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panda/src/express/threadNsprImpl.cxx

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// Filename: threadNsprImpl.cxx
// Created by:  drose (08Aug02)
//
////////////////////////////////////////////////////////////////////
//
// PANDA 3D SOFTWARE
// Copyright (c) 2001, Disney Enterprises, Inc.  All rights reserved
//
// All use of this software is subject to the terms of the Panda 3d
// Software license.  You should have received a copy of this license
// along with this source code; you will also find a current copy of
// the license at http://www.panda3d.org/license.txt .
//
// To contact the maintainers of this program write to
// panda3d@yahoogroups.com .
//
////////////////////////////////////////////////////////////////////

#include "threadNsprImpl.h"
#include "selectThreadImpl.h"

#ifdef THREAD_NSPR_IMPL

#include "pointerTo.h"
#include "config_express.h"
#include "mutexHolder.h"

PRUintn ThreadNsprImpl::_pt_ptr_index = 0;
bool ThreadNsprImpl::_got_pt_ptr_index = false;

////////////////////////////////////////////////////////////////////
//     Function: ThreadNsprImpl::Destructor
//       Access: Public
//  Description: 
////////////////////////////////////////////////////////////////////
ThreadNsprImpl::
~ThreadNsprImpl() {
  if (thread_cat.is_debug()) {
    thread_cat.debug() << "Deleting thread " << _parent_obj->get_name() << "\n";
  }

  // If the thread object is destructing, it means the last pointer
  // has gone away.  This can happen in one of three cases:

  // (1) start() was never called, and the last user reference has
  // gone away.  In this case, we should do nothing.

  // (2) There are no more user references, and the thread is still
  // running but is about to exit root_func().  In this case, no one
  // will ever call join().

  // (3) The thread terminated a while ago, and the last user
  // reference has just gone away.  In this case, we should call
  // join() if no one else has, to clean up whatever internal
  // structures NSPR might keep around for a non-detached thread.


  if (_thread == (PRThread *)NULL) {
    // Since the _thread pointer is still NULL, we must either be in
    // case (1), or case (3) but someone else has already called
    // join().  Do nothing.
    return;
  }

  PRThread *current_thread = PR_GetCurrentThread();
  if (current_thread == _thread) {
    // Since we are currently executing *this* thread, we must be in
    // case (2).  Unfortunately, we cannot now indicate we need to
    // clean up the thread, since NSPR doesn't have an interface to
    // make a thread unjoinable after it has been created, and a
    // thread can't join itself (can it?).
    if (_joinable) {
      thread_cat.warning()
        << "thread " << _parent_obj->get_name() << " was never joined.\n";
    }
    return;
  }

  // This is case (3).  The pointer went away and the thread has
  // already terminated; furthermore, no one has called join() yet.
  // We should do it.
  join();
}

////////////////////////////////////////////////////////////////////
//     Function: ThreadNsprImpl::start
//       Access: Public
//  Description: 
////////////////////////////////////////////////////////////////////
bool ThreadNsprImpl::
start(ThreadPriority priority, bool global, bool joinable) {
  MutexHolder holder(_mutex);
  if (thread_cat.is_debug()) {
    thread_cat.debug() << "Starting thread " << _parent_obj->get_name() << "\n";
  }
  nassertr(_thread == (PRThread *)NULL, false);
  _joinable = joinable;

  if (!_got_pt_ptr_index) {
    // Allocate a new index to store the Thread parent pointer as a
    // piece of per-thread private data.
    PRStatus result = PR_NewThreadPrivateIndex(&_pt_ptr_index, NULL);
    if (result == PR_SUCCESS) {
      _got_pt_ptr_index = true;
    } else {
      thread_cat.error()
        << "Unable to associate Thread pointers with threads.\n";
      return false;
    }
  }

  PRThreadPriority nspr_pri;

  switch (priority) {
  case TP_low:
    nspr_pri = PR_PRIORITY_LOW;
    break;

  case TP_normal:
    nspr_pri = PR_PRIORITY_NORMAL;
    break;

  case TP_high:
    nspr_pri = PR_PRIORITY_HIGH;
    break;

  case TP_urgent:
    nspr_pri = PR_PRIORITY_URGENT;
    break;

  default:
    nassertr(false, false);
  }

  PRThreadScope nspr_scope = (global) ? PR_GLOBAL_THREAD : PR_LOCAL_THREAD;

  PRThreadState nspr_state = (_joinable) ? PR_JOINABLE_THREAD : PR_UNJOINABLE_THREAD;

  // Increment the parent object's reference count first.  The thread
  // will eventually decrement it when it terminates.
  _parent_obj->ref();
  _thread = 
    PR_CreateThread(PR_USER_THREAD, &root_func, (void *)_parent_obj,
                    nspr_pri, nspr_scope, nspr_state, 0);

  if (_thread == (PRThread *)NULL) {
    // Oops, we couldn't start the thread.  Be sure to decrement the
    // reference count we incremented above, and return false to
    // indicate failure.
    unref_delete(_parent_obj);
    return false;
  }

  // Thread was successfully started.
  return true;
}

////////////////////////////////////////////////////////////////////
//     Function: ThreadNsprImpl::join
//       Access: Public
//  Description: 
////////////////////////////////////////////////////////////////////
void ThreadNsprImpl::
join() {
  MutexHolder holder(_mutex);
  if (_joinable && _thread != (PRThread *)NULL) {
    PR_JoinThread(_thread);
    _thread = (PRThread *)NULL;
  }
}

////////////////////////////////////////////////////////////////////
//     Function: ThreadNsprImpl::root_func
//       Access: Private, Static
//  Description: The entry point of each thread.
////////////////////////////////////////////////////////////////////
void ThreadNsprImpl::
root_func(void *data) {
  Thread *parent_obj = (Thread *)data;
  PRStatus result = PR_SetThreadPrivate(_pt_ptr_index, parent_obj);
  nassertv(result == PR_SUCCESS);
  parent_obj->thread_main();

  if (thread_cat.is_debug()) {
    thread_cat.debug()
      << "Terminating thread " << parent_obj->get_name() 
      << ", count = " << parent_obj->get_ref_count() << "\n";
  }

  // Now drop the parent object reference that we grabbed in start().
  // This might delete the parent object, and in turn, delete the
  // ThreadNsprImpl object.
  unref_delete(parent_obj);
}

#endif  // THREAD_NSPR_IMPL

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