MKNetworkKit的断点续传SIDownloader下载

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https://github.com/MugunthKumar/MKNetworkKit

使用MKNetworkKit

首先把clone下来的MKNetworkKit文件夹拖进你的项目里面
到项目里面增加CFNetwork.Framework SystemConfiguration.framework 和 Security.framework.
把MKNetworkKit.h包含到你的pch文件里面。
如果是 如果是Mac，删除UIAlertView+MKNetworkKitAdditions.h这个文件

这样，再看看介绍里面的例子。应该就能看懂普通用法了。然后畅快的使用MKNetworkKit库了。

改写目标

上次写的ASIHTTPRequest续传其实已经可以用了。但是为什么需要重新写呢。就是重用！！！

一直都很少自己设计接口什么的。其实只是做了写体力的劳动，把一堆逻辑换成代码给堆了起来。觉得没有人会去重用自己的代码。很少去花心思想怎么样才能写好。

这次改写就只有一个目标，为了更好更多人能使用断点续传来功能

下载应该在下载继续进行。

保持进度条

每次进入暂停恢复 可以随时暂停下载

这次改写，这些功能都实现了，啊哈哈哈。

实现

MKNetworkKit库修改

最开始使用MKNetworkKit库做

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {

  NSUInteger size = [self.response expectedContentLength] < 0 ? 0 : [self.response expectedContentLength];
  self.response = (NSHTTPURLResponse*) response;

  // dont\' save data if the operation was created to download directly to a stream.
  if([self.downloadStreams count] == 0)
    self.mutableData = [NSMutableData dataWithCapacity:size];
  else
    self.mutableData = nil;

  for(NSOutputStream *stream in self.downloadStreams)
    [stream open];

  NSDictionary *httpHeaders = [self.response allHeaderFields];

  // if you attach a stream to the operation, MKNetworkKit will not cache the response.
  // Streams are usually "big data chunks" that doesn\'t need caching anyways.

  if([self.request.HTTPMethod isEqualToString:@"GET"] && [self.downloadStreams count] == 0) {

    // We have all this complicated cache handling since NSURLRequestReloadRevalidatingCacheData is not implemented
    // do cache processing only if the request is a "GET" method
    NSString *lastModified = [httpHeaders objectForKey:@"Last-Modified"];
    NSString *eTag = [httpHeaders objectForKey:@"ETag"];
    NSString *expiresOn = [httpHeaders objectForKey:@"Expires"];

    NSString *contentType = [httpHeaders objectForKey:@"Content-Type"];
    // if contentType is image,

    NSDate *expiresOnDate = nil;

    if([contentType rangeOfString:@"image"].location != NSNotFound) {

      // For images let\'s assume a expiry date of 7 days if there is no eTag or Last Modified.
      if(!eTag && !lastModified)
        expiresOnDate = [[NSDate date] dateByAddingTimeInterval:kMKNetworkKitDefaultImageCacheDuration];
      else
        expiresOnDate = [[NSDate date] dateByAddingTimeInterval:kMKNetworkKitDefaultImageHeadRequestDuration];
    }

    NSString *cacheControl = [httpHeaders objectForKey:@"Cache-Control"]; // max-age, must-revalidate, no-cache
    NSArray *cacheControlEntities = [cacheControl componentsSeparatedByString:@","];

    for(NSString *substring in cacheControlEntities) {

      if([substring rangeOfString:@"max-age"].location != NSNotFound) {

        // do some processing to calculate expiresOn
        NSString *