glibmm  2.32.0
Public Member Functions
Glib::Threads::Cond Class Reference

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

#include <glibmm/threads.h>

List of all members.

Public Member Functions

 Cond ()
 ~Cond ()
void signal ()
 If threads are waiting for this Cond, exactly one of them is woken up.
void broadcast ()
 If threads are waiting for this Cond, all of them are woken up.
void wait (Mutex& mutex)
 Waits until this thread is woken up on this Cond.
bool wait_until (Mutex& mutex, gint64 end_time)
 Waits until this thread is woken up on this Cond, but not longer than until the time, that is specified by abs_time.
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 = 0;

 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 = 0;

   return data;
 }
Examples:
thread/thread.cc.

Constructor & Destructor Documentation


Member Function Documentation

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.

GCond* Glib::Threads::Cond::gobj ( ) [inline]

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.

void Glib::Threads::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:
mutexa Mutex that is currently locked.
Note:
It is important to use the wait() and wait_until() 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.
bool Glib::Threads::Cond::wait_until ( Mutex mutex,
gint64  end_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:
mutexa Mutex that is currently locked.
abs_timea max time to wait.
Note:
It is important to use the wait() and wait_until() 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.