juce/source/src/threads/juce_Thread.h

   1 /*
   2   ==============================================================================
   3
   4    This file is part of the JUCE library - "Jules' Utility Class Extensions"
   5    Copyright 2004-11 by Raw Material Software Ltd.
   6
   7   ------------------------------------------------------------------------------
   8
   9    JUCE can be redistributed and/or modified under the terms of the GNU General
  10    Public License (Version 2), as published by the Free Software Foundation.
  11    A copy of the license is included in the JUCE distribution, or can be found
  12    online at www.gnu.org/licenses.
  13
  14    JUCE is distributed in the hope that it will be useful, but WITHOUT ANY
  15    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
  16    A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
  17
  18   ------------------------------------------------------------------------------
  19
  20    To release a closed-source product which uses JUCE, commercial licenses are
  21    available: visit www.rawmaterialsoftware.com/juce for more information.
  22
  23   ==============================================================================
  24 */
  25
  26 #ifndef __JUCE_THREAD_JUCEHEADER__
  27 #define __JUCE_THREAD_JUCEHEADER__
  28
  29 #include "juce_WaitableEvent.h"
  30 #include "juce_CriticalSection.h"
  31
  32
  33 //==============================================================================
  34 /**
  35     Encapsulates a thread.
  36
  37     Subclasses derive from Thread and implement the run() method, in which they
  38     do their business. The thread can then be started with the startThread() method
  39     and controlled with various other methods.
  40
  41     This class also contains some thread-related static methods, such
  42     as sleep(), yield(), getCurrentThreadId() etc.
  43
  44     @see CriticalSection, WaitableEvent, Process, ThreadWithProgressWindow,
  45          MessageManagerLock
  46 */
  47 class JUCE_API  Thread
  48 {
  49 public:
  50     //==============================================================================
  51     /**
  52         Creates a thread.
  53
  54         When first created, the thread is not running. Use the startThread()
  55         method to start it.
  56     */
  57     explicit Thread (const String& threadName);
  58
  59     /** Destructor.
  60
  61         Deleting a Thread object that is running will only give the thread a
  62         brief opportunity to stop itself cleanly, so it's recommended that you
  63         should always call stopThread() with a decent timeout before deleting,
  64         to avoid the thread being forcibly killed (which is a Bad Thing).
  65     */
  66     virtual ~Thread();
  67
  68     //==============================================================================
  69     /** Must be implemented to perform the thread's actual code.
  70
  71         Remember that the thread must regularly check the threadShouldExit()
  72         method whilst running, and if this returns true it should return from
  73         the run() method as soon as possible to avoid being forcibly killed.
  74
  75         @see threadShouldExit, startThread
  76     */
  77     virtual void run() = 0;
  78
  79     //==============================================================================
  80     // Thread control functions..
  81
  82     /** Starts the thread running.
  83
  84         This will start the thread's run() method.
  85         (if it's already started, startThread() won't do anything).
  86
  87         @see stopThread
  88     */
  89     void startThread();
  90
  91     /** Starts the thread with a given priority.
  92
  93         Launches the thread with a given priority, where 0 = lowest, 10 = highest.
  94         If the thread is already running, its priority will be changed.
  95
  96         @see startThread, setPriority
  97     */
  98     void startThread (int priority);
  99
 100     /** Attempts to stop the thread running.
 101
 102         This method will cause the threadShouldExit() method to return true
 103         and call notify() in case the thread is currently waiting.
 104
 105         Hopefully the thread will then respond to this by exiting cleanly, and
 106         the stopThread method will wait for a given time-period for this to
 107         happen.
 108
 109         If the thread is stuck and fails to respond after the time-out, it gets
 110         forcibly killed, which is a very bad thing to happen, as it could still
 111         be holding locks, etc. which are needed by other parts of your program.
 112
 113         @param timeOutMilliseconds  The number of milliseconds to wait for the
 114                                     thread to finish before killing it by force. A negative
 115                                     value in here will wait forever.
 116         @see signalThreadShouldExit, threadShouldExit, waitForThreadToExit, isThreadRunning
 117     */
 118     void stopThread (int timeOutMilliseconds);
 119
 120     //==============================================================================
 121     /** Returns true if the thread is currently active */
 122     bool isThreadRunning() const;
 123
 124     /** Sets a flag to tell the thread it should stop.
 125
 126         Calling this means that the threadShouldExit() method will then return true.
 127         The thread should be regularly checking this to see whether it should exit.
 128
 129         If your thread makes use of wait(), you might want to call notify() after calling
 130         this method, to interrupt any waits that might be in progress, and allow it
 131         to reach a point where it can exit.
 132
 133         @see threadShouldExit
 134         @see waitForThreadToExit
 135     */
 136     void signalThreadShouldExit();
 137
 138     /** Checks whether the thread has been told to stop running.
 139
 140         Threads need to check this regularly, and if it returns true, they should
 141         return from their run() method at the first possible opportunity.
 142
 143         @see signalThreadShouldExit
 144     */
 145     inline bool threadShouldExit() const                { return threadShouldExit_; }
 146
 147     /** Waits for the thread to stop.
