wxWidgets/include/wx/thread.h

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/////////////////////////////////////////////////////////////////////////////
// Name: wx/thread.h
// Purpose: Thread API
// Author: Guilhem Lavaux
// Modified by: Vadim Zeitlin (modifications partly inspired by omnithreads
// package from Olivetti & Oracle Research Laboratory)
// Created: 04/13/98
// RCS-ID: $Id$
// Copyright: (c) Guilhem Lavaux
// Licence: wxWindows licence
/////////////////////////////////////////////////////////////////////////////
#ifndef _WX_THREAD_H_
#define _WX_THREAD_H_
// ----------------------------------------------------------------------------
// headers
// ----------------------------------------------------------------------------
// get the value of wxUSE_THREADS configuration flag
#include "wx/defs.h"
#if wxUSE_THREADS
// only for wxUSE_THREADS - otherwise we'd get undefined symbols
#if defined(__GNUG__) && !defined(__APPLE__)
#pragma interface "thread.h"
#endif
// Windows headers define it
#ifdef Yield
#undef Yield
#endif
#include "wx/module.h"
// ----------------------------------------------------------------------------
// constants
// ----------------------------------------------------------------------------
enum wxMutexError
{
wxMUTEX_NO_ERROR = 0, // operation completed successfully
wxMUTEX_INVALID, // mutex hasn't been initialized
wxMUTEX_DEAD_LOCK, // mutex is already locked by the calling thread
wxMUTEX_BUSY, // mutex is already locked by another thread
wxMUTEX_UNLOCKED, // attempt to unlock a mutex which is not locked
wxMUTEX_MISC_ERROR // any other error
};
enum wxCondError
{
wxCOND_NO_ERROR = 0,
wxCOND_INVALID,
wxCOND_TIMEOUT, // WaitTimeout() has timed out
wxCOND_MISC_ERROR
};
enum wxSemaError
{
wxSEMA_NO_ERROR = 0,
wxSEMA_INVALID, // semaphore hasn't been initialized successfully
wxSEMA_BUSY, // returned by TryWait() if Wait() would block
wxSEMA_TIMEOUT, // returned by WaitTimeout()
wxSEMA_OVERFLOW, // Post() would increase counter past the max
wxSEMA_MISC_ERROR
};
enum wxThreadError
{
wxTHREAD_NO_ERROR = 0, // No error
wxTHREAD_NO_RESOURCE, // No resource left to create a new thread
wxTHREAD_RUNNING, // The thread is already running
wxTHREAD_NOT_RUNNING, // The thread isn't running
wxTHREAD_KILLED, // Thread we waited for had to be killed
wxTHREAD_MISC_ERROR // Some other error
};
enum wxThreadKind
{
wxTHREAD_DETACHED,
wxTHREAD_JOINABLE
};
// defines the interval of priority
enum
{
WXTHREAD_MIN_PRIORITY = 0u,
WXTHREAD_DEFAULT_PRIORITY = 50u,
WXTHREAD_MAX_PRIORITY = 100u
};
// There are 2 types of mutexes: normal mutexes and recursive ones. The attempt
// to lock a normal mutex by a thread which already owns it results in
// undefined behaviour (it always works under Windows, it will almost always
// result in a deadlock under Unix). Locking a recursive mutex in such
// situation always succeeds and it must be unlocked as many times as it has
// been locked.
//
// However recursive mutexes have several important drawbacks: first, in the
// POSIX implementation, they're less efficient. Second, and more importantly,
// they CAN NOT BE USED WITH CONDITION VARIABLES under Unix! Using them with
// wxCondition will work under Windows and some Unices (notably Linux) but will
// deadlock under other Unix versions (e.g. Solaris). As it might be difficult
// to ensure that a recursive mutex is not used with wxCondition, it is a good
// idea to avoid using recursive mutexes at all. Also, the last problem with
// them is that some (older) Unix versions don't support this at all -- which
// results in a configure warning when building and a deadlock when using them.
enum wxMutexType
{
// normal mutex: try to always use this one
wxMUTEX_DEFAULT,
// recursive mutex: don't use these ones with wxCondition
wxMUTEX_RECURSIVE
};
// forward declarations
class WXDLLEXPORT wxConditionInternal;
class WXDLLEXPORT wxMutexInternal;
class WXDLLEXPORT wxSemaphoreInternal;
class WXDLLEXPORT wxThreadInternal;
// ----------------------------------------------------------------------------
// A mutex object is a synchronization object whose state is set to signaled
// when it is not owned by any thread, and nonsignaled when it is owned. Its
// name comes from its usefulness in coordinating mutually-exclusive access to
// a shared resource. Only one thread at a time can own a mutex object.
