Source/MessageQueue.m

   1 /*
   2  * MacGDBp
   3  * Copyright (c) 2013, Blue Static <http://www.bluestatic.org>
   4  *
   5  * This program is free software; you can redistribute it and/or modify it under the terms of the GNU
   6  * General Public License as published by the Free Software Foundation; either version 2 of the
   7  * License, or (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
  10  * even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along with this program; if not,
  14  * write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
  15  */
  16
  17 #import "MessageQueue.h"
  18
  19 #include <dispatch/dispatch.h>
  20 #include <netinet/in.h>
  21 #include <stdlib.h>
  22 #include <sys/socket.h>
  23 #include <sys/types.h>
  24 #include <unistd.h>
  25
  26 #import "BSProtocolThreadInvoker.h"
  27
  28 @implementation MessageQueue {
  29   // The port number on which to open a listening socket.
  30   NSUInteger _port;
  31
  32   // All the ivars beneath this must be accessed from this queue.
  33   //////////////////////////////////////////////////////////////////////////////
  34   dispatch_queue_t _dispatchQueue;
  35
  36   // Whether or not the message queue is connected to a client.
  37   BOOL _connected;
  38
  39   // A queue of messages that are waiting to be sent.
  40   NSMutableArray* _messageQueue;
  41
  42   // The delegate for this class.
  43   BSProtocolThreadInvoker<MessageQueueDelegate>* _delegate;
  44
  45   // The socket for the queue. This will either be a listening socket, waiting
  46   // to accept connections. Or it will be a connected socket with a server.
  47   int _socket;
  48
  49   // The dispatch sources for |_socket|, run on |_dispatchQueue|. If this is
  50   // for a listening socket, only |_readSource| will be non-NULL. If
  51   // |_connected| is false, both will be NULL.
  52   dispatch_source_t _readSource;
  53   dispatch_source_t _writeSource;
  54
  55   // Whether |_writeSource| has been suspended through |-dequeueAndSend|.
  56   BOOL _writeSuspended;
  57
  58   // When a message is being read, this temporary buffer is used to build up
  59   // the complete message from successive reads.
  60   NSMutableString* _message;
  61   NSUInteger _totalMessageSize;
  62   NSUInteger _messageSize;
  63 }
  64
  65 - (id)initWithPort:(NSUInteger)port delegate:(id<MessageQueueDelegate>)delegate {
  66   if ((self = [super init])) {
  67     _port = port;
  68     _dispatchQueue = dispatch_queue_create(
  69         [[NSString stringWithFormat:@"org.bluestatic.MacGDBp.MessageQueue.%p", self] UTF8String],
  70         DISPATCH_QUEUE_SERIAL);
  71     _messageQueue = [[NSMutableArray alloc] init];
  72     _delegate = (BSProtocolThreadInvoker<MessageQueueDelegate>*)
  73         [[BSProtocolThreadInvoker alloc] initWithObject:delegate
  74                                          protocol:@protocol(MessageQueueDelegate)
  75                                            thread:[NSThread currentThread]];
  76     _socket = -1;
  77   }
  78   return self;
  79 }
  80
  81 - (void)dealloc {
  82   dispatch_sync(_dispatchQueue, ^{ [self disconnectClient]; });
  83   dispatch_release(_dispatchQueue);
  84   [_messageQueue release];
  85   [_delegate release];
  86   [super dealloc];
  87 }
  88
  89 - (BOOL)isConnected {
  90   BOOL __block connected;
  91   dispatch_sync(_dispatchQueue, ^{ connected = _connected; });
  92   return connected;
  93 }
  94
  95 - (void)connect {
  96   dispatch_async(_dispatchQueue, ^{
  97     if (_connected)
  98       return;
  99
 100     [self openListeningSocket];
 101   });
 102 }
 103
 104 - (void)disconnect {
 105   dispatch_async(_dispatchQueue, ^{ [self disconnectClient]; });
 106 }
 107
 108 - (void)sendMessage:(NSString*)message {
 109   dispatch_async(_dispatchQueue, ^{
 110     [_messageQueue addObject:message];
 111     [self dequeueAndSend];
 112   });
 113 }
 114
 115 // Private /////////////////////////////////////////////////////////////////////
 116
 117 - (void)openListeningSocket {
 118   // Create a socket.
