/Pods/CocoaAsyncSocket/GCD/GCDAsyncSocket.m

Large files files are truncated, but you can click here to view the full file

//
//  GCDAsyncSocket.m
//  
//  This class is in the public domain.
//  Originally created by Robbie Hanson in Q4 2010.
//  Updated and maintained by Deusty LLC and the Apple development community.
//
//  https://github.com/robbiehanson/CocoaAsyncSocket
//

#import "GCDAsyncSocket.h"

#if TARGET_OS_IPHONE
#import <CFNetwork/CFNetwork.h>
#endif

#import <arpa/inet.h>
#import <fcntl.h>
#import <ifaddrs.h>
#import <netdb.h>
#import <netinet/in.h>
#import <net/if.h>
#import <sys/socket.h>
#import <sys/types.h>
#import <sys/ioctl.h>
#import <sys/poll.h>
#import <sys/uio.h>
#import <sys/un.h>
#import <unistd.h>

#if ! __has_feature(objc_arc)
#warning This file must be compiled with ARC. Use -fobjc-arc flag (or convert project to ARC).
// For more information see: https://github.com/robbiehanson/CocoaAsyncSocket/wiki/ARC
#endif

/**
 * Does ARC support support GCD objects?
 * It does if the minimum deployment target is iOS 6+ or Mac OS X 10.8+
**/
#if TARGET_OS_IPHONE

  // Compiling for iOS

  #if __IPHONE_OS_VERSION_MIN_REQUIRED >= 60000 // iOS 6.0 or later
    #define NEEDS_DISPATCH_RETAIN_RELEASE 0
  #else                                         // iOS 5.X or earlier
    #define NEEDS_DISPATCH_RETAIN_RELEASE 1
  #endif

#else

  // Compiling for Mac OS X

  #if MAC_OS_X_VERSION_MIN_REQUIRED >= 1080     // Mac OS X 10.8 or later
    #define NEEDS_DISPATCH_RETAIN_RELEASE 0
  #else
    #define NEEDS_DISPATCH_RETAIN_RELEASE 1     // Mac OS X 10.7 or earlier
  #endif

#endif


#if 0

// Logging Enabled - See log level below

// Logging uses the CocoaLumberjack framework (which is also GCD based).
// https://github.com/robbiehanson/CocoaLumberjack
// 
// It allows us to do a lot of logging without significantly slowing down the code.
#import "DDLog.h"

#define LogAsync   YES
#define LogContext 65535

#define LogObjc(flg, frmt, ...) LOG_OBJC_MAYBE(LogAsync, logLevel, flg, LogContext, frmt, ##__VA_ARGS__)
#define LogC(flg, frmt, ...)    LOG_C_MAYBE(LogAsync, logLevel, flg, LogContext, frmt, ##__VA_ARGS__)

#define LogError(frmt, ...)     LogObjc(LOG_FLAG_ERROR,   (@"%@: " frmt), THIS_FILE, ##__VA_ARGS__)
#define LogWarn(frmt, ...)      LogObjc(LOG_FLAG_WARN,    (@"%@: " frmt), THIS_FILE, ##__VA_ARGS__)
#define LogInfo(frmt, ...)      LogObjc(LOG_FLAG_INFO,    (@"%@: " frmt), THIS_FILE, ##__VA_ARGS__)
#define LogVerbose(frmt, ...)   LogObjc(LOG_FLAG_VERBOSE, (@"%@: " frmt), THIS_FILE, ##__VA_ARGS__)

#define LogCError(frmt, ...)    LogC(LOG_FLAG_ERROR,   (@"%@: " frmt), THIS_FILE, ##__VA_ARGS__)
#define LogCWarn(frmt, ...)     LogC(LOG_FLAG_WARN,    (@"%@: " frmt), THIS_FILE, ##__VA_ARGS__)
#define LogCInfo(frmt, ...)     LogC(LOG_FLAG_INFO,    (@"%@: " frmt), THIS_FILE, ##__VA_ARGS__)
#define LogCVerbose(frmt, ...)  LogC(LOG_FLAG_VERBOSE, (@"%@: " frmt), THIS_FILE, ##__VA_ARGS__)

#define LogTrace()              LogObjc(LOG_FLAG_VERBOSE, @"%@: %@", THIS_FILE, THIS_METHOD)
#define LogCTrace()             LogC(LOG_FLAG_VERBOSE, @"%@: %s", THIS_FILE, __FUNCTION__)

// Log levels : off, error, warn, info, verbose
static const int logLevel = LOG_LEVEL_VERBOSE;

#else

// Logging Disabled

#define LogError(frmt, ...)     {}
#define LogWarn(frmt, ...)      {}
#define LogInfo(frmt, ...)      {}
#define LogVerbose(frmt, ...)   {}

#define LogCError(frmt, ...)    {}
#define LogCWarn(frmt, ...)     {}
#define LogCInfo(frmt, ...)     {}
#define LogCVerbose(frmt, ...)  {}

#define LogTrace()              {}
#define LogCTrace(frmt, ...)    {}

#endif

/**
 * Seeing a return statements within an inner block
 * can sometimes be mistaken for a return point of the enclosing method.
 * This makes inline blocks a bit easier to read.
**/
#define return_from_block  return

/**
 * A socket file descriptor is really just an integer.
 * It represents the index of the socket within the kernel.
 * This makes invalid file descriptor comparisons easier to read.
**/
#define SOCKET_NULL -1


NSString *const GCDAsyncSocketException = @"GCDAsyncSocketException";
NSString *const GCDAsyncSocketErrorDomain = @"GCDAsyncSocketErrorDomain";

NSString *const GCDAsyncSocketQueueName = @"GCDAsyncSocket";
NSString *const GCDAsyncSocketThreadName = @"GCDAsyncSocket-CFStream";

#if SECURE_TRANSPORT_MAYBE_AVAILABLE
NSString *const GCDAsyncSocketSSLCipherSuites = @"GCDAsyncSocketSSLCipherSuites";
#if TARGET_OS_IPHONE
NSString *const GCDAsyncSocketSSLProtocolVersionMin = @"GCDAsyncSocketSSLProtocolVersionMin";
NSString *const GCDAsyncSocketSSLProtocolVersionMax = @"GCDAsyncSocketSSLProtocolVersionMax";
#else
NSString *const GCDAsyncSocketSSLDiffieHellmanParameters = @"GCDAsyncSocketSSLDiffieHellmanParameters";
#endif
#endif