// ----------------------------------------------------------------------------
// you should consider wxMutexLocker whenever possible instead of directly
// working with wxMutex class - it is safer
class WXDLLEXPORT wxMutex
{
public:
// constructor & destructor
// ------------------------
// create either default (always safe) or recursive mutex
wxMutex(wxMutexType mutexType = wxMUTEX_DEFAULT);
// destroys the mutex kernel object
~wxMutex();
// test if the mutex has been created successfully
bool IsOk() const;
// mutex operations
// ----------------
// Lock the mutex, blocking on it until it is unlocked by the other thread.
// The result of locking a mutex already locked by the current thread
// depend on the mutex type.
//
// The caller must call Unlock() later if Lock() returned wxMUTEX_NO_ERROR.
wxMutexError Lock();
// Try to lock the mutex: if it is currently locked, return immediately
// with an error. Otherwise the caller must call Unlock().
wxMutexError TryLock();
// Unlock the mutex. It is an error to unlock an already unlocked mutex
wxMutexError Unlock();
protected:
wxMutexInternal *m_internal;
friend class wxConditionInternal;
DECLARE_NO_COPY_CLASS(wxMutex)
};
// a helper class which locks the mutex in the ctor and unlocks it in the dtor:
// this ensures that mutex is always unlocked, even if the function returns or
// throws an exception before it reaches the end
class WXDLLEXPORT wxMutexLocker
{
public:
// lock the mutex in the ctor
wxMutexLocker(wxMutex& mutex)
: m_isOk(FALSE), m_mutex(mutex)
{ m_isOk = ( m_mutex.Lock() == wxMUTEX_NO_ERROR ); }
// returns TRUE if mutex was successfully locked in ctor
bool IsOk() const
{ return m_isOk; }
// unlock the mutex in dtor
~wxMutexLocker()
{ if ( IsOk() ) m_mutex.Unlock(); }
private:
// no assignment operator nor copy ctor
wxMutexLocker(const wxMutexLocker&);
wxMutexLocker& operator=(const wxMutexLocker&);
bool m_isOk;
wxMutex& m_mutex;
};
// ----------------------------------------------------------------------------
// Critical section: this is the same as mutex but is only visible to the
// threads of the same process. For the platforms which don't have native
// support for critical sections, they're implemented entirely in terms of
// mutexes.
//
// NB: wxCriticalSection object does not allocate any memory in its ctor
// which makes it possible to have static globals of this class
// ----------------------------------------------------------------------------
// in order to avoid any overhead under platforms where critical sections are
// just mutexes make all wxCriticalSection class functions inline
#if !defined(__WXMSW__) && !defined(__WXPM__)
#define wxCRITSECT_IS_MUTEX 1
#define wxCRITSECT_INLINE inline
#else // MSW || OS2
#define wxCRITSECT_IS_MUTEX 0
#define wxCRITSECT_INLINE
#endif // MSW/!MSW
// you should consider wxCriticalSectionLocker whenever possible instead of
// directly working with wxCriticalSection class - it is safer
class WXDLLEXPORT wxCriticalSection
{
public:
// ctor & dtor
wxCRITSECT_INLINE wxCriticalSection();
wxCRITSECT_INLINE ~wxCriticalSection();
// enter the section (the same as locking a mutex)
wxCRITSECT_INLINE void Enter();
// leave the critical section (same as unlocking a mutex)
wxCRITSECT_INLINE void Leave();
private:
#if wxCRITSECT_IS_MUTEX
wxMutex m_mutex;
#elif defined(__WXMSW__)
// we can't allocate any memory in the ctor, so use placement new -
// unfortunately, we have to hardcode the sizeof() here because we can't
// include windows.h from this public header and we also have to use the
// union to force the correct (i.e. maximal) alignment
//
// if CRITICAL_SECTION size changes in Windows, you'll get an assert from
// thread.cpp and will need to increase the buffer size
//
// finally, we need this typedef instead of declaring m_buffer directly
// because otherwise the assert mentioned above wouldn't compile with some
// compilers (notably CodeWarrior 8)
typedef char wxCritSectBuffer[24];
union
{
unsigned long m_dummy1;
void *m_dummy2;
wxCritSectBuffer m_buffer;
};
#else
// nothing for OS/2
#endif // Unix/Win32/OS2
DECLARE_NO_COPY_CLASS(wxCriticalSection)
};
#if wxCRITSECT_IS_MUTEX
// implement wxCriticalSection using mutexes
inline wxCriticalSection::wxCriticalSection() { }
inline wxCriticalSection::~wxCriticalSection() { }
inline void wxCriticalSection::Enter() { (void)m_mutex.Lock(); }
inline void wxCriticalSection::Leave() { (void)m_mutex.Unlock(); }
#endif // wxCRITSECT_IS_MUTEX
#undef wxCRITSECT_INLINE
#undef wxCRITSECT_IS_MUTEX
