Increase stability and reliability of file operations

TOFileSystemObserver/Categories/NSURL+TOFileSystemAttributes.m

@@ -30,7 +30,9 @@ - (BOOL)to_isCopying
 {
     // When files are still being copied, their
     // modification date is equal to the current device time.
-    return [self.to_modificationDate timeIntervalSinceDate:[NSDate date]]
+    NSDate *modificationDate = self.to_modificationDate;
+    if (modificationDate == nil) { return NO; }
+    return [modificationDate timeIntervalSinceDate:[NSDate date]]
                         > (-kTOFileSystemObserverCopyingTimeDelay - FLT_EPSILON);
 }
 

TOFileSystemObserver/Categories/NSURL+TOFileSystemUUID.h

@@ -40,11 +40,11 @@ NS_ASSUME_NONNULL_BEGIN
 /** Returns the unique UUID value assigned to this file. */
 - (nullable NSString *)to_fileSystemUUID;
 
-/** Sets a predetermined UUID to be the value of the file. */
-- (void)to_setFileSystemUUID:(NSString *)uuid;
+/** Sets a predetermined UUID to be the value of the file. Returns YES if the attribute was written. */
+- (BOOL)to_setFileSystemUUID:(NSString *)uuid;
 
-/** Regardless if one exists, generate and save a new UUID. */
-- (NSString *)to_generateFileSystemUUID;
+/** Regardless if one exists, generate and save a new UUID. Returns nil if the write failed. */
+- (nullable NSString *)to_generateFileSystemUUID;
 
 @end
 

TOFileSystemObserver/Categories/NSURL+TOFileSystemUUID.m

@@ -40,11 +40,14 @@ - (NSString *)to_fileSystemUUID
     // Allocate a buffer for the value (UUID values are always 36 characters)
     char value[36];
 
-    // Fetch the value from disk
-    getxattr(filePath, keyName, value, 36, 0, 0);
+    // Fetch the value from disk. A short read means there's no valid UUID stored.
+    ssize_t bytesRead = getxattr(filePath, keyName, value, sizeof(value), 0, 0);
+    if (bytesRead != (ssize_t)sizeof(value)) {
+        return nil;
+    }
 
     // Convert to a string, and return if successful
-    NSString *uuid = [[NSString alloc] initWithBytes:value length:36 encoding:NSUTF8StringEncoding];
+    NSString *uuid = [[NSString alloc] initWithBytes:value length:bytesRead encoding:NSUTF8StringEncoding];
     if (uuid.length == 0) {
         return nil;
     }
@@ -64,9 +67,10 @@ - (NSString *)to_fileSystemUUID
     return uuid;
 }
 
-- (void)to_setFileSystemUUID:(NSString *)uuid
+- (BOOL)to_setFileSystemUUID:(NSString *)uuid
 {
-    if (uuid.length > 0 && uuid.length != 36) {
+    if (uuid.length == 0) { return NO; }
+    if (uuid.length != 36) {
         @throw [NSException exceptionWithName:NSInternalInconsistencyException
                                        reason:@"UUID must be 36 characters long!"
                                      userInfo:nil];
@@ -78,15 +82,16 @@ - (void)to_setFileSystemUUID:(NSString *)uuid
 
     // Convert the string to a C byte string
     const char *uuidString = [uuid cStringUsingEncoding:NSUTF8StringEncoding];
+    if (uuidString == NULL) { return NO; }
 
-    // Save it to this file
-    setxattr(filePath, keyName, uuidString, strlen(uuidString), 0, 0);
+    // Save it to this file. UUID strings are always 36 ASCII bytes.
+    return setxattr(filePath, keyName, uuidString, 36, 0, 0) == 0;
 }
 
 - (NSString *)to_generateFileSystemUUID
 {
     NSString *uuid = [NSUUID UUID].UUIDString;
-    [self to_setFileSystemUUID:uuid];
+    if (![self to_setFileSystemUUID:uuid]) { return nil; }
     return uuid;
 }
 

TOFileSystemObserver/Entities/Collections/TOFileSystemItemMapTable.h

@@ -29,14 +29,17 @@ NS_ASSUME_NONNULL_BEGIN
  used to store re-usable instances of item and list
  objects.
  */
-@interface TOFileSystemItemMapTable : NSObject<NSFastEnumeration>
+@interface TOFileSystemItemMapTable : NSObject
 
 @property (nonatomic, readonly) NSInteger count;
 
 - (void)setItem:(id)object forUUID:(NSString *)uuid;
 - (id)itemForUUID:(NSString *)uuid;
 - (void)removeItemForUUID:(NSString *)uuid;
 
+/** A point-in-time snapshot of all current items. Safe to iterate while the table is being mutated. */
+- (NSArray *)allItems;
+
 /** Implementations for allowing dictionary style literal syntax. */
 - (void)setObject:(nullable id)object forKeyedSubscript:(nonnull NSString *)key;
 - (nullable id)objectForKeyedSubscript:(NSString *)key;

TOFileSystemObserver/Entities/Collections/TOFileSystemItemMapTable.m

@@ -81,6 +81,17 @@ - (void)removeItemForUUID:(NSString *)uuid
     });
 }
 
+- (NSArray *)allItems
+{
+    __block NSArray *items = nil;
+    dispatch_sync(self.dispatchQueue, ^{
+        @autoreleasepool {
+            items = self.mapTable.objectEnumerator.allObjects;
+        }
+    });
+    return items ?: @[];
+}
+
 - (void)setObject:(nullable id)object forKeyedSubscript:(nonnull NSString *)key
 {
     [self setItem:object forUUID:key];
@@ -91,13 +102,4 @@ - (nullable id)objectForKeyedSubscript:(NSString *)key
     return [self itemForUUID:key];
 }
 
