SDWebImage/SDWebImage/SDWebImageDownloaderOperation.m

/*
 * This file is part of the SDWebImage package.
 * (c) Olivier Poitrey <rs@dailymotion.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

#import "SDWebImageDownloaderOperation.h"
#import "SDWebImageDecoder.h"
#import <ImageIO/ImageIO.h>

@interface SDWebImageDownloaderOperation ()

@property (copy, nonatomic) SDWebImageDownloaderProgressBlock progressBlock;
@property (copy, nonatomic) SDWebImageDownloaderCompletedBlock completedBlock;
@property (copy, nonatomic) void (^cancelBlock)();

@property (assign, nonatomic, getter = isExecuting) BOOL executing;
@property (assign, nonatomic, getter = isFinished) BOOL finished;
@property (assign, nonatomic) long long expectedSize;
@property (strong, nonatomic) NSMutableData *imageData;
@property (strong, nonatomic) NSURLConnection *connection;
@property (SDDispatchQueueSetterSementics, nonatomic) dispatch_queue_t queue;

@end

@implementation SDWebImageDownloaderOperation
{
    size_t width, height;
}

- (id)initWithRequest:(NSURLRequest *)request queue:(dispatch_queue_t)queue options:(SDWebImageDownloaderOptions)options progress:(void (^)(NSUInteger, long long))progressBlock completed:(void (^)(UIImage *, NSData *, NSError *, BOOL))completedBlock cancelled:(void (^)())cancelBlock
{
    if ((self = [super init]))
    {
        _queue = queue;
        _request = request;
        _options = options;
        _progressBlock = [progressBlock copy];
        _completedBlock = [completedBlock copy];
        _cancelBlock = [cancelBlock copy];
        _executing = NO;
        _finished = NO;
        _expectedSize = 0;
    }
    return self;
}

- (void)start
{
    dispatch_async(dispatch_get_main_queue(), ^
    {
        if (self.isCancelled)
        {
            self.finished = YES;
            [self reset];
            return;
        }

        self.executing = YES;
        self.connection = [NSURLConnection.alloc initWithRequest:self.request delegate:self startImmediately:NO];

        // If not in low priority mode, ensure we aren't blocked by UI manipulations (default runloop mode for NSURLConnection is NSEventTrackingRunLoopMode)
        if (!(self.options & SDWebImageDownloaderLowPriority))
        {
            [self.connection scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
        }

        [self.connection start];

        if (self.connection)
        {
            if (self.progressBlock)
            {
                self.progressBlock(0, -1);
            }
            [[NSNotificationCenter defaultCenter] postNotificationName:SDWebImageDownloadStartNotification object:self];
        }
        else
        {
            if (self.completedBlock)
            {
                self.completedBlock(nil, nil, [NSError errorWithDomain:NSURLErrorDomain code:0 userInfo:@{NSLocalizedDescriptionKey: @"Connection can't be initialized"}], YES);
            }
        }
    });
}

- (void)cancel
{
    if (self.isFinished) return;
    [super cancel];
    if (self.cancelBlock) self.cancelBlock();

    if (self.connection)
    {
        [self.connection cancel];
        [[NSNotificationCenter defaultCenter] postNotificationName:SDWebImageDownloadStopNotification object:self];

        // As we cancelled the connection, its callback won't be called and thus won't
        // maintain the isFinished and isExecuting flags.
        if (self.isExecuting) self.executing = NO;
        if (!self.isFinished) self.finished = YES;
    }

    [self reset];
}

- (void)done
{
    self.finished = YES;
    self.executing = NO;
    [self reset];
}

- (void)reset
{
    dispatch_async(dispatch_get_main_queue(), ^
    {
        self.cancelBlock = nil;
        self.completedBlock = nil;
        self.progressBlock = nil;
        self.connection = nil;
        self.imageData = nil;
    });
}

- (void)setFinished:(BOOL)finished
{
    [self willChangeValueForKey:@"isFinished"];
    _finished = finished;
    [self didChangeValueForKey:@"isFinished"];
}

- (void)setExecuting:(BOOL)executing
{
    [self willChangeValueForKey:@"isExecuting"];
    _executing = executing;
    [self didChangeValueForKey:@"isExecuting"];
}

- (BOOL)isConcurrent
{
    return YES;
}

#pragma mark NSURLConnection (delegate)

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    if (![response respondsToSelector:@selector(statusCode)] || [((NSHTTPURLResponse *)response) statusCode] < 400)
    {
        NSUInteger expected = response.expectedContentLength > 0 ? (NSUInteger)response.expectedContentLength : 0;
        self.expectedSize = expected;
        if (self.progressBlock)
        {
            self.progressBlock(0, expected);
        }

        dispatch_async(self.queue, ^
        {
            self.imageData = [NSMutableData.alloc initWithCapacity:expected];
        });
    }
    else
    {
        [self.connection cancel];

