JUCE  v6.1.6 (6.0.8-1114)
JUCE API
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juce::Thread Class Referenceabstract

Encapsulates a thread. More...

#include <juce_Thread.h>

Inheritance diagram for juce::Thread:
Collaboration diagram for juce::Thread:

Classes

class  Listener
 Used to receive callbacks for thread exit calls. More...
 

Public Types

enum  { realtimeAudioPriority = -1 }
 Special realtime audio thread priority. More...
 
using ThreadID = void *
 A value type used for thread IDs. More...
 

Public Member Functions

 Thread (const String &threadName, size_t threadStackSize=0)
 Creates a thread. More...
 
virtual ~Thread ()
 Destructor. More...
 
void addListener (Listener *)
 Add a listener to this thread which will receive a callback when signalThreadShouldExit was called on this thread. More...
 
ThreadID getThreadId () const noexcept
 Returns the ID of this thread. More...
 
const StringgetThreadName () const noexcept
 Returns the name of the thread. More...
 
bool isThreadRunning () const
 Returns true if the thread is currently active. More...
 
void notify () const
 Wakes up the thread. More...
 
void removeListener (Listener *)
 Removes a listener added with addListener. More...
 
virtual void run ()=0
 Must be implemented to perform the thread's actual code. More...
 
void setAffinityMask (uint32 affinityMask)
 Sets the affinity mask for the thread. More...
 
bool setPriority (int priority)
 Changes the thread's priority. More...
 
void signalThreadShouldExit ()
 Sets a flag to tell the thread it should stop. More...
 
void startThread ()
 Starts the thread running. More...
 
void startThread (int priority)
 Starts the thread with a given priority. More...
 
bool stopThread (int timeOutMilliseconds)
 Attempts to stop the thread running. More...
 
bool threadShouldExit () const
 Checks whether the thread has been told to stop running. More...
 
bool wait (int timeOutMilliseconds) const
 Suspends the execution of this thread until either the specified timeout period has elapsed, or another thread calls the notify() method to wake it up. More...
 
bool waitForThreadToExit (int timeOutMilliseconds) const
 Waits for the thread to stop. More...
 

Static Public Member Functions

static bool currentThreadShouldExit ()
 Checks whether the current thread has been told to stop running. More...
 
static ThreadgetCurrentThread ()
 Finds the thread object that is currently running. More...
 
static ThreadID getCurrentThreadId ()
 Returns an id that identifies the caller thread. More...
 
static void initialiseJUCE (void *jniEnv, void *jContext)
 Initialises the JUCE subsystem for projects not created by the Projucer. More...
 
static void launch (std::function< void()> functionToRun)
 Invokes a lambda or function on its own thread. More...
 
static void setCurrentThreadAffinityMask (uint32 affinityMask)
 Changes the affinity mask for the caller thread. More...
 
static void setCurrentThreadName (const String &newThreadName)
 Changes the name of the caller thread. More...
 
static bool setCurrentThreadPriority (int priority)
 Changes the priority of the caller thread. More...
 
static void sleep (int milliseconds)
 Suspends the execution of the current thread until the specified timeout period has elapsed (note that this may not be exact). More...
 
static void yield ()
 Yields the current thread's CPU time-slot and allows a new thread to run. More...
 

Private Member Functions

void closeThreadHandle ()
 
void killThread ()
 
void launchThread ()
 
void threadEntryPoint ()
 

Static Private Member Functions

static int getAdjustedPriority (int)
 
static bool setThreadPriority (void *, int)
 

Private Attributes

uint32 affinityMask = 0
 
WaitableEvent defaultEvent
 
bool deleteOnThreadEnd = false
 
bool isAndroidRealtimeThread = false
 
ListenerList< Listener, Array< Listener *, CriticalSection > > listeners
 
Atomic< int32shouldExit { 0 }
 
CriticalSection startStopLock
 
WaitableEvent startSuspensionEvent
 
Atomic< void * > threadHandle { nullptr }
 
Atomic< ThreadIDthreadId = {}
 
const String threadName
 
int threadPriority = 5
 
size_t threadStackSize
 

Detailed Description

Encapsulates a thread.

Subclasses derive from Thread and implement the run() method, in which they do their business. The thread can then be started with the startThread() method and controlled with various other methods.

This class also contains some thread-related static methods, such as sleep(), yield(), getCurrentThreadId() etc.

