Encapsulates a thread. More...

#include "juce_Thread.h"

Inheritance diagram for juce::Thread:

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

struct	RealtimeOptions
	A selection of options available when creating realtime threads. More...

Public Types
enum class	Priority { highest , high , normal , low , background }
	The different runtime priorities of non-realtime threads. More...

using	ThreadID = void *
	A value type used for thread IDs.

Public Member Functions
	Thread (const String &threadName, size_t threadStackSize=osDefaultStackSize)
	Creates a thread.

virtual	~Thread ()
	Destructor.

virtual void	run ()=0
	Must be implemented to perform the thread's actual code.

bool	startThread ()
	Attempts to start a new thread with default ('Priority::normal') priority.

bool	startThread (Priority newPriority)
	Attempts to start a new thread with a given priority.

bool	startRealtimeThread (const RealtimeOptions &options)
	Starts the thread with realtime performance characteristics on platforms that support it.

bool	stopThread (int timeOutMilliseconds)
	Attempts to stop the thread running.

bool	isThreadRunning () const
	Returns true if the thread is currently active.

void	signalThreadShouldExit ()
	Sets a flag to tell the thread it should stop.

bool	threadShouldExit () const
	Checks whether the thread has been told to stop running.

bool	waitForThreadToExit (int timeOutMilliseconds) const
	Waits for the thread to stop.

void	addListener (Listener *)
	Add a listener to this thread which will receive a callback when signalThreadShouldExit was called on this thread.

void	removeListener (Listener *)
	Removes a listener added with addListener.

bool	isRealtime () const
	Returns true if this Thread represents a realtime thread.

void	setAffinityMask (uint32 affinityMask)
	Sets the affinity mask for the thread.

bool	wait (double 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.

void	notify () const
	Wakes up the thread.

ThreadID	getThreadId () const noexcept
	Returns the ID of this thread.

const String &	getThreadName () const noexcept
	Returns the name of the thread.

Static Public Member Functions
static bool	launch (std::function< void()> functionToRun)
	Invokes a lambda or function on its own thread with the default priority.

static bool	launch (Priority priority, std::function< void()> functionToRun)
	Invokes a lambda or function on its own thread with a custom priority.

static bool	currentThreadShouldExit ()
	Checks whether the current thread has been told to stop running.

static void JUCE_CALLTYPE	setCurrentThreadAffinityMask (uint32 affinityMask)
	Changes the affinity mask for the caller thread.

static void JUCE_CALLTYPE	sleep (int milliseconds)
	Suspends the execution of the current thread until the specified timeout period has elapsed (note that this may not be exact).

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.

static Thread *JUCE_CALLTYPE	getCurrentThread ()
	Finds the thread object that is currently running.

static void JUCE_CALLTYPE	setCurrentThreadName (const String &newThreadName)
	Changes the name of the caller thread.

static void	initialiseJUCE (void jniEnv, void jContext)
	Initialises the JUCE subsystem for projects not created by the Projucer.

Static Public Attributes
static constexpr size_t	osDefaultStackSize

Protected Member Functions
Priority	getPriority () const
	Returns the current priority of this thread.

bool	setPriority (Priority newPriority)
	Attempts to set the priority for this thread.

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() or startRealtimeThread() methods 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}

Definition at line 42 of file juce_Thread.h.

Member Typedef Documentation

◆ ThreadID

using juce::Thread::ThreadID = void*

A value type used for thread IDs.

See also: getCurrentThreadId(), getThreadId()

Definition at line 477 of file juce_Thread.h.

Member Enumeration Documentation

◆ Priority

enum class juce::Thread::Priority

strong

The different runtime priorities of non-realtime threads.

See also: startThread

Enumerator
highest	The highest possible priority that isn't a dedicated realtime thread.
high	Makes use of performance cores and higher clocks.
normal	The OS default. It will balance out across all cores.
low	Uses efficiency cores when possible.
background	Restricted to efficiency cores on platforms that have them.

Definition at line 53 of file juce_Thread.h.

