Initial revision

+//
+//  DMImageCache.h
+//  Dailymotion
+//
+//  Created by Olivier Poitrey on 19/09/09.
+//  Copyright 2009 Dailymotion. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+
+@interface DMImageCache : NSObject
+{
+    NSMutableDictionary *cache;
+    NSString *diskCachePath;
+}
+
++ (DMImageCache *)sharedImageCache;
+- (void)storeImage:(UIImage *)image forKey:(NSString *)key;
+- (void)storeImage:(UIImage *)image forKey:(NSString *)key toDisk:(BOOL)toDisk;
+- (UIImage *)imageFromKey:(NSString *)key;
+- (UIImage *)imageFromKey:(NSString *)key fromDisk:(BOOL)fromDisk;
+- (void)removeImageForKey:(NSString *)key;
+- (void)clearMemory;
+- (void)clearDisk;
+- (void)cleanDisk;
+
+@end

+//
+//  DMImageCache.m
+//  Dailymotion
+//
+//  Created by Olivier Poitrey on 19/09/09.
+//  Copyright 2009 Dailymotion. All rights reserved.
+//
+
+#import "DMImageCache.h"
+#import <CommonCrypto/CommonDigest.h>
+
+static NSInteger kMaxCacheAge = 60*60*24*7; // 1 week
+
+static DMImageCache *instance;
+
+@implementation DMImageCache
+
+#pragma mark NSObject
+
+- (id)init
+{
+    if (self = [super init])
+    {
+        cache = [[NSMutableDictionary alloc] init];
+        
+        [[NSNotificationCenter defaultCenter] addObserver:self
+                                                 selector:@selector(didReceiveMemoryWarning:)
+                                                     name:UIApplicationDidReceiveMemoryWarningNotification  
+                                                   object:nil];
+
+        [[NSNotificationCenter defaultCenter] addObserver:self
+                                                 selector:@selector(willTerminate)
+                                                     name:UIApplicationWillTerminateNotification  
+                                                   object:nil];
+        
+        // Init the cache
+        NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
+        diskCachePath = [[[paths objectAtIndex:0] stringByAppendingPathComponent:@"ImageCache"] retain];
+        		
+        if (![[NSFileManager defaultManager] fileExistsAtPath:diskCachePath])
+        {
+            [[NSFileManager defaultManager] createDirectoryAtPath:diskCachePath attributes:nil];
+        }
+    }
+
+    return self;
+}
+
+- (void)dealloc
+{
+    [cache release];
+
+    [[NSNotificationCenter defaultCenter] removeObserver:self
+                                                    name:UIApplicationDidReceiveMemoryWarningNotification  
+                                                  object:nil];  
+
+    [[NSNotificationCenter defaultCenter] removeObserver:self
+                                                    name:UIApplicationWillTerminateNotification  
+                                                  object:nil];  
+    
+    [super dealloc];
+}
+
+- (void)didReceiveMemoryWarning:(void *)object
+{
+    [self clearMemory];
