libs-base/Source/NSThread.m

/** Control of executable units within a shared virtual memory space
   Copyright (C) 1996-2000 Free Software Foundation, Inc.

   Original Author:  Scott Christley <scottc@net-community.com>
   Rewritten by: Andrew Kachites McCallum <mccallum@gnu.ai.mit.edu>
   Created: 1996
   Rewritten by: Richard Frith-Macdonald <richard@brainstorm.co.uk>
   to add optimisations features for faster thread access.
   Modified by: Nicola Pero <n.pero@mi.flashnet.it>
   to add GNUstep extensions allowing to interact with threads created
   by external libraries/code (eg, a Java Virtual Machine).

   This file is part of the GNUstep Objective-C Library.

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2 of the License, or (at your option) any later version.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, write to the Free
   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
   Boston, MA 02111 USA.

   <title>NSThread class reference</title>
   $Date$ $Revision$
*/

#import "common.h"
#define	EXPOSE_NSThread_IVARS	1
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_NANOSLEEP
#include <time.h>
#endif
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
#ifdef HAVE_SYS_RESOURCE_H
#include <sys/resource.h>
#endif
#ifdef HAVE_PTHREAD_H
#include <pthread.h>
#endif
#ifdef HAVE_SYS_FILE_H
#include <sys/file.h>
#endif
#ifdef HAVE_SYS_FCNTL_H
#include <sys/fcntl.h>
#endif

#include <errno.h>

#ifdef	__POSIX_SOURCE
#define NBLK_OPT     O_NONBLOCK
#else
#define NBLK_OPT     FNDELAY
#endif

#import "Foundation/NSException.h"
#import "Foundation/NSThread.h"
#import "Foundation/NSLock.h"
#import "Foundation/NSNotification.h"
#import "Foundation/NSNotificationQueue.h"
#import "Foundation/NSRunLoop.h"
#import "Foundation/NSConnection.h"
#import "Foundation/NSInvocation.h"
#import "Foundation/NSUserDefaults.h"
#import "Foundation/NSGarbageCollector.h"

#import "GSPrivate.h"
#import "GSRunLoopCtxt.h"

#if	GS_WITH_GC
#include	<gc/gc.h>
#endif
#if __OBJC_GC__
#include <objc/objc-auto.h>
#endif

#if defined(__FreeBSD__) || defined(__OpenBSD__)
#  include <pthread_np.h>
#  define IS_MAIN_PTHREAD (pthread_main_np() == 1)
#else
#  define IS_MAIN_PTHREAD (1)
#endif


// Some older BSD systems used a non-standard range of thread priorities.
// Use these if they exist, otherwise define standard ones.
#ifndef PTHREAD_MAX_PRIORITY
#define PTHREAD_MAX_PRIORITY 31
#endif
#ifndef PTHREAD_MIN_PRIORITY
#define PTHREAD_MIN_PRIORITY 0
#endif


@interface NSAutoreleasePool (NSThread)
+ (void) _endThread: (NSThread*)thread;
@end

static Class threadClass = Nil;
static NSNotificationCenter *nc = nil;

/**
 * This class performs a dual function ...
 * <p>
 *   As a class, it is responsible for handling incoming events from
 *   the main runloop on a special inputFd.  This consumes any bytes
 *   written to wake the main runloop.<br />
 *   During initialisation, the default runloop is set up to watch
 *   for data arriving on inputFd.
 * </p>
 * <p>
 *   As instances, each  instance retains perform receiver and argument
 *   values as long as they are needed, and handles locking to support
 *   methods which want to block until an action has been performed.
 * </p>
 * <p>
 *   The initialize method of this class is called before any new threads
 *   run.
 * </p>
 */
@interface GSPerformHolder : NSObject
{
  id			receiver;
  id			argument;
  SEL			selector;
  NSConditionLock	*lock;		// Not retained.
  NSArray		*modes;
  BOOL                  invalidated;
}
+ (GSPerformHolder*) newForReceiver: (id)r
			   argument: (id)a
			   selector: (SEL)s
			      modes: (NSArray*)m
			       lock: (NSConditionLock*)l;
- (void) fire;
- (void) invalidate;
- (BOOL) isInvalidated;
- (NSArray*) modes;
@end

