1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
// Take a look at the license at the top of the repository in the LICENSE file.

use std::{future::Future, panic, ptr};

use futures_channel::oneshot;

use crate::translate::*;

#[derive(Debug)]
#[doc(alias = "GThreadPool")]
pub struct ThreadPool(ptr::NonNull<ffi::GThreadPool>);

unsafe impl Send for ThreadPool {}
unsafe impl Sync for ThreadPool {}

// rustdoc-stripper-ignore-next
/// A handle to a thread running on a [`ThreadPool`].
///
/// Like [`std::thread::JoinHandle`] for a GLib thread. The return value from the task can be
/// retrieved by calling [`ThreadHandle::join`]. Dropping the handle "detaches" the thread,
/// allowing it to complete but discarding the return value.
#[derive(Debug)]
pub struct ThreadHandle<T> {
    rx: std::sync::mpsc::Receiver<std::thread::Result<T>>,
}

impl<T> ThreadHandle<T> {
    // rustdoc-stripper-ignore-next
    /// Waits for the associated thread to finish.
    ///
    /// Blocks until the associated thread returns. Returns `Ok` with the value returned from the
    /// thread, or `Err` if the thread panicked. This function will return immediately if the
    /// associated thread has already finished.
    #[inline]
    pub fn join(self) -> std::thread::Result<T> {
        self.rx.recv().unwrap()
    }
}

impl ThreadPool {
    #[doc(alias = "g_thread_pool_new")]
    pub fn shared(max_threads: Option<u32>) -> Result<Self, crate::Error> {
        unsafe {
            let mut err = ptr::null_mut();
            let pool = ffi::g_thread_pool_new(
                Some(spawn_func),
                ptr::null_mut(),
                max_threads.map(|v| v as i32).unwrap_or(-1),
                ffi::GFALSE,
                &mut err,
            );
            if pool.is_null() {
                Err(from_glib_full(err))
            } else {
                Ok(ThreadPool(ptr::NonNull::new_unchecked(pool)))
            }
        }
    }

    #[doc(alias = "g_thread_pool_new")]
    pub fn exclusive(max_threads: u32) -> Result<Self, crate::Error> {
        unsafe {
            let mut err = ptr::null_mut();
            let pool = ffi::g_thread_pool_new(
                Some(spawn_func),
                ptr::null_mut(),
                max_threads as i32,
                ffi::GTRUE,
                &mut err,
            );
            if pool.is_null() {
                Err(from_glib_full(err))
            } else {
                Ok(ThreadPool(ptr::NonNull::new_unchecked(pool)))
            }
        }
    }

    /// Inserts `data` into the list of tasks to be executed by `self`.
    ///
    /// When the number of currently running threads is lower than the
    /// maximal allowed number of threads, a new thread is started (or
    /// reused) with the properties given to [`new()`][Self::new()].
    /// Otherwise, `data` stays in the queue until a thread in this pool
    /// finishes its previous task and processes `data`.
    ///
    /// `error` can be [`None`] to ignore errors, or non-[`None`] to report
    /// errors. An error can only occur when a new thread couldn't be
    /// created. In that case `data` is simply appended to the queue of
    /// work to do.
    ///
    /// Before version 2.32, this function did not return a success status.
    ///
    /// # Returns
    ///
    /// [`true`] on success, [`false`] if an error occurred
    #[doc(alias = "g_thread_pool_push")]
    pub fn push<T: Send + 'static, F: FnOnce() -> T + Send + 'static>(
        &self,
        func: F,
    ) -> Result<ThreadHandle<T>, crate::Error> {
        let (tx, rx) = std::sync::mpsc::sync_channel(1);
        unsafe {
            let func: Box<dyn FnOnce() + Send + 'static> = Box::new(move || {
                let _ = tx.send(panic::catch_unwind(panic::AssertUnwindSafe(func)));
            });
            let func = Box::new(func);
            let mut err = ptr::null_mut();

            let func = Box::into_raw(func);
            let ret: bool = from_glib(ffi::g_thread_pool_push(
                self.0.as_ptr(),
                func as *mut _,
                &mut err,
            ));
            if ret {
                Ok(ThreadHandle { rx })
            } else {
                let _ = Box::from_raw(func);
                Err(from_glib_full(err))
            }
        }
    }

    pub fn push_future<T: Send + 'static, F: FnOnce() -> T + Send + 'static>(
        &self,
        func: F,
    ) -> Result<impl Future<Output = std::thread::Result<T>> + Send + Sync + 'static, crate::Error>
    {
        let (sender, receiver) = oneshot::channel();

        self.push(move || {
            let _ = sender.send(panic::catch_unwind(panic::AssertUnwindSafe(func)));
        })?;

