load disk icons asynchronously

Mini vMac/InsertDiskViewController.m

@@ -531,6 +531,9 @@
 @end
 
 @implementation FileTableViewCell
+{
+    UIImage *defaultIcon;
+}
 
 - (void)prepareForReuse {
     [super prepareForReuse];
@@ -540,25 +543,34 @@
     self.imageView.image = nil;
     self.imageView.alpha = 1.0;
     self.detailTextLabel.text = nil;
+    if (_filePath) {
+        [[NSNotificationCenter defaultCenter] removeObserver:self name:DidUpdateIconForDiskImageNotification object:_filePath];
+        _filePath = nil;
+    }
 }
 
 - (void)setFilePath:(NSString *)filePath {
+    NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter];
+    if (_filePath) {
+        [notificationCenter removeObserver:self name:DidUpdateIconForDiskImageNotification object:_filePath];
+    }
     _filePath = filePath;
+    if (_filePath) {
+        [notificationCenter addObserver:self selector:@selector(didUpdateDiskIcon:) name:DidUpdateIconForDiskImageNotification object:_filePath];
+    }
     NSString *fileName = filePath.lastPathComponent;
     self.textLabel.text = self.showExtension ? fileName : fileName.stringByDeletingPathExtension;
     NSDictionary *attributes = [[NSURL fileURLWithPath:filePath] resourceValuesForKeys:@[NSURLTotalFileSizeKey, NSURLFileSizeKey] error:NULL];
     if (attributes && attributes[NSURLTotalFileSizeKey]) {
         BOOL isDiskImage = [[AppDelegate sharedInstance].diskImageExtensions containsObject:fileName.pathExtension.lowercaseString];
         if (isDiskImage) {
-            UIImage *icon = [UIImage imageWithIconForDiskImage:filePath];
-            if (icon == nil) {
-                NSInteger fileSize = [attributes[NSURLTotalFileSizeKey] integerValue];
-                NSInteger numBlocks = fileSize / 512;
-                icon = [UIImage imageNamed:numBlocks == 800 || numBlocks == 1600 ? @"floppy" : @"floppyV"];
-            }
-            self.imageView.image = icon;
+            NSInteger fileSize = [attributes[NSURLTotalFileSizeKey] integerValue];
+            NSInteger numBlocks = fileSize / 512;
+            defaultIcon = [UIImage imageNamed:numBlocks == 800 || numBlocks == 1600 ? @"floppy" : @"floppyV"];
+            self.imageView.image = [UIImage imageWithIconForDiskImage:filePath] ?: defaultIcon;
         } else {
-            self.imageView.image = [UIImage imageNamed:@"document"];
+            defaultIcon = [UIImage imageNamed:@"document"];
+            self.imageView.image = defaultIcon;
         }
         NSString *sizeString = [NSByteCountFormatter stringFromByteCount:[attributes[NSURLTotalFileSizeKey] longLongValue] countStyle:NSByteCountFormatterCountStyleBinary];
         self.detailTextLabel.text = sizeString;
@@ -568,6 +580,13 @@
     }
 }
 
+- (void)didUpdateDiskIcon:(NSNotification*)notification {
+    if ([_filePath isEqual:notification.object]) {
+        UIImage *icon = notification.userInfo[@"icon"];
+        self.imageView.image = icon ?: defaultIcon;
+    }
+}
+
 - (void)share:(id)sender {
     UIActivityViewController *avc = [[UIActivityViewController alloc] initWithActivityItems:@[[NSURL fileURLWithPath:self.filePath]] applicationActivities:nil];
     if ([avc respondsToSelector:@selector(popoverPresentationController)]) {

Mini vMac/UIImage+DiskImageIcon.h

@@ -8,6 +8,8 @@
 
 #import <UIKit/UIKit.h>
 
+extern NSString *DidUpdateIconForDiskImageNotification;
+
 @interface UIImage (DiskImageIcon)
 
 + (UIImage *)imageWithIconForDiskImage:(NSString *)path;

