/* GLIB - Library of useful routines for C programming
* Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
*
* GAsyncQueue: asynchronous queue implementation, based on Gqueue.
* Copyright (C) 2000 Sebastian Wilhelmi; University of Karlsruhe
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
/*
* MT safe
*/
#include "config.h"
#include "gasyncqueue.h"
#include "gmem.h"
#include "gqueue.h"
#include "gtestutils.h"
#include "gthread.h"
/**
* SECTION: async_queues
* @title: Asynchronous Queues
* @short_description: asynchronous communication between threads
*
* Often you need to communicate between different threads. In general
* it's safer not to do this by shared memory, but by explicit message
* passing. These messages only make sense asynchronously for
* multi-threaded applications though, as a synchronous operation could
* as well be done in the same thread.
*
* Asynchronous queues are an exception from most other GLib data
* structures, as they can be used simultaneously from multiple threads
* without explicit locking and they bring their own builtin reference
* counting. This is because the nature of an asynchronous queue is that
* it will always be used by at least 2 concurrent threads.
*
* For using an asynchronous queue you first have to create one with
* g_async_queue_new(). A newly-created queue will get the reference
* count 1. Whenever another thread is creating a new reference of (that
* is, pointer to) the queue, it has to increase the reference count
* (using g_async_queue_ref()). Also, before removing this reference,
* the reference count has to be decreased (using g_async_queue_unref()).
* After that the queue might no longer exist so you must not access
* it after that point.
*
* A thread, which wants to send a message to that queue simply calls
* g_async_queue_push() to push the message to the queue.
*
* A thread, which is expecting messages from an asynchronous queue
* simply calls g_async_queue_pop() for that queue. If no message is
* available in the queue at that point, the thread is now put to sleep
* until a message arrives. The message will be removed from the queue
* and returned. The functions g_async_queue_try_pop() and
* g_async_queue_timed_pop() can be used to only check for the presence
* of messages or to only wait a certain time for messages respectively.
*
* For almost every function there exist two variants, one that locks
* the queue and one that doesn't. That way you can hold the queue lock
* (acquire it with g_async_queue_lock() and release it with
* g_async_queue_unlock()) over multiple queue accessing instructions.
* This can be necessary to ensure the integrity of the queue, but should
* only be used when really necessary, as it can make your life harder
* if used unwisely. Normally you should only use the locking function
* variants (those without the suffix _unlocked)
*/
/**
* GAsyncQueue:
*
* The GAsyncQueue struct is an opaque data structure, which represents
* an asynchronous queue. It should only be accessed through the
* <function>g_async_queue_*</function> functions.
*/
struct _GAsyncQueue
{
GMutex *mutex;
GCond *cond;
GQueue queue;
GDestroyNotify item_free_func;
guint waiting_threads;
gint32 ref_count;
};
typedef struct {
GCompareDataFunc func;
gpointer user_data;
} SortData;
/**
* g_async_queue_new:
*
* Creates a new asynchronous queue with the initial reference count of 1.
*
* Return value: the new #GAsyncQueue.
**/
GAsyncQueue*
g_async_queue_new (void)
{
GAsyncQueue* retval = g_new (GAsyncQueue, 1);
retval->mutex = g_mutex_new ();
retval->cond = NULL;
g_queue_init (&retval->queue);
retval->waiting_threads = 0;
retval->ref_count = 1;
retval->item_free_func = NULL;
return retval;
}
/**
* g_async_queue_new_full:
* @item_free_func: function to free queue elements
*
* Creates a new asynchronous queue with an initial reference count of 1 and
* sets up a destroy notify function that is used to free any remaining
* queue items when the queue is destroyed after the final unref.
*
* Return value: the new #GAsyncQueue.
*
* Since: 2.16
**/
GAsyncQueue*
g_async_queue_new_full (GDestroyNotify item_free_func)
{
GAsyncQueue *async_queue = g_async_queue_new ();
async_queue->item_free_func = item_free_func;
return async_queue;
}
/**
* g_async_queue_ref:
* @queue: a #GAsyncQueue.
*
* Increases the reference count of the asynchronous @queue by 1. You
* do not need to hold the lock to call this function.
