Encapsulates a thread. More...

Inheritance diagram for Thread:

Classes

class  Listener
 

Public Types

enum  { realtimeAudioPriority = -1 }
 Special realtime audio thread priority. More...
 
typedef void * ThreadID
 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...
 
virtual void run ()=0
 Must be implemented to perform the thread's actual code. 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 isThreadRunning () const
 Returns true if the thread is currently active. More...
 
void signalThreadShouldExit ()
 Sets a flag to tell the thread it should stop. More...
 
bool threadShouldExit () const
 Checks whether the thread has been told to stop running. More...
 
bool waitForThreadToExit (int timeOutMilliseconds) const
 Waits for the thread to stop. More...
 
void addListener (Listener *)
 Add a listener to this thread which will receive a callback when signalThreadShouldExit was called on this thread. More...
 
void removeListener (Listener *)
 Removes a listener added with addListener. More...
 
bool setPriority (int priority)
 Changes the thread's priority. More...
 
void setAffinityMask (uint32 affinityMask)
 Sets the affinity mask for the thread. More...
 
bool wait (int timeOutMilliseconds) const
 Makes the thread wait for a notification. More...
 
void notify () const
 Wakes up the thread. More...
 
ThreadID getThreadId () const noexcept
 Returns the ID of this thread. More...
 
const StringgetThreadName () const noexcept
 Returns the name of the thread. More...
 

Static Public Member Functions

static void launch (std::function< void()> functionToRun)
 Invokes a lambda or function on its own thread. More...
 
static bool currentThreadShouldExit ()
 Checks whether the current thread has been told to stop running. More...
 
static bool setCurrentThreadPriority (int priority)
 Changes the priority of the caller thread. More...
 
static void JUCE_CALLTYPE setCurrentThreadAffinityMask (uint32 affinityMask)
 Changes the affinity mask for the caller thread. More...
 
static void JUCE_CALLTYPE sleep (int milliseconds)
 
static void JUCE_CALLTYPE yield ()
 Yields the calling thread's current time-slot. More...
 
static ThreadID JUCE_CALLTYPE getCurrentThreadId ()
 Returns an id that identifies the caller thread. More...
 
static Thread *JUCE_CALLTYPE getCurrentThread ()
 Finds the thread object that is currently running. More...
 
static void JUCE_CALLTYPE setCurrentThreadName (const String &newThreadName)
 Changes the name of the caller thread. More...
 

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

Member Typedef Documentation

◆ ThreadID

typedef void* Thread::ThreadID

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 support.

In this case, JUCE will ask OpenSL to consturct 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()

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 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

◆ run()

virtual void 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

Referenced by MidiOutput::getName().

◆ startThread() [1/2]

void 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 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 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 time-out, 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

◆ launch()

static void 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.

◆ isThreadRunning()

bool Thread::isThreadRunning ( ) const

Returns true if the thread is currently active.

◆ signalThreadShouldExit()

void 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

◆ threadShouldExit()

bool 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

◆ currentThreadShouldExit()

static bool 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

◆ waitForThreadToExit()

bool 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.

◆ addListener()

void 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

◆ removeListener()

void Thread::removeListener ( Listener )

Removes a listener added with addListener.

◆ setPriority()

bool 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

◆ setCurrentThreadPriority()

static bool 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

◆ setAffinityMask()

void 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()

static void JUCE_CALLTYPE 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

◆ sleep()

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

◆ yield()

static void JUCE_CALLTYPE Thread::yield ( )
static

Yields the calling thread's current time-slot.

◆ wait()

bool Thread::wait ( int  timeOutMilliseconds) const

Makes the thread wait for a notification.

This puts the thread to sleep until either the timeout period expires, or another thread calls the notify() method to wake it up.

A negative time-out value means that the method will wait indefinitely.

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

◆ notify()

void Thread::notify ( ) const

Wakes up the thread.

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

See also
wait

◆ getCurrentThreadId()

static ThreadID JUCE_CALLTYPE 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 ThreadLocalValue< Type >::get(), and ThreadLocalValue< Type >::releaseCurrentThreadStorage().

◆ getCurrentThread()

static Thread* JUCE_CALLTYPE 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.

◆ getThreadId()

ThreadID 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& Thread::getThreadName ( ) const
noexcept

Returns the name of the thread.

This is the name that gets set in the constructor.

References JUCE_API, JUCE_CALLTYPE, and JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR.

◆ setCurrentThreadName()

static void JUCE_CALLTYPE 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.


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