Glib::Cond Class Reference

An opaque data structure to represent a condition. More...

#include <glibmm/thread.h>

Public Member Functions
	Cond ()
	Cond (const Cond &)=delete
Cond &	operator= (const Cond &)=delete
	~Cond ()
void	signal ()
	If threads are waiting for this Cond, exactly one of them is woken up. More...
void	broadcast ()
	If threads are waiting for this Cond, all of them are woken up. More...
void	wait (Mutex & mutex)
	Waits until this thread is woken up on this Cond. More...
bool	timed_wait (Mutex & mutex, const Glib::TimeVal & abs_time)
	Waits until this thread is woken up on this Cond, but not longer than until the time, that is specified by abs_time. More...
GCond *	gobj ()

Detailed Description

An opaque data structure to represent a condition.

A Cond is an object that threads can block on, if they find a certain condition to be false. If other threads change the state of this condition they can signal the Cond, such that the waiting thread is woken up.

Usage example:

Glib::Cond  data_cond;
Glib::Mutex data_mutex;
void* current_data = nullptr;
 
void push_data(void* data)
{
  Glib::Mutex::Lock lock (data_mutex);
 
  current_data = data;
  data_cond.signal();
}
 
void* pop_data()
{
  Glib::Mutex::Lock lock (data_mutex);
 
  while (!current_data)
    data_cond.wait(data_mutex);
 
  void *const data = current_data;
  current_data = nullptr;
 
  return data;
}

Deprecated:

Use Glib::Threads::Cond instead.

Constructor & Destructor Documentation

Cond() [1/2]

Glib::Cond::Cond

(

)

Cond() [2/2]

Glib::Cond::Cond ( const Cond &  )

delete

~Cond()

Glib::Cond::~Cond

(

)

Member Function Documentation

broadcast()

void Glib::Cond::broadcast

(

)

If threads are waiting for this Cond, all of them are woken up.

It is good practice to hold the same lock as the waiting thread, while calling this method, though not required.

gobj()

GCond * Glib::Cond::gobj ( )

inline

operator=()

Cond & Glib::Cond::operator= ( const Cond &  )

delete

signal()

void Glib::Cond::signal

(

)

If threads are waiting for this Cond, exactly one of them is woken up.

It is good practice to hold the same lock as the waiting thread, while calling this method, though not required.

timed_wait()

bool Glib::Cond::timed_wait	(	Mutex &	mutex,
		const Glib::TimeVal &	abs_time
	)

Waits until this thread is woken up on this Cond, but not longer than until the time, that is specified by abs_time.

The mutex is unlocked before falling asleep and locked again before resuming.

Parameters

mutex	a Mutex that is currently locked.
abs_time	a max time to wait.

Note

It is important to use the wait() and timed_wait() methods only inside a loop, which checks for the condition to be true as it is not guaranteed that the waiting thread will find it fulfilled, even if the signaling thread left the condition in that state. This is because another thread can have altered the condition, before the waiting thread got the chance to be woken up, even if the condition itself is protected by a Mutex.

wait()

void Glib::Cond::wait

(

Mutex &

mutex

)

Waits until this thread is woken up on this Cond.

The mutex is unlocked before falling asleep and locked again before resuming.

Parameters

mutex

a Mutex that is currently locked.

Note

It is important to use the wait() and timed_wait() methods only inside a loop, which checks for the condition to be true as it is not guaranteed that the waiting thread will find it fulfilled, even if the signaling thread left the condition in that state. This is because another thread can have altered the condition, before the waiting thread got the chance to be woken up, even if the condition itself is protected by a Mutex.