Optimise appendPostDataFromFile: to remove temporary memory use spike

Fiddle with iPhone upload sample to demonstrate file streaming

@@ -213,18 +213,18 @@ static NSError *ASIUnableToCreateRequestError;
 	[self setupPostBody];
 	NSInputStream *stream = [[[NSInputStream alloc] initWithFileAtPath:file] autorelease];
 	[stream open];
-	NSMutableData *d;
+	int bytesRead;
 	while ([stream hasBytesAvailable]) {
-		d = [NSMutableData dataWithLength:256*1024];
-		int bytesRead = [stream read:[d mutableBytes] maxLength:256*1024];
+		
+		unsigned char buffer[1024*256];
+		bytesRead = [stream read:buffer maxLength:sizeof(buffer)];
 		if (bytesRead == 0) {
 			break;
 		}
-		[d setLength:bytesRead];
 		if ([self shouldStreamPostDataFromDisk]) {
-			[[self postBodyWriteStream] write:[d mutableBytes] maxLength:bytesRead];
+			[[self postBodyWriteStream] write:buffer maxLength:bytesRead];
 		} else {
-			[[self postBody] appendData:[NSData dataWithBytes:[d mutableBytes] length:bytesRead]];
+			[[self postBody] appendData:[NSData dataWithBytes:buffer length:bytesRead]];
 		}
 	}
 	[stream close];

@@ -30,7 +30,17 @@
 	[request setPostValue:@"test" forKey:@"value2"];
 	[request setPostValue:@"test" forKey:@"value3"];
 	[request setTimeOutSeconds:20];
-	[request setData:[NSMutableData dataWithLength:1024*1024] forKey:@"1mb-of-crap"];
+	
+	//Create a 256KB file
+	NSData *data = [[[NSMutableData alloc] initWithLength:256*1024] autorelease];
+	NSString *path = [[[[NSBundle mainBundle] bundlePath] stringByDeletingLastPathComponent] stringByAppendingPathComponent:@"file"];
+	[data writeToFile:path atomically:NO];
+	
+	//Add the file 8 times to the request, for a total request size around 4MB
+	int i;
+	for (i=0; i<16; i++) {
+		[request setFile:path forKey:[NSString stringWithFormat:@"file-%hi",i]];
+	}
 	
 	[networkQueue addOperation:request];
 	[networkQueue go];