// wxCriticalSectionLocker is the same to critical sections as wxMutexLocker is
// to th mutexes
class WXDLLEXPORT wxCriticalSectionLocker
{
public:
wxCriticalSectionLocker(wxCriticalSection& cs)
: m_critsect(cs)
{
m_critsect.Enter();
}
~wxCriticalSectionLocker()
{
m_critsect.Leave();
}
private:
wxCriticalSection& m_critsect;
DECLARE_NO_COPY_CLASS(wxCriticalSectionLocker)
};
// ----------------------------------------------------------------------------
// wxCondition models a POSIX condition variable which allows one (or more)
// thread(s) to wait until some condition is fulfilled
// ----------------------------------------------------------------------------
class WXDLLEXPORT wxCondition
{
public:
// Each wxCondition object is associated with a (single) wxMutex object.
// The mutex object MUST be locked before calling Wait()
wxCondition(wxMutex& mutex);
// dtor is not virtual, don't use this class polymorphically
~wxCondition();
// return TRUE if the condition has been created successfully
bool IsOk() const;
// NB: the associated mutex MUST be locked beforehand by the calling thread
//
// it atomically releases the lock on the associated mutex
// and starts waiting to be woken up by a Signal()/Broadcast()
// once its signaled, then it will wait until it can reacquire
// the lock on the associated mutex object, before returning.
wxCondError Wait();
// exactly as Wait() except that it may also return if the specified
// timeout ellapses even if the condition hasn't been signalled: in this
// case, the return value is FALSE, otherwise (i.e. in case of a normal
// return) it is TRUE
//
// the timeeout parameter specifies a interval that needs to be waited in
// milliseconds
wxCondError WaitTimeout(unsigned long milliseconds);
// NB: the associated mutex may or may not be locked by the calling thread
//
// this method unblocks one thread if any are blocking on the condition.
// if no thread is blocking in Wait(), then the signal is NOT remembered
// The thread which was blocking on Wait(), will then reacquire the lock
// on the associated mutex object before returning
wxCondError Signal();
// NB: the associated mutex may or may not be locked by the calling thread
//
// this method unblocks all threads if any are blocking on the condition.
// if no thread is blocking in Wait(), then the signal is NOT remembered
// The threads which were blocking on Wait(), will then reacquire the lock
// on the associated mutex object before returning.
wxCondError Broadcast();
// deprecated version, don't use
bool Wait(unsigned long milliseconds)
{ return WaitTimeout(milliseconds) == wxCOND_NO_ERROR; }
private:
wxConditionInternal *m_internal;
DECLARE_NO_COPY_CLASS(wxCondition)
};
// ----------------------------------------------------------------------------
// wxSemaphore: a counter limiting the number of threads concurrently accessing
// a shared resource
// ----------------------------------------------------------------------------
class WXDLLEXPORT wxSemaphore
{
public:
// specifying a maxcount of 0 actually makes wxSemaphore behave as if there
// is no upper limit, if maxcount is 1 the semaphore behaves as a mutex
wxSemaphore( int initialcount = 0, int maxcount = 0 );
// dtor is not virtual, don't use this class polymorphically
~wxSemaphore();
// return TRUE if the semaphore has been created successfully
bool IsOk() const;
// wait indefinitely, until the semaphore count goes beyond 0
// and then decrement it and return (this method might have been called
// Acquire())
wxSemaError Wait();
// same as Wait(), but does not block, returns wxSEMA_NO_ERROR if
// successful and wxSEMA_BUSY if the count is currently zero
wxSemaError TryWait();
// same as Wait(), but as a timeout limit, returns wxSEMA_NO_ERROR if the
// semaphore was acquired and wxSEMA_TIMEOUT if the timeout has ellapsed
wxSemaError WaitTimeout(unsigned long milliseconds);
// increments the semaphore count and signals one of the waiting threads
wxSemaError Post();
private:
wxSemaphoreInternal *m_internal;
DECLARE_NO_COPY_CLASS(wxSemaphore)
};
// ----------------------------------------------------------------------------
// wxThread: class encpasulating a thread of execution
// ----------------------------------------------------------------------------
// there are two different kinds of threads: joinable and detached (default)
// ones. Only joinable threads can return a return code and only detached
// threads auto-delete themselves - the user should delete the joinable
// threads manually.