 148
 149         This will waits until isThreadRunning() is false or until a timeout expires.
 150
 151         @param timeOutMilliseconds  the time to wait, in milliseconds. If this value
 152                                     is less than zero, it will wait forever.
 153         @returns    true if the thread exits, or false if the timeout expires first.
 154     */
 155     bool waitForThreadToExit (int timeOutMilliseconds) const;
 156
 157     //==============================================================================
 158     /** Changes the thread's priority.
 159         May return false if for some reason the priority can't be changed.
 160
 161         @param priority     the new priority, in the range 0 (lowest) to 10 (highest). A priority
 162                             of 5 is normal.
 163     */
 164     bool setPriority (int priority);
 165
 166     /** Changes the priority of the caller thread.
 167
 168         Similar to setPriority(), but this static method acts on the caller thread.
 169         May return false if for some reason the priority can't be changed.
 170
 171         @see setPriority
 172     */
 173     static bool setCurrentThreadPriority (int priority);
 174
 175     //==============================================================================
 176     /** Sets the affinity mask for the thread.
 177
 178         This will only have an effect next time the thread is started - i.e. if the
 179         thread is already running when called, it'll have no effect.
 180
 181         @see setCurrentThreadAffinityMask
 182     */
 183     void setAffinityMask (uint32 affinityMask);
 184
 185     /** Changes the affinity mask for the caller thread.
 186
 187         This will change the affinity mask for the thread that calls this static method.
 188
 189         @see setAffinityMask
 190     */
 191     static void setCurrentThreadAffinityMask (uint32 affinityMask);
 192
 193     //==============================================================================
 194     // this can be called from any thread that needs to pause..
 195     static void JUCE_CALLTYPE sleep (int milliseconds);
 196
 197     /** Yields the calling thread's current time-slot. */
 198     static void JUCE_CALLTYPE yield();
 199
 200     //==============================================================================
 201     /** Makes the thread wait for a notification.
 202
 203         This puts the thread to sleep until either the timeout period expires, or
 204         another thread calls the notify() method to wake it up.
 205
 206         A negative time-out value means that the method will wait indefinitely.
 207
 208         @returns    true if the event has been signalled, false if the timeout expires.
 209     */
 210     bool wait (int timeOutMilliseconds) const;
 211
 212     /** Wakes up the thread.
 213
 214         If the thread has called the wait() method, this will wake it up.
 215
 216         @see wait
 217     */
 218     void notify() const;
 219
 220     //==============================================================================
 221     /** A value type used for thread IDs.
 222         @see getCurrentThreadId(), getThreadId()
 223     */
 224     typedef void* ThreadID;
 225
 226     /** Returns an id that identifies the caller thread.
 227
 228         To find the ID of a particular thread object, use getThreadId().
 229
 230         @returns    a unique identifier that identifies the calling thread.
 231         @see getThreadId
 232     */
 233     static ThreadID getCurrentThreadId();
 234
 235     /** Finds the thread object that is currently running.
 236
 237         Note that the main UI thread (or other non-Juce threads) don't have a Thread
 238         object associated with them, so this will return 0.
 239     */
 240     static Thread* getCurrentThread();
 241
 242     /** Returns the ID of this thread.
 243
 244         That means the ID of this thread object - not of the thread that's calling the method.
 245
 246         This can change when the thread is started and stopped, and will be invalid if the
 247         thread's not actually running.
 248
 249         @see getCurrentThreadId
 250     */
 251     ThreadID getThreadId() const noexcept                           { return threadId_; }
 252
 253     /** Returns the name of the thread.
 254
 255         This is the name that gets set in the constructor.
 256     */
 257     const String& getThreadName() const                             { return threadName_; }
 258
 259     /** Changes the name of the caller thread.
 260         Different OSes may place different length or content limits on this name.
 261     */
 262     static void setCurrentThreadName (const String& newThreadName);
 263
 264     //==============================================================================
 265     /** Returns the number of currently-running threads.
 266
 267         @returns  the number of Thread objects known to be currently running.
 268         @see stopAllThreads
 269     */
 270     static int getNumRunningThreads();
 271
 272     /** Tries to stop all currently-running threads.
 273
 274         This will attempt to stop all the threads known to be running at the moment.
 275     */
 276     static void stopAllThreads (int timeoutInMillisecs);
 277
 278
 279 private:
 280     //==============================================================================
 281     const String threadName_;
 282     void* volatile threadHandle_;
 283     ThreadID threadId_;
 284     CriticalSection startStopLock;
 285     WaitableEvent startSuspensionEvent_, defaultEvent_;
 286     int threadPriority_;
 287     uint32 affinityMask_;
 288     bool volatile threadShouldExit_;
 289
 290    #ifndef DOXYGEN
 291     friend class MessageManager;
 292     friend void JUCE_API juce_threadEntryPoint (void*);
 293    #endif
 294
 295     void launchThread();
 296     void closeThreadHandle();
 297     void killThread();
 298     void threadEntryPoint();
 299     static bool setThreadPriority (void* handle, int priority);
 300
 301     JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (Thread);
 302 };
 303
 304 #endif   // __JUCE_THREAD_JUCEHEADER__