Dear Nick and all,
Thanks so much for your reply! I am still a new Cocoa developer so that I
need to improve during the programming procedure.
Now I modify the code and it works fine. The code is as follows.
But I still have a question. If the autoreleased data will keep alive until
the pool is drained, what if the data is autoreleased in a Cocoa
auto-created pool? It will keep alive unless the process is shutdown?
Thanks!
Bing
- (NSString *) receiveMessage
{
NSMutableString *receivedString;
NSString *message;
[isConnectedLock lock];
@try
{
if (isConnected)
{
char buffer[Constants.WWW.BUFFER_SIZE];
ssize_t numBytesReceived = recv(destinationSocket,
buffer, Constants.WWW.BUFFER_SIZE, 0);
if (numBytesReceived <= 0)
{
return Constants.WWW.NO_RECEIVED_MESSAGE;
}
buffer[numBytesReceived] = '\0';
receivedString = [[NSMutableString alloc]
initWithBytes:buffer length:numBytesReceived encoding:NSUTF8StringEncoding];
NSRange range = [receivedString
rangeOfString:Constants.WWW.DELIMITER];
if (range.location > 0 && range.location <
[receivedString length])
{
message = [receivedString
substringToIndex:range.location];
return message;
}
else
{
while (numBytesReceived > 0)
{
NSAutoreleasePool *loopPool =
[[NSAutoreleasePool alloc] init];
numBytesReceived =
recv(destinationSocket, buffer, Constants.WWW.BUFFER_SIZE, 0);
if (numBytesReceived <= 0)
{
[loopPool drain];
break;
}
buffer[numBytesReceived] = '\0';
NSString *newReceivedString =
[[[NSString alloc] initWithBytes:buffer length:numBytesReceived
encoding:NSUTF8StringEn
coding] autorelease];
[receivedString
appendString:newReceivedString];
range = [receivedString
rangeOfString:Constants.WWW.DELIMITER];
if (range.location > 0 &&
range.location < [receivedString length])
{
message = [receivedString
substringToIndex:range.location];
[loopPool drain];
break;
}
[loopPool drain];
}
}
return message;
}
else
{
return Constants.WWW.NO_RECEIVED_MESSAGE;
}
}
@catch (NSException *e)
{
NSLog(@"%@", e);
return Constants.WWW.NO_RECEIVED_MESSAGE;
}
@finally
{
[isConnectedLock unlock];
[receivedString autorelease];
}
}
On Tue, May 31, 2011 at 11:13 AM, Nick Zitzmann <n...@chronosnet.com> wrote:
>
> On May 30, 2011, at 8:15 PM, Bing Li wrote:
>
> > - (NSString *) receiveMessage
> > {
> > NSMutableString *receivedString;
> > NSString *message;
> > NSString *newReceivedString;
> > [isConnectedLock lock];
> > @try
> > {
> > if (isConnected)
> > {
> > char buffer[Constants.WWW.BUFFER_SIZE];
> >
> > // Receive remote data
> > ssize_t numBytesReceived = recv(destinationSocket,
> > buffer, Constants.WWW.BUFFER_SIZE, 0);
> > if (numBytesReceived <= 0)
> > {
> > return Constants.WWW.NO_RECEIVED_MESSAGE;
> > }
> > buffer[numBytesReceived] = '\0';
> >
> >
> > // Convert data to NSString locally
> > receivedString = [[NSMutableString alloc]
> > initWithBytes:buffer length:numBytesReceived
> encoding:NSUTF8StringEncoding];
> > message = [[NSString alloc]
> > initWithString:Constants.WWW.EMPTY_STRING];
>
> Why are you storing a non-autoreleased object to a pointer and then writing
> over it later?
>
> >
> >
> > // Since the data has specific formats, some
> simple
> > parsing jobs by delimiter are done as follows.
> >
> > NSRange range = [receivedString
> > rangeOfString:Constants.WWW.DELIMITER];
> > if (range.location > 0 && range.location <
> > [receivedString length])
> > {
> > message = [receivedString
> > substringToIndex:range.location];
>
> Here you're overwriting a pointer to an object you own with an autoreleased
> object.
>
> >
> > // Return data after parsing
> > return message;
> > }
> > else
> > {
> > // Receive remote data continually if the
> > receivedString is longer than expected
> > while (numBytesReceived > 0)
> > {
> > NSAutoreleasePool *loopPool =
> > [[NSAutoreleasePool alloc] init];
> >
> > // Receive data
> > numBytesReceived =
> > recv(destinationSocket, buffer, Constants.WWW.BUFFER_SIZE, 0);
> > if (numBytesReceived <= 0)
> > {
> > return
> > Constants.WWW.NO_RECEIVED_MESSAGE;
>
> Here you're leaking the autorelease pool you created above.
>
> > }
> >
> >
> > buffer[numBytesReceived] = '\0';
> > newReceivedString = [[[NSString
> > alloc] initWithBytes:buffer length:numBytesReceived
> > encoding:NSUTF8StringEncoding] autorelease];
> > range = [receivedString
> > rangeOfString:Constants.WWW.DELIMITER];
> > if (range.location > 0 &&
> > range.location < [receivedString length])
> > {
> > message = [receivedString
> > substringToIndex:range.location];
> >
> > // Return data after
> parsing
> > return message;
>
> Here you're placing a new object in the autorelease pool, and then leaking
> the autorelease pool.
>
> > }
> > [loopPool drain];
> > }
> > }
> > return Constants.WWW.NO_RECEIVED_MESSAGE;
> > }
> > else
> > {
> > return Constants.WWW.NO_RECEIVED_MESSAGE;
> > }
> > }
> > @catch (NSException *e)
> > {
> > return Constants.WWW.NO_RECEIVED_MESSAGE;
> > }
> > @finally
> > {
> > [isConnectedLock unlock];
> >
> > // Before returning received data, autorelease them here.
> > [receivedString autorelease];
> > [message autorelease];
>
> Here you're autoreleasing a pointer that may or may not have been
> autoreleased already.
>
> I suggest you re-read the memory management rules again and pay attention
> to the rules regarding release and autorelease. If anyone tries to re-state
> it here, we're inevitably going to get something wrong. <
> http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/MemoryMgmt/MemoryMgmt.html
> >
>
> Also, I cannot recommend writing an object to a pointer that the program is
> never going to read. If you're concerned about accidentally accessing an
> uninitialized pointer, then just set it to nil instead.
>
> Nick Zitzmann
> <http://www.chronosnet.com/>
>
>
>
>
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