// NB: in the function descriptions the words "this thread" mean the thread
// created by the wxThread object while "main thread" is the thread created
// during the process initialization (a.k.a. the GUI thread)
// On VMS thread pointers are 64 bits (also needed for other systems???
#ifdef __VMS
typedef unsigned long long wxThreadIdType;
#else
typedef unsigned long wxThreadIdType;
#endif
class WXDLLEXPORT wxThread
{
public:
// the return type for the thread function
typedef void *ExitCode;
// static functions
// Returns the wxThread object for the calling thread. NULL is returned
// if the caller is the main thread (but it's recommended to use
// IsMain() and only call This() for threads other than the main one
// because NULL is also returned on error). If the thread wasn't
// created with wxThread class, the returned value is undefined.
static wxThread *This();
// Returns true if current thread is the main thread.
static bool IsMain();
// Release the rest of our time slice leting the other threads run
static void Yield();
// Sleep during the specified period of time in milliseconds
//
// NB: at least under MSW worker threads can not call ::wxSleep()!
static void Sleep(unsigned long milliseconds);
// get the number of system CPUs - useful with SetConcurrency()
// (the "best" value for it is usually number of CPUs + 1)
//
// Returns -1 if unknown, number of CPUs otherwise
static int GetCPUCount();
// Get the platform specific thread ID and return as a long. This
// can be used to uniquely identify threads, even if they are not
// wxThreads. This is used by wxPython.
static wxThreadIdType GetCurrentId();
// sets the concurrency level: this is, roughly, the number of threads
// the system tries to schedule to run in parallel. 0 means the
// default value (usually acceptable, but may not yield the best
// performance for this process)
//
// Returns TRUE on success, FALSE otherwise (if not implemented, for
// example)
static bool SetConcurrency(size_t level);
// constructor only creates the C++ thread object and doesn't create (or
// start) the real thread
wxThread(wxThreadKind kind = wxTHREAD_DETACHED);
// functions that change the thread state: all these can only be called
// from _another_ thread (typically the thread that created this one, e.g.
// the main thread), not from the thread itself
// create a new thread and optionally set the stack size on
// platforms that support that - call Run() to start it
// (special cased for watcom which won't accept 0 default)
wxThreadError Create(unsigned int stackSize = 0);
// starts execution of the thread - from the moment Run() is called
// the execution of wxThread::Entry() may start at any moment, caller
// shouldn't suppose that it starts after (or before) Run() returns.
wxThreadError Run();
// stops the thread if it's running and deletes the wxThread object if
// this is a detached thread freeing its memory - otherwise (for
// joinable threads) you still need to delete wxThread object
// yourself.
//
// this function only works if the thread calls TestDestroy()
// periodically - the thread will only be deleted the next time it
// does it!
//
// will fill the rc pointer with the thread exit code if it's !NULL
wxThreadError Delete(ExitCode *rc = (ExitCode *)NULL);
// waits for a joinable thread to finish and returns its exit code
//
// Returns (ExitCode)-1 on error (for example, if the thread is not
// joinable)
ExitCode Wait();
// kills the thread without giving it any chance to clean up - should
// not be used in normal circumstances, use Delete() instead. It is a
// dangerous function that should only be used in the most extreme
// cases!
//
// The wxThread object is deleted by Kill() if the thread is
// detachable, but you still have to delete it manually for joinable
// threads.
wxThreadError Kill();
// pause a running thread: as Delete(), this only works if the thread
// calls TestDestroy() regularly
wxThreadError Pause();
// resume a paused thread
wxThreadError Resume();
// priority
// Sets the priority to "prio": see WXTHREAD_XXX_PRIORITY constants
//
// NB: the priority can only be set before the thread is created
void SetPriority(unsigned int prio);
// Get the current priority.
unsigned int GetPriority() const;
// thread status inquiries
// Returns true if the thread is alive: i.e. running or suspended
bool IsAlive() const;
// Returns true if the thread is running (not paused, not killed).
bool IsRunning() const;
// Returns true if the thread is suspended
bool IsPaused() const;
// is the thread of detached kind?
