nt.cpp

tightvnc源码

//				Package : omnithread
// omnithread/nt.cc		Created : 6/95 tjr
//
//    Copyright (C) 1999 AT&T Laboratories Cambridge. All Rights Reserved.
//
//    This file is part of the omnithread library
//
//    The omnithread library is free software; you can redistribute it and/or
//    modify it under the terms of the GNU Library 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 Library General Public
//    License along with this library; if not, write to the Free
//    Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  
//    02111-1307, USA
//

//
// Implementation of OMNI thread abstraction for NT threads
//

#include <stdlib.h>
#include <errno.h>
#include "omnithread.h"
#include <process.h>

#define DB(x) // x 
//#include <iostream.h> or #include <iostream> if DB is on.

static void get_time_now(unsigned long* abs_sec, unsigned long* abs_nsec);

///////////////////////////////////////////////////////////////////////////
//
// Mutex
//
///////////////////////////////////////////////////////////////////////////


omni_mutex::omni_mutex(void)
{
    InitializeCriticalSection(&crit);
}

omni_mutex::~omni_mutex(void)
{
    DeleteCriticalSection(&crit);
}

void
omni_mutex::lock(void)
{
    EnterCriticalSection(&crit);
}

void
omni_mutex::unlock(void)
{
    LeaveCriticalSection(&crit);
}



///////////////////////////////////////////////////////////////////////////
//
// Condition variable
//
///////////////////////////////////////////////////////////////////////////


//
// Condition variables are tricky to implement using NT synchronisation
// primitives, since none of them have the atomic "release mutex and wait to be
// signalled" which is central to the idea of a condition variable.  To get
// around this the solution is to record which threads are waiting and
// explicitly wake up those threads.
//
// Here we implement a condition variable using a list of waiting threads
// (protected by a critical section), and a per-thread semaphore (which
// actually only needs to be a binary semaphore).
//
// To wait on the cv, a thread puts itself on the list of waiting threads for
// that cv, then releases the mutex and waits on its own personal semaphore.  A
// signalling thread simply takes a thread from the head of the list and kicks
// that thread's semaphore.  Broadcast is simply implemented by kicking the
// semaphore of each waiting thread.
//
// The only other tricky part comes when a thread gets a timeout from a timed
// wait on its semaphore.  Between returning with a timeout from the wait and
// entering the critical section, a signalling thread could get in, kick the
// waiting thread's semaphore and remove it from the list.  If this happens,
// the waiting thread's semaphore is now out of step so it needs resetting, and
// the thread should indicate that it was signalled rather than that it timed
// out.
//
// It is possible that the thread calling wait or timedwait is not a
// omni_thread. In this case we have to provide a temporary data structure,
// i.e. for the duration of the call, for the thread to link itself on the
// list of waiting threads. _internal_omni_thread_dummy provides such
// a data structure and _internal_omni_thread_helper is a helper class to
// deal with this special case for wait() and timedwait(). Once created,
// the _internal_omni_thread_dummy is cached for use by the next wait() or
// timedwait() call from a non-omni_thread. This is probably worth doing
// because creating a Semaphore is quite heavy weight.

class _internal_omni_thread_helper;

class _internal_omni_thread_dummy : public omni_thread {
public:
  inline _internal_omni_thread_dummy() : next(0) { }
  inline ~_internal_omni_thread_dummy() { }
  friend class _internal_omni_thread_helper;
private:
  _internal_omni_thread_dummy* next;
};

class _internal_omni_thread_helper {
public:
  inline _internal_omni_thread_helper()  { 
    d = 0;
    t = omni_thread::self();
    if (!t) {
      omni_mutex_lock sync(cachelock);
      if (cache) {
	d = cache;
	cache = cache->next;
      }
      else {
	d = new _internal_omni_thread_dummy;
      }
      t = d;
    }
  }
  inline ~_internal_omni_thread_helper() { 
    if (d) {
      omni_mutex_lock sync(cachelock);
      d->next = cache;
      cache = d;
    }
  }
  inline operator omni_thread* () { return t; }
  inline omni_thread* operator->() { return t; }

  static _internal_omni_thread_dummy* cache;
  static omni_mutex                   cachelock;

private:
  _internal_omni_thread_dummy* d;
  omni_thread*                 t;
};

_internal_omni_thread_dummy* _internal_omni_thread_helper::cache = 0;
omni_mutex                   _internal_omni_thread_helper::cachelock;


omni_condition::omni_condition(omni_mutex* m) : mutex(m)
{
    InitializeCriticalSection(&crit);
    waiting_head = waiting_tail = NULL;
}


omni_condition::~omni_condition(void)
{
    DeleteCriticalSection(&crit);
    DB( if (waiting_head != NULL) {
	cerr << "omni_condition::~omni_condition: list of waiting threads "
	     << "is not empty\n";
    } )
}


void
omni_condition::wait(void)
{
    _internal_omni_thread_helper me;

    EnterCriticalSection(&crit);

    me->cond_next = NULL;
    me->cond_prev = waiting_tail;
    if (waiting_head == NULL)
	waiting_head = me;
    else
	waiting_tail->cond_next = me;
    waiting_tail = me;
    me->cond_waiting = TRUE;

    LeaveCriticalSection(&crit);

    mutex->unlock();