/**
 * Sleep until the current date/time is the specified time interval
 * past the reference date/time.<br />
 * Implemented as a function taking an NSTimeInterval argument in order
 * to avoid objc messaging and object allocation/deallocation (NSDate)
 * overheads.<br />
 * Used to implement [NSThread+sleepUntilDate:]
 * If the date is in the past, this function simply allows other threads
 * (if any) to run.
 */
void
GSSleepUntilIntervalSinceReferenceDate(NSTimeInterval when)
{
  NSTimeInterval delay;

  // delay is always the number of seconds we still need to wait
  delay = when - GSPrivateTimeNow();
  if (delay <= 0.0)
    {
      sched_yield();
      return;
    }

#ifdef	HAVE_NANOSLEEP
  // Avoid any possibility of overflow by sleeping in chunks.
  while (delay > 32768)
    {
      struct timespec request;

      request.tv_sec = (time_t)32768;
      request.tv_nsec = (long)0;
      nanosleep(&request, 0);
      delay = when - GSPrivateTimeNow();
    }
  if (delay > 0)
    {
      struct timespec request;
      struct timespec remainder;

      request.tv_sec = (time_t)delay;
      request.tv_nsec = (long)((delay - request.tv_sec) * 1000000000);
      remainder.tv_sec = 0;
      remainder.tv_nsec = 0;

      /*
       * With nanosleep, we can restart the sleep after a signal by using
       * the remainder information ... so we can be sure to sleep to the
       * desired limit without having to re-generate the delay needed.
       */
      while (nanosleep(&request, &remainder) < 0
	&& (remainder.tv_sec > 0 || remainder.tv_nsec > 0))
	{
	  request.tv_sec = remainder.tv_sec;
	  request.tv_nsec = remainder.tv_nsec;
	  remainder.tv_sec = 0;
	  remainder.tv_nsec = 0;
	}
    }
#else

  /*
   * Avoid integer overflow by breaking up long sleeps.
   */
  while (delay > 30.0*60.0)
    {
      // sleep 30 minutes
#if defined(__MINGW__)
      Sleep (30*60*1000);
#else
      sleep (30*60);
#endif
      delay = when - GSPrivateTimeNow();
    }

  /*
   * sleeping may return early because of signals, so we need to re-calculate
   * the required delay and check to see if we need to sleep again.
   */
  while (delay > 0)
    {
#if	defined(__MINGW__)
#if	defined(HAVE_USLEEP)
      /* On windows usleep() seems to perform a busy wait ... so we only
       * use it for short delays ... otherwise use the less accurate Sleep()
       */
      if (delay > 0.1)
	{
          Sleep ((NSInteger)(delay*1000));
	}
      else
	{
          usleep ((NSInteger)(delay*1000000));
	}
#else
      Sleep ((NSInteger)(delay*1000));
#endif	/* HAVE_USLEEP */
#else
#if	defined(HAVE_USLEEP)
      usleep ((NSInteger)(delay*1000000));
#else
      sleep ((NSInteger)delay);
#endif	/* HAVE_USLEEP */
#endif	/* __MINGW__ */
      delay = when - GSPrivateTimeNow();
    }
#endif	/* HAVE_NANOSLEEP */
}

static NSArray *
commonModes(void)
{
  static NSArray	*modes = nil;

  if (modes == nil)
    {
      [gnustep_global_lock lock];
      if (modes == nil)
	{
	  Class	c = NSClassFromString(@"NSApplication");
	  SEL	s = @selector(allRunLoopModes);

	  if (c != 0 && [c respondsToSelector: s])
	    {
	      modes = RETAIN([c performSelector: s]);
	    }
	  else
	    {
	      modes = [[NSArray alloc] initWithObjects:
		NSDefaultRunLoopMode, NSConnectionReplyMode, nil];
	    }
	}
      [gnustep_global_lock unlock];
    }
  return modes;
}

/*
 * Flag indicating whether the objc runtime ever went multi-threaded.
 */
static BOOL	entered_multi_threaded_state = NO;

static NSThread *defaultThread;

static pthread_key_t thread_object_key;

/**
 * Pthread cleanup call.
 *
 * We should normally not get here ... because threads should exit properly
 * and clean up, so that this function doesn't get called.  However if a
 * thread terminates for some reason without calling the exit method, we
 * can at least log it.
 *
 * We can't do anything more than that since at the point
 * when this function is called, the thread specific data is no longer
 * available, so the currentThread method will always fail and the
 * repercussions of that would well be a crash.
 *
 * As a special case, we ignore the exit of the default thread ... that one
 * will usually terminate without calling the exit method as it ends the
 * whole process by returning from the 'main' function.
 */
static void exitedThread(void *thread)
{
  if (thread != defaultThread)
    {
      fprintf(stderr, "WARNING thread %p terminated without calling +exit!\n",
        thread);
    }
}

