Source/DebuggerConnection.m

   1 /*
   2  * MacGDBp
   3  * Copyright (c) 2007 - 2010, 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 "DebuggerConnection.h"
  18
  19 #import <sys/socket.h>
  20 #import <netinet/in.h>
  21
  22 #import "AppDelegate.h"
  23 #import "LoggingController.h"
  24
  25 // DebuggerConnection (Private) ////////////////////////////////////////////////
  26
  27 @interface DebuggerConnection ()
  28
  29 @property (assign) CFSocketRef socket;
  30 @property (assign) CFReadStreamRef readStream;
  31 @property NSUInteger lastReadTransaction;
  32 @property (retain) NSMutableString* currentPacket;
  33 @property (assign) CFWriteStreamRef writeStream;
  34 @property NSUInteger lastWrittenTransaction;
  35 @property (retain) NSMutableArray* queuedWrites;
  36
  37 - (void)connectionThreadStart;
  38
  39 - (void)socketDidAccept;
  40 - (void)socketDisconnected;
  41 - (void)readStreamHasData;
  42
  43 - (void)performSend:(NSString*)command;
  44 - (void)sendQueuedWrites;
  45
  46 - (void)performQuitSignal;
  47
  48 - (void)handleResponse:(NSXMLDocument*)response;
  49 - (void)handlePacket:(NSString*)packet;
  50
  51 // Threadsafe wrappers for the delegate's methods.
  52 - (void)errorEncountered:(NSString*)error;
  53 - (LogEntry*)recordSend:(NSString*)command;
  54 - (LogEntry*)recordReceive:(NSString*)command;
  55
  56 @end
  57
  58 // CFNetwork Callbacks /////////////////////////////////////////////////////////
  59
  60 void ReadStreamCallback(CFReadStreamRef stream, CFStreamEventType eventType, void* connectionRaw)
  61 {
  62   DebuggerConnection* connection = (DebuggerConnection*)connectionRaw;
  63   switch (eventType)
  64   {
  65     case kCFStreamEventHasBytesAvailable:
  66       [connection readStreamHasData];
  67       break;
  68
  69     case kCFStreamEventErrorOccurred:
  70     {
  71       CFErrorRef error = CFReadStreamCopyError(stream);
  72       CFReadStreamUnscheduleFromRunLoop(stream, CFRunLoopGetCurrent(), kCFRunLoopCommonModes);
  73       CFReadStreamClose(stream);
  74       CFRelease(stream);
  75       [connection errorEncountered:[[(NSError*)error autorelease] description]];
  76       break;
  77     }
  78
  79     case kCFStreamEventEndEncountered:
  80       CFReadStreamUnscheduleFromRunLoop(stream, CFRunLoopGetCurrent(), kCFRunLoopCommonModes);
  81       CFReadStreamClose(stream);
  82       CFRelease(stream);
  83       [connection socketDisconnected];
  84       break;
  85   };
  86 }
  87
  88 void WriteStreamCallback(CFWriteStreamRef stream, CFStreamEventType eventType, void* connectionRaw)
  89 {
  90   DebuggerConnection* connection = (DebuggerConnection*)connectionRaw;
  91   switch (eventType)
  92   {
  93     case kCFStreamEventCanAcceptBytes:
  94       [connection sendQueuedWrites];
  95       break;
  96
  97     case kCFStreamEventErrorOccurred:
  98     {
  99       CFErrorRef error = CFWriteStreamCopyError(stream);
 100       CFWriteStreamUnscheduleFromRunLoop(stream, CFRunLoopGetCurrent(), kCFRunLoopCommonModes);
 101       CFWriteStreamClose(stream);
 102       CFRelease(stream);
 103       [connection errorEncountered:[[(NSError*)error autorelease] description]];
 104       break;
 105     }
 106
 107     case kCFStreamEventEndEncountered:
 108       CFWriteStreamUnscheduleFromRunLoop(stream, CFRunLoopGetCurrent(), kCFRunLoopCommonModes);
 109       CFWriteStreamClose(stream);
 110       CFRelease(stream);
 111       [connection socketDisconnected];
 112       break;
 113   }
 114 }
 115
 116 void SocketAcceptCallback(CFSocketRef socket,
 117                           CFSocketCallBackType callbackType,
 118                           CFDataRef address,
 119                           const void* data,
 120                           void* connectionRaw)
 121 {
 122   assert(callbackType == kCFSocketAcceptCallBack);
 123   NSLog(@"SocketAcceptCallback()");
 124
 125   DebuggerConnection* connection = (DebuggerConnection*)connectionRaw;
 126
 127   CFReadStreamRef readStream;
 128   CFWriteStreamRef writeStream;
 129
 130   // Create the streams on the socket.