enum GCDAsyncSocketFlags
{
	kSocketStarted                 = 1 <<  0,  // If set, socket has been started (accepting/connecting)
	kConnected                     = 1 <<  1,  // If set, the socket is connected
	kForbidReadsWrites             = 1 <<  2,  // If set, no new reads or writes are allowed
	kReadsPaused                   = 1 <<  3,  // If set, reads are paused due to possible timeout
	kWritesPaused                  = 1 <<  4,  // If set, writes are paused due to possible timeout
	kDisconnectAfterReads          = 1 <<  5,  // If set, disconnect after no more reads are queued
	kDisconnectAfterWrites         = 1 <<  6,  // If set, disconnect after no more writes are queued
	kSocketCanAcceptBytes          = 1 <<  7,  // If set, we know socket can accept bytes. If unset, it's unknown.
	kReadSourceSuspended           = 1 <<  8,  // If set, the read source is suspended
	kWriteSourceSuspended          = 1 <<  9,  // If set, the write source is suspended
	kQueuedTLS                     = 1 << 10,  // If set, we've queued an upgrade to TLS
	kStartingReadTLS               = 1 << 11,  // If set, we're waiting for TLS negotiation to complete
	kStartingWriteTLS              = 1 << 12,  // If set, we're waiting for TLS negotiation to complete
	kSocketSecure                  = 1 << 13,  // If set, socket is using secure communication via SSL/TLS
	kSocketHasReadEOF              = 1 << 14,  // If set, we have read EOF from socket
	kReadStreamClosed              = 1 << 15,  // If set, we've read EOF plus prebuffer has been drained
#if TARGET_OS_IPHONE
	kAddedStreamsToRunLoop         = 1 << 16,  // If set, CFStreams have been added to listener thread
	kUsingCFStreamForTLS           = 1 << 17,  // If set, we're forced to use CFStream instead of SecureTransport
	kSecureSocketHasBytesAvailable = 1 << 18,  // If set, CFReadStream has notified us of bytes available
#endif
};

enum GCDAsyncSocketConfig
{
	kIPv4Disabled              = 1 << 0,  // If set, IPv4 is disabled
	kIPv6Disabled              = 1 << 1,  // If set, IPv6 is disabled
	kPreferIPv6                = 1 << 2,  // If set, IPv6 is preferred over IPv4
	kAllowHalfDuplexConnection = 1 << 3,  // If set, the socket will stay open even if the read stream closes
};

#if TARGET_OS_IPHONE
  static NSThread *cfstreamThread;  // Used for CFStreams
#endif

@interface GCDAsyncSocket (Private)

// Accepting
- (BOOL)doAccept:(int)socketFD;

// Connecting
- (void)startConnectTimeout:(NSTimeInterval)timeout;
- (void)endConnectTimeout;
- (void)doConnectTimeout;
- (void)lookup:(int)aConnectIndex host:(NSString *)host port:(uint16_t)port;
- (void)lookup:(int)aConnectIndex didSucceedWithAddress4:(NSData *)address4 address6:(NSData *)address6;
- (void)lookup:(int)aConnectIndex didFail:(NSError *)error;
- (BOOL)connectWithAddress4:(NSData *)address4 address6:(NSData *)address6 error:(NSError **)errPtr;
- (BOOL)connectWithAddressUN:(NSData *)address error:(NSError **)errPtr;
- (void)didConnect:(int)aConnectIndex;
- (void)didNotConnect:(int)aConnectIndex error:(NSError *)error;

// Disconnect
- (void)closeWithError:(NSError *)error;
- (void)close;
- (void)maybeClose;

// Errors
- (NSError *)badConfigError:(NSString *)msg;
- (NSError *)badParamError:(NSString *)msg;
- (NSError *)gaiError:(int)gai_error;
- (NSError *)errnoError;
- (NSError *)errnoErrorWithReason:(NSString *)reason;
- (NSError *)connectTimeoutError;
- (NSError *)otherError:(NSString *)msg;

// Diagnostics
- (NSString *)connectedHost4;
- (NSString *)connectedHost6;
- (uint16_t)connectedPort4;
- (uint16_t)connectedPort6;
- (NSString *)localHost4;
- (NSString *)localHost6;
- (uint16_t)localPort4;
- (uint16_t)localPort6;
- (NSString *)connectedHostFromSocket4:(int)socketFD;
- (NSString *)connectedHostFromSocket6:(int)socketFD;
- (uint16_t)connectedPortFromSocket4:(int)socketFD;
- (uint16_t)connectedPortFromSocket6:(int)socketFD;
- (NSURL *)connectedUrlFromSocketUN:(int)socketFD;
- (NSString *)localHostFromSocket4:(int)socketFD;
- (NSString *)localHostFromSocket6:(int)socketFD;
- (uint16_t)localPortFromSocket4:(int)socketFD;
- (uint16_t)localPortFromSocket6:(int)socketFD;

// Utilities
- (void)getInterfaceAddress4:(NSMutableData **)addr4Ptr
                    address6:(NSMutableData **)addr6Ptr
             fromDescription:(NSString *)interfaceDescription
                        port:(uint16_t)port;
- (NSData *)getInterfaceAddressFromUrl:(NSURL *)url;
- (void)setupReadAndWriteSourcesForNewlyConnectedSocket:(int)socketFD;
- (void)suspendReadSource;
- (void)resumeReadSource;
- (void)suspendWriteSource;
- (void)resumeWriteSource;

// Reading
- (void)maybeDequeueRead;
- (void)flushSSLBuffers;
- (void)doReadData;
- (void)doReadEOF;
- (void)completeCurrentRead;
- (void)endCurrentRead;
- (void)setupReadTimerWithTimeout:(NSTimeInterval)timeout;
- (void)doReadTimeout;
- (void)doReadTimeoutWithExtension:(NSTimeInterval)timeoutExtension;

// Writing
- (void)maybeDequeueWrite;
- (void)doWriteData;
- (void)completeCurrentWrite;
- (void)endCurrentWrite;
- (void)setupWriteTimerWithTimeout:(NSTimeInterval)timeout;
- (void)doWriteTimeout;
- (void)doWriteTimeoutWithExtension:(NSTimeInterval)timeoutExtension;

// Security
- (void)maybeStartTLS;
#if SECURE_TRANSPORT_MAYBE_AVAILABLE
- (void)ssl_startTLS;
- (void)ssl_continueSSLHandshake;
#endif
#if TARGET_OS_IPHONE
- (void)cf_startTLS;
#endif

// CFStream
#if TARGET_OS_IPHONE
+ (void)startCFStreamThreadIfNeeded;
- (BOOL)createReadAndWriteStream;
- (BOOL)registerForStreamCallbacksIncludingReadWrite:(BOOL)includeReadWrite;
- (BOOL)addStreamsToRunLoop;
- (BOOL)openStreams;
- (void)removeStreamsFromRunLoop;
#endif

// Class Methods
+ (NSString *)hostFromSockaddr4:(const struct sockaddr_in *)pSockaddr4;
+ (NSString *)hostFromSockaddr6:(const struct sockaddr_in6 *)pSockaddr6;
+ (uint16_t)portFromSockaddr4:(const struct sockaddr_in *)pSockaddr4;
+ (uint16_t)portFromSockaddr6:(const struct sockaddr_in6 *)pSockaddr6;
+ (NSURL *)urlFromSockaddrUN:(const struct sockaddr_un *)pSockaddr;

@end

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
#pragma mark -
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

/**
 * A PreBuffer is used when there is more data available on the socket
 * than is being requested by current read request.
 * In this case we slurp up all data from the socket (to minimize sys calls),
 * and store additional yet unread data in a "prebuffer".
 * 
 * The prebuffer is entirely drained before we read from the socket again.
 * In other words, a large chunk of data is written is written to the prebuffer.
 * The prebuffer is then drained via a series of one or more reads (for subsequent read request(s)).
 * 
 * A ring buffer was once used for this purpose.
 * But a ring buffer takes up twice as much memory as needed (double the size for mirroring).
 * In fact, it generally takes up more than twice the needed size as everything has to be rounded up to vm_page_size.
 * And since the prebuffer is always completely drained after being written to, a full ring buffer isn't needed.
 * 
 * The current design is very simple and straight-forward, while also keeping memory requirements lower.
**/

