OpenShot Library | OpenShotAudio 0.2.2
juce_Thread.h
1
2/** @weakgroup juce_core-threads
3 * @{
4 */
5/*
6 ==============================================================================
7
8 This file is part of the JUCE library.
9 Copyright (c) 2017 - ROLI Ltd.
10
11 JUCE is an open source library subject to commercial or open-source
12 licensing.
13
14 The code included in this file is provided under the terms of the ISC license
15 http://www.isc.org/downloads/software-support-policy/isc-license. Permission
16 To use, copy, modify, and/or distribute this software for any purpose with or
17 without fee is hereby granted provided that the above copyright notice and
18 this permission notice appear in all copies.
19
20 JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
21 EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
22 DISCLAIMED.
23
24 ==============================================================================
25*/
26
27namespace juce
28{
29
30//==============================================================================
31/**
32 Encapsulates a thread.
33
34 Subclasses derive from Thread and implement the run() method, in which they
35 do their business. The thread can then be started with the startThread() method
36 and controlled with various other methods.
37
38 This class also contains some thread-related static methods, such
39 as sleep(), yield(), getCurrentThreadId() etc.
40
41 @see CriticalSection, WaitableEvent, Process, ThreadWithProgressWindow,
42 MessageManagerLock
43
44 @tags{Core}
45*/
47{
48public:
49 //==============================================================================
50 /**
51 Creates a thread.
52
53 When first created, the thread is not running. Use the startThread()
54 method to start it.
55
56 @param threadName The name of the thread which typically appears in
57 debug logs and profiles.
58 @param threadStackSize The size of the stack of the thread. If this value
59 is zero then the default stack size of the OS will
60 be used.
61 */
62 explicit Thread (const String& threadName, size_t threadStackSize = 0);
63
64 /** Destructor.
65
66 You must never attempt to delete a Thread object while it's still running -
67 always call stopThread() and make sure your thread has stopped before deleting
68 the object. Failing to do so will throw an assertion, and put you firmly into
69 undefined behaviour territory.
70 */
71 virtual ~Thread();
72
73 //==============================================================================
74 /** Must be implemented to perform the thread's actual code.
75
76 Remember that the thread must regularly check the threadShouldExit()
77 method whilst running, and if this returns true it should return from
78 the run() method as soon as possible to avoid being forcibly killed.
79
80 @see threadShouldExit, startThread
81 */
82 virtual void run() = 0;
83
84 //==============================================================================
85 /** Starts the thread running.
86
87 This will cause the thread's run() method to be called by a new thread.
88 If this thread is already running, startThread() won't do anything.
89
90 @see stopThread
91 */
92 void startThread();
93
94 /** Starts the thread with a given priority.
95
96 Launches the thread with a given priority, where 0 = lowest, 10 = highest.
97 If the thread is already running, its priority will be changed.
98
99 @see startThread, setPriority, realtimeAudioPriority
100 */
101 void startThread (int priority);
102
103 /** Attempts to stop the thread running.
104
105 This method will cause the threadShouldExit() method to return true
106 and call notify() in case the thread is currently waiting.
107
108 Hopefully the thread will then respond to this by exiting cleanly, and
109 the stopThread method will wait for a given time-period for this to
110 happen.
111
112 If the thread is stuck and fails to respond after the timeout, it gets
113 forcibly killed, which is a very bad thing to happen, as it could still
114 be holding locks, etc. which are needed by other parts of your program.
115
116 @param timeOutMilliseconds The number of milliseconds to wait for the
117 thread to finish before killing it by force. A negative
118 value in here will wait forever.
119 @returns true if the thread was cleanly stopped before the timeout, or false
120 if it had to be killed by force.
121 @see signalThreadShouldExit, threadShouldExit, waitForThreadToExit, isThreadRunning
122 */
123 bool stopThread (int timeOutMilliseconds);
124
125 //==============================================================================
126 /** Invokes a lambda or function on its own thread.
127
128 This will spin up a Thread object which calls the function and then exits.
129 Bear in mind that starting and stopping a thread can be a fairly heavyweight
130 operation, so you might prefer to use a ThreadPool if you're kicking off a lot
131 of short background tasks.
132
133 Also note that using an anonymous thread makes it very difficult to interrupt
134 the function when you need to stop it, e.g. when your app quits. So it's up to
135 you to deal with situations where the function may fail to stop in time.
136 */
137 static void launch (std::function<void()> functionToRun);
138
139 //==============================================================================
140 /** Returns true if the thread is currently active */
141 bool isThreadRunning() const;
142
143 /** Sets a flag to tell the thread it should stop.
144
145 Calling this means that the threadShouldExit() method will then return true.
146 The thread should be regularly checking this to see whether it should exit.
147
148 If your thread makes use of wait(), you might want to call notify() after calling
149 this method, to interrupt any waits that might be in progress, and allow it
150 to reach a point where it can exit.