 131   CFStreamCreatePairWithSocket(kCFAllocatorDefault,
 132                                *(CFSocketNativeHandle*)data,  // Socket handle.
 133                                &readStream,  // Read stream in-pointer.
 134                                &writeStream);  // Write stream in-pointer.
 135
 136   // Create struct to register callbacks for the stream.
 137   CFStreamClientContext context;
 138   context.version = 0;
 139   context.info = connection;
 140   context.retain = NULL;
 141   context.release = NULL;
 142   context.copyDescription = NULL;
 143
 144   // Set the client of the read stream.
 145   CFOptionFlags readFlags =
 146       kCFStreamEventOpenCompleted |
 147       kCFStreamEventHasBytesAvailable |
 148       kCFStreamEventErrorOccurred |
 149       kCFStreamEventEndEncountered;
 150   if (CFReadStreamSetClient(readStream, readFlags, ReadStreamCallback, &context))
 151     // Schedule in run loop to do asynchronous communication with the engine.
 152     CFReadStreamScheduleWithRunLoop(readStream, CFRunLoopGetCurrent(), kCFRunLoopCommonModes);
 153   else
 154     return;
 155
 156   // Open the stream now that it's scheduled on the run loop.
 157   if (!CFReadStreamOpen(readStream))
 158   {
 159     CFStreamError error = CFReadStreamGetError(readStream);
 160     NSLog(@"error! %@", error);
 161     return;
 162   }
 163
 164   // Set the client of the write stream.
 165   CFOptionFlags writeFlags =
 166       kCFStreamEventOpenCompleted |
 167       kCFStreamEventCanAcceptBytes |
 168       kCFStreamEventErrorOccurred |
 169       kCFStreamEventEndEncountered;
 170   if (CFWriteStreamSetClient(writeStream, writeFlags, WriteStreamCallback, &context))
 171     // Schedule it in the run loop to receive error information.
 172     CFWriteStreamScheduleWithRunLoop(writeStream, CFRunLoopGetCurrent(), kCFRunLoopCommonModes);
 173   else
 174     return;
 175
 176   // Open the write stream.
 177   if (!CFWriteStreamOpen(writeStream))
 178   {
 179     CFStreamError error = CFWriteStreamGetError(writeStream);
 180     NSLog(@"error! %@", error);
 181     return;
 182   }
 183
 184   connection.readStream = readStream;
 185   connection.writeStream = writeStream;
 186   [connection socketDidAccept];
 187 }
 188
 189 // Other Run Loop Callbacks ////////////////////////////////////////////////////
 190
 191 void PerformQuitSignal(void* info)
 192 {
 193   DebuggerConnection* obj = (DebuggerConnection*)info;
 194   [obj performQuitSignal];
 195 }
 196
 197 ////////////////////////////////////////////////////////////////////////////////
 198
 199 @implementation DebuggerConnection
 200
 201 @synthesize port = port_;
 202 @synthesize connected = connected_;
 203 @synthesize delegate = delegate_;
 204
 205 @synthesize socket = socket_;
 206 @synthesize readStream = readStream_;
 207 @synthesize lastReadTransaction = lastReadTransaction_;
 208 @synthesize currentPacket = currentPacket_;
 209 @synthesize writeStream = writeStream_;
 210 @synthesize lastWrittenTransaction = lastWrittenTransaction_;
 211 @synthesize queuedWrites = queuedWrites_;
 212
 213 - (id)initWithPort:(NSUInteger)aPort
 214 {
 215   if (self = [super init])
 216   {
 217     port_ = aPort;
 218   }
 219   return self;
 220 }
 221
 222 - (void)dealloc
 223 {
 224   self.currentPacket = nil;
 225   [super dealloc];
 226 }
 227
 228 /**
 229  * Kicks off the socket on another thread.