Constructor & Destructor Documentation

◆ Thread()

juce::Thread::Thread	(	const String &	threadName,
		size_t	threadStackSize = `osDefaultStackSize`
	)

explicit

Creates a thread.

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

Parameters

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

Definition at line 26 of file juce_Thread.cpp.

◆ ~Thread()

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.

Definition at line 31 of file juce_Thread.cpp.

Member Function Documentation

◆ addListener()

void juce::Thread::addListener ( Listener * listener )

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

See also: signalThreadShouldExit, removeListener

Definition at line 267 of file juce_Thread.cpp.

◆ currentThreadShouldExit()

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

Definition at line 207 of file juce_Thread.cpp.

◆ getCurrentThread()

Thread *JUCE_CALLTYPE 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.

Definition at line 185 of file juce_Thread.cpp.

◆ getCurrentThreadId()

Thread::ThreadID JUCE_CALLTYPE 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

Definition at line 1002 of file juce_SharedCode_posix.h.

◆ getPriority()

Thread::Priority juce::Thread::getPriority ( ) const

protected

Returns the current priority of this thread.

This can only be called from the target thread. Doing so from another thread will cause an assert.

See also: setPriority

Definition at line 55 of file juce_Threads_linux.cpp.

◆ getThreadId()

Thread::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

Definition at line 190 of file juce_Thread.cpp.

◆ getThreadName()

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

noexcept

Returns the name of the thread.

This is the name that gets set in the constructor.

Definition at line 506 of file juce_Thread.h.

◆ 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);

juce::unalignedPointerCast

Type unalignedPointerCast(void *ptr) noexcept

Casts a pointer to another type via void*, which suppresses the cast-align warning which sometimes ar...

Definition juce_Memory.h:88

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

jniEnv	this is a pointer to JNI's JNIEnv variable. Any callback from Java into C++ will have this passed in as it's first parameter.
jContext	this is a jobject referring to your app/service/receiver/ provider's Context. JUCE needs this for many of it's internal functions.

◆ isRealtime()

bool juce::Thread::isRealtime ( ) const

Returns true if this Thread represents a realtime thread.

Definition at line 277 of file juce_Thread.cpp.

◆ isThreadRunning()

bool juce::Thread::isThreadRunning ( ) const

Returns true if the thread is currently active.

Definition at line 180 of file juce_Thread.cpp.

◆ launch() [1/2]

bool juce::Thread::launch	(	Priority	priority,
		std::function< void()>	functionToRun
	)

static

Invokes a lambda or function on its own thread with a custom priority.

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.

Parameters

priority	The priority the thread is started with.
functionToRun	The lambda to be called from the new Thread.

Returns: true if the thread started successfully, or false if it failed.

Definition at line 319 of file juce_Thread.cpp.

◆ launch() [2/2]

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

static

Invokes a lambda or function on its own thread with the default priority.

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.

Parameters

functionToRun The lambda to be called from the new Thread.

Returns: true if the thread started successfully, or false if it failed.

See also: launch.

Definition at line 314 of file juce_Thread.cpp.

◆ 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

Definition at line 293 of file juce_Thread.cpp.

◆ removeListener()

void juce::Thread::removeListener ( Listener * listener )

Removes a listener added with addListener.

Definition at line 272 of file juce_Thread.cpp.

◆ 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::FallbackDownloadTask, juce::LambdaThread, juce::ThreadPool::ThreadPoolThread, juce::InterprocessConnection::ConnectionThread, and juce::Timer::TimerThread.

◆ 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

Definition at line 282 of file juce_Thread.cpp.

◆ setCurrentThreadAffinityMask()

void JUCE_CALLTYPE 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

Definition at line 1021 of file juce_SharedCode_posix.h.

◆ setCurrentThreadName()

void JUCE_CALLTYPE 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.

Definition at line 984 of file juce_SharedCode_posix.h.

◆ setPriority()

bool juce::Thread::setPriority ( Priority newPriority )

protected

Attempts to set the priority for this thread.

Returns true if the new priority was set successfully, false if not.

This can only be called from the target thread. Doing so from another thread will cause an assert.