@interface GCDAsyncSocketPreBuffer : NSObject
{
	uint8_t *preBuffer;
	size_t preBufferSize;
	
	uint8_t *readPointer;
	uint8_t *writePointer;
}

- (id)initWithCapacity:(size_t)numBytes;

- (void)ensureCapacityForWrite:(size_t)numBytes;

- (size_t)availableBytes;
- (uint8_t *)readBuffer;

- (void)getReadBuffer:(uint8_t **)bufferPtr availableBytes:(size_t *)availableBytesPtr;

- (size_t)availableSpace;
- (uint8_t *)writeBuffer;

- (void)getWriteBuffer:(uint8_t **)bufferPtr availableSpace:(size_t *)availableSpacePtr;

- (void)didRead:(size_t)bytesRead;
- (void)didWrite:(size_t)bytesWritten;

- (void)reset;

@end

@implementation GCDAsyncSocketPreBuffer

- (id)initWithCapacity:(size_t)numBytes
{
	if ((self = [super init]))
	{
		preBufferSize = numBytes;
		preBuffer = malloc(preBufferSize);
		
		readPointer = preBuffer;
		writePointer = preBuffer;
	}
	return self;
}

- (void)dealloc
{
	if (preBuffer)
		free(preBuffer);
}

- (void)ensureCapacityForWrite:(size_t)numBytes
{
	size_t availableSpace = preBufferSize - (writePointer - readPointer);
	
	if (numBytes > availableSpace)
	{
		size_t additionalBytes = numBytes - availableSpace;
		
		size_t newPreBufferSize = preBufferSize + additionalBytes;
		uint8_t *newPreBuffer = realloc(preBuffer, newPreBufferSize);
		
		size_t readPointerOffset = readPointer - preBuffer;
		size_t writePointerOffset = writePointer - preBuffer;
		
		preBuffer = newPreBuffer;
		preBufferSize = newPreBufferSize;
		
		readPointer = preBuffer + readPointerOffset;
		writePointer = preBuffer + writePointerOffset;
	}
}

- (size_t)availableBytes
{
	return writePointer - readPointer;
}

- (uint8_t *)readBuffer
{
	return readPointer;
}

- (void)getReadBuffer:(uint8_t **)bufferPtr availableBytes:(size_t *)availableBytesPtr
{
	if (bufferPtr) *bufferPtr = readPointer;
	if (availableBytesPtr) *availableBytesPtr = writePointer - readPointer;
}

- (void)didRead:(size_t)bytesRead
{
	readPointer += bytesRead;
	
	if (readPointer == writePointer)
	{
		// The prebuffer has been drained. Reset pointers.
		readPointer  = preBuffer;
		writePointer = preBuffer;
	}
}

- (size_t)availableSpace
{
	return preBufferSize - (writePointer - readPointer);
}

- (uint8_t *)writeBuffer
{
	return writePointer;
}

- (void)getWriteBuffer:(uint8_t **)bufferPtr availableSpace:(size_t *)availableSpacePtr
{
	if (bufferPtr) *bufferPtr = writePointer;
	if (availableSpacePtr) *availableSpacePtr = preBufferSize - (writePointer - readPointer);
}

- (void)didWrite:(size_t)bytesWritten
{
	writePointer += bytesWritten;
}

- (void)reset
{
	readPointer  = preBuffer;
	writePointer = preBuffer;
}

@end

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
#pragma mark -
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

/**
 * The GCDAsyncReadPacket encompasses the instructions for any given read.
 * The content of a read packet allows the code to determine if we're:
 *  - reading to a certain length
 *  - reading to a certain separator
 *  - or simply reading the first chunk of available data
**/
@interface GCDAsyncReadPacket : NSObject
{
  @public
	NSMutableData *buffer;
	NSUInteger startOffset;
	NSUInteger bytesDone;
	NSUInteger maxLength;
	NSTimeInterval timeout;
	NSUInteger readLength;
	NSData *term;
	BOOL bufferOwner;
	NSUInteger originalBufferLength;
	long tag;
}
- (id)initWithData:(NSMutableData *)d
       startOffset:(NSUInteger)s
         maxLength:(NSUInteger)m
           timeout:(NSTimeInterval)t
        readLength:(NSUInteger)l
        terminator:(NSData *)e
               tag:(long)i;

- (void)ensureCapacityForAdditionalDataOfLength:(NSUInteger)bytesToRead;

- (NSUInteger)optimalReadLengthWithDefault:(NSUInteger)defaultValue shouldPreBuffer:(BOOL *)shouldPreBufferPtr;

- (NSUInteger)readLengthForNonTermWithHint:(NSUInteger)bytesAvailable;
- (NSUInteger)readLengthForTermWithHint:(NSUInteger)bytesAvailable shouldPreBuffer:(BOOL *)shouldPreBufferPtr;
- (NSUInteger)readLengthForTermWithPreBuffer:(GCDAsyncSocketPreBuffer *)preBuffer found:(BOOL *)foundPtr;

- (NSInteger)searchForTermAfterPreBuffering:(ssize_t)numBytes;

@end

@implementation GCDAsyncReadPacket

- (id)initWithData:(NSMutableData *)d
       startOffset:(NSUInteger)s
         maxLength:(NSUInteger)m
           timeout:(NSTimeInterval)t
        readLength:(NSUInteger)l
        terminator:(NSData *)e
               tag:(long)i
{
	if((self = [super init]))
	{
		bytesDone = 0;
		maxLength = m;
		timeout = t;
		readLength = l;
		term = [e copy];
		tag = i;
		
		if (d)
		{
			buffer = d;
			startOffset = s;
			bufferOwner = NO;
			originalBufferLength = [d length];
		}
		else
		{
			if (readLength > 0)
				buffer = [[NSMutableData alloc] initWithLength:readLength];
			else
				buffer = [[NSMutableData alloc] initWithLength:0];
			
			startOffset = 0;
			bufferOwner = YES;
			originalBufferLength = 0;
		}
	}
	return self;
}

/**
 * Increases the length of the buffer (if needed) to ensure a read of the given size will fit.
**/
- (void)ensureCapacityForAdditionalDataOfLength:(NSUInteger)bytesToRead
{
	NSUInteger buffSize = [buffer length];
	NSUInteger buffUsed = startOffset + bytesDone;
	
	NSUInteger buffSpace = buffSize - buffUsed;
	
	if (bytesToRead > buffSpace)
	{
		NSUInteger buffInc = bytesToRead - buffSpace;
		
		[buffer increaseLengthBy:buffInc];
	}
}

/**
 * This method is used when we do NOT know how much data is available to be read from the socket.
 * This method returns the default value unless it exceeds the specified readLength or maxLength.
 * 
 * Furthermore, the shouldPreBuffer decision is based upon the packet type,
 * and whether the returned value would fit in the current buffer without requiring a resize of the buffer.
**/
- (NSUInteger)optimalReadLengthWithDefault:(NSUInteger)defaultValue shouldPreBuffer:(BOOL *)shouldPreBufferPtr
{
	NSUInteger result;
	
	if (readLength > 0)
	{
		// Read a specific length of data
		
		result = MIN(defaultValue, (readLength - bytesDone));
		