 230  */
 231 - (void)connect
 232 {
 233   if (thread_ && !connected_) {
 234     // A thread has been detached but the socket has yet to connect. Do not
 235     // spawn a new thread otherwise multiple threads will be blocked on the same
 236     // socket.
 237     return;
 238   }
 239   [NSThread detachNewThreadSelector:@selector(connectionThreadStart) toTarget:self withObject:nil];
 240 }
 241
 242 /**
 243  * Creates, connects to, and schedules a CFSocket.
 244  */
 245 - (void)connectionThreadStart
 246 {
 247   NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
 248
 249   thread_ = [NSThread currentThread];
 250   runLoop_ = [NSRunLoop currentRunLoop];
 251
 252   // Pass ourselves to the callback so we don't have to use ugly globals.
 253   CFSocketContext context;
 254   context.version = 0;
 255   context.info = self;
 256   context.retain = NULL;
 257   context.release = NULL;
 258   context.copyDescription = NULL;
 259
 260   // Create the address structure.
 261   struct sockaddr_in address;
 262   memset(&address, 0, sizeof(address));
 263   address.sin_len = sizeof(address);
 264   address.sin_family = AF_INET;
 265   address.sin_port = htons(port_);
 266   address.sin_addr.s_addr = htonl(INADDR_ANY);
 267
 268   // Create the socket signature.
 269   CFSocketSignature signature;
 270   signature.protocolFamily = PF_INET;
 271   signature.socketType = SOCK_STREAM;
 272   signature.protocol = IPPROTO_TCP;
 273   signature.address = (CFDataRef)[NSData dataWithBytes:&address length:sizeof(address)];
 274
 275   do {
 276     socket_ = CFSocketCreateWithSocketSignature(kCFAllocatorDefault,
 277                                                 &signature,  // Socket signature.
 278                                                 kCFSocketAcceptCallBack,  // Callback types.
 279                                                 SocketAcceptCallback,  // Callout function pointer.
 280                                                 &context);  // Context to pass to callout.
 281     if (!socket_) {
 282       [self errorEncountered:@"Could not open socket."];
 283       sleep(1);
 284     }
 285   } while (!socket_);
 286
 287   // Allow old, yet-to-be recycled sockets to be reused.
 288   BOOL yes = YES;
 289   setsockopt(CFSocketGetNative(socket_), SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(BOOL));
 290   setsockopt(CFSocketGetNative(socket_), SOL_SOCKET, SO_REUSEPORT, &yes, sizeof(BOOL));
 291
 292   // Schedule the socket on the run loop.
 293   CFRunLoopSourceRef source = CFSocketCreateRunLoopSource(kCFAllocatorDefault, socket_, 0);
 294   CFRunLoopAddSource([runLoop_ getCFRunLoop], source, kCFRunLoopCommonModes);
 295   CFRelease(source);
 296
 297   // Create a source that is used to quit.
 298   CFRunLoopSourceContext quitContext = { 0 };
 299   quitContext.version = 0;
 300   quitContext.info = self;
 301   quitContext.perform = PerformQuitSignal;
 302   quitSource_ = CFRunLoopSourceCreate(kCFAllocatorDefault, 0, &quitContext);
 303   CFRunLoopAddSource([runLoop_ getCFRunLoop], quitSource_, kCFRunLoopCommonModes);
 304
 305   CFRunLoopRun();
 306
 307   thread_ = nil;
 308   runLoop_ = nil;
 309
 310   CFRunLoopSourceInvalidate(quitSource_);
 311   CFRelease(quitSource_);
 312   quitSource_ = NULL;
 313
 314   [pool release];
 315 }
 316
 317 /**
 318  * Called by SocketWrapper after the connection is successful. This immediately calls
 319  * -[SocketWrapper receive] to clear the way for communication, though the information
 320  * could be useful server information that we don't use right now.