/**
 * These functions needed because sending messages to classes is a seriously
 * slow process with gcc and the gnu runtime.
 */
inline NSThread*
GSCurrentThread(void)
{
  NSThread *thr = pthread_getspecific(thread_object_key);
  if (nil == thr)
    {
      assert(GSRegisterCurrentThread() && @"Failed to register thread");
      thr = pthread_getspecific(thread_object_key);
      if ((nil == defaultThread) && IS_MAIN_PTHREAD)
        {
          defaultThread = [thr retain];
        }
    }
  assert(nil != thr && @"No main thread");
  return thr;
}

NSMutableDictionary*
GSDictionaryForThread(NSThread *t)
{
  if (nil == t)
    {
      t = GSCurrentThread();
    }
  return [t threadDictionary];
}

/**
 * Fast access function for thread dictionary of current thread.
 */
NSMutableDictionary*
GSCurrentThreadDictionary(void)
{
  return GSDictionaryForThread(nil);
}

/*
 * Callback function so send notifications on becoming multi-threaded.
 */
static void
gnustep_base_thread_callback(void)
{
  /*
   * Protect this function with locking ... to avoid any possibility
   * of multiple threads registering with the system simultaneously,
   * and so that all NSWillBecomeMultiThreadedNotifications are sent
   * out before any second thread can interfere with anything.
   */
  if (entered_multi_threaded_state == NO)
    {
      [gnustep_global_lock lock];
      if (entered_multi_threaded_state == NO)
	{
	  /*
	   * For apple compatibility ... and to make things easier for
	   * code called indirectly within a will-become-multi-threaded
	   * notification handler, we set the flag to say we are multi
	   * threaded BEFORE sending the notifications.
	   */
	  entered_multi_threaded_state = YES;
#if	GS_WITH_GC && defined(HAVE_GC_ALLOW_REGISTER_THREADS)
	  /* This function needs to be called before going multi-threaded
	   * so that the garbage collection library knows to support
	   * registration of new threads.
	   */
	  GS_allow_register_threads();
#endif
	  NS_DURING
	    {
	      [GSPerformHolder class];	// Force initialization

	      /*
	       * Post a notification if this is the first new thread
	       * to be created.
	       * Won't work properly if threads are not all created
	       * by this class, but it's better than nothing.
	       */
	      if (nc == nil)
		{
		  nc = RETAIN([NSNotificationCenter defaultCenter]);
		}
#if	!defined(HAVE_INITIALIZE)
	      if (NO == [[NSUserDefaults standardUserDefaults]
		boolForKey: @"GSSilenceInitializeWarning"])
		{
		  NSLog(@"WARNING your program is becoming multi-threaded, but you are using an ObjectiveC runtime library which does not have a thread-safe implementation of the +initialize method.  This means that any classes not already used may be incorrectly initialised, potentially causing strange behaviors and crashes.\nTo put this into context, the runtime bug has been knoown for several years and only rarely causes problems ... the easy workaround being to ensure that any classes used by a new thread have already been used in the main thread before the new thread starts.\nIf you are worried, please build/run GNUstep with a runtime which supports the +initialize method. The GNUstep stable runtime (libobjc) and experimental runtime (libobjc2), available from the GNUstep website and subversion repository, should both work.\nTo disable this warning (eg. for an application which does not suffer any problems caused by this runtime bug), please set the GSSilenceInitializeWarning user default to YES.");
		}
#endif
	      [nc postNotificationName: NSWillBecomeMultiThreadedNotification
				object: nil
			      userInfo: nil];
	    }
	  NS_HANDLER
	    {
	      fprintf(stderr,
"ALERT ... exception while becoming multi-threaded ... system may not be\n"
"properly initialised.\n");
	      fflush(stderr);
	    }
	  NS_ENDHANDLER
	}
      [gnustep_global_lock unlock];
    }
}


@implementation NSThread

static void
setThreadForCurrentThread(NSThread *t)
{
  [[NSGarbageCollector defaultCollector] disableCollectorForPointer: t];
  pthread_setspecific(thread_object_key, t);
  gnustep_base_thread_callback();
}

static void
unregisterActiveThread(NSThread *thread)
{
  if (thread->_active == YES)
    {
      /*
       * Set the thread to be inactive to avoid any possibility of recursion.
       */
      thread->_active = NO;
      thread->_finished = YES;