See also
CriticalSection, WaitableEvent, Process, ThreadWithProgressWindow, MessageManagerLock

@tags{Core}

Member Typedef Documentation

◆ ThreadID

using juce::Thread::ThreadID = void*

A value type used for thread IDs.

See also
getCurrentThreadId(), getThreadId()

Member Enumeration Documentation

◆ anonymous enum

anonymous enum

Special realtime audio thread priority.

This priority will create a high-priority thread which is best suited for realtime audio processing.

Currently, this priority is identical to priority 9, except when building for Android with OpenSL/Oboe support.

In this case, JUCE will ask OpenSL/Oboe to construct a super high priority thread specifically for realtime audio processing.

Note that this priority can only be set before the thread has started. Switching to this priority, or from this priority to a different priority, is not supported under Android and will assert.

For best performance this thread should yield at regular intervals and not call any blocking APIs.

See also
startThread, setPriority, sleep, WaitableEvent
Enumerator
realtimeAudioPriority 

Constructor & Destructor Documentation

◆ Thread()

juce::Thread::Thread ( const String threadName,
size_t  threadStackSize = 0 
)
explicit

Creates a thread.

When first created, the thread is not running. Use the startThread() method to start it.

Parameters
threadNameThe name of the thread which typically appears in debug logs and profiles.
threadStackSizeThe size of the stack of the thread. If this value is zero then the default stack size of the OS will be used.

◆ ~Thread()

virtual juce::Thread::~Thread ( )
virtual

Destructor.

You must never attempt to delete a Thread object while it's still running - always call stopThread() and make sure your thread has stopped before deleting the object. Failing to do so will throw an assertion, and put you firmly into undefined behaviour territory.

Member Function Documentation

◆ addListener()

void juce::Thread::addListener ( Listener )

Add a listener to this thread which will receive a callback when signalThreadShouldExit was called on this thread.

See also
signalThreadShouldExit, removeListener

◆ closeThreadHandle()

void juce::Thread::closeThreadHandle ( )
private

References threadHandle, and threadId.

◆ currentThreadShouldExit()

static bool juce::Thread::currentThreadShouldExit ( )
static

Checks whether the current thread has been told to stop running.

On the message thread, this will always return false, otherwise it will return threadShouldExit() called on the current thread.

See also
threadShouldExit

◆ getAdjustedPriority()

static int juce::Thread::getAdjustedPriority ( int  )
staticprivate

◆ getCurrentThread()

static Thread* juce::Thread::getCurrentThread ( )
static

Finds the thread object that is currently running.

Note that the main UI thread (or other non-JUCE threads) don't have a Thread object associated with them, so this will return nullptr.

◆ getCurrentThreadId()

Thread::ThreadID juce::Thread::getCurrentThreadId ( )
static

Returns an id that identifies the caller thread.

To find the ID of a particular thread object, use getThreadId().

Returns
a unique identifier that identifies the calling thread.
See also
getThreadId

Referenced by juce::ThreadLocalValue< Type >::get(), and juce::ThreadLocalValue< Type >::releaseCurrentThreadStorage().

◆ getThreadId()

ThreadID juce::Thread::getThreadId ( ) const
noexcept

Returns the ID of this thread.

That means the ID of this thread object - not of the thread that's calling the method. This can change when the thread is started and stopped, and will be invalid if the thread's not actually running.

See also
getCurrentThreadId

◆ getThreadName()

const String& juce::Thread::getThreadName ( ) const
inlinenoexcept

Returns the name of the thread.

This is the name that gets set in the constructor.

◆ initialiseJUCE()

static void juce::Thread::initialiseJUCE ( void *  jniEnv,
void *  jContext 
)
static

Initialises the JUCE subsystem for projects not created by the Projucer.

On Android, JUCE needs to be initialised once before it is used. The Projucer will automatically generate the necessary java code to do this. However, if you are using JUCE without the Projucer or are creating a library made with JUCE intended for use in non-JUCE apks, then you must call this method manually once on apk startup.