 321  */
 322 - (void)socketDidAccept
 323 {
 324   connected_ = YES;
 325   transactionID = 1;
 326   self.queuedWrites = [NSMutableArray array];
 327   writeQueueLock_ = [NSRecursiveLock new];
 328 }
 329
 330 /**
 331  * Closes a socket and releases the ref.
 332  */
 333 - (void)close
 334 {
 335   if (thread_) {
 336     [thread_ cancel];
 337   }
 338   if (runLoop_ && quitSource_) {
 339     CFRunLoopSourceSignal(quitSource_);
 340     CFRunLoopWakeUp([runLoop_ getCFRunLoop]);
 341   }
 342 }
 343
 344 /**
 345  * Quits the run loop and stops the thread.
 346  */
 347 - (void)performQuitSignal
 348 {
 349   self.queuedWrites = nil;
 350   connected_ = NO;
 351   [writeQueueLock_ release];
 352
 353   if (runLoop_) {
 354     CFRunLoopStop([runLoop_ getCFRunLoop]);
 355   }
 356
 357   // The socket goes down, so do the streams, which clean themselves up.
 358   if (socket_) {
 359     NSLog(@"invalidating socket");
 360     CFSocketInvalidate(socket_);
 361     CFRelease(socket_);
 362     socket_ = NULL;
 363   }
 364 }
 365
 366 /**
 367  * Notification that the socket disconnected.
 368  */
 369 - (void)socketDisconnected
 370 {
 371   if (connected_) {
 372     // The state still is connected, which means that we did not get here
 373     // through normal disconnected procedure (a call to |-close|, followed by
 374     // the downing of the socket and the stream, which also produces this
 375     // messsage). Instead, the stream callbacks encountered EOF unexpectedly.
 376     [self close];
 377   }
 378   if ([delegate_ respondsToSelector:@selector(connectionDidClose:)])
 379     [delegate_ connectionDidClose:self];
 380 }
 381
 382 /**
 383  * Writes a command into the write stream. If the stream is ready for writing,
 384  * we do so immediately. If not, the command is queued and will be written
 385  * when the stream is ready.
 386  */
 387 - (void)send:(NSString*)command
 388 {
 389   if (lastReadTransaction_ >= lastWrittenTransaction_ && CFWriteStreamCanAcceptBytes(writeStream_)) {
 390     [self performSend:command];
 391   } else {
 392     [writeQueueLock_ lock];
 393     [queuedWrites_ addObject:command];
 394     [writeQueueLock_ unlock];
 395   }
 396   [self sendQueuedWrites];
 397 }
 398
 399 /**
 400  * This will send a command to the debugger engine. It will append the
 401  * transaction ID automatically. It accepts a NSString command along with a
 402  * a variable number of arguments to substitute into the command, a la
 403  * +[NSString stringWithFormat:]. Returns the transaction ID as a NSNumber.
 404  */
 405 - (NSNumber*)sendCommandWithFormat:(NSString*)format, ...
 406 {
 407   // Collect varargs and format command.
 408   va_list args;
 409   va_start(args, format);
 410   NSString* command = [[NSString alloc] initWithFormat:format arguments:args];
 411   va_end(args);
 412
 413   NSNumber* callbackKey = [NSNumber numberWithInt:transactionID++];
 414   NSString* taggedCommand = [NSString stringWithFormat:@"%@ -i %@", [command autorelease], callbackKey];
 415   [self performSelector:@selector(send:)
 416                onThread:thread_
 417              withObject:taggedCommand
 418           waitUntilDone:connected_];
 419
 420   return callbackKey;
 421 }
 422
 423 /**
 424  * Given a file path, this returns a file:// URI and escapes any spaces for the
 425  * debugger engine.
 426  */
 427 - (NSString*)escapedURIPath:(NSString*)path
 428 {
 429   // Custon GDBp paths are fine.
 430   if ([[path substringToIndex:4] isEqualToString:@"gdbp"])
 431     return path;
 432
 433   // Create a temporary URL that will escape all the nasty characters.