bool IsDetached() const { return m_isDetached; }
// Get the thread ID - a platform dependent number which uniquely
// identifies a thread inside a process
wxThreadIdType GetId() const;
// called when the thread exits - in the context of this thread
//
// NB: this function will not be called if the thread is Kill()ed
virtual void OnExit() { }
// dtor is public, but the detached threads should never be deleted - use
// Delete() instead (or leave the thread terminate by itself)
virtual ~wxThread();
protected:
// Returns TRUE if the thread was asked to terminate: this function should
// be called by the thread from time to time, otherwise the main thread
// will be left forever in Delete()!
bool TestDestroy();
// exits from the current thread - can be called only from this thread
void Exit(ExitCode exitcode = 0);
// entry point for the thread - called by Run() and executes in the context
// of this thread.
virtual void *Entry() = 0;
private:
// no copy ctor/assignment operator
wxThread(const wxThread&);
wxThread& operator=(const wxThread&);
friend class wxThreadInternal;
// the (platform-dependent) thread class implementation
wxThreadInternal *m_internal;
// protects access to any methods of wxThreadInternal object
wxCriticalSection m_critsect;
// true if the thread is detached, false if it is joinable
bool m_isDetached;
};
// ----------------------------------------------------------------------------
// Automatic initialization
// ----------------------------------------------------------------------------
// GUI mutex handling.
void WXDLLEXPORT wxMutexGuiEnter();
void WXDLLEXPORT wxMutexGuiLeave();
// macros for entering/leaving critical sections which may be used without
// having to take them inside "#if wxUSE_THREADS"
#define wxENTER_CRIT_SECT(cs) (cs).Enter()
#define wxLEAVE_CRIT_SECT(cs) (cs).Leave()
#define wxCRIT_SECT_DECLARE(cs) static wxCriticalSection cs
#define wxCRIT_SECT_LOCKER(name, cs) wxCriticalSectionLocker name(cs)
#else // !wxUSE_THREADS
// no thread support
inline void WXDLLEXPORT wxMutexGuiEnter() { }
inline void WXDLLEXPORT wxMutexGuiLeave() { }
// macros for entering/leaving critical sections which may be used without
// having to take them inside "#if wxUSE_THREADS"
#define wxENTER_CRIT_SECT(cs)
#define wxLEAVE_CRIT_SECT(cs)
#define wxCRIT_SECT_DECLARE(cs)
#define wxCRIT_SECT_LOCKER(name, cs)
#endif // wxUSE_THREADS/!wxUSE_THREADS
// mark part of code as being a critical section: this macro declares a
// critical section with the given name and enters it immediately and leaves
// it at the end of the current scope
//
// example:
//
// int Count()
// {
// static int s_counter = 0;
//
// wxCRITICAL_SECTION(counter);
//
// return ++s_counter;
// }
//
// this function is MT-safe in presence of the threads but there is no
// overhead when the library is compiled without threads
#define wxCRITICAL_SECTION(name) \
wxCRIT_SECT_DECLARE(s_cs##name); \
wxCRIT_SECT_LOCKER(cs##name##Locker, s_cs##name)
// automatically lock GUI mutex in ctor and unlock it in dtor
class WXDLLEXPORT wxMutexGuiLocker
{
public:
wxMutexGuiLocker() { wxMutexGuiEnter(); }
~wxMutexGuiLocker() { wxMutexGuiLeave(); }
};
// -----------------------------------------------------------------------------
// implementation only until the end of file
// -----------------------------------------------------------------------------
#if wxUSE_THREADS
#if defined(__WXMSW__) || defined(__WXMAC__) || defined(__WXPM__)
// unlock GUI if there are threads waiting for and lock it back when
// there are no more of them - should be called periodically by the main
// thread
extern void WXDLLEXPORT wxMutexGuiLeaveOrEnter();
// returns TRUE if the main thread has GUI lock
extern bool WXDLLEXPORT wxGuiOwnedByMainThread();
#ifndef __WXPM__
// wakes up the main thread if it's sleeping inside ::GetMessage()
extern void WXDLLEXPORT wxWakeUpMainThread();
#endif // !OS/2
// return TRUE if the main thread is waiting for some other to terminate:
// wxApp then should block all "dangerous" messages
extern bool WXDLLEXPORT wxIsWaitingForThread();
#endif // MSW, Mac, OS/2
#endif // wxUSE_THREADS
#endif // _WX_THREAD_H_