Check if a file is open
     ///
     /// Returns `true` if it's open, `false`, otherwise.
-    fn file_is_open(&self, volume: Volume, starting_cluster: ClusterId) -> bool {
+    fn file_is_open(&self, volume: Volume, dir_entry: &DirEntry) -> bool {
         for f in self.open_files.iter() {
-            if f.volume_id == volume && f.entry.cluster == starting_cluster {
+            if f.volume_id == volume
+                && f.entry.entry_block == dir_entry.entry_block
+                && f.entry.entry_offset == dir_entry.entry_offset
+            {
                 return true;
             }
         }