 434   NSURL* url = [NSURL fileURLWithPath:path];
 435   NSString* urlString = [url absoluteString];
 436
 437   // Remove the host because this is a file:// URL;
 438   urlString = [urlString stringByReplacingOccurrencesOfString:[url host] withString:@""];
 439
 440   // Escape % for use in printf-style NSString formatters.
 441   urlString = [urlString stringByReplacingOccurrencesOfString:@"%" withString:@"%%"];
 442   return urlString;
 443 }
 444
 445 /**
 446  * Returns the transaction_id from an NSXMLDocument.
 447  */
 448 - (NSInteger)transactionIDFromResponse:(NSXMLDocument*)response
 449 {
 450   return [[[[response rootElement] attributeForName:@"transaction_id"] stringValue] intValue];
 451 }
 452
 453 /**
 454  * Scans a command string for the transaction ID component. If it is not found,
 455  * returns NSNotFound.
 456  */
 457 - (NSInteger)transactionIDFromCommand:(NSString*)command
 458 {
 459   NSRange occurrence = [command rangeOfString:@"-i "];
 460   if (occurrence.location == NSNotFound)
 461     return NSNotFound;
 462   NSString* transaction = [command substringFromIndex:occurrence.location + occurrence.length];
 463   return [transaction intValue];
 464 }
 465
 466 // Private /////////////////////////////////////////////////////////////////////
 467 #pragma mark Private
 468
 469 // Delegate Thread-Safe Wrappers ///////////////////////////////////////////////
 470
 471 /**
 472  * Receives errors from the SocketWrapper and updates the display
 473  */
 474 - (void)errorEncountered:(NSString*)error
 475 {
 476   if (![delegate_ respondsToSelector:@selector(errorEncountered:)])
 477     return;
 478   [delegate_ performSelectorOnMainThread:@selector(errorEncountered:)
 479                               withObject:error
 480                            waitUntilDone:NO];
 481 }
 482
 483 - (LogEntry*)recordSend:(NSString*)command
 484 {
 485   LoggingController* logger = [[AppDelegate instance] loggingController];
 486   LogEntry* entry = [LogEntry newSendEntry:command];
 487   entry.lastReadTransactionID = lastReadTransaction_;
 488   entry.lastWrittenTransactionID = lastWrittenTransaction_;
 489   [logger performSelectorOnMainThread:@selector(recordEntry:)
 490                            withObject:entry
 491                         waitUntilDone:NO];
 492   return [entry autorelease];
 493 }
 494
 495 - (LogEntry*)recordReceive:(NSString*)command
 496 {
 497   LoggingController* logger = [[AppDelegate instance] loggingController];
 498   LogEntry* entry = [LogEntry newReceiveEntry:command];
 499   entry.lastReadTransactionID = lastReadTransaction_;
 500   entry.lastWrittenTransactionID = lastWrittenTransaction_;
 501   [logger performSelectorOnMainThread:@selector(recordEntry:)
 502                            withObject:entry
 503                         waitUntilDone:NO];
 504   return [entry autorelease];
 505 }
 506
 507 // Stream Managers /////////////////////////////////////////////////////////////
 508
 509 /**
 510  * Callback from the CFReadStream that there is data waiting to be read.
 511  */
 512 - (void)readStreamHasData
 513 {
 514   const NSUInteger kBufferSize = 1024;
 515   UInt8 buffer[kBufferSize];
 516   CFIndex bufferOffset = 0;  // Starting point in |buffer| to work with.
 517   CFIndex bytesRead = CFReadStreamRead(readStream_, buffer, kBufferSize);
 518   const char* charBuffer = (const char*)buffer;
 519
 520   // The read loop works by going through the buffer until all the bytes have
 521   // been processed.
 522   while (bufferOffset < bytesRead)
 523   {
 524     // Find the NULL separator, or the end of the string.
 525     NSUInteger partLength = 0;
 526     for (NSUInteger i = bufferOffset; i < bytesRead && charBuffer[i] != '\0'; ++i, ++partLength) ;
 527
 528     // If there is not a current packet, set some state.
 529     if (!self.currentPacket)
 530     {
 531       // Read the message header: the size.  This will be |partLength| bytes.
