How to stop the connection in libxml parser at some point in iphone sdk?

I need to stop the connection of the libxml parser at certain point.Can anyone suggest me how to do this.

This is the method I used to establish the connection.

 - (BOOL)parseWithLibXML2Parser 
{
BOOL success = NO;
ZohoAppDelegate *appDelegate = (ZohoAppDelegate*) [ [UIApplication sharedApplication] delegate];
NSString* curl;
if ([self.lateFeeName length] == 0) 
{
    curl = @"https://invoice.zoho.com/api/view/settings/latefees?ticket=";
    curl = [curl stringByAppendingString:appDelegate.ticket];
    curl = [curl stringByAppendingString:@"&apikey=bfc9c6dde7c889a19f8deea9d75345cd"];
    curl = [curl stringByReplacingOccurrencesOfString:@"\n"开发者_运维知识库 withString:@""];
}

NSURLRequest *theRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:curl]];

NSLog(@"the request parserWithLibXml2Parser %@",theRequest);
NSURLConnection *con = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self];

self.connection = con;
[con release];
// This creates a context for "push" parsing in which chunks of data that are 
// not "well balanced" can be passed to the context for streaming parsing. 
// The handler structure defined above will be used for all the parsing. The
// second argument, self, will be passed as user data to each of the SAX
// handlers. The last three arguments are left blank to avoid creating a tree
// in memory.
_xmlParserContext = xmlCreatePushParserCtxt(&simpleSAXHandlerStruct, self, NULL, 0, NULL);
if(self.connection != nil) 
{
    do 
    {
        [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
    } while (!_done && !self.error);
}
if(self.error) 
{
    [self.delegate parser:self encounteredError:nil];
} else 
{
    success = YES;
}
return success;
}

Actually I am getting the exception when I tap the back button when the loading of data is under process.

// Called when a chunk of data has been downloaded.
- (void)connection:(NSURLConnection *)connection 
didReceiveData:(NSData *)data 
{
// Process the downloaded chunk of data.
xmlParseChunk(_xmlParserContext, (const char *)[data bytes], [data length], 0);//....Getting Exception at this line.
}

Anyone's help will me much appreciated.

Thank you, Monish.

The xmlStopParser-function, available in the libxml2 API, might be what you are looking for.

Specified in the docs as void xmlStopParser(xmlParserCtxtPtr context).

The documentation is available here: http://xmlsoft.org/html/libxml-parser.html#xmlStopParser

Also, Alex Deem has a good tip in this thread: Is it possible to stop a libxml parser while the process is running?