DB(cerr << "omni_thread::init: NT implementation initialising\n");

    self_tls_index = TlsAlloc();

    if (self_tls_index == 0xffffffff)
	throw omni_thread_fatal(GetLastError());

    next_id_mutex = new omni_mutex;

    //
    // Create object for this (i.e. initial) thread.
    //

    omni_thread* t = new omni_thread;

    t->_state = STATE_RUNNING;

    if (!DuplicateHandle(GetCurrentProcess(), GetCurrentThread(),
			 GetCurrentProcess(), &t->handle,
			 0, FALSE, DUPLICATE_SAME_ACCESS))
	throw omni_thread_fatal(GetLastError());

    t->nt_id = GetCurrentThreadId();

    DB(cerr << "initial thread " << t->id() << " NT thread id " << t->nt_id
       << endl);

    if (!TlsSetValue(self_tls_index, (LPVOID)t))
	throw omni_thread_fatal(GetLastError());

    if (!SetThreadPriority(t->handle, nt_priority(PRIORITY_NORMAL)))
	throw omni_thread_fatal(GetLastError());
}

//
// Wrapper for thread creation.
//

extern "C" 
unsigned __stdcall
omni_thread_wrapper(void* ptr)
{
    omni_thread* me = (omni_thread*)ptr;

    DB(cerr << "omni_thread_wrapper: thread " << me->id()
       << " started\n");

    if (!TlsSetValue(self_tls_index, (LPVOID)me))
	throw omni_thread_fatal(GetLastError());

    //
    // Now invoke the thread function with the given argument.
    //

    if (me->fn_void != NULL) {
	(*me->fn_void)(me->thread_arg);
	omni_thread::exit();
    }

    if (me->fn_ret != NULL) {
	void* return_value = (*me->fn_ret)(me->thread_arg);
	omni_thread::exit(return_value);
    }

    if (me->detached) {
	me->run(me->thread_arg);
	omni_thread::exit();
    } else {
	void* return_value = me->run_undetached(me->thread_arg);
	omni_thread::exit(return_value);
    }

    // should never get here.
    return 0;
}


//
// Constructors for omni_thread - set up the thread object but don't
// start it running.
//

// construct a detached thread running a given function.

omni_thread::omni_thread(void (*fn)(void*), void* arg, priority_t pri)
{
    common_constructor(arg, pri, 1);
    fn_void = fn;
    fn_ret = NULL;
}

// construct an undetached thread running a given function.

omni_thread::omni_thread(void* (*fn)(void*), void* arg, priority_t pri)
{
    common_constructor(arg, pri, 0);
    fn_void = NULL;
    fn_ret = fn;
}

// construct a thread which will run either run() or run_undetached().

omni_thread::omni_thread(void* arg, priority_t pri)
{
    common_constructor(arg, pri, 1);
    fn_void = NULL;
    fn_ret = NULL;
}

// common part of all constructors.

void
omni_thread::common_constructor(void* arg, priority_t pri, int det)
{
    _state = STATE_NEW;
    _priority = pri;

    next_id_mutex->lock();
    _id = next_id++;
    next_id_mutex->unlock();

    thread_arg = arg;
    detached = det;	// may be altered in start_undetached()

    cond_semaphore = CreateSemaphore(NULL, 0, SEMAPHORE_MAX, NULL);

    if (cond_semaphore == NULL)
	throw omni_thread_fatal(GetLastError());

    cond_next = cond_prev = NULL;
    cond_waiting = FALSE;

    handle = NULL;
}


//
// Destructor for omni_thread.
//

omni_thread::~omni_thread(void)
{
    DB(cerr << "destructor called for thread " << id() << endl);
    if ((handle != NULL) && !CloseHandle(handle))
	throw omni_thread_fatal(GetLastError());
    if (!CloseHandle(cond_semaphore))
	throw omni_thread_fatal(GetLastError());
}


//
// Start the thread
//

void
omni_thread::start(void)
{
    omni_mutex_lock l(mutex);

    if (_state != STATE_NEW)
	throw omni_thread_invalid();

    unsigned int t;
    handle = (HANDLE)_beginthreadex(
                        NULL,
			0,
			omni_thread_wrapper,
			(LPVOID)this,
			CREATE_SUSPENDED, 
			&t);
    nt_id = t;
    if (handle == NULL)
      throw omni_thread_fatal(GetLastError());

    if (!SetThreadPriority(handle, _priority))
      throw omni_thread_fatal(GetLastError());

    if (ResumeThread(handle) == 0xffffffff)
	throw omni_thread_fatal(GetLastError());

    _state = STATE_RUNNING;
}


//
// Start a thread which will run the member function run_undetached().
//

void
omni_thread::start_undetached(void)
{
    if ((fn_void != NULL) || (fn_ret != NULL))
	throw omni_thread_invalid();

    detached = 0;
    start();
}


//
// join - simply check error conditions & call WaitForSingleObject.
//

void
omni_thread::join(void** status)
{
    mutex.lock();

    if ((_state != STATE_RUNNING) && (_state != STATE_TERMINATED)) {
	mutex.unlock();
	throw omni_thread_invalid();
    }

    mutex.unlock();

    if (this == self())
	throw omni_thread_invalid();

    if (detached)
	throw omni_thread_invalid();