		// There is no need to prebuffer since we know exactly how much data we need to read.
		// Even if the buffer isn't currently big enough to fit this amount of data,
		// it would have to be resized eventually anyway.
		
		if (shouldPreBufferPtr)
			*shouldPreBufferPtr = NO;
	}
	else
	{
		// Either reading until we find a specified terminator,
		// or we're simply reading all available data.
		// 
		// In other words, one of:
		// 
		// - readDataToData packet
		// - readDataWithTimeout packet
		
		if (maxLength > 0)
			result =  MIN(defaultValue, (maxLength - bytesDone));
		else
			result = defaultValue;
		
		// Since we don't know the size of the read in advance,
		// the shouldPreBuffer decision is based upon whether the returned value would fit
		// in the current buffer without requiring a resize of the buffer.
		// 
		// This is because, in all likelyhood, the amount read from the socket will be less than the default value.
		// Thus we should avoid over-allocating the read buffer when we can simply use the pre-buffer instead.
		
		if (shouldPreBufferPtr)
		{
			NSUInteger buffSize = [buffer length];
			NSUInteger buffUsed = startOffset + bytesDone;
			
			NSUInteger buffSpace = buffSize - buffUsed;
			
			if (buffSpace >= result)
				*shouldPreBufferPtr = NO;
			else
				*shouldPreBufferPtr = YES;
		}
	}
	
	return result;
}

/**
 * For read packets without a set terminator, returns the amount of data
 * that can be read without exceeding the readLength or maxLength.
 * 
 * The given parameter indicates the number of bytes estimated to be available on the socket,
 * which is taken into consideration during the calculation.
 * 
 * The given hint MUST be greater than zero.
**/
- (NSUInteger)readLengthForNonTermWithHint:(NSUInteger)bytesAvailable
{
	NSAssert(term == nil, @"This method does not apply to term reads");
	NSAssert(bytesAvailable > 0, @"Invalid parameter: bytesAvailable");
	
	if (readLength > 0)
	{
		// Read a specific length of data
		
		return MIN(bytesAvailable, (readLength - bytesDone));
		
		// No need to avoid resizing the buffer.
		// If the user provided their own buffer,
		// and told us to read a certain length of data that exceeds the size of the buffer,
		// then it is clear that our code will resize the buffer during the read operation.
		// 
		// This method does not actually do any resizing.
		// The resizing will happen elsewhere if needed.
	}
	else
	{
		// Read all available data
		
		NSUInteger result = bytesAvailable;
		
		if (maxLength > 0)
		{
			result = MIN(result, (maxLength - bytesDone));
		}
		
		// No need to avoid resizing the buffer.
		// If the user provided their own buffer,
		// and told us to read all available data without giving us a maxLength,
		// then it is clear that our code might resize the buffer during the read operation.
		// 
		// This method does not actually do any resizing.
		// The resizing will happen elsewhere if needed.
		
		return result;
	}
}

/**
 * For read packets with a set terminator, returns the amount of data
 * that can be read without exceeding the maxLength.
 * 
 * The given parameter indicates the number of bytes estimated to be available on the socket,
 * which is taken into consideration during the calculation.
 * 
 * To optimize memory allocations, mem copies, and mem moves
 * the shouldPreBuffer boolean value will indicate if the data should be read into a prebuffer first,
 * or if the data can be read directly into the read packet's buffer.
**/
- (NSUInteger)readLengthForTermWithHint:(NSUInteger)bytesAvailable shouldPreBuffer:(BOOL *)shouldPreBufferPtr
{
	NSAssert(term != nil, @"This method does not apply to non-term reads");
	NSAssert(bytesAvailable > 0, @"Invalid parameter: bytesAvailable");
	
	
	NSUInteger result = bytesAvailable;
	
	if (maxLength > 0)
	{
		result = MIN(result, (maxLength - bytesDone));
	}
	
	// Should the data be read into the read packet's buffer, or into a pre-buffer first?
	// 
	// One would imagine the preferred option is the faster one.
	// So which one is faster?
	// 
	// Reading directly into the packet's buffer requires:
	// 1. Possibly resizing packet buffer (malloc/realloc)
	// 2. Filling buffer (read)
	// 3. Searching for term (memcmp)
	// 4. Possibly copying overflow into prebuffer (malloc/realloc, memcpy)
	// 
	// Reading into prebuffer first:
	// 1. Possibly resizing prebuffer (malloc/realloc)
	// 2. Filling buffer (read)
	// 3. Searching for term (memcmp)
	// 4. Copying underflow into packet buffer (malloc/realloc, memcpy)
	// 5. Removing underflow from prebuffer (memmove)
	// 
	// Comparing the performance of the two we can see that reading
	// data into the prebuffer first is slower due to the extra memove.
	// 
	// However:
	// The implementation of NSMutableData is open source via core foundation's CFMutableData.
	// Decreasing the length of a mutable data object doesn't cause a realloc.
	// In other words, the capacity of a mutable data object can grow, but doesn't shrink.
	// 
	// This means the prebuffer will rarely need a realloc.
	// The packet buffer, on the other hand, may often need a realloc.
	// This is especially true if we are the buffer owner.
	// Furthermore, if we are constantly realloc'ing the packet buffer,
	// and then moving the overflow into the prebuffer,
	// then we're consistently over-allocating memory for each term read.
	// And now we get into a bit of a tradeoff between speed and memory utilization.
	// 
	// The end result is that the two perform very similarly.
	// And we can answer the original question very simply by another means.
	// 
	// If we can read all the data directly into the packet's buffer without resizing it first,
	// then we do so. Otherwise we use the prebuffer.
	
	if (shouldPreBufferPtr)
	{
		NSUInteger buffSize = [buffer length];
		NSUInteger buffUsed = startOffset + bytesDone;
		
		if ((buffSize - buffUsed) >= result)
			*shouldPreBufferPtr = NO;
		else
			*shouldPreBufferPtr = YES;
	}
	
	return result;
}

/**
 * For read packets with a set terminator,
 * returns the amount of data that can be read from the given preBuffer,
 * without going over a terminator or the maxLength.
 * 
 * It is assumed the terminator has not already been read.
**/
- (NSUInteger)readLengthForTermWithPreBuffer:(GCDAsyncSocketPreBuffer *)preBuffer found:(BOOL *)foundPtr
{
	NSAssert(term != nil, @"This method does not apply to non-term reads");
	NSAssert([preBuffer availableBytes] > 0, @"Invoked with empty pre buffer!");
	
