### Struct

# GLib ThreadPool

since: 2.0

#### Description

    struct GThreadPool {
      GFunc func;
      gpointer user_data;
      gboolean exclusive;
    }

The `GThreadPool` struct represents a thread pool.

A thread pool is useful when you wish to asynchronously fork out the execution of work and continue working in your own thread. If that will happen often, the overhead of starting and destroying a thread each time might be too high. In such cases reusing already started threads seems like a good idea. And it indeed is, but implementing this can be tedious and error-prone.

Therefore GLib provides thread pools for your convenience. An added advantage is, that the threads can be shared between the different subsystems of your program, when they are using GLib.

To create a new thread pool, you use `g_thread_pool_new()`. It is destroyed by `g_thread_pool_free()`.

If you want to execute a certain task within a thread pool, use `g_thread_pool_push()`.

To get the current number of running threads you call `g_thread_pool_get_num_threads()`. To get the number of still unprocessed tasks you call `g_thread_pool_unprocessed()`. To control the maximum number of threads for a thread pool, you use `g_thread_pool_get_max_threads()`. and `g_thread_pool_set_max_threads()`.

Finally you can control the number of unused threads, that are kept alive by GLib for future use. The current number can be fetched with `g_thread_pool_get_num_unused_threads()`. The maximum number can be controlled by `g_thread_pool_get_max_unused_threads()` and `g_thread_pool_set_max_unused_threads()`. All currently unused threads can be stopped by calling `g_thread_pool_stop_unused_threads()`.

###### Structure members

`func`

  The function to execute in the threads of this pool.

`user_data`

  The user data for the threads of this pool.

`exclusive`

  Are all threads exclusive to this pool.

Available since: 2.0

#### Functions

###### g_thread_pool_get_max_idle_time

This function will return the maximum `interval` that a thread will wait in the thread pool for new tasks before being stopped.

since: 2.10

###### g_thread_pool_get_max_unused_threads

Returns the maximal allowed number of unused threads.

since: 2.0

###### g_thread_pool_get_num_unused_threads

Returns the number of currently unused threads.

since: 2.0

###### g_thread_pool_new

This function creates a new thread pool.

since: 2.0

###### g_thread_pool_new_full

This function creates a new thread pool similar to `g_thread_pool_new()` but allowing `item_free_func` to be specified to free the data passed to `g_thread_pool_push()` in the case that the `GThreadPool` is stopped and freed before all tasks have been executed.

since: 2.70

###### g_thread_pool_set_max_idle_time

This function will set the maximum `interval` that a thread waiting in the pool for new tasks can be idle for before being stopped. This function is similar to calling `g_thread_pool_stop_unused_threads()` on a regular timeout, except this is done on a per thread basis.

since: 2.10

###### g_thread_pool_set_max_unused_threads

Sets the maximal number of unused threads to `max_threads`. If `max_threads` is -1, no limit is imposed on the number of unused threads.

since: 2.0

###### g_thread_pool_stop_unused_threads

Stops all currently unused threads. This does not change the maximal number of unused threads. This function can be used to regularly stop all unused threads e.g. from g_timeout_add().

since: 2.0

#### Instance methods

###### g_thread_pool_free

Frees all resources allocated for `pool`.

since: 2.0

###### g_thread_pool_get_max_threads

Returns the maximal number of threads for `pool`.

since: 2.0

###### g_thread_pool_get_num_threads

Returns the number of threads currently running in `pool`.

since: 2.0

###### g_thread_pool_move_to_front

Moves the item to the front of the queue of unprocessed items, so that it will be processed next.

since: 2.46

###### g_thread_pool_push

Inserts `data` into the list of tasks to be executed by `pool`.

since: 2.0

###### g_thread_pool_set_max_threads

Sets the maximal allowed number of threads for `pool`. A value of -1 means that the maximal number of threads is unlimited. If `pool` is an exclusive thread pool, setting the maximal number of threads to -1 is not allowed.

since: 2.0

###### g_thread_pool_set_sort_function

Sets the function used to sort the list of tasks. This allows the tasks to be processed by a priority determined by `func`, and not just in the order in which they were added to the pool.

since: 2.10

###### g_thread_pool_unprocessed

Returns the number of tasks still unprocessed in `pool`.

since: 2.0