You can call this method from C++ or directly from java by calling the following java method:

com.rmsl.juce.Java.initialiseJUCE (myContext);

Note that the above java method is only available in Android Studio projects created by the Projucer. If you need to call this from another type of project then you need to add the following java file to your project:

package com.rmsl.juce;
public class Java
{
static { System.loadLibrary ("juce_jni"); }
public native static void initialiseJUCE (Context context);
}
Parameters
jniEnvthis is a pointer to JNI's JNIEnv variable. Any callback from Java into C++ will have this passed in as it's first parameter.
jContextthis is a jobject referring to your app/service/receiver/ provider's Context. JUCE needs this for many of it's internal functions.

◆ isThreadRunning()

bool juce::Thread::isThreadRunning ( ) const

Returns true if the thread is currently active.

◆ killThread()

void juce::Thread::killThread ( )
private

◆ launch()

static void juce::Thread::launch ( std::function< void()>  functionToRun)
static

Invokes a lambda or function on its own thread.

This will spin up a Thread object which calls the function and then exits. Bear in mind that starting and stopping a thread can be a fairly heavyweight operation, so you might prefer to use a ThreadPool if you're kicking off a lot of short background tasks.

Also note that using an anonymous thread makes it very difficult to interrupt the function when you need to stop it, e.g. when your app quits. So it's up to you to deal with situations where the function may fail to stop in time.

◆ launchThread()

◆ notify()

void juce::Thread::notify ( ) const

Wakes up the thread.

If the thread has called the wait() method, this will wake it up.

See also
wait

◆ removeListener()

void juce::Thread::removeListener ( Listener )

Removes a listener added with addListener.

◆ run()

virtual void juce::Thread::run ( )
pure virtual

Must be implemented to perform the thread's actual code.

Remember that the thread must regularly check the threadShouldExit() method whilst running, and if this returns true it should return from the run() method as soon as possible to avoid being forcibly killed.

See also
threadShouldExit, startThread

Implemented in juce::MidiOutput, juce::ThreadedAnalyticsDestination::EventDispatcher, juce::NetworkServiceDiscovery::AvailableServiceList, juce::InterprocessConnectionServer, and juce::NetworkServiceDiscovery::Advertiser.

◆ setAffinityMask()

void juce::Thread::setAffinityMask ( uint32  affinityMask)

Sets the affinity mask for the thread.

This will only have an effect next time the thread is started - i.e. if the thread is already running when called, it'll have no effect.

See also
setCurrentThreadAffinityMask

◆ setCurrentThreadAffinityMask()

void juce::Thread::setCurrentThreadAffinityMask ( uint32  affinityMask)
static

Changes the affinity mask for the caller thread.

This will change the affinity mask for the thread that calls this static method.

See also
setAffinityMask

References affinityMask, juce::ignoreUnused(), and jassertfalse.

◆ setCurrentThreadName()

void juce::Thread::setCurrentThreadName ( const String newThreadName)
static

Changes the name of the caller thread.

Different OSes may place different length or content limits on this name.

References JUCE_AUTORELEASEPOOL, juce::juceStringToNS(), and juce::gl::name.

Referenced by juce::MessageThread::start().

◆ setCurrentThreadPriority()

static bool juce::Thread::setCurrentThreadPriority ( int  priority)
static

Changes the priority of the caller thread.

Similar to setPriority(), but this static method acts on the caller thread. May return false if for some reason the priority can't be changed.

See also
setPriority

Referenced by juce::MessageThread::start().

◆ setPriority()

bool juce::Thread::setPriority ( int  priority)

Changes the thread's priority.

May return false if for some reason the priority can't be changed.

Parameters
prioritythe new priority, in the range 0 (lowest) to 10 (highest). A priority of 5 is normal.
See also
realtimeAudioPriority

◆ setThreadPriority()

bool juce::Thread::setThreadPriority ( void *  handle,
int  priority 
)
staticprivate

◆ signalThreadShouldExit()

void juce::Thread::signalThreadShouldExit ( )

Sets a flag to tell the thread it should stop.

Calling this means that the threadShouldExit() method will then return true. The thread should be regularly checking this to see whether it should exit.

If your thread makes use of wait(), you might want to call notify() after calling this method, to interrupt any waits that might be in progress, and allow it to reach a point where it can exit.

See also
threadShouldExit, waitForThreadToExit

◆ sleep()

void juce::Thread::sleep ( int  milliseconds)
static

Suspends the execution of the current thread until the specified timeout period has elapsed (note that this may not be exact).

The timeout period must not be negative and whilst sleeping the thread cannot be woken up so it should only be used for short periods of time and when other methods such as using a WaitableEvent or CriticalSection are not possible.