    DWORD result = WaitForSingleObject(me->cond_semaphore, INFINITE);

    mutex->lock();

    if (result != WAIT_OBJECT_0)
	throw omni_thread_fatal(GetLastError());
}


int
omni_condition::timedwait(unsigned long abs_sec, unsigned long abs_nsec)
{
    _internal_omni_thread_helper me;

    EnterCriticalSection(&crit);

    me->cond_next = NULL;
    me->cond_prev = waiting_tail;
    if (waiting_head == NULL)
	waiting_head = me;
    else
	waiting_tail->cond_next = me;
    waiting_tail = me;
    me->cond_waiting = TRUE;

    LeaveCriticalSection(&crit);

    mutex->unlock();

    unsigned long now_sec, now_nsec;

    get_time_now(&now_sec, &now_nsec);

    DWORD timeout = (abs_sec-now_sec) * 1000 + (abs_nsec-now_nsec) / 1000000;

    if ((abs_sec <= now_sec) && ((abs_sec < now_sec) || (abs_nsec < abs_nsec)))
	timeout = 0;

    DWORD result = WaitForSingleObject(me->cond_semaphore, timeout);

    if (result == WAIT_TIMEOUT) {
	EnterCriticalSection(&crit);

	if (me->cond_waiting) {
	    if (me->cond_prev != NULL)
		me->cond_prev->cond_next = me->cond_next;
	    else
		waiting_head = me->cond_next;
	    if (me->cond_next != NULL)
		me->cond_next->cond_prev = me->cond_prev;
	    else
		waiting_tail = me->cond_prev;
	    me->cond_waiting = FALSE;

	    LeaveCriticalSection(&crit);

	    mutex->lock();
	    return 0;
	}

	//
	// We timed out but another thread still signalled us.  Wait for
	// the semaphore (it _must_ have been signalled) to decrement it
	// again.  Return that we were signalled, not that we timed out.
	//

	LeaveCriticalSection(&crit);

	result = WaitForSingleObject(me->cond_semaphore, INFINITE);
    }

    if (result != WAIT_OBJECT_0)
	throw omni_thread_fatal(GetLastError());

    mutex->lock();
    return 1;
}


void
omni_condition::signal(void)
{
    EnterCriticalSection(&crit);

    if (waiting_head != NULL) {
	omni_thread* t = waiting_head;
	waiting_head = t->cond_next;
	if (waiting_head == NULL)
	    waiting_tail = NULL;
	else
	    waiting_head->cond_prev = NULL;
	t->cond_waiting = FALSE;

	if (!ReleaseSemaphore(t->cond_semaphore, 1, NULL)) {
	    int rc = GetLastError();
	    LeaveCriticalSection(&crit);
	    throw omni_thread_fatal(rc);
	}
    }

    LeaveCriticalSection(&crit);
}


void
omni_condition::broadcast(void)
{
    EnterCriticalSection(&crit);

    while (waiting_head != NULL) {
	omni_thread* t = waiting_head;
	waiting_head = t->cond_next;
	if (waiting_head == NULL)
	    waiting_tail = NULL;
	else
	    waiting_head->cond_prev = NULL;
	t->cond_waiting = FALSE;

	if (!ReleaseSemaphore(t->cond_semaphore, 1, NULL)) {
	    int rc = GetLastError();
	    LeaveCriticalSection(&crit);
	    throw omni_thread_fatal(rc);
	}
    }

    LeaveCriticalSection(&crit);
}



///////////////////////////////////////////////////////////////////////////
//
// Counting semaphore
//
///////////////////////////////////////////////////////////////////////////


#define SEMAPHORE_MAX 0x7fffffff


omni_semaphore::omni_semaphore(unsigned int initial)
{
    nt_sem = CreateSemaphore(NULL, initial, SEMAPHORE_MAX, NULL);

    if (nt_sem == NULL) {
      DB( cerr << "omni_semaphore::omni_semaphore: CreateSemaphore error "
	     << GetLastError() << endl );
      throw omni_thread_fatal(GetLastError());
    }
}


omni_semaphore::~omni_semaphore(void)
{
  if (!CloseHandle(nt_sem)) {
    DB( cerr << "omni_semaphore::~omni_semaphore: CloseHandle error "
	     << GetLastError() << endl );
    throw omni_thread_fatal(GetLastError());
  }
}


void
omni_semaphore::wait(void)
{
    if (WaitForSingleObject(nt_sem, INFINITE) != WAIT_OBJECT_0)
	throw omni_thread_fatal(GetLastError());
}


int
omni_semaphore::trywait(void)
{
    switch (WaitForSingleObject(nt_sem, 0)) {

    case WAIT_OBJECT_0:
	return 1;
    case WAIT_TIMEOUT:
	return 0;
    }

    throw omni_thread_fatal(GetLastError());
    return 0; /* keep msvc++ happy */
}


void
omni_semaphore::post(void)
{
    if (!ReleaseSemaphore(nt_sem, 1, NULL))
	throw omni_thread_fatal(GetLastError());
}



///////////////////////////////////////////////////////////////////////////
//
// Thread
//
///////////////////////////////////////////////////////////////////////////


//
// Static variables
//

int omni_thread::init_t::count = 0;

omni_mutex* omni_thread::next_id_mutex;
int omni_thread::next_id = 0;
static DWORD self_tls_index;

//
// Initialisation function (gets called before any user code).
//

omni_thread::init_t::init_t(void)
{
    if (count++ != 0)	// only do it once however many objects get created.
	return;