+}
+
+- (void)willTerminate
+{
+    [self cleanDisk];
+}
+
+#pragma mark ImageCache (private)
+
+- (NSString *)cachePathForKey:(NSString *)key
+{
+    const char *str = [key UTF8String];
+    unsigned char r[CC_MD5_DIGEST_LENGTH];
+    CC_MD5(str, strlen(str), r);
+    NSString *filename = [NSString stringWithFormat:@"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
+                          r[0], r[1], r[2], r[3], r[4], r[5], r[6], r[7], r[8], r[9], r[10], r[11], r[12], r[13], r[14], r[15]];
+
+    return [diskCachePath stringByAppendingPathComponent:filename];
+}
+
+#pragma mark ImageCache
+
++ (DMImageCache *)sharedImageCache
+{
+    if (instance == nil)
+    {
+        instance = [[DMImageCache alloc] init];
+    }
+
+    return instance;
+}
+
+- (void)storeImage:(UIImage *)image forKey:(NSString *)key
+{
+    [self storeImage:image forKey:key toDisk:YES];
+}
+
+- (void)storeImage:(UIImage *)image forKey:(NSString *)key toDisk:(BOOL)toDisk
+{
+    if (image == nil)
+    {
+        return;
+    }
+
+    [cache setObject:image forKey:key];
+
+    if (toDisk)
+    {
+        [[NSFileManager defaultManager] createFileAtPath:[self cachePathForKey:key] contents:UIImageJPEGRepresentation(image, 1.0) attributes:nil];
+    }
+}
+
+- (UIImage *)imageFromKey:(NSString *)key
+{
+    return [self imageFromKey:key fromDisk:YES];
+}
+
+- (UIImage *)imageFromKey:(NSString *)key fromDisk:(BOOL)fromDisk
+{
+    UIImage *image = [cache objectForKey:key];
+
+    if (!image && fromDisk)
+    {
+        image = [[UIImage alloc] initWithData:[NSData dataWithContentsOfFile:[self cachePathForKey:key]]];
+        if (image != nil)
+        {
+            [cache setObject:image forKey:key];
+            [image release];
+        }
+    }
+
+    return image;
+}
+
+- (void)removeImageForKey:(NSString *)key
+{
+    [cache removeObjectForKey:key];
+    [[NSFileManager defaultManager] removeItemAtPath:[self cachePathForKey:key] error:nil];
+}
+
+- (void)clearMemory
+{
+    [cache removeAllObjects];
+}
+
+- (void)clearDisk
+{
+    [[NSFileManager defaultManager] removeItemAtPath:diskCachePath error:nil];
+    [[NSFileManager defaultManager] createDirectoryAtPath:diskCachePath attributes:nil];    
+}
+
+- (void)cleanDisk
+{
+    NSDate *expirationDate = [NSDate dateWithTimeIntervalSinceNow:-kMaxCacheAge];
+    NSDirectoryEnumerator *fileEnumerator = [[NSFileManager defaultManager] enumeratorAtPath:diskCachePath];
+    for (NSString *fileName in fileEnumerator)
+    {
+        NSString *filePath = [diskCachePath stringByAppendingPathComponent:fileName];
+        NSDictionary *attrs = [[NSFileManager defaultManager] attributesOfItemAtPath:filePath error:nil];
+        if ([[[attrs fileModificationDate] laterDate:expirationDate] isEqualToDate:expirationDate])
+        {
+            [[NSFileManager defaultManager] removeItemAtPath:filePath error:nil];
+        }
+    }
+}
+
+@end