References juce::UnitTestCategories::time.

Referenced by juce::OpenGLContext::NativeContext::initialiseOnRenderThread(), juce::MessageThread::start(), and juce::OpenGLContext::NativeContext::swapBuffers().

◆ startThread() [1/2]

void juce::Thread::startThread ( )

Starts the thread running.

This will cause the thread's run() method to be called by a new thread. If this thread is already running, startThread() won't do anything.

See also
stopThread

◆ startThread() [2/2]

void juce::Thread::startThread ( int  priority)

Starts the thread with a given priority.

Launches the thread with a given priority, where 0 = lowest, 10 = highest. If the thread is already running, its priority will be changed.

See also
startThread, setPriority, realtimeAudioPriority

◆ stopThread()

bool juce::Thread::stopThread ( int  timeOutMilliseconds)

Attempts to stop the thread running.

This method will cause the threadShouldExit() method to return true and call notify() in case the thread is currently waiting.

Hopefully the thread will then respond to this by exiting cleanly, and the stopThread method will wait for a given time-period for this to happen.

If the thread is stuck and fails to respond after the timeout, it gets forcibly killed, which is a very bad thing to happen, as it could still be holding locks, etc. which are needed by other parts of your program.

Parameters
timeOutMillisecondsThe number of milliseconds to wait for the thread to finish before killing it by force. A negative value in here will wait forever.
Returns
true if the thread was cleanly stopped before the timeout, or false if it had to be killed by force.
See also
signalThreadShouldExit, threadShouldExit, waitForThreadToExit, isThreadRunning

◆ threadEntryPoint()

void juce::Thread::threadEntryPoint ( )
private

◆ threadShouldExit()

bool juce::Thread::threadShouldExit ( ) const

Checks whether the thread has been told to stop running.

Threads need to check this regularly, and if it returns true, they should return from their run() method at the first possible opportunity.

See also
signalThreadShouldExit, currentThreadShouldExit

◆ wait()

bool juce::Thread::wait ( int  timeOutMilliseconds) const

Suspends the execution of this thread until either the specified timeout period has elapsed, or another thread calls the notify() method to wake it up.

A negative timeout value means that the method will wait indefinitely.

Returns
true if the event has been signalled, false if the timeout expires.

◆ waitForThreadToExit()

bool juce::Thread::waitForThreadToExit ( int  timeOutMilliseconds) const

Waits for the thread to stop.

This will wait until isThreadRunning() is false or until a timeout expires.

Parameters
timeOutMillisecondsthe time to wait, in milliseconds. If this value is less than zero, it will wait forever.
Returns
true if the thread exits, or false if the timeout expires first.

◆ yield()

void juce::Thread::yield ( )
static

Yields the current thread's CPU time-slot and allows a new thread to run.

If there are no other threads of equal or higher priority currently running then this will return immediately and the current thread will continue to run.

Member Data Documentation

◆ affinityMask

uint32 juce::Thread::affinityMask = 0
private

◆ defaultEvent

WaitableEvent juce::Thread::defaultEvent
private

◆ deleteOnThreadEnd

bool juce::Thread::deleteOnThreadEnd = false
private

◆ isAndroidRealtimeThread

bool juce::Thread::isAndroidRealtimeThread = false
private

Referenced by launchThread().

◆ listeners

ListenerList<Listener, Array<Listener*, CriticalSection> > juce::Thread::listeners
private

◆ shouldExit

Atomic<int32> juce::Thread::shouldExit { 0 }
private

◆ startStopLock

CriticalSection juce::Thread::startStopLock
private

◆ startSuspensionEvent

WaitableEvent juce::Thread::startSuspensionEvent
private

◆ threadHandle

Atomic<void*> juce::Thread::threadHandle { nullptr }
private

◆ threadId

Atomic<ThreadID> juce::Thread::threadId = {}
private

Referenced by closeThreadHandle(), and launchThread().

◆ threadName

const String juce::Thread::threadName
private

◆ threadPriority

int juce::Thread::threadPriority = 5
private

◆ threadStackSize

size_t juce::Thread::threadStackSize
private

Referenced by launchThread().


The documentation for this class was generated from the following files:
juce::Thread::initialiseJUCE
static void initialiseJUCE(void *jniEnv, void *jContext)
Initialises the JUCE subsystem for projects not created by the Projucer.