      /*
       * Let observers know this thread is exiting.
       */
      if (nc == nil)
	{
	  nc = RETAIN([NSNotificationCenter defaultCenter]);
	}
      [nc postNotificationName: NSThreadWillExitNotification
			object: thread
		      userInfo: nil];

      [(GSRunLoopThreadInfo*)thread->_runLoopInfo invalidate];
      [thread  release];
	  
      [[NSGarbageCollector defaultCollector] enableCollectorForPointer: thread];
      pthread_setspecific(thread_object_key, nil);
    }
}

+ (NSArray*) callStackReturnAddresses
{
  NSMutableArray        *stack = GSPrivateStackAddresses();

  return stack;
}

+ (BOOL) _createThreadForCurrentPthread
{
  NSThread	*t = pthread_getspecific(thread_object_key);

  if (t == nil)
    {
      t = [self new];
      t->_active = YES;
      [[NSGarbageCollector defaultCollector] disableCollectorForPointer: t];
      pthread_setspecific(thread_object_key, t);
      GS_CONSUMED(t);
      return YES;
    }
  return NO;
}

+ (NSThread*) currentThread
{
  return GSCurrentThread();
}

+ (void) detachNewThreadSelector: (SEL)aSelector
		        toTarget: (id)aTarget
                      withObject: (id)anArgument
{
  NSThread	*thread;

  /*
   * Create the new thread.
   */
  thread = [[NSThread alloc] initWithTarget: aTarget
                                   selector: aSelector
                                     object: anArgument];

  [thread start];
  RELEASE(thread);
}

+ (void) exit
{
  NSThread	*t;

  t = GSCurrentThread();
  if (t->_active == YES)
    {
      unregisterActiveThread (t);

      if (t == defaultThread || defaultThread == nil)
	{
	  /* For the default thread, we exit the process.
	   */
	  exit(0);
	}
      else
	{
          pthread_exit(NULL);
	}
    }
}

/*
 * Class initialization
 */
+ (void) initialize
{
  if (self == [NSThread class])
    {
      if (pthread_key_create(&thread_object_key, exitedThread))
	{
	  [NSException raise: NSInternalInconsistencyException
		      format: @"Unable to create thread key!"];
	}
      /*
       * Ensure that the default thread exists.
       */
      threadClass = self;

      GSCurrentThread();
    }
}

+ (BOOL) isMainThread
{
  return (GSCurrentThread() == defaultThread ? YES : NO);
}

+ (BOOL) isMultiThreaded
{
  return entered_multi_threaded_state;
}

+ (NSThread*) mainThread
{
  return defaultThread;
}

/**
 * Set the priority of the current thread.  This is a value in the
 * range 0.0 (lowest) to 1.0 (highest) which is mapped to the underlying
 * system priorities.  
 */
+ (void) setThreadPriority: (double)pri
{
#ifdef _POSIX_THREAD_PRIORITY_SCHEDULING
  int	policy;
  struct sched_param param;

  // Clamp pri into the required range.
  if (pri > 1) { pri = 1; }
  if (pri < 0) { pri = 0; }

  // Scale pri based on the range of the host system.
  pri *= (PTHREAD_MAX_PRIORITY - PTHREAD_MIN_PRIORITY);
  pri += PTHREAD_MIN_PRIORITY;

  pthread_getschedparam(pthread_self(), &policy, &param);
  param.sched_priority = pri;
  pthread_setschedparam(pthread_self(), policy, &param);
#endif
}

+ (void) sleepForTimeInterval: (NSTimeInterval)ti
{
  GSSleepUntilIntervalSinceReferenceDate(GSPrivateTimeNow() + ti);
}

/**
 * Delaying a thread ... pause until the specified date.
 */
+ (void) sleepUntilDate: (NSDate*)date
{
  GSSleepUntilIntervalSinceReferenceDate([date timeIntervalSinceReferenceDate]);
}


/**
 * Return the priority of the current thread.
 */
+ (double) threadPriority
{
  double pri = 0;
#ifdef _POSIX_THREAD_PRIORITY_SCHEDULING
  int policy;
  struct sched_param param;

  pthread_getschedparam(pthread_self(), &policy, &param);
  pri = param.sched_priority;
  // Scale pri based on the range of the host system.
  pri -= PTHREAD_MIN_PRIORITY;
  pri /= (PTHREAD_MAX_PRIORITY - PTHREAD_MIN_PRIORITY);