    DB(cerr << "omni_thread::join: doing WaitForSingleObject\n");

    if (WaitForSingleObject(handle, INFINITE) != WAIT_OBJECT_0)
	throw omni_thread_fatal(GetLastError());

    DB(cerr << "omni_thread::join: WaitForSingleObject succeeded\n");

    if (status)
      *status = return_val;

    delete this;
}


//
// Change this thread's priority.
//

void
omni_thread::set_priority(priority_t pri)
{
    omni_mutex_lock l(mutex);

    if (_state != STATE_RUNNING)
	throw omni_thread_invalid();

    _priority = pri;

    if (!SetThreadPriority(handle, nt_priority(pri)))
	throw omni_thread_fatal(GetLastError());
}


//
// create - construct a new thread object and start it running.  Returns thread
// object if successful, null pointer if not.
//

// detached version

omni_thread*
omni_thread::create(void (*fn)(void*), void* arg, priority_t pri)
{
    omni_thread* t = new omni_thread(fn, arg, pri);
    t->start();
    return t;
}

// undetached version

omni_thread*
omni_thread::create(void* (*fn)(void*), void* arg, priority_t pri)
{
    omni_thread* t = new omni_thread(fn, arg, pri);
    t->start();
    return t;
}


//
// exit() _must_ lock the mutex even in the case of a detached thread.  This is
// because a thread may run to completion before the thread that created it has
// had a chance to get out of start().  By locking the mutex we ensure that the
// creating thread must have reached the end of start() before we delete the
// thread object.  Of course, once the call to start() returns, the user can
// still incorrectly refer to the thread object, but that's their problem.
//

void
omni_thread::exit(void* return_value)
{
    omni_thread* me = self();

    if (me)
      {
	me->mutex.lock();

	me->_state = STATE_TERMINATED;

	me->mutex.unlock();

	DB(cerr << "omni_thread::exit: thread " << me->id() << " detached "
	   << me->detached << " return value " << return_value << endl);

	if (me->detached) {
	  delete me;
	} else {
	  me->return_val = return_value;
	}
      }
    else
      {
	DB(cerr << "omni_thread::exit: called with a non-omnithread. Exit quietly." << endl);
      }
    //   _endthreadex() does not automatically closes the thread handle.
    //   The omni_thread dtor closes the thread handle.
    _endthreadex(0);
}


omni_thread*
omni_thread::self(void)
{
    LPVOID me;

    me = TlsGetValue(self_tls_index);

    if (me == NULL) {
      DB(cerr << "omni_thread::self: called with a non-ominthread. NULL is returned." << endl);
    }
    return (omni_thread*)me;
}


void
omni_thread::yield(void)
{
    Sleep(0);
}


#define MAX_SLEEP_SECONDS (DWORD)4294966	// (2**32-2)/1000

void
omni_thread::sleep(unsigned long secs, unsigned long nanosecs)
{
    if (secs <= MAX_SLEEP_SECONDS) {
	Sleep(secs * 1000 + nanosecs / 1000000);
	return;
    }

    DWORD no_of_max_sleeps = secs / MAX_SLEEP_SECONDS;

    for (DWORD i = 0; i < no_of_max_sleeps; i++)
	Sleep(MAX_SLEEP_SECONDS * 1000);

    Sleep((secs % MAX_SLEEP_SECONDS) * 1000 + nanosecs / 1000000);
}


void
omni_thread::get_time(unsigned long* abs_sec, unsigned long* abs_nsec,
		      unsigned long rel_sec, unsigned long rel_nsec)
{
    get_time_now(abs_sec, abs_nsec);
    *abs_nsec += rel_nsec;
    *abs_sec += rel_sec + *abs_nsec / 1000000000;
    *abs_nsec = *abs_nsec % 1000000000;
}


int
omni_thread::nt_priority(priority_t pri)
{
    switch (pri) {

    case PRIORITY_LOW:
	return THREAD_PRIORITY_LOWEST;

    case PRIORITY_NORMAL:
	return THREAD_PRIORITY_NORMAL;

    case PRIORITY_HIGH:
	return THREAD_PRIORITY_HIGHEST;
    }

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


static void
get_time_now(unsigned long* abs_sec, unsigned long* abs_nsec)
{
    static int days_in_preceding_months[12]
	= { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 };
    static int days_in_preceding_months_leap[12]
	= { 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335 };

    SYSTEMTIME st;

    GetSystemTime(&st);
    *abs_nsec = st.wMilliseconds * 1000000;

    // this formula should work until 1st March 2100

    DWORD days = ((st.wYear - 1970) * 365 + (st.wYear - 1969) / 4
		  + ((st.wYear % 4)
		     ? days_in_preceding_months[st.wMonth - 1]
		     : days_in_preceding_months_leap[st.wMonth - 1])
		  + st.wDay - 1);

    *abs_sec = st.wSecond + 60 * (st.wMinute + 60 * (st.wHour + 24 * days));
}