Parameters

newPriority The new priority to be applied to the thread. Note: This has no effect on Linux platforms, subsequent calls to 'getPriority' will return this value.

See also: Priority

Definition at line 62 of file juce_Threads_linux.cpp.

◆ 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

Definition at line 196 of file juce_Thread.cpp.

◆ sleep()

void JUCE_CALLTYPE 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.

Definition at line 44 of file juce_SharedCode_posix.h.

◆ startRealtimeThread()

bool juce::Thread::startRealtimeThread ( const RealtimeOptions & options )

Starts the thread with realtime performance characteristics on platforms that support it.

You cannot change the options of a running realtime thread, nor switch a non-realtime thread to a realtime thread. To make these changes you must first stop the thread and then restart with different options.

Parameters

options Realtime options the thread should be created with.

See also: startThread, RealtimeOptions

Definition at line 163 of file juce_Thread.cpp.

◆ startThread() [1/2]

bool juce::Thread::startThread ( )

Attempts to start a new thread with default ('Priority::normal') priority.

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.

If a thread cannot be created with the requested priority, this will return false and Thread::run() will not be called. An exception to this is the Android platform, which always starts a thread and attempts to upgrade the thread after creation.

Returns: true if the thread started successfully. false if it was unsuccesful.

See also: stopThread

Definition at line 145 of file juce_Thread.cpp.

◆ startThread() [2/2]

bool juce::Thread::startThread ( Priority newPriority )

Attempts to start a new thread with a given priority.

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.

If a thread cannot be created with the requested priority, this will return false and Thread::run() will not be called. An exception to this is the Android platform, which always starts a thread and attempts to upgrade the thread after creation.

Parameters

newPriority Priority the thread should be assigned. This parameter is ignored on Linux.

Returns: true if the thread started successfully, false if it was unsuccesful.

See also: startThread, setPriority, startRealtimeThread

Definition at line 150 of file juce_Thread.cpp.

◆ 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

timeOutMilliseconds The 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

Definition at line 233 of file juce_Thread.cpp.

◆ 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

Definition at line 202 of file juce_Thread.cpp.

◆ wait()

bool juce::Thread::wait ( double 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.

Definition at line 288 of file juce_Thread.cpp.

◆ 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

timeOutMilliseconds the 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.

Definition at line 215 of file juce_Thread.cpp.

◆ yield()

void JUCE_CALLTYPE 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.

Definition at line 1007 of file juce_SharedCode_posix.h.

Member Data Documentation

◆ osDefaultStackSize

constexpr size_t juce::Thread::osDefaultStackSize

staticconstexpr

Definition at line 46 of file juce_Thread.h.

The documentation for this class was generated from the following files:

juce_core/threads/juce_Thread.h
juce_core/native/juce_SharedCode_posix.h
juce_core/native/juce_Threads_linux.cpp
juce_core/threads/juce_Thread.cpp

Classes

Public Types

Public Member Functions

Static Public Member Functions

Static Public Attributes

Protected Member Functions

Detailed Description

Member Typedef Documentation

◆ ThreadID

Member Enumeration Documentation

◆ Priority

Constructor & Destructor Documentation

◆ Thread()

◆ ~Thread()

Member Function Documentation

◆ addListener()

◆ currentThreadShouldExit()

◆ getCurrentThread()

◆ getCurrentThreadId()

◆ getPriority()

◆ getThreadId()

◆ getThreadName()

◆ initialiseJUCE()

◆ isRealtime()

◆ isThreadRunning()

◆ launch() [1/2]

◆ launch() [2/2]

◆ notify()

◆ removeListener()

◆ run()

◆ setAffinityMask()

◆ setCurrentThreadAffinityMask()

◆ setCurrentThreadName()

◆ setPriority()

◆ signalThreadShouldExit()

◆ sleep()

◆ startRealtimeThread()

◆ startThread() [1/2]

◆ startThread() [2/2]

◆ stopThread()

◆ threadShouldExit()

◆ wait()

◆ waitForThreadToExit()

◆ yield()

Member Data Documentation

◆ osDefaultStackSize