	// We know that the terminator, as a whole, doesn't exist in our own buffer.
	// But it is possible that a _portion_ of it exists in our buffer.
	// So we're going to look for the terminator starting with a portion of our own buffer.
	// 
	// Example:
	// 
	// term length      = 3 bytes
	// bytesDone        = 5 bytes
	// preBuffer length = 5 bytes
	// 
	// If we append the preBuffer to our buffer,
	// it would look like this:
	// 
	// ---------------------
	// |B|B|B|B|B|P|P|P|P|P|
	// ---------------------
	// 
	// So we start our search here:
	// 
	// ---------------------
	// |B|B|B|B|B|P|P|P|P|P|
	// -------^-^-^---------
	// 
	// And move forwards...
	// 
	// ---------------------
	// |B|B|B|B|B|P|P|P|P|P|
	// ---------^-^-^-------
	// 
	// Until we find the terminator or reach the end.
	// 
	// ---------------------
	// |B|B|B|B|B|P|P|P|P|P|
	// ---------------^-^-^-
	
	BOOL found = NO;
	
	NSUInteger termLength = [term length];
	NSUInteger preBufferLength = [preBuffer availableBytes];
	
	if ((bytesDone + preBufferLength) < termLength)
	{
		// Not enough data for a full term sequence yet
		return preBufferLength;
	}
	
	NSUInteger maxPreBufferLength;
	if (maxLength > 0) {
		maxPreBufferLength = MIN(preBufferLength, (maxLength - bytesDone));
		
		// Note: maxLength >= termLength
	}
	else {
		maxPreBufferLength = preBufferLength;
	}
	
	uint8_t seq[termLength];
	const void *termBuf = [term bytes];
	
	NSUInteger bufLen = MIN(bytesDone, (termLength - 1));
	uint8_t *buf = (uint8_t *)[buffer mutableBytes] + startOffset + bytesDone - bufLen;
	
	NSUInteger preLen = termLength - bufLen;
	const uint8_t *pre = [preBuffer readBuffer];
	
	NSUInteger loopCount = bufLen + maxPreBufferLength - termLength + 1; // Plus one. See example above.
	
	NSUInteger result = maxPreBufferLength;
	
	NSUInteger i;
	for (i = 0; i < loopCount; i++)
	{
		if (bufLen > 0)
		{
			// Combining bytes from buffer and preBuffer
			
			memcpy(seq, buf, bufLen);
			memcpy(seq + bufLen, pre, preLen);
			
			if (memcmp(seq, termBuf, termLength) == 0)
			{
				result = preLen;
				found = YES;
				break;
			}
			
			buf++;
			bufLen--;
			preLen++;
		}
		else
		{
			// Comparing directly from preBuffer
			
			if (memcmp(pre, termBuf, termLength) == 0)
			{
				NSUInteger preOffset = pre - [preBuffer readBuffer]; // pointer arithmetic
				
				result = preOffset + termLength;
				found = YES;
				break;
			}
			
			pre++;
		}
	}
	
	// There is no need to avoid resizing the buffer in this particular situation.
	
	if (foundPtr) *foundPtr = found;
	return result;
}

/**
 * For read packets with a set terminator, scans the packet buffer for the term.
 * It is assumed the terminator had not been fully read prior to the new bytes.
 * 
 * If the term is found, the number of excess bytes after the term are returned.
 * If the term is not found, this method will return -1.
 * 
 * Note: A return value of zero means the term was found at the very end.
 * 
 * Prerequisites:
 * The given number of bytes have been added to the end of our buffer.
 * Our bytesDone variable has NOT been changed due to the prebuffered bytes.
**/
- (NSInteger)searchForTermAfterPreBuffering:(ssize_t)numBytes
{
	NSAssert(term != nil, @"This method does not apply to non-term reads");
	
	// The implementation of this method is very similar to the above method.
	// See the above method for a discussion of the algorithm used here.
	
	uint8_t *buff = [buffer mutableBytes];
	NSUInteger buffLength = bytesDone + numBytes;
	
	const void *termBuff = [term bytes];
	NSUInteger termLength = [term length];
	
	// Note: We are dealing with unsigned integers,
	// so make sure the math doesn't go below zero.
	
	NSUInteger i = ((buffLength - numBytes) >= termLength) ? (buffLength - numBytes - termLength + 1) : 0;
	
	while (i + termLength <= buffLength)
	{
		uint8_t *subBuffer = buff + startOffset + i;
		
		if (memcmp(subBuffer, termBuff, termLength) == 0)
		{
			return buffLength - (i + termLength);
		}
		
		i++;
	}
	
	return -1;
}


@end

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
#pragma mark -
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

/**
 * The GCDAsyncWritePacket encompasses the instructions for any given write.
**/
@interface GCDAsyncWritePacket : NSObject
{
  @public
	NSData *buffer;
	NSUInteger bytesDone;
	long tag;
	NSTimeInterval timeout;
}
- (id)initWithData:(NSData *)d timeout:(NSTimeInterval)t tag:(long)i;
@end

@implementation GCDAsyncWritePacket

- (id)initWithData:(NSData *)d timeout:(NSTimeInterval)t tag:(long)i
{
	if((self = [super init]))
	{
		buffer = d; // Retain not copy. For performance as documented in header file.
		bytesDone = 0;
		timeout = t;
		tag = i;
	}
	return self;
}


@end

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
#pragma mark -
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

/**
 * The GCDAsyncSpecialPacket encompasses special instructions for interruptions in the read/write queues.
 * This class my be altered to support more than just TLS in the future.
**/
@interface GCDAsyncSpecialPacket : NSObject
{
  @public
	NSDictionary *tlsSettings;
}
- (id)initWithTLSSettings:(NSDictionary *)settings;
@end

@implementation GCDAsyncSpecialPacket

- (id)initWithTLSSettings:(NSDictionary *)settings
{
	if((self = [super init]))
	{
		tlsSettings = [settings copy];
	}
	return self;
}


@end

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
#pragma mark -
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

@implementation GCDAsyncSocket

- (id)init
{
	return [self initWithDelegate:nil delegateQueue:NULL socketQueue:NULL];
}

- (id)initWithSocketQueue:(dispatch_queue_t)sq
{
	return [self initWithDelegate:nil delegateQueue:NULL socketQueue:sq];
}

- (id)initWithDelegate:(id)aDelegate delegateQueue:(dispatch_queue_t)dq
{
	return [self initWithDelegate:aDelegate delegateQueue:dq socketQueue:NULL];
}

- (id)initWithDelegate:(id)aDelegate delegateQueue:(dispatch_queue_t)dq socketQueue:(dispatch_queue_t)sq
{
	if((self = [super init]))
	{
		delegate = aDelegate;
		delegateQueue = dq;
		
		#if NEEDS_DISPATCH_RETAIN_RELEASE
		if (dq) dispatch_retain(dq);
		#endif
		
		socket4FD = SOCKET_NULL;
		socket6FD = SOCKET_NULL;
		socketUN = SOCKET_NULL;
		socketUrl = nil;
		connectIndex = 0;
		
		if (sq)
		{
			NSAssert(sq != dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0),
			         @"The given socketQueue parameter must not be a concurrent queue.");
			NSAssert(sq != dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0),
			         @"The given socketQueue parameter must not be a concurrent queue.");
			NSAssert(sq != dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0),
			         @"The given socketQueue parameter must not be a concurrent queue.");
			
			socketQueue = sq;
			#if NEEDS_DISPATCH_RETAIN_RELEASE
			dispatch_retain(sq);
			#endif
		}
		else
		{
			socketQueue = dispatch_queue_create([GCDAsyncSocketQueueName UTF8String], NULL);
		}
		
		readQueue = [[NSMutableArray alloc] initWithCapacity:5];
		currentRead = nil;
		
		writeQueue = [[NSMutableArray alloc] initWithCapacity:5];
		currentWrite = nil;
		
		preBuffer = [[GCDAsyncSocketPreBuffer alloc] initWithCapacity:(1024 * 4)];
	}
	return self;
}