-- (NSUInteger)countByEnumeratingWithState:(NSFastEnumerationState *)state
-                                  objects:(id __unsafe_unretained _Nullable [_Nonnull])buffer
-                                    count:(NSUInteger)len
-{
-    return [_mapTable countByEnumeratingWithState:state
-                                       objects:buffer
-                                         count:len];
-}
-
 @end

TOFileSystemObserver/Entities/Items/TOFileSystemItemList.m

@@ -131,7 +131,7 @@ - (void)rebuildItemListForListingOrder
     }
 
     // Trigger the notification blocks to update any UI with this new order
-    for (TOFileSystemNotificationToken *token in self.notificationTokens) {
+    for (TOFileSystemNotificationToken *token in self.notificationTokens.allObjects) {
         TOFileSystemItemListCallBlock(token.notificationBlock, self, changes);
     }
 }
@@ -242,7 +242,7 @@ - (void)addItemWithUUID:(NSString *)uuid itemURL:(NSURL *)url
     // Perform the broadcast to any observing objects that this update ocurred
     TOFileSystemItemListChanges *changes = [[TOFileSystemItemListChanges alloc] init];
     [changes addInsertionIndex:sortedIndex];
-    for (TOFileSystemNotificationToken *token in self.notificationTokens) {
+    for (TOFileSystemNotificationToken *token in self.notificationTokens.allObjects) {
         TOFileSystemItemListCallBlock(token.notificationBlock, self, changes);
     }
 }
@@ -267,7 +267,7 @@ - (void)removeItemWithUUID:(NSString *)uuid fileURL:(NSURL *)url
     TOFileSystemItemListChanges *changes = [[TOFileSystemItemListChanges alloc] init];
     [changes addDeletionIndex:index];
 
-    for (TOFileSystemNotificationToken *token in self.notificationTokens) {
+    for (TOFileSystemNotificationToken *token in self.notificationTokens.allObjects) {
         TOFileSystemItemListCallBlock(token.notificationBlock, self, changes);
     }
 }
@@ -300,7 +300,7 @@ - (void)itemDidRefreshWithUUID:(NSString *)uuid
     [changes addModificationIndex:newIndex];
 
     // Broadcast the changes
-    for (TOFileSystemNotificationToken *token in self.notificationTokens) {
+    for (TOFileSystemNotificationToken *token in self.notificationTokens.allObjects) {
         TOFileSystemItemListCallBlock(token.notificationBlock, self, changes);
     }
 }
@@ -322,16 +322,17 @@ - (void)synchronizeWithDisk
     // Skip if every file was accounted for
     if (changes.deletions.count == 0) { return; }
 
-    // Remove all of the deleted files from the list
-    for (NSNumber *deletedIndex in changes.deletions) {
+    // Remove all of the deleted files from the list. Iterate from highest index
+    // to lowest so each removal doesn't shift the indices we still need to use.
+    for (NSNumber *deletedIndex in [changes.deletions reverseObjectEnumerator]) {
         NSString *uuid = self.sortedItems[deletedIndex.intValue];
         [self.sortedItems removeObjectAtIndex:deletedIndex.intValue];
         [self.items removeObjectForKey:uuid];
     }
 
     // Broadcast the changes
     dispatch_async(dispatch_get_main_queue(), ^{
-        for (TOFileSystemNotificationToken *token in self.notificationTokens) {
+        for (TOFileSystemNotificationToken *token in self.notificationTokens.allObjects) {
             TOFileSystemItemListCallBlock(token.notificationBlock, self, changes);
         }
     });

TOFileSystemObserver/TOFileSystemObserver.m

@@ -607,7 +607,7 @@ - (void)scanOperationWillBeginFullScan:(TOFileSystemScanOperation *)scanOperatio
     }
 
     // Inform all notification tokens registered
-    for (TOFileSystemNotificationToken *token in self.notificationTokens) {
+    for (TOFileSystemNotificationToken *token in self.notificationTokens.allObjects) {
         TOFileSystemObserverCallBlock(token.notificationBlock,
                                       self,
                                       TOFileSystemObserverNotificationTypeWillBeginFullScan,
@@ -618,8 +618,8 @@ - (void)scanOperationWillBeginFullScan:(TOFileSystemScanOperation *)scanOperatio
 - (void)scanOperationDidCompleteFullScan:(TOFileSystemScanOperation *)scanOperation
 {
     // Loop through the list one more time to remove any headless entries
-    for (NSString *listUUID in self.itemListTable) {
-        [self.itemListTable[listUUID] synchronizeWithDisk];
+    for (TOFileSystemItemList *list in self.itemListTable.allItems) {
+        [list synchronizeWithDisk];
     }
 
     // Perform the Notification Center broadcast
@@ -631,7 +631,7 @@ - (void)scanOperationDidCompleteFullScan:(TOFileSystemScanOperation *)scanOperat
     }
 
     // Inform all notification tokens registered
-    for (TOFileSystemNotificationToken *token in self.notificationTokens) {
+    for (TOFileSystemNotificationToken *token in self.notificationTokens.allObjects) {
         TOFileSystemObserverCallBlock(token.notificationBlock,
                                       self,
                                       TOFileSystemObserverNotificationTypeDidCompleteFullScan,
@@ -667,7 +667,7 @@ - (void)postNotificationsWithChanges:(TOFileSystemChanges *)changes
     }
 
     // Inform all notification tokens registered
-    for (TOFileSystemNotificationToken *token in self.notificationTokens) {
+    for (TOFileSystemNotificationToken *token in self.notificationTokens.allObjects) {
         TOFileSystemObserverCallBlock(token.notificationBlock,
                                       self,
                                       TOFileSystemObserverNotificationTypeDidChange,