*
* Returns: the @queue that was passed in (since 2.6)
**/
GAsyncQueue *
g_async_queue_ref (GAsyncQueue *queue)
{
g_return_val_if_fail (queue, NULL);
g_return_val_if_fail (g_atomic_int_get (&queue->ref_count) > 0, NULL);
g_atomic_int_inc (&queue->ref_count);
return queue;
}
/**
* g_async_queue_ref_unlocked:
* @queue: a #GAsyncQueue.
*
* Increases the reference count of the asynchronous @queue by 1.
*
* @Deprecated: Since 2.8, reference counting is done atomically
* so g_async_queue_ref() can be used regardless of the @queue's
* lock.
**/
void
g_async_queue_ref_unlocked (GAsyncQueue *queue)
{
g_return_if_fail (queue);
g_return_if_fail (g_atomic_int_get (&queue->ref_count) > 0);
g_atomic_int_inc (&queue->ref_count);
}
/**
* g_async_queue_unref_and_unlock:
* @queue: a #GAsyncQueue.
*
* Decreases the reference count of the asynchronous @queue by 1 and
* releases the lock. This function must be called while holding the
* @queue's lock. If the reference count went to 0, the @queue will be
* destroyed and the memory allocated will be freed.
*
* @Deprecated: Since 2.8, reference counting is done atomically
* so g_async_queue_unref() can be used regardless of the @queue's
* lock.
**/
void
g_async_queue_unref_and_unlock (GAsyncQueue *queue)
{
g_return_if_fail (queue);
g_return_if_fail (g_atomic_int_get (&queue->ref_count) > 0);
g_mutex_unlock (queue->mutex);
g_async_queue_unref (queue);
}
/**
* g_async_queue_unref:
* @queue: a #GAsyncQueue.
*
* Decreases the reference count of the asynchronous @queue by 1. If
* the reference count went to 0, the @queue will be destroyed and the
* memory allocated will be freed. So you are not allowed to use the
* @queue afterwards, as it might have disappeared. You do not need to
* hold the lock to call this function.
**/
void
g_async_queue_unref (GAsyncQueue *queue)
{
g_return_if_fail (queue);
g_return_if_fail (g_atomic_int_get (&queue->ref_count) > 0);
if (g_atomic_int_dec_and_test (&queue->ref_count))
{
g_return_if_fail (queue->waiting_threads == 0);
g_mutex_free (queue->mutex);
if (queue->cond)
g_cond_free (queue->cond);
if (queue->item_free_func)
g_queue_foreach (&queue->queue, (GFunc) queue->item_free_func, NULL);
g_queue_clear (&queue->queue);
g_free (queue);
}
}
/**
* g_async_queue_lock:
* @queue: a #GAsyncQueue.
*
* Acquires the @queue's lock. After that you can only call the
* <function>g_async_queue_*_unlocked()</function> function variants on that
* @queue. Otherwise it will deadlock.
**/
void
g_async_queue_lock (GAsyncQueue *queue)
{
g_return_if_fail (queue);
g_return_if_fail (g_atomic_int_get (&queue->ref_count) > 0);
g_mutex_lock (queue->mutex);
}
/**
* g_async_queue_unlock:
* @queue: a #GAsyncQueue.
*
* Releases the queue's lock.
**/
void
g_async_queue_unlock (GAsyncQueue *queue)
{
g_return_if_fail (queue);
g_return_if_fail (g_atomic_int_get (&queue->ref_count) > 0);
g_mutex_unlock (queue->mutex);
}
/**
* g_async_queue_push:
* @queue: a #GAsyncQueue.
* @data: @data to push into the @queue.
*
* Pushes the @data into the @queue. @data must not be %NULL.
**/
void
g_async_queue_push (GAsyncQueue* queue, gpointer data)
{
g_return_if_fail (queue);
g_return_if_fail (g_atomic_int_get (&queue->ref_count) > 0);
g_return_if_fail (data);
g_mutex_lock (queue->mutex);
g_async_queue_push_unlocked (queue, data);
g_mutex_unlock (queue->mutex);
}
/**
* g_async_queue_push_unlocked:
* @queue: a #GAsyncQueue.