- (void)dealloc
{
	LogInfo(@"%@ - %@ (start)", THIS_METHOD, self);
	
	if (dispatch_get_current_queue() == socketQueue)
	{
		[self closeWithError:nil];
	}
	else
	{
		dispatch_sync(socketQueue, ^{
			[self closeWithError:nil];
		});
	}
	
	delegate = nil;
	
	#if NEEDS_DISPATCH_RETAIN_RELEASE
	if (delegateQueue) dispatch_release(delegateQueue);
	#endif
	delegateQueue = NULL;
	
	#if NEEDS_DISPATCH_RETAIN_RELEASE
	if (socketQueue) dispatch_release(socketQueue);
	#endif
	socketQueue = NULL;
	
	LogInfo(@"%@ - %@ (finish)", THIS_METHOD, self);
}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
#pragma mark Configuration
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

- (id)delegate
{
	if (dispatch_get_current_queue() == socketQueue)
	{
		return delegate;
	}
	else
	{
		__block id result;
		
		dispatch_sync(socketQueue, ^{
			result = delegate;
		});
		
		return result;
	}
}

- (void)setDelegate:(id)newDelegate synchronously:(BOOL)synchronously
{
	dispatch_block_t block = ^{
		delegate = newDelegate;
	};
	
	if (dispatch_get_current_queue() == socketQueue) {
		block();
	}
	else {
		if (synchronously)
			dispatch_sync(socketQueue, block);
		else
			dispatch_async(socketQueue, block);
	}
}

- (void)setDelegate:(id)newDelegate
{
	[self setDelegate:newDelegate synchronously:NO];
}

- (void)synchronouslySetDelegate:(id)newDelegate
{
	[self setDelegate:newDelegate synchronously:YES];
}

- (dispatch_queue_t)delegateQueue
{
	if (dispatch_get_current_queue() == socketQueue)
	{
		return delegateQueue;
	}
	else
	{
		__block dispatch_queue_t result;
		
		dispatch_sync(socketQueue, ^{
			result = delegateQueue;
		});
		
		return result;
	}
}

- (void)setDelegateQueue:(dispatch_queue_t)newDelegateQueue synchronously:(BOOL)synchronously
{
	dispatch_block_t block = ^{
		
		#if NEEDS_DISPATCH_RETAIN_RELEASE
		if (delegateQueue) dispatch_release(delegateQueue);
		if (newDelegateQueue) dispatch_retain(newDelegateQueue);
		#endif
		
		delegateQueue = newDelegateQueue;
	};
	
	if (dispatch_get_current_queue() == socketQueue) {
		block();
	}
	else {
		if (synchronously)
			dispatch_sync(socketQueue, block);
		else
			dispatch_async(socketQueue, block);
	}
}

- (void)setDelegateQueue:(dispatch_queue_t)newDelegateQueue
{
	[self setDelegateQueue:newDelegateQueue synchronously:NO];
}

- (void)synchronouslySetDelegateQueue:(dispatch_queue_t)newDelegateQueue
{
	[self setDelegateQueue:newDelegateQueue synchronously:YES];
}

- (void)getDelegate:(id *)delegatePtr delegateQueue:(dispatch_queue_t *)delegateQueuePtr
{
	if (dispatch_get_current_queue() == socketQueue)
	{
		if (delegatePtr) *delegatePtr = delegate;
		if (delegateQueuePtr) *delegateQueuePtr = delegateQueue;
	}
	else
	{
		__block id dPtr = NULL;
		__block dispatch_queue_t dqPtr = NULL;
		
		dispatch_sync(socketQueue, ^{
			dPtr = delegate;
			dqPtr = delegateQueue;
		});
		
		if (delegatePtr) *delegatePtr = dPtr;
		if (delegateQueuePtr) *delegateQueuePtr = dqPtr;
	}
}

- (void)setDelegate:(id)newDelegate delegateQueue:(dispatch_queue_t)newDelegateQueue synchronously:(BOOL)synchronously
{
	dispatch_block_t block = ^{
		
		delegate = newDelegate;
		
		#if NEEDS_DISPATCH_RETAIN_RELEASE
		if (delegateQueue) dispatch_release(delegateQueue);
		if (newDelegateQueue) dispatch_retain(newDelegateQueue);
		#endif
		
		delegateQueue = newDelegateQueue;
	};
	
	if (dispatch_get_current_queue() == socketQueue) {
		block();
	}
	else {
		if (synchronously)
			dispatch_sync(socketQueue, block);
		else
			dispatch_async(socketQueue, block);
	}
}

- (void)setDelegate:(id)newDelegate delegateQueue:(dispatch_queue_t)newDelegateQueue
{
	[self setDelegate:newDelegate delegateQueue:newDelegateQueue synchronously:NO];
}

- (void)synchronouslySetDelegate:(id)newDelegate delegateQueue:(dispatch_queue_t)newDelegateQueue
{
	[self setDelegate:newDelegate delegateQueue:newDelegateQueue synchronously:YES];
}

- (BOOL)autoDisconnectOnClosedReadStream
{
	// Note: YES means kAllowHalfDuplexConnection is OFF
	
	if (dispatch_get_current_queue() == socketQueue)
	{
		return ((config & kAllowHalfDuplexConnection) == 0);
	}
	else
	{
		__block BOOL result;
		
		dispatch_sync(socketQueue, ^{
			result = ((config & kAllowHalfDuplexConnection) == 0);
		});
		
		return result;
	}
}

- (void)setAutoDisconnectOnClosedReadStream:(BOOL)flag
{
	// Note: YES means kAllowHalfDuplexConnection is OFF
	
	dispatch_block_t block = ^{
		
		if (flag)
			config &= ~kAllowHalfDuplexConnection;
		else
			config |= kAllowHalfDuplexConnection;
	};
	
	if (dispatch_get_current_queue() == socketQueue)
		block();
	else
		dispatch_async(socketQueue, block);
}

- (BOOL)isIPv4Enabled
{
	// Note: YES means kIPv4Disabled is OFF
	
	if (dispatch_get_current_queue() == socketQueue)
	{
		return ((config & kIPv4Disabled) == 0);
	}
	else
	{
		__block BOOL result;
		
		dispatch_sync(socketQueue, ^{
			result = ((config & kIPv4Disabled) == 0);
		});
		
		return result;
	}
}

- (void)setIPv4Enabled:(BOOL)flag
{
	// Note: YES means kIPv4Disabled is OFF
	
	dispatch_block_t block = ^{
		
		if (flag)
			config &= ~kIPv4Disabled;
		else
			config |= kIPv4Disabled;
	};
	
	if (dispatch_get_current_queue() == socketQueue)
		block();
	else
		dispatch_async(socketQueue, block);
}

