glibmm: Glib::Threads::Cond Class Reference
An opaque data structure to represent a condition. More...
#include <glibmm/threads.h>
Public Member Functions |
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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.
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void | broadcast () |
If threads are waiting for this
Cond
, all of them are woken up.
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void | wait ( Mutex & mutex) |
Waits until this thread is woken up on this
Cond
.
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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 specified by
end_time
.
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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.
- Deprecated:
- Please use std::condition_variable instead.
- Usage example:
-
Glib::Threads::Cond data_cond;Glib::Threads::Mutex data_mutex;void * current_data = nullptr ;void push_data( void * data){Glib::Threads::Mutex::Lock lock (data_mutex);current_data = data;data_cond. signal ();}void * pop_data(){Glib::Threads::Mutex::Lock lock (data_mutex);while (!current_data)data_cond. wait (data_mutex);void * const data = current_data;current_data = nullptr ;return data;}
Constructor & Destructor Documentation
Glib::Threads::Cond::Cond | ( | ) |
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delete |
Glib::Threads::Cond::~Cond | ( | ) |
Member Function Documentation
void Glib::Threads::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 threads, while calling this method, though not required.
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inline |
void Glib::Threads::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.
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
-
mutex A 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 specified by end_time .
The mutex is unlocked before falling asleep and locked again before resuming.
- Usage example:
-
Extending the example presented in the documentation of class
Cond
.
void * pop_data_timed(){Glib::Threads::Mutex::Lock lock (data_mutex);// Wait at most 5 seconds.const gint64 end_time = g_get_monotonic_time() + 5 * G_TIME_SPAN_SECOND;while (!current_data)if (!data_cond. wait_until (data_mutex, end_time)return nullptr ; // timeoutvoid * const data = current_data;current_data = nullptr ;return data;}
- Parameters
-
mutex A Mutex that is currently locked. end_time The monotonic time to wait until, in microseconds. See g_get_monotonic_time().
- Returns
-
true
if the condition variable was signalled (or in the case of a spurious wakeup),false
if end_time has passed.
- 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 .