 532       packetSize_ = atoi(charBuffer + bufferOffset);
 533       currentPacketIndex_ = 0;
 534       self.currentPacket = [NSMutableString stringWithCapacity:packetSize_];
 535       bufferOffset += partLength + 1;  // Pass over the NULL byte.
 536       continue;  // Spin the loop to begin reading actual data.
 537     }
 538
 539     // Substring the byte stream and append it to the packet string.
 540     CFStringRef bufferString = CFStringCreateWithBytes(kCFAllocatorDefault,
 541                                                        buffer + bufferOffset,  // Byte pointer, offset by start index.
 542                                                        partLength,  // Length.
 543                                                        kCFStringEncodingUTF8,
 544                                                        true);
 545     [self.currentPacket appendString:(NSString*)bufferString];
 546     CFRelease(bufferString);
 547
 548     // Advance counters.
 549     currentPacketIndex_ += partLength;
 550     bufferOffset += partLength + 1;
 551
 552     // If this read finished the packet, handle it and reset.
 553     if (currentPacketIndex_ >= packetSize_)
 554     {
 555       [self handlePacket:[[currentPacket_ retain] autorelease]];
 556       self.currentPacket = nil;
 557       packetSize_ = 0;
 558       currentPacketIndex_ = 0;
 559     }
 560   }
 561 }
 562
 563 /**
 564  * Performs the packet handling of a raw string XML packet. From this point on,
 565  * the packets are associated with a transaction and are then dispatched.
 566  */
 567 - (void)handlePacket:(NSString*)packet
 568 {
 569   // Test if we can convert it into an NSXMLDocument.
 570   NSError* error = nil;
 571   NSXMLDocument* xmlTest = [[NSXMLDocument alloc] initWithXMLString:currentPacket_ options:NSXMLDocumentTidyXML error:&error];
 572
 573   // Try to recover if we encountered an error.
 574   if (!xmlTest)
 575   {
 576     // We do not want to starve the write queue, so manually parse out the
 577     // transaction ID.
 578     NSRange location = [currentPacket_ rangeOfString:@"transaction_id"];
 579     if (location.location != NSNotFound)
 580     {
 581       NSUInteger start = location.location + location.length;
 582       NSUInteger end = start;
 583
 584       NSCharacterSet* numericSet = [NSCharacterSet decimalDigitCharacterSet];
 585
 586       // Loop over the characters after the attribute name to extract the ID.
 587       while (end < [currentPacket_ length])
 588       {
 589         unichar c = [currentPacket_ characterAtIndex:end];
 590         if ([numericSet characterIsMember:c])
 591         {
 592           // If this character is numeric, extend the range to substring.
 593           ++end;
 594         }
 595         else
 596         {
 597           if (start == end)
 598           {
 599             // If this character is nonnumeric and we have nothing in the
 600             // range, skip this character.
 601             ++start;
 602             ++end;
 603           }
 604           else
 605           {
 606             // We've moved past the numeric ID so we should stop searching.
 607             break;
 608           }
 609         }
 610       }
 611
 612       // If we were able to extract the transaction ID, update the last read.
 613       NSRange substringRange = NSMakeRange(start, end - start);
 614       NSString* transactionStr = [currentPacket_ substringWithRange:substringRange];
 615       if ([transactionStr length])
 616         lastReadTransaction_ = [transactionStr intValue];
 617     }
 618
 619     // Otherwise, assume +1 and hope it works.
 620     ++lastReadTransaction_;
 621   }
 622   else
 623   {
 624     // See if the transaction can be parsed out.
 625     NSInteger transaction = [self transactionIDFromResponse:xmlTest];
 626     if (transaction < lastReadTransaction_)
 627     {
 628       NSLog(@"tx = %d vs %d", transaction, lastReadTransaction_);
 629       NSLog(@"out of date transaction %@", packet);
 630       return;
 631     }
 632
 633     if (transaction != lastWrittenTransaction_)
 634       NSLog(@"txn %d <> %d last written, %d last read", transaction, lastWrittenTransaction_, lastReadTransaction_);
 635
 636     lastReadTransaction_ = transaction;
 637   }
 638
 639   // Log this receive event.