- (BOOL)isIPv6Enabled
{
	// Note: YES means kIPv6Disabled is OFF
	
	if (dispatch_get_current_queue() == socketQueue)
	{
		return ((config & kIPv6Disabled) == 0);
	}
	else
	{
		__block BOOL result;
		
		dispatch_sync(socketQueue, ^{
			result = ((config & kIPv6Disabled) == 0);
		});
		
		return result;
	}
}

- (void)setIPv6Enabled:(BOOL)flag
{
	// Note: YES means kIPv6Disabled is OFF
	
	dispatch_block_t block = ^{
		
		if (flag)
			config &= ~kIPv6Disabled;
		else
			config |= kIPv6Disabled;
	};
	
	if (dispatch_get_current_queue() == socketQueue)
		block();
	else
		dispatch_async(socketQueue, block);
}

- (BOOL)isIPv4PreferredOverIPv6
{
	// Note: YES means kPreferIPv6 is OFF
	
	if (dispatch_get_current_queue() == socketQueue)
	{
		return ((config & kPreferIPv6) == 0);
	}
	else
	{
		__block BOOL result;
		
		dispatch_sync(socketQueue, ^{
			result = ((config & kPreferIPv6) == 0);
		});
		
		return result;
	}
}

- (void)setPreferIPv4OverIPv6:(BOOL)flag
{
	// Note: YES means kPreferIPv6 is OFF
	
	dispatch_block_t block = ^{
		
		if (flag)
			config &= ~kPreferIPv6;
		else
			config |= kPreferIPv6;
	};
	
	if (dispatch_get_current_queue() == socketQueue)
		block();
	else
		dispatch_async(socketQueue, block);
}

- (id)userData
{
	__block id result = nil;
	
	dispatch_block_t block = ^{
		
		result = userData;
	};
	
	if (dispatch_get_current_queue() == socketQueue)
		block();
	else
		dispatch_sync(socketQueue, block);
	
	return result;
}

- (void)setUserData:(id)arbitraryUserData
{
	dispatch_block_t block = ^{
		
		if (userData != arbitraryUserData)
		{
			userData = arbitraryUserData;
		}
	};
	
	if (dispatch_get_current_queue() == socketQueue)
		block();
	else
		dispatch_async(socketQueue, block);
}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
#pragma mark Accepting
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

- (BOOL)acceptOnPort:(uint16_t)port error:(NSError **)errPtr
{
	return [self acceptOnInterface:nil port:port error:errPtr];
}

- (BOOL)acceptOnInterface:(NSString *)inInterface port:(uint16_t)port error:(NSError **)errPtr
{
	LogTrace();
	
	// Just in-case interface parameter is immutable.
	NSString *interface = [inInterface copy];
	
	__block BOOL result = NO;
	__block NSError *err = nil;
	
	// CreateSocket Block
	// This block will be invoked within the dispatch block below.
	
	int(^createSocket)(int, NSData*) = ^int (int domain, NSData *interfaceAddr) {
		
		int socketFD = socket(domain, SOCK_STREAM, 0);
		
		if (socketFD == SOCKET_NULL)
		{
			NSString *reason = @"Error in socket() function";
			err = [self errnoErrorWithReason:reason];
			
			return SOCKET_NULL;
		}
		
		int status;
		
		// Set socket options
		
		status = fcntl(socketFD, F_SETFL, O_NONBLOCK);
		if (status == -1)
		{
			NSString *reason = @"Error enabling non-blocking IO on socket (fcntl)";
			err = [self errnoErrorWithReason:reason];
			
			LogVerbose(@"close(socketFD)");
			close(socketFD);
			return SOCKET_NULL;
		}
		
		int reuseOn = 1;
		status = setsockopt(socketFD, SOL_SOCKET, SO_REUSEADDR, &reuseOn, sizeof(reuseOn));
		if (status == -1)
		{
			NSString *reason = @"Error enabling address reuse (setsockopt)";
			err = [self errnoErrorWithReason:reason];
			
			LogVerbose(@"close(socketFD)");
			close(socketFD);
			return SOCKET_NULL;
		}
		
		// Bind socket
		
		const struct sockaddr *addr = (const struct sockaddr *)[interfaceAddr bytes];
		status = bind(socketFD, addr, addr->sa_len);
		if (status == -1)
		{
			NSString *reason = @"Error in bind() function";
			err = [self errnoErrorWithReason:reason];
			
			LogVerbose(@"close(socketFD)");
			close(socketFD);
			return SOCKET_NULL;
		}
		
		// Listen
		
		status = listen(socketFD, 1024);
		if (status == -1)
		{
			NSString *reason = @"Error in listen() function";
			err = [self errnoErrorWithReason:reason];
			
			LogVerbose(@"close(socketFD)");
			close(socketFD);
			return SOCKET_NULL;
		}
		
		return socketFD;
	};
	
	// Create dispatch block and run on socketQueue
	
	dispatch_block_t block = ^{ @autoreleasepool {
		
		if (delegate == nil) // Must have delegate set
		{
			NSString *msg = @"Attempting to accept without a delegate. Set a delegate first.";
			err = [self badConfigError:msg];
			
			return_from_block;
		}
		
		if (delegateQueue == NULL) // Must have delegate queue set
		{
			NSString *msg = @"Attempting to accept without a delegate queue. Set a delegate queue first.";
			err = [self badConfigError:msg];
			
			return_from_block;
		}
		
		BOOL isIPv4Disabled = (config & kIPv4Disabled) ? YES : NO;
		BOOL isIPv6Disabled = (config & kIPv6Disabled) ? YES : NO;
		
		if (isIPv4Disabled && isIPv6Disabled) // Must have IPv4 or IPv6 enabled
		{
			NSString *msg = @"Both IPv4 and IPv6 have been disabled. Must enable at least one protocol first.";
			err = [self badConfigError:msg];
			
			return_from_block;
		}
		
		if (![self isDisconnected]) // Must be disconnected
		{
			NSString *msg = @"Attempting to accept while connected or accepting connections. Disconnect first.";
			err = [self badConfigError:msg];
			
			return_from_block;
		}
		
		// Clear queues (spurious read/write requests post disconnect)
		[readQueue removeAllObjects];
		[writeQueue removeAllObjects];
		
		// Resolve interface from description
		
		NSMutableData *interface4 = nil;
		NSMutableData *interface6 = nil;
		
		[self getInterfaceAddress4:&interface4 address6:&interface6 fromDescription:interface port:port];
		
		if ((interface4 == nil) && (interface6 == nil))
		{
			NSString *msg = @"Unknown interface. Specify valid interface by name (e.g. \"en1\") or IP address.";
			err = [self badParamError:msg];
			
			return_from_block;
		}
		
		if (isIPv4Disabled && (interface6 == nil))
		{
			NSString *msg = @"IPv4 has been disabled and specified interface doesn't support IPv6.";
			err = [self badParamError:msg];
			
			return_from_block;
		}
		
		if (isIPv6Disabled && (interface4 == nil))
		{
			NSString *msg = @"IPv6 has been disabled and specified interface doesn't support IPv4.";
			err = [self badParamError:msg];
			
			return_from_block;
		}
		
		BOOL enableIPv4 = !isIPv4Disabled && (interface4 != nil);
		BOOL enableIPv6 = !isIPv6Disabled && (interface6 != nil);
		
