barrier/lib/mt/CThread.h

/*
 * synergy -- mouse and keyboard sharing utility
 * Copyright (C) 2002 Chris Schoeneman
 * 
 * This package is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * found in the file COPYING that should have accompanied this file.
 * 
 * This package 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 General Public License for more details.
 */

#ifndef CTHREAD_H
#define CTHREAD_H

#include "IArchMultithread.h"

class IJob;

//! Thread handle
/*!
Creating a CThread creates a new context of execution (i.e. thread) that
runs simulatenously with the calling thread.  A CThread is only a handle
to a thread;  deleting a CThread does not cancel or destroy the thread it
refers to and multiple CThread objects can refer to the same thread.

Threads can terminate themselves but cannot be forced to terminate by
other threads.  However, other threads can signal a thread to terminate
itself by cancelling it.  And a thread can wait (block) on another thread
to terminate.

Most functions that can block for an arbitrary time are cancellation
points.  A cancellation point is a function that can be interrupted by
a request to cancel the thread.  Cancellation points are noted in the
documentation.
*/
// note -- do not derive from this class
class CThread {
public:
	//! Result of waitForEvent()
	enum EWaitResult {
		kEvent,				//!< An event is pending
		kExit,				//!< Thread exited
		kTimeout			//!< Wait timed out
	};

	//! Run \c adoptedJob in a new thread
	/*!
	Create and start a new thread executing the \c adoptedJob.  The
	new thread takes ownership of \c adoptedJob and will delete it.
	*/
	CThread(IJob* adoptedJob);

	//! Duplicate a thread handle
	/*!
	Make a new thread object that refers to an existing thread.
	This does \b not start a new thread.
	*/
	CThread(const CThread&);

	//! Release a thread handle
	/*!
	Release a thread handle.  This does not terminate the thread.  A thread
	will keep running until the job completes or calls exit() or allows
	itself to be cancelled.
	*/
	~CThread();

	//! @name manipulators
	//@{

	//! Assign thread handle
	/*!
	Assign a thread handle.  This has no effect on the threads, it simply
	makes this thread object refer to another thread.  It does \b not
	start a new thread.
	*/
	CThread&			operator=(const CThread&);

	//! Terminate the calling thread
	/*!
	Terminate the calling thread.  This function does not return but
	the stack is unwound and automatic objects are destroyed, as if
	exit() threw an exception (which is, in fact, what it does).  The
	argument is saved as the result returned by getResult().  If you
	have \c catch(...) blocks then you should add the following before
	each to avoid catching the exit:
	\code
	catch(CThreadExit&) { throw; }
	\endcode
	or add the \c RETHROW_XTHREAD macro to the \c catch(...) block.
	*/
	static void			exit(void*);

	//! Cancel thread
	/*!
	Cancel the thread.  cancel() never waits for the thread to
	terminate;  it just posts the cancel and returns.  A thread will
	terminate when it enters a cancellation point with cancellation
	enabled.  If cancellation is disabled then the cancel is
	remembered but not acted on until the first call to a
	cancellation point after cancellation is enabled.
	
	A cancellation point is a function that can act on cancellation.
	A cancellation point does not return if there's a cancel pending.
	Instead, it unwinds the stack and destroys automatic objects, as
	if cancel() threw an exception (which is, in fact, what it does).
	Threads must take care to unlock and clean up any resources they
	may have, especially mutexes.  They can \c catch(XThreadCancel) to
	do that then rethrow the exception or they can let it happen
	automatically by doing clean up in the d'tors of automatic
	objects (like CLock).  Clients are strongly encouraged to do the latter.
	During cancellation, further cancel() calls are ignored (i.e.
	a thread cannot be interrupted by a cancel during cancellation).
	
	Clients that \c catch(XThreadCancel) must always rethrow the
	exception.  Clients that \c catch(...) must either rethrow the
	exception or include a \c catch(XThreadCancel) handler that
	rethrows.  The \c RETHROW_XTHREAD macro may be useful for that.
	*/
	void				cancel();

	//! Change thread priority
	/*!
	Change the priority of the thread.  Normal priority is 0, 1 is
	the next lower, etc.  -1 is the next higher, etc. but boosting
	the priority may not be permitted and will be silenty ignored.
	*/
	void				setPriority(int n);

	//@}
	//! @name accessors
	//@{

	//! Get current thread's handle
	/*!
	Return a CThread object representing the calling thread.
	*/
	static CThread		getCurrentThread();

	//! Test for cancellation
	/*!
	testCancel() does nothing but is a cancellation point.  Call
	this to make a function itself a cancellation point.  If the
	thread was cancelled and cancellation is enabled this will
	cause the thread to unwind the stack and terminate.

	(cancellation point)
	*/
	static void			testCancel();

	//! Wait for thread to terminate
	/*!
	Waits for the thread to terminate (by exit() or cancel() or
	by returning from the thread job) for up to \c timeout seconds,
	returning true if the thread terminated and false otherwise.
	This returns immediately with false if called by a thread on
	itself and immediately with true if the thread has already
	terminated.  This will wait forever if \c timeout < 0.0.

	(cancellation point)
	*/
	bool				wait(double timeout = -1.0) const;

	//! Wait for an event (win32)
	/*!
	Wait for the message queue to contain a message or for the thread
	to exit for up to \c timeout seconds.  This returns immediately if
	any message is available (including messages that were already in
	the queue during the last call to \c GetMessage() or
	\c PeekMessage() or waitForEvent().  Returns kEvent if a message
	is available, kExit if the thread exited, and kTimeout otherwise.
	This will wait forever if \c timeout < 0.0.

	This method is available under win32 only.

	(cancellation point)
	*/
	EWaitResult			waitForEvent(double timeout = -1.0) const;

	//! Get the exit result
	/*!
	Returns the exit result.  This does an implicit wait().  It returns
	NULL immediately if called by a thread on itself or on a thread that
	was cancelled.

	(cancellation point)
	*/
	void*				getResult() const;

	//! Get the thread id
	/*!
	Returns an integer id for this thread.  This id must not be used to
	check if two CThread objects refer to the same thread.  Use
	operator==() for that.
	*/
	IArchMultithread::ThreadID
						getID() const;

	//! Compare thread handles
	/*!
	Returns true if two CThread objects refer to the same thread.
	*/
	bool				operator==(const CThread&) const;

	//! Compare thread handles
	/*!
	Returns true if two CThread objects do not refer to the same thread.
	*/
	bool				operator!=(const CThread&) const;

	//@}

private:
	CThread(CArchThread);

	static void*		threadFunc(void*);

private:
	CArchThread			m_thread;
};

#endif