+//
+//  DMWebImageView.h
+//  Dailymotion
+//
+//  Created by Olivier Poitrey on 18/09/09.
+//  Copyright 2009 Dailymotion. All rights reserved.
+//
+
+#import <UIKit/UIKit.h>
+
+@class DMWebImageDownloadOperation;
+
+@interface DMWebImageView : UIImageView
+{
+    UIImage *placeHolderImage;  
+    DMWebImageDownloadOperation *currentOperation;
+}
+
+- (void)setImageWithURL:(NSURL *)url;
+- (void)downloadFinishedWithImage:(UIImage *)image;
+
+@end
+
+@interface DMWebImageDownloadOperation : NSOperation
+{
+    NSURL *url;
+    DMWebImageView *delegate;
+}
+
+@property (retain) NSURL *url;
+@property (assign) DMWebImageView *delegate;
+
+- (id)initWithURL:(NSURL *)url delegate:(DMWebImageView *)delegate;
+
+@end

+//
+//  DMWebImageView.m
+//  Dailymotion
+//
+//  Created by Olivier Poitrey on 18/09/09.
+//  Copyright 2009 Dailymotion. All rights reserved.
+//
+
+#import "DMWebImageView.h"
+#import "DMImageCache.h"
+
+static NSOperationQueue *downloadQueue;
+static NSOperationQueue *cacheInQueue;
+
+@implementation DMWebImageView
+
+- (void)dealloc
+{
+    [placeHolderImage release];
+    [currentOperation release];
+    [super dealloc];
+}
+
+#pragma mark RemoteImageView
+
+- (void)setImageWithURL:(NSURL *)url
+{
+    if (currentOperation != nil)
+    {
+        [currentOperation cancel]; // remove from queue
+        [currentOperation release];
+        currentOperation = nil;
+    }
+
+    // Save the placeholder image in order to re-apply it when view is reused
+    if (placeHolderImage == nil)
+    {
+        placeHolderImage = [self.image retain];
+    }
+    else
+    {
+        self.image = placeHolderImage;
+    }
+
+    UIImage *cachedImage = [[DMImageCache sharedImageCache] imageFromKey:[url absoluteString]];
+
+    if (cachedImage)
+    {
+        self.image = cachedImage;
+    }
+    else
+    {
+        if (downloadQueue == nil)
+        {
+            downloadQueue = [[NSOperationQueue alloc] init];
+            [downloadQueue setMaxConcurrentOperationCount:8];
+        }
+        
+        currentOperation = [[DMWebImageDownloadOperation alloc] initWithURL:url delegate:self];
+        [downloadQueue addOperation:currentOperation];
+    }
+}
+
+- (void)downloadFinishedWithImage:(UIImage *)anImage
+{
+    self.image = anImage;
+    [currentOperation release];
+    currentOperation = nil;
+}
+
+@end
+
+@implementation DMWebImageDownloadOperation
+
+@synthesize url, delegate;
+
+- (void)dealloc
+{
+    [url release];
+    [super dealloc];
+}
+
+
+- (id)initWithURL:(NSURL *)anUrl delegate:(DMWebImageView *)aDelegate
+{
+    if (self = [super init])
+    {
+        self.url = anUrl;
+        self.delegate = aDelegate;
+    }
+
+    return self;
+}
+
+- (void)main 
+{
+    if (self.isCancelled)
+    {
+        return;
+    }
+    
+    NSData *data = [[NSData alloc] initWithContentsOfURL:url];
+    UIImage *image = [[UIImage alloc] initWithData:data];
+    [data release];
+    
+    if (!self.isCancelled)
+    {
+        [delegate performSelectorOnMainThread:@selector(downloadFinishedWithImage:) withObject:image waitUntilDone:YES];
+    }
+
+    if (cacheInQueue == nil)
+    {
+        cacheInQueue = [[NSOperationQueue alloc] init];
+        [cacheInQueue setMaxConcurrentOperationCount:2];
+    }
+
+    NSString *cacheKey = [url absoluteString];
+
+    DMImageCache *imageCache = [DMImageCache sharedImageCache];
+
+    // Store image in memory cache NOW, no need to wait for the cache-in operation queue completion
+    [imageCache storeImage:image forKey:cacheKey toDisk:NO];
+
+    // Perform the cache-in in another operation queue in order to not block a download operation slot
+    NSInvocation *cacheInInvocation = [NSInvocation invocationWithMethodSignature:[[imageCache class] instanceMethodSignatureForSelector:@selector(storeImage:forKey:)]];
+    [cacheInInvocation setTarget:imageCache];
+    [cacheInInvocation setSelector:@selector(storeImage:forKey:)];
+    [cacheInInvocation setArgument:&image atIndex:2];
+    [cacheInInvocation setArgument:&cacheKey atIndex:3];
+    [cacheInInvocation retainArguments];
+    NSInvocationOperation *cacheInOperation = [[NSInvocationOperation alloc] initWithInvocation:cacheInInvocation];
+    [cacheInQueue addOperation:cacheInOperation];
+    [cacheInOperation release];
+    
+    [image release];
+}
+
+@end

+Dailymotion Web Image
+=====================
+
+This library provides a drop-in remplacement for UIImageVIew with support for image coming from the web.
+
+TODO: doc