检测SDWebImage有没有缓存图片 IOS 获取网络图片大小

//讨厌警告
-(id)diskImageDataBySearchingAllPathsForKey:(id)key{return nil;}
+(CGSize)downloadImageSizeWithURL:(id)p_w_picpathURL
{
    NSURL* URL = nil;
    if([p_w_picpathURL isKindOfClass:[NSURL class]]){
        URL = p_w_picpathURL;
    }
    if([p_w_picpathURL isKindOfClass:[NSString class]]){
        URL = [NSURL URLWithString:p_w_picpathURL];
    }
    if(URL == nil)
        return CGSizeZero;
     
    NSString* absoluteString = URL.absoluteString;
     
#ifdef dispatch_main_sync_safe
    if([[SDImageCache sharedImageCache] diskImageExistsWithKey:absoluteString])
    {
        UIImage* p_w_picpath = [[SDImageCache sharedImageCache] p_w_picpathFromMemoryCacheForKey:absoluteString];
        if(!p_w_picpath)
        {
            NSData* data = [[SDImageCache sharedImageCache] performSelector:@selector(diskImageDataBySearchingAllPathsForKey:) withObject:URL.absoluteString];
            p_w_picpath = [UIImage p_w_picpathWithData:data];
        }
        if(!p_w_picpath)
        {
            return p_w_picpath.size;
        }
    }
#endif
     
    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:URL];
    NSString* pathExtendsion = [URL.pathExtension lowercaseString];
     
    CGSize size = CGSizeZero;
    if([pathExtendsion isEqualToString:@"png"]){
        size =  [self downloadPNGImageSizeWithRequest:request];
    }
    else if([pathExtendsion isEqual:@"gif"])
    {
        size =  [self downloadGIFImageSizeWithRequest:request];
    }
    else{
        size = [self downloadJPGImageSizeWithRequest:request];
    }
    if(CGSizeEqualToSize(CGSizeZero, size))
    {
        NSData* data = [NSURLConnection sendSynchronousRequest:[NSURLRequest requestWithURL:URL] returningResponse:nil error:nil];
        UIImage* p_w_picpath = [UIImage p_w_picpathWithData:data];
        if(p_w_picpath)
        {
#ifdef dispatch_main_sync_safe
            [[SDImageCache sharedImageCache] storeImage:p_w_picpath recalculateFromImage:YES p_w_picpathData:data forKey:URL.absoluteString toDisk:YES];
#endif
            size = p_w_picpath.size;
        }
    }
    return size;
}
+(CGSize)downloadPNGImageSizeWithRequest:(NSMutableURLRequest*)request
{
    [request setValue:@"bytes=16-23" forHTTPHeaderField:@"Range"];
    NSData* data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
    if(data.length == 8)
    {
        int w1 = 0, w2 = 0, w3 = 0, w4 = 0;
        [data getBytes:&w1; range:NSMakeRange(0, 1)];
        [data getBytes:&w2; range:NSMakeRange(1, 1)];
        [data getBytes:&w3; range:NSMakeRange(2, 1)];
        [data getBytes:&w4; range:NSMakeRange(3, 1)];
        int w = (w1 << 24) + (w2 << 16) + (w3 << 8) + w4;
        int h2 = 0, h3 = 0, h4 = 0, h5 = 0;
        [data getBytes:&h2; range:NSMakeRange(4, 1)];
        [data getBytes:&h3; range:NSMakeRange(5, 1)];
        [data getBytes:&h4; range:NSMakeRange(6, 1)];
        [data getBytes:&h5; range:NSMakeRange(7, 1)];
        int h = (h2 << 24) + (h3 << 16) + (h4 << 8) + h5;
        return CGSizeMake(w, h);
    }
    return CGSizeZero;
}
+(CGSize)downloadGIFImageSizeWithRequest:(NSMutableURLRequest*)request
{
    [request setValue:@"bytes=6-9" forHTTPHeaderField:@"Range"];
    NSData* data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
    if(data.length == 4)
    {
        short w1 = 0, w2 = 0;
        [data getBytes:&w1; range:NSMakeRange(0, 1)];
        [data getBytes:&w2; range:NSMakeRange(1, 1)];
        short w = w1 + (w2 << 8);
        short h2 = 0, h3 = 0;
        [data getBytes:&h2; range:NSMakeRange(2, 1)];
        [data getBytes:&h3; range:NSMakeRange(3, 1)];
        short h = h2 + (h3 << 8);
        return CGSizeMake(w, h);
    }
    return CGSizeZero;
}
+(CGSize)downloadJPGImageSizeWithRequest:(NSMutableURLRequest*)request
{
    [request setValue:@"bytes=0-209" forHTTPHeaderField:@"Range"];
    NSData* data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
     
    if ([data length] <= 0x58) {
        return CGSizeZero;
    }
     
    if ([data length] < 210) {// 肯定只有一个DQT字段
        short w1 = 0, w2 = 0;
        [data getBytes:&w1; range:NSMakeRange(0x60, 0x1)];
        [data getBytes:&w2; range:NSMakeRange(0x61, 0x1)];
        short w = (w1 << 8) + w2;
        short h2 = 0, h3 = 0;
        [data getBytes:&h2; range:NSMakeRange(0x5e, 0x1)];
        [data getBytes:&h3; range:NSMakeRange(0x5f, 0x1)];
        short h = (h2 << 8) + h3;
        return CGSizeMake(w, h);
    } else {
        short word = 0x0;
        [data getBytes:&word; range:NSMakeRange(0x15, 0x1)];
        if (word == 0xdb) {
            [data getBytes:&word; range:NSMakeRange(0x5a, 0x1)];
            if (word == 0xdb) {// 两个DQT字段
                short w1 = 0, w2 = 0;
                [data getBytes:&w1; range:NSMakeRange(0xa5, 0x1)];
                [data getBytes:&w2; range:NSMakeRange(0xa6, 0x1)];
                short w = (w1 << 8) + w2;
                short h2 = 0, h3 = 0;
                [data getBytes:&h2; range:NSMakeRange(0xa3, 0x1)];
                [data getBytes:&h3; range:NSMakeRange(0xa4, 0x1)];
                short h = (h2 << 8) + h3;
                return CGSizeMake(w, h);
            } else {// 一个DQT字段
                short w1 = 0, w2 = 0;
                [data getBytes:&w1; range:NSMakeRange(0x60, 0x1)];
                [data getBytes:&w2; range:NSMakeRange(0x61, 0x1)];
                short w = (w1 << 8) + w2;
                short h2 = 0, h3 = 0;
                [data getBytes:&h2; range:NSMakeRange(0x5e, 0x1)];
                [data getBytes:&h3; range:NSMakeRange(0x5f, 0x1)];
                short h = (h2 << 8) + h3;
                return CGSizeMake(w, h);
            }
        } else {
            return CGSizeZero;
        }
    }
}