#else
#warning Your pthread implementation does not support thread priorities
#endif
  return pri;

}



/*
 * Thread instance methods.
 */

- (void) cancel
{
  _cancelled = YES;
}

- (void) dealloc
{
  if (_active == YES)
    {
      [NSException raise: NSInternalInconsistencyException
		  format: @"Deallocating an active thread without [+exit]!"];
    }
  if (_runLoopInfo != 0)
    {
      GSRunLoopThreadInfo       *info = (GSRunLoopThreadInfo*)_runLoopInfo;

      _runLoopInfo = 0;
      [info release];
    }
  DESTROY(_thread_dictionary);
  DESTROY(_target);
  DESTROY(_arg);
  DESTROY(_name);
  if (_autorelease_vars.pool_cache != 0)
    {
      [NSAutoreleasePool _endThread: self];
    }

  if (_thread_dictionary != nil)
    {
      /*
       * Try again to get rid of thread dictionary.
       */
      DESTROY(_thread_dictionary);
      if (_autorelease_vars.pool_cache != 0)
	{
	  [NSAutoreleasePool _endThread: self];
	}
      if (_thread_dictionary != nil)
	{
	  NSLog(@"Oops - leak - thread dictionary is %@", _thread_dictionary);
	  if (_autorelease_vars.pool_cache != 0)
	    {
	      [NSAutoreleasePool _endThread: self];
	    }
	}
    }
  DESTROY(_gcontext);
  [super dealloc];
}

- (id) init
{
  init_autorelease_thread_vars(&_autorelease_vars);
  return self;
}

- (id) initWithTarget: (id)aTarget
             selector: (SEL)aSelector
               object: (id)anArgument
{
  /* initialize our ivars. */
  _selector = aSelector;
  _target = RETAIN(aTarget);
  _arg = RETAIN(anArgument);
  init_autorelease_thread_vars(&_autorelease_vars);
  return self;
}

- (BOOL) isCancelled
{
  return _cancelled;
}

- (BOOL) isExecuting
{
  return _active;
}

- (BOOL) isFinished
{
  return _finished;
}

- (BOOL) isMainThread
{
  return (self == defaultThread ? YES : NO);
}

- (void) main
{
  if (_active == NO)
    {
      [NSException raise: NSInternalInconsistencyException
                  format: @"[%@-$@] called on inactive thread",
        NSStringFromClass([self class]),
        NSStringFromSelector(_cmd)];
    }

  [_target performSelector: _selector withObject: _arg];

}

- (NSString*) name
{
  return _name;
}

- (void) setName: (NSString*)aName
{
  ASSIGN(_name, aName);
}

- (void) setStackSize: (NSUInteger)stackSize
{
  _stackSize = stackSize;
}

- (NSUInteger) stackSize
{
  return _stackSize;
}

/**
 * Trampoline function called to launch the thread
 */
static void *nsthreadLauncher(void* thread)
{
    NSThread *t = (NSThread*)thread;
    setThreadForCurrentThread(t);
#if __OBJC_GC__
	objc_registerThreadWithCollector();
#endif
#if	GS_WITH_GC && defined(HAVE_GC_REGISTER_MY_THREAD)
  {
    struct GC_stack_base	base;

    if (GC_get_stack_base(&base) == GC_SUCCESS)
      {
	int	result;

	result = GC_register_my_thread(&base);
	if (result != GC_SUCCESS && result != GC_DUPLICATE)
	  {
	    fprintf(stderr, "Argh ... no thread support in garbage collection library\n");
	  }
      }
    else
      {
	fprintf(stderr, "Unable to determine stack base to register new thread for garbage collection\n");
      }
  }
#endif

  /*
   * Let observers know a new thread is starting.
   */
  if (nc == nil)
    {
      nc = RETAIN([NSNotificationCenter defaultCenter]);
    }
  [nc postNotificationName: NSThreadDidStartNotification
		    object: t
		  userInfo: nil];

  [t main];