* @data: @data to push into the @queue.
*
* Pushes the @data into the @queue. @data must not be %NULL. This
* function must be called while holding the @queue's lock.
**/
void
g_async_queue_push_unlocked (GAsyncQueue* queue, gpointer data)
{
g_return_if_fail (queue);
g_return_if_fail (g_atomic_int_get (&queue->ref_count) > 0);
g_return_if_fail (data);
g_queue_push_head (&queue->queue, data);
if (queue->waiting_threads > 0)
g_cond_signal (queue->cond);
}
/**
* g_async_queue_push_sorted:
* @queue: a #GAsyncQueue
* @data: the @data to push into the @queue
* @func: the #GCompareDataFunc is used to sort @queue. This function
* is passed two elements of the @queue. The function should return
* 0 if they are equal, a negative value if the first element
* should be higher in the @queue or a positive value if the first
* element should be lower in the @queue than the second element.
* @user_data: user data passed to @func.
*
* Inserts @data into @queue using @func to determine the new
* position.
*
* This function requires that the @queue is sorted before pushing on
* new elements.
*
* This function will lock @queue before it sorts the queue and unlock
* it when it is finished.
*
* For an example of @func see g_async_queue_sort().
*
* Since: 2.10
**/
void
g_async_queue_push_sorted (GAsyncQueue *queue,
gpointer data,
GCompareDataFunc func,
gpointer user_data)
{
g_return_if_fail (queue != NULL);
g_mutex_lock (queue->mutex);
g_async_queue_push_sorted_unlocked (queue, data, func, user_data);
g_mutex_unlock (queue->mutex);
}
static gint
g_async_queue_invert_compare (gpointer v1,
gpointer v2,
SortData *sd)
{
return -sd->func (v1, v2, sd->user_data);
}
/**
* g_async_queue_push_sorted_unlocked:
* @queue: a #GAsyncQueue
* @data: the @data to push into the @queue
* @func: the #GCompareDataFunc is used to sort @queue. This function
* is passed two elements of the @queue. The function should return
* 0 if they are equal, a negative value if the first element
* should be higher in the @queue or a positive value if the first
* element should be lower in the @queue than the second element.
* @user_data: user data passed to @func.
*
* Inserts @data into @queue using @func to determine the new
* position.
*
* This function requires that the @queue is sorted before pushing on
* new elements.
*
* This function is called while holding the @queue's lock.
*
* For an example of @func see g_async_queue_sort().
*
* Since: 2.10
**/
void
g_async_queue_push_sorted_unlocked (GAsyncQueue *queue,
gpointer data,
GCompareDataFunc func,
gpointer user_data)
{
SortData sd;
g_return_if_fail (queue != NULL);
sd.func = func;
sd.user_data = user_data;
g_queue_insert_sorted (&queue->queue,
data,
(GCompareDataFunc)g_async_queue_invert_compare,
&sd);
if (queue->waiting_threads > 0)
g_cond_signal (queue->cond);
}
static gpointer
g_async_queue_pop_intern_unlocked (GAsyncQueue *queue,
gboolean try,
GTimeVal *end_time)
{
gpointer retval;
if (!g_queue_peek_tail_link (&queue->queue))
{
if (try)
return NULL;
if (!queue->cond)
queue->cond = g_cond_new ();
if (!end_time)
{
queue->waiting_threads++;
while (!g_queue_peek_tail_link (&queue->queue))
g_cond_wait (queue->cond, queue->mutex);
queue->waiting_threads--;
}
else
{
queue->waiting_threads++;
while (!g_queue_peek_tail_link (&queue->queue))
if (!g_cond_timed_wait (queue->cond, queue->mutex, end_time))
break;
queue->waiting_threads--;
if (!g_queue_peek_tail_link (&queue->queue))
return NULL;
}
}
retval = g_queue_pop_tail (&queue->queue);
g_assert (retval);
return retval;
}
/**
* g_async_queue_pop:
* @queue: a #GAsyncQueue.
*
* Pops data from the @queue. This function blocks until data become
* available.