151
152 @see threadShouldExit, waitForThreadToExit
153 */
154 void signalThreadShouldExit();
155
156 /** Checks whether the thread has been told to stop running.
157
158 Threads need to check this regularly, and if it returns true, they should
159 return from their run() method at the first possible opportunity.
160
161 @see signalThreadShouldExit, currentThreadShouldExit
162 */
163 bool threadShouldExit() const;
164
165 /** Checks whether the current thread has been told to stop running.
166 On the message thread, this will always return false, otherwise
167 it will return threadShouldExit() called on the current thread.
168
169 @see threadShouldExit
170 */
171 static bool currentThreadShouldExit();
172
173 /** Waits for the thread to stop.
174 This will wait until isThreadRunning() is false or until a timeout expires.
175
176 @param timeOutMilliseconds the time to wait, in milliseconds. If this value
177 is less than zero, it will wait forever.
178 @returns true if the thread exits, or false if the timeout expires first.
179 */
180 bool waitForThreadToExit (int timeOutMilliseconds) const;
181
182 //==============================================================================
183 /** Used to receive callbacks for thread exit calls */
185 {
186 public:
187 virtual ~Listener() = default;
188
189 /** Called if Thread::signalThreadShouldExit was called.
190 @see Thread::threadShouldExit, Thread::addListener, Thread::removeListener
191 */
192 virtual void exitSignalSent() = 0;
193 };
194
195 /** Add a listener to this thread which will receive a callback when
196 signalThreadShouldExit was called on this thread.
197
198 @see signalThreadShouldExit, removeListener
199 */
200 void addListener (Listener*);
201
202 /** Removes a listener added with addListener. */
203 void removeListener (Listener*);
204
205 //==============================================================================
206 /** Special realtime audio thread priority
207
208 This priority will create a high-priority thread which is best suited
209 for realtime audio processing.
210
211 Currently, this priority is identical to priority 9, except when building
212 for Android with OpenSL/Oboe support.
213
214 In this case, JUCE will ask OpenSL/Oboe to construct a super high priority thread
215 specifically for realtime audio processing.
216
217 Note that this priority can only be set **before** the thread has
218 started. Switching to this priority, or from this priority to a different
219 priority, is not supported under Android and will assert.
220
221 For best performance this thread should yield at regular intervals
222 and not call any blocking APIs.
223
224 @see startThread, setPriority, sleep, WaitableEvent
225 */
226 enum
227 {
228 realtimeAudioPriority = -1
229 };
230
231 /** Changes the thread's priority.
232
233 May return false if for some reason the priority can't be changed.
234
235 @param priority the new priority, in the range 0 (lowest) to 10 (highest). A priority
236 of 5 is normal.
237 @see realtimeAudioPriority
238 */
239 bool setPriority (int priority);
240
241 /** Changes the priority of the caller thread.
242
243 Similar to setPriority(), but this static method acts on the caller thread.
244 May return false if for some reason the priority can't be changed.
245
246 @see setPriority
247 */
248 static bool setCurrentThreadPriority (int priority);
249
250 //==============================================================================
251 /** Sets the affinity mask for the thread.
252
253 This will only have an effect next time the thread is started - i.e. if the
254 thread is already running when called, it'll have no effect.
255
256 @see setCurrentThreadAffinityMask
257 */
258 void setAffinityMask (uint32 affinityMask);
259
260 /** Changes the affinity mask for the caller thread.
261
262 This will change the affinity mask for the thread that calls this static method.
263
264 @see setAffinityMask
265 */
266 static void JUCE_CALLTYPE setCurrentThreadAffinityMask (uint32 affinityMask);
267
268 //==============================================================================
269 /** Suspends the execution of the current thread until the specified timeout period
270 has elapsed (note that this may not be exact).
271
272 The timeout period must not be negative and whilst sleeping the thread cannot
273 be woken up so it should only be used for short periods of time and when other
274 methods such as using a WaitableEvent or CriticalSection are not possible.
275 */
276 static void JUCE_CALLTYPE sleep (int milliseconds);
277
278 /** Yields the current thread's CPU time-slot and allows a new thread to run.
279
280 If there are no other threads of equal or higher priority currently running then
281 this will return immediately and the current thread will continue to run.
282 */
283 static void JUCE_CALLTYPE yield();
284
285 //==============================================================================
286 /** Suspends the execution of this thread until either the specified timeout period
287 has elapsed, or another thread calls the notify() method to wake it up.
288
289 A negative timeout value means that the method will wait indefinitely.
290
291 @returns true if the event has been signalled, false if the timeout expires.
292 */
293 bool wait (int timeOutMilliseconds) const;
294
295 /** Wakes up the thread.
296
297 If the thread has called the wait() method, this will wake it up.
298
299 @see wait
300 */
301 void notify() const;
302
303 //==============================================================================
304 /** A value type used for thread IDs.
305
306 @see getCurrentThreadId(), getThreadId()
307 */
308 using ThreadID = void*;
309
310 /** Returns an id that identifies the caller thread.