  [NSThread exit];
  // Not reached
  return NULL;
}

- (void) start
{
  pthread_attr_t	attr;
  pthread_t		thr;

  if (_active == YES)
    {
      [NSException raise: NSInternalInconsistencyException
                  format: @"[%@-$@] called on active thread",
        NSStringFromClass([self class]),
        NSStringFromSelector(_cmd)];
    }
  if (_cancelled == YES)
    {
      [NSException raise: NSInternalInconsistencyException
                  format: @"[%@-$@] called on cancelled thread",
        NSStringFromClass([self class]),
        NSStringFromSelector(_cmd)];
    }
  if (_finished == YES)
    {
      [NSException raise: NSInternalInconsistencyException
                  format: @"[%@-$@] called on finished thread",
        NSStringFromClass([self class]),
        NSStringFromSelector(_cmd)];
    }

  /* Make sure the notification is posted BEFORE the new thread starts.
   */
  gnustep_base_thread_callback();

  /* The thread must persist until it finishes executing.
   */
  [self retain];

  /* Mark the thread as active whiul it's running.
   */
  _active = YES;

  errno = 0;
  pthread_attr_init(&attr);
  /* Create this thread detached, because we never use the return state from
   * threads.
   */
  pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
  /* Set the stack size when the thread is created.  Unlike the old setrlimit
   * code, this actually works.
   */
  if (_stackSize > 0)
    {
      pthread_attr_setstacksize(&attr, _stackSize);
    }
  if (pthread_create(&thr, &attr, nsthreadLauncher, self))
    {
      DESTROY(self);
      [NSException raise: NSInternalInconsistencyException
                  format: @"Unable to detach thread (last error %@)",
                  [NSError _last]];
    }
}

/**
 * Return the thread dictionary.  This dictionary can be used to store
 * arbitrary thread specific data.<br />
 * NB. This cannot be autoreleased, since we cannot be sure that the
 * autorelease pool for the thread will continue to exist for the entire
 * life of the thread!
 */
- (NSMutableDictionary*) threadDictionary
{
  if (_thread_dictionary == nil)
    {
      _thread_dictionary = [NSMutableDictionary new];
    }
  return _thread_dictionary;
}

@end



@implementation GSRunLoopThreadInfo
- (void) addPerformer: (id)performer
{
  [lock lock];
  [performers addObject: performer];
#if defined(__MINGW__)
  if (SetEvent(event) == 0)
    {
      NSLog(@"Set event failed - %@", [NSError _last]);
    }
#else
  /* The write could concievably fail if the pipe is full.
   * In that case we need to release the lock teporarily to allow the other
   * thread to consume data from the pipe.  It's possible that the thread
   * and its runloop might stop during that ... so we need to check that
   * outputFd is still valid.
   */
  while (outputFd >= 0 && write(outputFd, "0", 1) != 1)
    {
      [lock unlock];
      [lock lock];
    }
#endif
  [lock unlock];
}

- (void) dealloc
{
  [self invalidate];
  DESTROY(performers);
  DESTROY(lock);
  DESTROY(loop);
  [super dealloc];
}

- (id) init
{
#ifdef __MINGW__
  if ((event = CreateEvent(NULL, TRUE, FALSE, NULL)) == INVALID_HANDLE_VALUE)
    {
      DESTROY(self);
      [NSException raise: NSInternalInconsistencyException
        format: @"Failed to create event to handle perform in thread"];
    }
#else
  int	fd[2];

  if (pipe(fd) == 0)
    {
      int	e;

      inputFd = fd[0];
      outputFd = fd[1];
      if ((e = fcntl(inputFd, F_GETFL, 0)) >= 0)
	{
	  e |= NBLK_OPT;
	  if (fcntl(inputFd, F_SETFL, e) < 0)
	    {
	      [NSException raise: NSInternalInconsistencyException
		format: @"Failed to set non block flag for perform in thread"];
	    }
	}
      else
	{
	  [NSException raise: NSInternalInconsistencyException
	    format: @"Failed to get non block flag for perform in thread"];
	}
      if ((e = fcntl(outputFd, F_GETFL, 0)) >= 0)
	{
	  e |= NBLK_OPT;
	  if (fcntl(outputFd, F_SETFL, e) < 0)
	    {
	      [NSException raise: NSInternalInconsistencyException
		format: @"Failed to set non block flag for perform in thread"];
	    }
	}
      else
	{
	  [NSException raise: NSInternalInconsistencyException
	    format: @"Failed to get non block flag for perform in thread"];
	}
    }
  else
    {
      DESTROY(self);
      [NSException raise: NSInternalInconsistencyException
        format: @"Failed to create pipe to handle perform in thread"];
    }
#endif  
  lock = [NSLock new];
  performers = [NSMutableArray new];
  return self;
}