 640   LogEntry* log = [self recordReceive:currentPacket_];
 641   log.error = error;
 642
 643   // Finally, dispatch the handler for this response.
 644   [self handleResponse:[xmlTest autorelease]];
 645 }
 646
 647 - (void)handleResponse:(NSXMLDocument*)response
 648 {
 649   // Check and see if there's an error.
 650   NSArray* error = [[response rootElement] elementsForName:@"error"];
 651   if ([error count] > 0)
 652   {
 653     NSLog(@"Xdebug error: %@", error);
 654     NSString* errorMessage = [[[[error objectAtIndex:0] children] objectAtIndex:0] stringValue];
 655     [self errorEncountered:errorMessage];
 656   }
 657
 658   if ([[[response rootElement] name] isEqualToString:@"init"])
 659   {
 660     [delegate_ performSelectorOnMainThread:@selector(handleInitialResponse:)
 661                                 withObject:response
 662                              waitUntilDone:NO];
 663     return;
 664   }
 665
 666   if ([delegate_ respondsToSelector:@selector(handleResponse:)])
 667     [delegate_ performSelectorOnMainThread:@selector(handleResponse:)
 668                                 withObject:response
 669                              waitUntilDone:NO];
 670
 671   [self sendQueuedWrites];
 672 }
 673
 674 /**
 675  * This performs a blocking send. This should ONLY be called when we know we
 676  * have write access to the stream. We will busy wait in case we don't do a full
 677  * send.
 678  */
 679 - (void)performSend:(NSString*)command
 680 {
 681   // If this is an out-of-date transaction, do not bother sending it.
 682   NSInteger transaction = [self transactionIDFromCommand:command];
 683   if (transaction != NSNotFound && transaction < lastWrittenTransaction_)
 684     return;
 685
 686   BOOL done = NO;
 687
 688   char* string = (char*)[command UTF8String];
 689   int stringLength = strlen(string);
 690
 691   // Busy wait while writing. BAADD. Should background this operation.
 692   while (!done)
 693   {
 694     if (CFWriteStreamCanAcceptBytes(writeStream_))
 695     {
 696       // Include the NULL byte in the string when we write.
 697       int bytesWritten = CFWriteStreamWrite(writeStream_, (UInt8*)string, stringLength + 1);
 698       if (bytesWritten < 0)
 699       {
 700         NSLog(@"write error");
 701       }
 702       // Incomplete write.
 703       else if (bytesWritten < strlen(string))
 704       {
 705         // Adjust the buffer and wait for another chance to write.
 706         stringLength -= bytesWritten;
 707         memmove(string, string + bytesWritten, stringLength);
 708       }
 709       else
 710       {
 711         done = YES;
 712
 713         // We need to scan the string to find the transactionID.
 714         if (transaction == NSNotFound)
 715         {
 716           NSLog(@"sent %@ without a transaction ID", command);
 717           continue;
 718         }
 719         lastWrittenTransaction_ = transaction;
 720       }
 721     }
 722   }
 723
 724   // Log this trancation.
 725   [self recordSend:command];
 726 }
 727
 728 /**
 729  * Checks if there are unsent commands in the |queuedWrites_| queue and sends
 730  * them if it's OK to do so. This will not block.
 731  */
 732 - (void)sendQueuedWrites
 733 {
 734   if (!connected_)
 735     return;
 736
 737   [writeQueueLock_ lock];
 738   if (lastReadTransaction_ >= lastWrittenTransaction_ && [queuedWrites_ count] > 0)
 739   {
 740     NSString* command = [queuedWrites_ objectAtIndex:0];
 741
 742     // We don't want to block because this is called from the main thread.
 743     // |-performSend:| busy waits when the stream is not ready. Bail out
 744     // before we do that becuase busy waiting is BAD.
 745     if (CFWriteStreamCanAcceptBytes(writeStream_))
 746     {
 747       [self performSend:command];
 748       [queuedWrites_ removeObjectAtIndex:0];
 749     }
 750   }
 751   [writeQueueLock_ unlock];
 752 }
 753
 754 @end