MRo Blog

For quite some time I ranted about not being able to use compressed network communcation out-of-the-box on the iPhone.

Despite being undocumented (or I just overlooked the hint), NSURLConnection does gzip decompression transparently!

That’s how to use it:

1. ensure the webserver sends gzipped content, use e.g. wget to verify:

   $ wget --header='Accept-Encoding: gzip' \ --server-response http://example.com/demo.xmlz

   It should (in case of a gzipped xml document) look like

   HTTP/1.1 200 OK ... Content-Type: text/xml Content-Encoding: gzip ...

2. If your webserver doesn’t support transparent compression, you can still upload gzipped content and tell the server to send the correct response headers by setting up a .htaccess file:

   ... AddType text/xml .xml .xmlz AddEncoding gzip .gz .xmlz   # inspired by # http://betterexplained.com/articles/ # how-to-optimize-your-site-with-gzip-compression/ # compress all text & html: AddOutputFilterByType DEFLATE text/html text/plain text/xml ...

3. to verify from within your app, log the response header in the NSURLConnection callbacks:

   - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response { NSLog(@"didReceiveResponse %@: %@", [response URL], [(NSHTTPURLResponse*)response allHeaderFields]); buffer = [[NSMutableData dataWithCapacity:1024*1024] retain]; }   - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)dat { [buffer appendData:dat]; }   - (void)connectionDidFinishLoading:(NSURLConnection *)connection { NSLog(@"connectionDidFinishLoading %d bytes", [buffer length]); [buffer release]; }

   It should look like

   2009-06-28 14:31:09.722 DemoApp[3981:20b] \ didReceiveResponse http://example.com/demo.xmlz: { ... "Content-Type" = "text/xml"; "Content-Encoding" = gzip; "Content-Length" = 123042; } ... 2009-06-28 14:31:11.619 DemoApp[3981:20b] \ connectionDidFinishLoading 602979 bytes

   As you can see we received way more bytes than went over the wire.

4. enjoy lightning fast network communication!

P.S.: It seems not to be necessary setting the request header yourself:

NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url
    cachePolicy:NSURLRequestReloadIgnoringLocalCacheData
    timeoutInterval:60.0];
// set explicitly:
[request setValue:@"gzip" forHTTPHeaderField:@"Accept-Encoding"];

For quite some time I ranted about not being able to use compressed network communcation out-of-the-box on the iPhone. Despite being undocumented (or I just overlooked the hint), NSURLConnection does...