		// Create sockets, configure, bind, and listen
		
		if (enableIPv4)
		{
			LogVerbose(@"Creating IPv4 socket");
			socket4FD = createSocket(AF_INET, interface4);
			
			if (socket4FD == SOCKET_NULL)
			{
				return_from_block;
			}
		}
		
		if (enableIPv6)
		{
			LogVerbose(@"Creating IPv6 socket");
			
			if (enableIPv4 && (port == 0))
			{
				// No specific port was specified, so we allowed the OS to pick an available port for us.
				// Now we need to make sure the IPv6 socket listens on the same port as the IPv4 socket.
				
				struct sockaddr_in6 *addr6 = (struct sockaddr_in6 *)[interface6 mutableBytes];
				addr6->sin6_port = htons([self localPort4]);
			}
			
			socket6FD = createSocket(AF_INET6, interface6);
			
			if (socket6FD == SOCKET_NULL)
			{
				if (socket4FD != SOCKET_NULL)
				{
					LogVerbose(@"close(socket4FD)");
					close(socket4FD);
				}
				
				return_from_block;
			}
		}
		
		// Create accept sources
		
		if (enableIPv4)
		{
			accept4Source = dispatch_source_create(DISPATCH_SOURCE_TYPE_READ, socket4FD, 0, socketQueue);
			
			int socketFD = socket4FD;
			dispatch_source_t acceptSource = accept4Source;
			
			dispatch_source_set_event_handler(accept4Source, ^{ @autoreleasepool {
				
				LogVerbose(@"event4Block");
				
				unsigned long i = 0;
				unsigned long numPendingConnections = dispatch_source_get_data(acceptSource);
				
				LogVerbose(@"numPendingConnections: %lu", numPendingConnections);
				
				while ([self doAccept:socketFD] && (++i < numPendingConnections));
			}});
			
			dispatch_source_set_cancel_handler(accept4Source, ^{
				
				#if NEEDS_DISPATCH_RETAIN_RELEASE
				LogVerbose(@"dispatch_release(accept4Source)");
				dispatch_release(acceptSource);
				#endif
				
				LogVerbose(@"close(socket4FD)");
				close(socketFD);
			});
			
			LogVerbose(@"dispatch_resume(accept4Source)");
			dispatch_resume(accept4Source);
		}
		
		if (enableIPv6)
		{
			accept6Source = dispatch_source_create(DISPATCH_SOURCE_TYPE_READ, socket6FD, 0, socketQueue);
			
			int socketFD = socket6FD;
			dispatch_source_t acceptSource = accept6Source;
			
			dispatch_source_set_event_handler(accept6Source, ^{ @autoreleasepool {
				
				LogVerbose(@"event6Block");
				
				unsigned long i = 0;
				unsigned long numPendingConnections = dispatch_source_get_data(acceptSource);
				
				LogVerbose(@"numPendingConnections: %lu", numPendingConnections);
				
				while ([self doAccept:socketFD] && (++i < numPendingConnections));
			}});
			
			dispatch_source_set_cancel_handler(accept6Source, ^{
				
				#if NEEDS_DISPATCH_RETAIN_RELEASE
				LogVerbose(@"dispatch_release(accept6Source)");
				dispatch_release(acceptSource);
				#endif
				
				LogVerbose(@"close(socket6FD)");
				close(socketFD);
			});
			
			LogVerbose(@"dispatch_resume(accept6Source)");
			dispatch_resume(accept6Source);
		}
		
		flags |= kSocketStarted;
		
		result = YES;
	}};
	
	if (dispatch_get_current_queue() == socketQueue)
		block();
	else
		dispatch_sync(socketQueue, block);
	
	if (result == NO)
	{
		LogInfo(@"Error in accept: %@", err);
		
		if (errPtr)
			*errPtr = err;
	}
	
	return result;
}

- (BOOL)acceptOnUrl:(NSURL *)url error:(NSError **)errPtr;
{
	LogTrace();
	
	__block BOOL result = NO;
	__block NSError *err = nil;
	
	// CreateSocket Block
	// This block will be invoked within the dispatch block below.
	
	int(^createSocket)(int, NSData*) = ^int (int domain, NSData *interfaceAddr) {
		
		int socketFD = socket(domain, SOCK_STREAM, 0);
		
		if (socketFD == SOCKET_NULL)
		{
			NSString *reason = @"Error in socket() function";
			err = [self errnoErrorWithReason:reason];
			
			return SOCKET_NULL;
		}
		
		int status;
		
		// Set socket options
		
		status = fcntl(socketFD, F_SETFL, O_NONBLOCK);
		if (status == -1)
		{
			NSString *reason = @"Error enabling non-blocking IO on socket (fcntl)";
			err = [self errnoErrorWithReason:reason];
			
			LogVerbose(@"close(socketFD)");
			close(socketFD);
			return SOCKET_NULL;
		}
		
		int reuseOn = 1;
		status = setsockopt(socketFD, SOL_SOCKET, SO_REUSEADDR, &reuseOn, sizeof(reuseOn));
		if (status == -1)
		{
			NSString *reason = @"Error enabling address reuse (setsockopt)";
			err = [self errnoErrorWithReason:reason];
			
			LogVerbose(@"close(socketFD)");
			close(socketFD);
			return SOCKET_NULL;
		}
		
		// Bind socket
		
		status = bind(socketFD, (const struct sockaddr *)[interfaceAddr bytes], (socklen_t)[interfaceAddr length]);
		if (status == -1)
		{
			NSString *reason = @"Error in bind() function";
			err = [self errnoErrorWithReason:reason];
			
			LogVerbose(@"close(socketFD)");
			close(socketFD);
			return SOCKET_NULL;
		}
		
		// Listen
		
		status = listen(socketFD, 1024);
		if (status == -1)
		{
			NSString *reason = @"Error in listen() function";
			err = [self errnoErrorWithReason:reason];
			
			LogVerbose(@"close(socketFD)");
			close(socketFD);
			return SOCKET_NULL;
		}
		
		return socketFD;
	};
	
	// Create dispatch block and run on socketQueue
	
	dispatch_block_t block = ^{ @autoreleasepool {
		
		if (delegate == nil) // Must have delegate set
		{
			NSString *msg = @"Attempting to accept without a delegate. Set a delegate first.";
			err = [self badConfigError:msg];
			
			return_from_block;
		}
		
		if (delegateQueue == NULL) // Must have delegate queue set
		{
			NSString *msg = @"Attempting to accept without a delegate queue. Set a delegate queue first.";
			err = [self badConfigError:msg];
			
			return_from_block;
		}
		
		if (![self isDisconnected]) // Must be disconnected
		{
			NSString *msg = @"Attempting to accept while connected or accepting connections. Disconnect first.";
			err = [self badConfigError:msg];
			
			return_from_block;
		}
		
		// Clear queues (spurious read/write requests post disconnect)
		[readQueue removeAllObjects];
		[writeQueue removeAllObjects];
		
		// Remove a previous socket
		
		NSError *error = nil;
		NSFileManager *fileManager = [NSFileManager defaultManager];
		if ([fileManager fileExistsAtPath:url.path]) {
			if (![[NSFileManager defaultManager] removeItemAtURL:url error:&error]) {
				NSString *msg = @"Could not remove previous unix domain socket at given url.";
				err…