Mini vMac/UIImage+DiskImageIcon.m

@@ -11,6 +11,10 @@
 #import "res.h"
 #import "mfs.h"
 #import "AppDelegate.h"
+#import <sys/xattr.h>
+
+NSString *DidUpdateIconForDiskImageNotification = @"didUpdateIconForDiskImage";
+static const char kDiskImageIconAttributeName[] = "net.namedfork.DiskImageIcon";
 
 #define kDiskImageHasDC42Header 1 << 0
 #define RSHORT(base, offset) ntohs(*((short *)((base) + (offset))))
@@ -23,37 +27,58 @@
 
 @end
 
-static NSCache<NSString*,UIImage*> *diskImageIconCache = nil;
-
 @implementation UIImage (DiskImageIcon)
 
-+ (NSCache<NSString*,UIImage*> *)diskImageIconCache {
-    static dispatch_once_t onceToken;
-    dispatch_once(&onceToken, ^{
-        diskImageIconCache = [NSCache new];
-        diskImageIconCache.name = @"net.namedfork.minivmac.icon-cache";
-        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(_didEjectDisk:) name:[AppDelegate sharedEmulator].ejectDiskNotification object:nil];
-    });
-    return diskImageIconCache;
-}
-
 + (void)_didEjectDisk:(NSNotification*)notification {
     NSString *path = [notification.userInfo[@"path"] stringByStandardizingPath];
-    // reload icon
-    [diskImageIconCache removeObjectForKey:path];
-    [self imageWithIconForDiskImage:path];
+    [self loadIconForDiskImageAndNotify:path];
 }
 
 + (UIImage *)imageWithIconForDiskImage:(NSString *)path {
-    path = path.stringByStandardizingPath;
-    UIImage *icon = [[self diskImageIconCache] objectForKey:path];
-    if (icon == nil) {
-        icon = [[DiskImageIconReader new] iconForDiskImage:path];
-        if (icon != nil) {
-            [diskImageIconCache setObject:icon forKey:path];
-        }
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(_didEjectDisk:) name:[AppDelegate sharedEmulator].ejectDiskNotification object:nil];
+    });
+    
+    // check attribute
+    ssize_t attrLen = getxattr(path.fileSystemRepresentation, kDiskImageIconAttributeName, NULL, 0, 0, 0);
+    if (attrLen == -1) {
+        [self loadIconForDiskImageAndNotify:path];
+        return nil;
+    }
+    
+    // read data
+    void *attrData = malloc(attrLen);
+    getxattr(path.fileSystemRepresentation, kDiskImageIconAttributeName, attrData, attrLen, 0, 0);
+    return [UIImage imageWithData:[NSData dataWithBytesNoCopy:attrData length:attrLen freeWhenDone:YES]];
+}
+
++ (void)loadIconForDiskImageAndNotify:(NSString *)path {
+    if ([NSThread isMainThread]) {
+        dispatch_async(dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0), ^{
+            [self loadIconForDiskImageAndNotify:path];
+        });
+        return;
+    }
+    
+    // get current value
+    ssize_t attrLen = getxattr(path.fileSystemRepresentation, kDiskImageIconAttributeName, NULL, 0, 0, 0);
+    NSData *previousData = nil;
+    if (attrLen != -1) {
+        void *attrData = malloc(attrLen);
+        getxattr(path.fileSystemRepresentation, kDiskImageIconAttributeName, attrData, attrLen, 0, 0);
+        previousData = [NSData dataWithBytesNoCopy:attrData length:attrLen freeWhenDone:YES];
+    }
+    
+    // load new icon
+    UIImage *icon = [[DiskImageIconReader new] iconForDiskImage:path];
+    NSData *newData = UIImagePNGRepresentation(icon);
+    if (![newData isEqualToData:previousData]) {
+        // save new icon and notify
+        setxattr(path.fileSystemRepresentation, kDiskImageIconAttributeName, newData.bytes, newData.length, 0, 0);
+        NSNotification *newIconNotification = [[NSNotification alloc] initWithName:DidUpdateIconForDiskImageNotification object:path userInfo:icon ? @{@"icon": icon} : nil];
+        [[NSNotificationCenter defaultCenter] performSelectorOnMainThread:@selector(postNotification:) withObject:newIconNotification waitUntilDone:NO];
     }
-    return icon;
 }
 
 @end