 119   _socket = socket(PF_INET, SOCK_STREAM, 0);
 120   if (_socket < 0) {
 121     NSLog(@"Could not connect to socket: %d %s", errno, strerror(errno));
 122     return;
 123   }
 124
 125   // Allow old, yet-to-be recycled sockets to be reused.
 126   int yes = 1;
 127   setsockopt(_socket, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int));
 128   setsockopt(_socket, SOL_SOCKET, SO_REUSEPORT, &yes, sizeof(int));
 129
 130   // Bind to the address.
 131   struct sockaddr_in address = {0};
 132   address.sin_len = sizeof(address);
 133   address.sin_family = AF_INET;
 134   address.sin_port = htons(_port);
 135   address.sin_addr.s_addr = htonl(INADDR_ANY);
 136
 137   int rv;
 138   do {
 139     rv = bind(_socket, (struct sockaddr*)&address, sizeof(address));
 140     if (rv !=  0) {
 141       NSLog(@"Could not bind to socket: %d, %s", errno, strerror(errno));
 142     }
 143   } while (rv != 0);
 144
 145   // Listen for a connection.
 146   rv = listen(_socket, 1);
 147   if (rv < 0) {
 148     NSLog(@"Could not listen on socket: %d, %s", errno, strerror(errno));
 149     close(_socket);
 150     _socket = -1;
 151     return;
 152   }
 153   _readSource = dispatch_source_create(DISPATCH_SOURCE_TYPE_READ, _socket, 0, _dispatchQueue);
 154   dispatch_source_set_event_handler(_readSource, ^{
 155     [self acceptConnection];
 156   });
 157   dispatch_resume(_readSource);
 158
 159   _connected = YES;
 160 }
 161
 162 // Closes down the listening socket, the child socket, and the streams.
 163 - (void)disconnectClient {
 164   if (!_connected)
 165     return;
 166
 167   if (_readSource) {
 168     dispatch_source_cancel(_readSource);
 169     dispatch_release(_readSource);
 170     _readSource = NULL;
 171   }
 172
 173   if (_writeSource) {
 174     if (_writeSuspended) {
 175       _writeSuspended = NO;
 176       dispatch_resume(_writeSource);
 177     }
 178     dispatch_source_cancel(_writeSource);
 179     dispatch_release(_writeSource);
 180     _writeSource = NULL;
 181   }
 182
 183   if (_socket != -1) {
 184     close(_socket);
 185     _socket = -1;
 186   }
 187
 188   [_messageQueue removeAllObjects];
 189
 190   _connected = NO;
 191   [_delegate messageQueueDidDisconnect:self];
 192 }
 193
 194 // If the write stream is ready and there is data to send, sends the next message.
 195 - (void)dequeueAndSend {
 196   if ([_messageQueue count] == 0) {
 197     // There are no outgoing messages, so suspend the dispatch source to avoid
 198     // needless callouts to this method.
 199     if (_writeSource) {
 200       _writeSuspended = YES;
 201       dispatch_suspend(_writeSource);
 202     }
 203     return;
 204   } else if (_writeSuspended) {
 205     // A new message has arrived with the source suspended. Resume it, which
 206     // will arrange for a callout back here when the socket is ready.
 207     _writeSuspended = NO;
 208     dispatch_resume(_writeSource);
 209     return;
 210   }
 211
 212   NSString* message = [_messageQueue objectAtIndex:0];
 213   [self performSend:message];
 214   [_messageQueue removeObjectAtIndex:0];
 215 }
 216
 217 // Writes the string into the write stream.
 218 - (void)performSend:(NSString*)message {
 219   // TODO: May need to negotiate with the server as to the string encoding.
 220   const NSStringEncoding kEncoding = NSUTF8StringEncoding;
 221   // Add space for the NUL byte.
 222   NSUInteger maxBufferSize = [message maximumLengthOfBytesUsingEncoding:kEncoding] + 1;
 223
 224   UInt8* buffer = calloc(maxBufferSize, sizeof(UInt8));
 225   NSUInteger bufferSize = 0;
 226   if (![message getBytes:buffer
 227                maxLength:maxBufferSize
 228               usedLength:&bufferSize
 229                 encoding:kEncoding
 230                  options:0
 231                    range:NSMakeRange(0, [message length])
 232           remainingRange:NULL]) {
 233     free(buffer);
 234     return;
 235   }
 236
 237   // Include a NUL byte.