- (void) invalidate
{
  [lock lock];
  [performers makeObjectsPerformSelector: @selector(invalidate)];
  [performers removeAllObjects];
#ifdef __MINGW__
  if (event != INVALID_HANDLE_VALUE)
    {
      CloseHandle(event);
      event = INVALID_HANDLE_VALUE;
    }
#else
  if (inputFd >= 0)
    {
      close(inputFd);
      inputFd = -1;
    }
  if (outputFd >= 0)
    {
      close(outputFd);
      outputFd = -1;
    }
#endif
  [lock unlock];
}

- (void) fire
{
  NSArray	*toDo;
  unsigned int	i;
  unsigned int	c;

  [lock lock];
#if defined(__MINGW__)
  if (event != INVALID_HANDLE_VALUE)
    {
      if (ResetEvent(event) == 0)
        {
          NSLog(@"Reset event failed - %@", [NSError _last]);
        }
    }
#else
  if (inputFd >= 0)
    {
      char	buf[BUFSIZ];

      /* We don't care how much we read.  If there have been multiple
       * performers queued then there will be multiple bytes available,
       * but we always handle all available performers, so we can also
       * read all available bytes.
       * The descriptor is non-blocking ... so it's safe to ask for more
       * bytes than are available.
       */
      while (read(inputFd, buf, sizeof(buf)) > 0)
	;
    }
#endif

  c = [performers count];
  if (0 == c)
    {
      /* We deal with all available performers each time we fire, so
       * it's likely that we will fire when we have no performers left.
       * In that case we can skip the copying and emptying of the array.
       */
      [lock unlock];
      return;
    }
  toDo = [NSArray arrayWithArray: performers];
  [performers removeAllObjects];
  [lock unlock];

  for (i = 0; i < c; i++)
    {
      GSPerformHolder	*h = [toDo objectAtIndex: i];

      [loop performSelector: @selector(fire)
		     target: h
		   argument: nil
		      order: 0
		      modes: [h modes]];
    }
}
@end

GSRunLoopThreadInfo *
GSRunLoopInfoForThread(NSThread *aThread)
{
  GSRunLoopThreadInfo   *info;

  if (aThread == nil)
    {
      aThread = GSCurrentThread();
    }
  if (aThread->_runLoopInfo == nil)
    {
      [gnustep_global_lock lock];
      if (aThread->_runLoopInfo == nil)
        {
          aThread->_runLoopInfo = [GSRunLoopThreadInfo new];
	}
      [gnustep_global_lock unlock];
    }
  info = aThread->_runLoopInfo;
  return info;
}

@implementation GSPerformHolder

+ (GSPerformHolder*) newForReceiver: (id)r
			   argument: (id)a
			   selector: (SEL)s
			      modes: (NSArray*)m
			       lock: (NSConditionLock*)l
{
  GSPerformHolder	*h;

  h = (GSPerformHolder*)NSAllocateObject(self, 0, NSDefaultMallocZone());
  h->receiver = RETAIN(r);
  h->argument = RETAIN(a);
  h->selector = s;
  h->modes = RETAIN(m);
  h->lock = l;

  return h;
}

- (void) dealloc
{
  DESTROY(receiver);
  DESTROY(argument);
  DESTROY(modes);
  if (lock != nil)
    {
      [lock lock];
      [lock unlockWithCondition: 1];
      lock = nil;
    }
  NSDeallocateObject(self);
  GSNOSUPERDEALLOC;
}

- (void) fire
{
  GSRunLoopThreadInfo   *threadInfo;

  if (receiver == nil)
    {
      return;	// Already fired!
    }
  threadInfo = GSRunLoopInfoForThread(GSCurrentThread());
  [threadInfo->loop cancelPerformSelectorsWithTarget: self];
  [receiver performSelector: selector withObject: argument];
  DESTROY(receiver);
  DESTROY(argument);
  DESTROY(modes);
  if (lock != nil)
    {
      NSConditionLock	*l = lock;

      [lock lock];
      lock = nil;
      [l unlockWithCondition: 1];
    }
}

- (void) invalidate
{
  if (invalidated == NO)
    {
      invalidated = YES;
      DESTROY(receiver);
      if (lock != nil)
        {
          NSConditionLock	*l = lock;