        [[NSNotificationCenter defaultCenter] postNotificationName:SDWebImageDownloadStopNotification object:nil];

        if (self.completedBlock)
        {
            self.completedBlock(nil, nil, [NSError errorWithDomain:NSURLErrorDomain code:[((NSHTTPURLResponse *)response) statusCode] userInfo:nil], YES);
        }

        [self done];
    }
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    dispatch_async(self.queue, ^
    {
        [self.imageData appendData:data];

        if ((self.options & SDWebImageDownloaderProgressiveDownload) && self.expectedSize > 0 && self.completedBlock)
        {
            // The following code is from http://www.cocoaintheshell.com/2011/05/progressive-images-download-imageio/
            // Thanks to the author @Nyx0uf

            // Get the total bytes downloaded
            const NSUInteger totalSize = self.imageData.length;

            // Update the data source, we must pass ALL the data, not just the new bytes
            CGImageSourceRef imageSource = CGImageSourceCreateIncremental(NULL);
            CGImageSourceUpdateData(imageSource, (__bridge  CFDataRef)self.imageData, totalSize == self.expectedSize);

            if (width + height == 0)
            {
                CFDictionaryRef properties = CGImageSourceCopyPropertiesAtIndex(imageSource, 0, NULL);
                if (properties)
                {
                    CFTypeRef val = CFDictionaryGetValue(properties, kCGImagePropertyPixelHeight);
                    if (val) CFNumberGetValue(val, kCFNumberLongType, &height);
                    val = CFDictionaryGetValue(properties, kCGImagePropertyPixelWidth);
                    if (val) CFNumberGetValue(val, kCFNumberLongType, &width);
                    CFRelease(properties);
                }
            }

            if (width + height > 0 && totalSize < self.expectedSize)
            {
                // Create the image
                CGImageRef partialImageRef = CGImageSourceCreateImageAtIndex(imageSource, 0, NULL);

#ifdef TARGET_OS_IPHONE
                // Workaround for iOS anamorphic image
                if (partialImageRef)
                {
                    const size_t partialHeight = CGImageGetHeight(partialImageRef);
                    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
                    CGContextRef bmContext = CGBitmapContextCreate(NULL, width, height, 8, width * 4, colorSpace, kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedFirst);
                    CGColorSpaceRelease(colorSpace);
                    if (bmContext)
                    {
                        CGContextDrawImage(bmContext, (CGRect){.origin.x = 0.0f, .origin.y = 0.0f, .size.width = width, .size.height = partialHeight}, partialImageRef);
                        CGImageRelease(partialImageRef);
                        partialImageRef = CGBitmapContextCreateImage(bmContext);
                        CGContextRelease(bmContext);
                    }
                    else
                    {
                        CGImageRelease(partialImageRef);
                        partialImageRef = nil;
                    }
                }
#endif

                if (partialImageRef)
                {
                    UIImage *image = [UIImage decodedImageWithImage:SDScaledImageForPath(self.request.URL.absoluteString, [UIImage imageWithCGImage:partialImageRef])];
                    CGImageRelease(partialImageRef);
                    dispatch_async(dispatch_get_main_queue(), ^
                    {
                        if (self.completedBlock)
                        {
                            self.completedBlock(image, nil, nil, NO);
                        }
                    });
                }
            }

            CFRelease(imageSource);
        }
        NSUInteger received = self.imageData.length;
        dispatch_async(dispatch_get_main_queue(), ^
        {
            if (self.progressBlock)
            {
                self.progressBlock(received, self.expectedSize);
            }
        });
    });
}

- (void)connectionDidFinishLoading:(NSURLConnection *)aConnection
{
    self.connection = nil;

    [[NSNotificationCenter defaultCenter] postNotificationName:SDWebImageDownloadStopNotification object:nil];

    SDWebImageDownloaderCompletedBlock completionBlock = self.completedBlock;
    if (completionBlock)
    {
        dispatch_async(self.queue, ^
        {
            UIImage *image = [UIImage decodedImageWithImage:SDScaledImageForPath(self.request.URL.absoluteString, self.imageData)];
            dispatch_async(dispatch_get_main_queue(), ^
            {
                if (CGSizeEqualToSize(image.size, CGSizeZero))
                {
                    completionBlock(nil, nil, [NSError errorWithDomain:@"SDWebImageErrorDomain" code:0 userInfo:@{NSLocalizedDescriptionKey: @"Downloaded image has 0 pixels"}], YES);
                }
                else
                {
                    completionBlock(image, self.imageData, nil, YES);
                }
                self.completionBlock = nil;
                [self done];
            });
        });
    }
    else
    {
        [self done];
    }
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    [[NSNotificationCenter defaultCenter] postNotificationName:SDWebImageDownloadStopNotification object:nil];

    if (self.completedBlock)
    {
        self.completedBlock(nil, nil, error, YES);
    }

    [self done];
}

- (NSCachedURLResponse *)connection:(NSURLConnection *)connection willCacheResponse:(NSCachedURLResponse *)cachedResponse
{
    // Prevents caching of responses
    return nil;
}


@end