*
* Return value: data from the queue.
**/
gpointer
g_async_queue_pop (GAsyncQueue* queue)
{
gpointer retval;
g_return_val_if_fail (queue, NULL);
g_return_val_if_fail (g_atomic_int_get (&queue->ref_count) > 0, NULL);
g_mutex_lock (queue->mutex);
retval = g_async_queue_pop_intern_unlocked (queue, FALSE, NULL);
g_mutex_unlock (queue->mutex);
return retval;
}
/**
* g_async_queue_pop_unlocked:
* @queue: a #GAsyncQueue.
*
* Pops data from the @queue. This function blocks until data become
* available. This function must be called while holding the @queue's
* lock.
*
* Return value: data from the queue.
**/
gpointer
g_async_queue_pop_unlocked (GAsyncQueue* queue)
{
g_return_val_if_fail (queue, NULL);
g_return_val_if_fail (g_atomic_int_get (&queue->ref_count) > 0, NULL);
return g_async_queue_pop_intern_unlocked (queue, FALSE, NULL);
}
/**
* g_async_queue_try_pop:
* @queue: a #GAsyncQueue.
*
* Tries to pop data from the @queue. If no data is available, %NULL is
* returned.
*
* Return value: data from the queue or %NULL, when no data is
* available immediately.
**/
gpointer
g_async_queue_try_pop (GAsyncQueue* queue)
{
gpointer retval;
g_return_val_if_fail (queue, NULL);
g_return_val_if_fail (g_atomic_int_get (&queue->ref_count) > 0, NULL);
g_mutex_lock (queue->mutex);
retval = g_async_queue_pop_intern_unlocked (queue, TRUE, NULL);
g_mutex_unlock (queue->mutex);
return retval;
}
/**
* g_async_queue_try_pop_unlocked:
* @queue: a #GAsyncQueue.
*
* Tries to pop data from the @queue. If no data is available, %NULL is
* returned. This function must be called while holding the @queue's
* lock.
*
* Return value: data from the queue or %NULL, when no data is
* available immediately.
**/
gpointer
g_async_queue_try_pop_unlocked (GAsyncQueue* queue)
{
g_return_val_if_fail (queue, NULL);
g_return_val_if_fail (g_atomic_int_get (&queue->ref_count) > 0, NULL);
return g_async_queue_pop_intern_unlocked (queue, TRUE, NULL);
}
/**
* g_async_queue_timed_pop:
* @queue: a #GAsyncQueue.
* @end_time: a #GTimeVal, determining the final time.
*
* Pops data from the @queue. If no data is received before @end_time,
* %NULL is returned.
*
* To easily calculate @end_time a combination of g_get_current_time()
* and g_time_val_add() can be used.
*
* Return value: data from the queue or %NULL, when no data is
* received before @end_time.
**/
gpointer
g_async_queue_timed_pop (GAsyncQueue* queue, GTimeVal *end_time)
{
gpointer retval;
g_return_val_if_fail (queue, NULL);
g_return_val_if_fail (g_atomic_int_get (&queue->ref_count) > 0, NULL);
g_mutex_lock (queue->mutex);
retval = g_async_queue_pop_intern_unlocked (queue, FALSE, end_time);
g_mutex_unlock (queue->mutex);
return retval;
}
/**
* g_async_queue_timed_pop_unlocked:
* @queue: a #GAsyncQueue.
* @end_time: a #GTimeVal, determining the final time.
*
* Pops data from the @queue. If no data is received before @end_time,
* %NULL is returned. This function must be called while holding the
* @queue's lock.
*
* To easily calculate @end_time a combination of g_get_current_time()
* and g_time_val_add() can be used.
*
* Return value: data from the queue or %NULL, when no data is
* received before @end_time.
**/
gpointer
g_async_queue_timed_pop_unlocked (GAsyncQueue* queue, GTimeVal *end_time)
{
g_return_val_if_fail (queue, NULL);
g_return_val_if_fail (g_atomic_int_get (&queue->ref_count) > 0, NULL);
return g_async_queue_pop_intern_unlocked (queue, FALSE, end_time);
}
/**
* g_async_queue_length:
* @queue: a #GAsyncQueue.
