Server/EchoConnection.m

/*
    File:       EchoConnection.m
 
    Contains:   Manages a single echo connection.
 
    Copyright:  Copyright (c) 2012 Apple Inc. All Rights Reserved.
 
    Disclaimer: IMPORTANT: This Apple software is supplied to you by Apple Inc.
                ("Apple") in consideration of your agreement to the following
                terms, and your use, installation, modification or
                redistribution of this Apple software constitutes acceptance of
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                not use, install, modify or redistribute this Apple software.
 
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                non-exclusive license, under Apple's copyrights in this
                original Apple software (the "Apple Software"), to use,
                reproduce, modify and redistribute the Apple Software, with or
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                APPLE MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
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*/
 
#import "EchoConnection.h"
 
NSString * EchoConnectionDidCloseNotification = @"EchoConnectionDidCloseNotification";
 
@interface EchoConnection () <NSStreamDelegate>
@end
 
@implementation EchoConnection
 
@synthesize inputStream  = _inputStream;
@synthesize outputStream = _outputStream;
 
- (id)initWithInputStream:(NSInputStream *)inputStream outputStream:(NSOutputStream *)outputStream
{
    self = [super init];
    if (self != nil) {
        self->_inputStream = inputStream;
        self->_outputStream = outputStream;
    }
    return self;
}
 
- (BOOL)open {
    [self.inputStream  setDelegate:self];
    [self.outputStream setDelegate:self];
    [self.inputStream  scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [self.outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [self.inputStream  open];
    [self.outputStream open];
    return YES;
}
 
- (void)close {
    [self.inputStream  setDelegate:nil];
    [self.outputStream setDelegate:nil];
    [self.inputStream  close];
    [self.outputStream close];
    [self.inputStream  removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [self.outputStream removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [(NSNotificationCenter *)[NSNotificationCenter defaultCenter] postNotificationName:EchoConnectionDidCloseNotification object:self];
}
 
- (void)stream:(NSStream *)aStream handleEvent:(NSStreamEvent)streamEvent {
    assert(aStream == self.inputStream || aStream == self.outputStream);
    #pragma unused(aStream)
    
    switch(streamEvent) {
        case NSStreamEventHasBytesAvailable: {
            uint8_t buffer[2048];
            NSInteger actuallyRead = [self.inputStream read:(uint8_t *)buffer maxLength:sizeof(buffer)];
            if (actuallyRead > 0) {
                NSInteger actuallyWritten = [self.outputStream write:buffer maxLength:(NSUInteger)actuallyRead];
                if (actuallyWritten != actuallyRead) {
                    // -write:maxLength: may return -1 to indicate an error or a non-negative 
                    // value less than maxLength to indicate a 'short write'.  In the case of an 
                    // error we just shut down the connection.  The short write case is more 
                    // interesting.  A short write means that the client has sent us data to echo but 
                    // isn't reading the data that we send back to it, thus causing its socket receive 
                    // buffer to fill up, thus causing our socket send buffer to fill up.  Again, our 
                    // response to this situation is that we simply drop the connection.
                    [self close];
                } else {
                    NSLog(@"Echoed %zd bytes.", (ssize_t) actuallyWritten);
                }
            } else {
                // A non-positive value from -read:maxLength: indicates either end of file (0) or 
                // an error (-1).  In either case we just wait for the corresponding stream event 
                // to come through.
            }
        } break;
        case NSStreamEventEndEncountered:
        case NSStreamEventErrorOccurred: {
            [self close];
        } break;
        case NSStreamEventHasSpaceAvailable:
        case NSStreamEventOpenCompleted:
        default: {
            // do nothing
        } break;
    }
}
 
@end