          [lock lock];
          lock = nil;
          [l unlockWithCondition: 1];
        }
    }
}

- (BOOL) isInvalidated
{
  return invalidated;
}

- (NSArray*) modes
{
  return modes;
}
@end

@implementation	NSObject (NSThreadPerformAdditions)

- (void) performSelectorOnMainThread: (SEL)aSelector
			  withObject: (id)anObject
		       waitUntilDone: (BOOL)aFlag
			       modes: (NSArray*)anArray
{
  /* It's possible that this method could be called before the NSThread
   * class is initialised, so we check and make sure it's initiailised
   * if necessary.
   */
  if (defaultThread == nil)
    {
      [NSThread currentThread];
    }
  [self performSelector: aSelector
               onThread: defaultThread
             withObject: anObject
          waitUntilDone: aFlag
                  modes: anArray];
}

- (void) performSelectorOnMainThread: (SEL)aSelector
			  withObject: (id)anObject
		       waitUntilDone: (BOOL)aFlag
{
  [self performSelectorOnMainThread: aSelector
			 withObject: anObject
		      waitUntilDone: aFlag
			      modes: commonModes()];
}

- (void) performSelector: (SEL)aSelector
                onThread: (NSThread*)aThread
              withObject: (id)anObject
           waitUntilDone: (BOOL)aFlag
                   modes: (NSArray*)anArray
{
  GSRunLoopThreadInfo   *info;
  NSThread	        *t;

  if ([anArray count] == 0)
    {
      return;
    }

  t = GSCurrentThread();
  if (aThread == nil)
    {
      aThread = t;
    }
  info = GSRunLoopInfoForThread(aThread);
  if (t == aThread)
    {
      /* Perform in current thread.
       */
      if (aFlag == YES || info->loop == nil)
	{
          /* Wait until done or no run loop.
           */
	  [self performSelector: aSelector withObject: anObject];
	}
      else
	{
          /* Don't wait ... schedule operation in run loop.
           */
	  [info->loop performSelector: aSelector
                               target: self
                             argument: anObject
                                order: 0
                                modes: anArray];
	}
    }
  else
    {
      GSPerformHolder   *h;
      NSConditionLock	*l = nil;

      if ([t isFinished] == YES)
        {
          [NSException raise: NSInternalInconsistencyException
                      format: @"perform on finished thread"];
        }
      if (aFlag == YES)
	{
	  l = [[NSConditionLock alloc] init];
	}

      h = [GSPerformHolder newForReceiver: self
				 argument: anObject
				 selector: aSelector
				    modes: anArray
				     lock: l];
      [info addPerformer: h];
      if (l != nil)
	{
          [l lockWhenCondition: 1];
	  [l unlock];
	  RELEASE(l);
          if ([h isInvalidated] == YES)
            {
              [NSException raise: NSInternalInconsistencyException
                          format: @"perform on finished thread"];
              RELEASE(h);
            }
	}
      RELEASE(h);
    }
}

- (void) performSelector: (SEL)aSelector
                onThread: (NSThread*)aThread
              withObject: (id)anObject
           waitUntilDone: (BOOL)aFlag
{
  [self performSelector: aSelector
               onThread: aThread
             withObject: anObject
          waitUntilDone: aFlag
                  modes: commonModes()];
}
@end

/**
 * <p>
 *   This function is provided to let threads started by some other
 *   software library register themselves to be used with the
 *   GNUstep system.  All such threads should call this function
 *   before attempting to use any GNUstep objects.
 * </p>
 * <p>
 *   Returns <code>YES</code> if the thread can be registered,
 *   <code>NO</code> if it is already registered.
 * </p>
 * <p>
 *   Sends out a <code>NSWillBecomeMultiThreadedNotification</code>
 *   if the process was not already multithreaded.
 * </p>
 */
BOOL
GSRegisterCurrentThread (void)
{
  return [NSThread _createThreadForCurrentPthread];
}
/**
 * <p>
 *   This function is provided to let threads started by some other
 *   software library unregister themselves from the GNUstep threading
 *   system.
 * </p>
 * <p>
 *   Calling this function causes a
 *   <code>NSThreadWillExitNotification</code>
 *   to be sent out, and destroys the GNUstep NSThread object
 *   associated with the thread (like [NSThread+exit]) but does
 *   not exit the underlying thread.
 * </p>
 */
void
GSUnregisterCurrentThread (void)
{
  unregisterActiveThread(GSCurrentThread());
}