*
* Returns the length of the queue, negative values mean waiting
* threads, positive values mean available entries in the
* @queue. Actually this function returns the number of data items in
* the queue minus the number of waiting threads. Thus a return value
* of 0 could mean 'n' entries in the queue and 'n' thread waiting.
* That can happen due to locking of the queue or due to
* scheduling.
*
* Return value: the length of the @queue.
**/
gint
g_async_queue_length (GAsyncQueue* queue)
{
gint retval;
g_return_val_if_fail (queue, 0);
g_return_val_if_fail (g_atomic_int_get (&queue->ref_count) > 0, 0);
g_mutex_lock (queue->mutex);
retval = queue->queue.length - queue->waiting_threads;
g_mutex_unlock (queue->mutex);
return retval;
}
/**
* g_async_queue_length_unlocked:
* @queue: a #GAsyncQueue.
*
* Returns the length of the queue, negative values mean waiting
* threads, positive values mean available entries in the
* @queue. Actually this function returns the number of data items in
* the queue minus the number of waiting threads. Thus a return value
* of 0 could mean 'n' entries in the queue and 'n' thread waiting.
* That can happen due to locking of the queue or due to
* scheduling. This function must be called while holding the @queue's
* lock.
*
* Return value: the length of the @queue.
**/
gint
g_async_queue_length_unlocked (GAsyncQueue* queue)
{
g_return_val_if_fail (queue, 0);
g_return_val_if_fail (g_atomic_int_get (&queue->ref_count) > 0, 0);
return queue->queue.length - queue->waiting_threads;
}
/**
* g_async_queue_sort:
* @queue: a #GAsyncQueue
* @func: the #GCompareDataFunc is used to sort @queue. This
* function is passed two elements of the @queue. The function
* should return 0 if they are equal, a negative value if the
* first element should be higher in the @queue or a positive
* value if the first element should be lower in the @queue than
* the second element.
* @user_data: user data passed to @func
*
* Sorts @queue using @func.
*
* This function will lock @queue before it sorts the queue and unlock
* it when it is finished.
*
* If you were sorting a list of priority numbers to make sure the
* lowest priority would be at the top of the queue, you could use:
* |[
* gint32 id1;
* gint32 id2;
*
* id1 = GPOINTER_TO_INT (element1);
* id2 = GPOINTER_TO_INT (element2);
*
* return (id1 > id2 ? +1 : id1 == id2 ? 0 : -1);
* ]|
*
* Since: 2.10
**/
void
g_async_queue_sort (GAsyncQueue *queue,
GCompareDataFunc func,
gpointer user_data)
{
g_return_if_fail (queue != NULL);
g_return_if_fail (func != NULL);
g_mutex_lock (queue->mutex);
g_async_queue_sort_unlocked (queue, func, user_data);
g_mutex_unlock (queue->mutex);
}
/**
* g_async_queue_sort_unlocked:
* @queue: a #GAsyncQueue
* @func: the #GCompareDataFunc is used to sort @queue. This
* function is passed two elements of the @queue. The function
* should return 0 if they are equal, a negative value if the
* first element should be higher in the @queue or a positive
* value if the first element should be lower in the @queue than
* the second element.
* @user_data: user data passed to @func
*
* Sorts @queue using @func.
*
* This function is called while holding the @queue's lock.
*
* Since: 2.10
**/
void
g_async_queue_sort_unlocked (GAsyncQueue *queue,
GCompareDataFunc func,
gpointer user_data)
{
SortData sd;
g_return_if_fail (queue != NULL);
g_return_if_fail (func != NULL);
sd.func = func;
sd.user_data = user_data;
g_queue_sort (&queue->queue,
(GCompareDataFunc)g_async_queue_invert_compare,
&sd);
}
/*
* Private API
*/
GMutex*
_g_async_queue_get_mutex (GAsyncQueue* queue)
{
g_return_val_if_fail (queue, NULL);
g_return_val_if_fail (g_atomic_int_get (&queue->ref_count) > 0, NULL);
return queue->mutex;
}