311
312 To find the ID of a particular thread object, use getThreadId().
313
314 @returns a unique identifier that identifies the calling thread.
315 @see getThreadId
316 */
317 static ThreadID JUCE_CALLTYPE getCurrentThreadId();
318
319 /** Finds the thread object that is currently running.
320
321 Note that the main UI thread (or other non-JUCE threads) don't have a Thread
322 object associated with them, so this will return nullptr.
323 */
324 static Thread* JUCE_CALLTYPE getCurrentThread();
325
326 /** Returns the ID of this thread.
327
328 That means the ID of this thread object - not of the thread that's calling the method.
329 This can change when the thread is started and stopped, and will be invalid if the
330 thread's not actually running.
331
332 @see getCurrentThreadId
333 */
334 ThreadID getThreadId() const noexcept;
335
336 /** Returns the name of the thread. This is the name that gets set in the constructor. */
337 const String& getThreadName() const noexcept { return threadName; }
338
339 /** Changes the name of the caller thread.
340
341 Different OSes may place different length or content limits on this name.
342 */
343 static void JUCE_CALLTYPE setCurrentThreadName (const String& newThreadName);
344
345 #if JUCE_ANDROID || defined (DOXYGEN)
346 //==============================================================================
347 /** Initialises the JUCE subsystem for projects not created by the Projucer
348
349 On Android, JUCE needs to be initialised once before it is used. The Projucer
350 will automatically generate the necessary java code to do this. However, if
351 you are using JUCE without the Projucer or are creating a library made with
352 JUCE intended for use in non-JUCE apks, then you must call this method
353 manually once on apk startup.
354
355 You can call this method from C++ or directly from java by calling the
356 following java method:
357
358 @code
359 com.roli.juce.Java.initialiseJUCE (myContext);
360 @endcode
361
362 Note that the above java method is only available in Android Studio projects
363 created by the Projucer. If you need to call this from another type of project
364 then you need to add the following java file to
365 your project:
366
367 @code
368 package com.roli.juce;
369
370 public class Java
371 {
372 static { System.loadLibrary ("juce_jni"); }
373 public native static void initialiseJUCE (Context context);
374 }
375 @endcode
376
377 @param jniEnv this is a pointer to JNI's JNIEnv variable. Any callback
378 from Java into C++ will have this passed in as it's first
379 parameter.
380 @param jContext this is a jobject referring to your app/service/receiver/
381 provider's Context. JUCE needs this for many of it's internal
382 functions.
383 */
384 static void initialiseJUCE (void* jniEnv, void* jContext);
385 #endif
386
387private:
388 //==============================================================================
389 const String threadName;
390 Atomic<void*> threadHandle { nullptr };
391 Atomic<ThreadID> threadId = {};
392 CriticalSection startStopLock;
393 WaitableEvent startSuspensionEvent, defaultEvent;
394 int threadPriority = 5;
395 size_t threadStackSize;
396 uint32 affinityMask = 0;
397 bool deleteOnThreadEnd = false;
398 Atomic<int32> shouldExit { 0 };
399 ListenerList<Listener, Array<Listener*, CriticalSection>> listeners;
400
401 #if JUCE_ANDROID
402 bool isAndroidRealtimeThread = false;
403 #endif
404
405 #ifndef DOXYGEN
406 friend void JUCE_API juce_threadEntryPoint (void*);
407 #endif
408
409 void launchThread();
410 void closeThreadHandle();
411 void killThread();
412 void threadEntryPoint();
413 static bool setThreadPriority (void*, int);
414
415 JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (Thread)
416};
417
418} // namespace juce
419
420/** @}*/
The JUCE String class!
Definition: juce_String.h:43
Used to receive callbacks for thread exit calls.
Definition: juce_Thread.h:185
virtual void exitSignalSent()=0
Called if Thread::signalThreadShouldExit was called.
Encapsulates a thread.
Definition: juce_Thread.h:47
static void initialiseJUCE(void *jniEnv, void *jContext)
Initialises the JUCE subsystem for projects not created by the Projucer.
static void JUCE_CALLTYPE setCurrentThreadAffinityMask(uint32 affinityMask)
Changes the affinity mask for the caller thread.
void * ThreadID
A value type used for thread IDs.
Definition: juce_Thread.h:308
static void JUCE_CALLTYPE sleep(int milliseconds)
Suspends the execution of the current thread until the specified timeout period has elapsed (note tha...
static void JUCE_CALLTYPE setCurrentThreadName(const String &newThreadName)
Changes the name of the caller thread.
virtual void run()=0
Must be implemented to perform the thread's actual code.
static void JUCE_CALLTYPE yield()
Yields the current thread's CPU time-slot and allows a new thread to run.
static ThreadID JUCE_CALLTYPE getCurrentThreadId()
Returns an id that identifies the caller thread.
#define JUCE_API
This macro is added to all JUCE public class declarations.