 238   ++bufferSize;
 239
 240   // Write the packet out, and spin in a busy wait loop if the stream is not ready. This
 241   // method is only ever called in response to a stream ready event.
 242   NSUInteger totalWritten = 0;
 243   while (totalWritten < bufferSize) {
 244     ssize_t bytesWritten = write(_socket, buffer + totalWritten, bufferSize - totalWritten);
 245     if (bytesWritten < 0) {
 246       NSLog(@"Failed to write to stream: %d, %s", errno, strerror(errno));
 247       break;
 248     }
 249     totalWritten += bytesWritten;
 250   }
 251
 252   [_delegate messageQueue:self didSendMessage:message];
 253
 254   free(buffer);
 255 }
 256
 257 // Reads bytes out of the read stream. This may be called multiple times if the
 258 // message cannot be read in one pass.
 259 - (void)readMessageFromStream {
 260   const NSUInteger kBufferSize = 1024;
 261   char buffer[kBufferSize];
 262   ssize_t bufferOffset = 0;  // Starting point in |buffer| to work with.
 263   ssize_t bytesRead = read(_socket, buffer, kBufferSize);
 264   if (bytesRead == 0) {
 265     [self disconnectClient];
 266     return;
 267   }
 268
 269   // The read loop works by going through the buffer until all the bytes have
 270   // been processed.
 271   while (bufferOffset < bytesRead) {
 272     // Find the NUL separator, or the end of the string.
 273     NSUInteger partLength = 0;
 274     for (ssize_t i = bufferOffset; i < bytesRead && buffer[i] != '\0'; ++i, ++partLength) ;
 275
 276     // If there is not a current packet, set some state.
 277     if (!_message) {
 278       // Read the message header: the size.  This will be |partLength| bytes.
 279       _totalMessageSize = atoi(buffer + bufferOffset);
 280       _messageSize = 0;
 281       _message = [[NSMutableString alloc] initWithCapacity:_totalMessageSize];
 282       bufferOffset += partLength + 1;  // Pass over the NUL byte.
 283       continue;  // Spin the loop to begin reading actual data.
 284     }
 285
 286     // Substring the byte stream and append it to the packet string.
 287     NSString* bufferString = [[NSString alloc] initWithBytesNoCopy:buffer + bufferOffset
 288                                                             length:partLength
 289                                                           encoding:NSUTF8StringEncoding
 290                                                       freeWhenDone:NO];
 291     [_message appendString:[bufferString autorelease]];
 292
 293     // Advance counters.
 294     _messageSize += partLength;
 295     bufferOffset += partLength + 1;
 296
 297     // If this read finished the packet, handle it and reset.
 298     if (_messageSize >= _totalMessageSize) {
 299       [_delegate messageQueue:self didReceiveMessage:[_message autorelease]];
 300       _message = nil;
 301     }
 302   }
 303 }
 304
 305 - (void)acceptConnection {
 306   struct sockaddr_in address = {0};
 307   socklen_t addressLength = sizeof(address);
 308   int connection = accept(_socket, (struct sockaddr*)&address, &addressLength);
 309   if (connection < 0) {
 310     NSLog(@"Failed to accept connection: %d, %s", errno, strerror(errno));
 311     [self disconnectClient];
 312     return;
 313   }
 314
 315   dispatch_source_cancel(_readSource);
 316   close(_socket);
 317
 318   _readSource = dispatch_source_create(DISPATCH_SOURCE_TYPE_READ, connection, 0, _dispatchQueue);
 319   dispatch_source_set_event_handler(_readSource, ^{
 320     [self readMessageFromStream];
 321   });
 322
 323   _writeSource = dispatch_source_create(DISPATCH_SOURCE_TYPE_WRITE, connection, 0, _dispatchQueue);
 324   dispatch_source_set_event_handler(_writeSource, ^{
 325     [self dequeueAndSend];
 326   });
 327
 328   _socket = connection;
 329
 330   dispatch_resume(_readSource);
 331   dispatch_resume(_writeSource);
 332
 333   [_delegate messageQueueDidConnect:self];
 334 }
 335
 336 @end