        Ok(async move { receiver.await.expect("Dropped before executing") })
    }

    /// Sets the maximal allowed number of threads for `self`.
    /// A value of -1 means that the maximal number of threads
    /// is unlimited. If `self` is an exclusive thread pool, setting
    /// the maximal number of threads to -1 is not allowed.
    ///
    /// Setting `max_threads` to 0 means stopping all work for `self`.
    /// It is effectively frozen until `max_threads` is set to a non-zero
    /// value again.
    ///
    /// A thread is never terminated while calling `func`, as supplied by
    /// [`new()`][Self::new()]. Instead the maximal number of threads only
    /// has effect for the allocation of new threads in [`push()`][Self::push()].
    /// A new thread is allocated, whenever the number of currently
    /// running threads in `self` is smaller than the maximal number.
    ///
    /// `error` can be [`None`] to ignore errors, or non-[`None`] to report
    /// errors. An error can only occur when a new thread couldn't be
    /// created.
    ///
    /// Before version 2.32, this function did not return a success status.
    /// ## `max_threads`
    /// a new maximal number of threads for `self`,
    ///  or -1 for unlimited
    ///
    /// # Returns
    ///
    /// [`true`] on success, [`false`] if an error occurred
    #[doc(alias = "g_thread_pool_set_max_threads")]
    pub fn set_max_threads(&self, max_threads: Option<u32>) -> Result<(), crate::Error> {
        unsafe {
            let mut err = ptr::null_mut();
            let ret: bool = from_glib(ffi::g_thread_pool_set_max_threads(
                self.0.as_ptr(),
                max_threads.map(|v| v as i32).unwrap_or(-1),
                &mut err,
            ));
            if ret {
                Ok(())
            } else {
                Err(from_glib_full(err))
            }
        }
    }

    #[doc(alias = "g_thread_pool_get_max_threads")]
    #[doc(alias = "get_max_threads")]
    pub fn max_threads(&self) -> Option<u32> {
        unsafe {
            let max_threads = ffi::g_thread_pool_get_max_threads(self.0.as_ptr());
            if max_threads == -1 {
                None
            } else {
                Some(max_threads as u32)
            }
        }
    }

    /// Returns the number of threads currently running in `self`.
    ///
    /// # Returns
    ///
    /// the number of threads currently running
    #[doc(alias = "g_thread_pool_get_num_threads")]
    #[doc(alias = "get_num_threads")]
    pub fn num_threads(&self) -> u32 {
        unsafe { ffi::g_thread_pool_get_num_threads(self.0.as_ptr()) }
    }

    /// Returns the number of tasks still unprocessed in `self`.
    ///
    /// # Returns
    ///
    /// the number of unprocessed tasks
    #[doc(alias = "g_thread_pool_unprocessed")]
    #[doc(alias = "get_unprocessed")]
    pub fn unprocessed(&self) -> u32 {
        unsafe { ffi::g_thread_pool_unprocessed(self.0.as_ptr()) }
    }

    /// 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.
    ///
    /// The default value is 2.
    /// ## `max_threads`
    /// maximal number of unused threads
    #[doc(alias = "g_thread_pool_set_max_unused_threads")]
    pub fn set_max_unused_threads(max_threads: Option<u32>) {
        unsafe {
            ffi::g_thread_pool_set_max_unused_threads(max_threads.map(|v| v as i32).unwrap_or(-1))
        }
    }

    /// Returns the maximal allowed number of unused threads.
    ///
    /// # Returns
    ///
    /// the maximal number of unused threads
    #[doc(alias = "g_thread_pool_get_max_unused_threads")]
    #[doc(alias = "get_max_unused_threads")]
    pub fn max_unused_threads() -> Option<u32> {
        unsafe {
            let max_unused_threads = ffi::g_thread_pool_get_max_unused_threads();
            if max_unused_threads == -1 {
                None
            } else {
                Some(max_unused_threads as u32)
            }
        }
    }

    /// Returns the number of currently unused threads.
    ///
    /// # Returns
    ///
    /// the number of currently unused threads
    #[doc(alias = "g_thread_pool_get_num_unused_threads")]
    #[doc(alias = "get_num_unused_threads")]
    pub fn num_unused_threads() -> u32 {
        unsafe { ffi::g_thread_pool_get_num_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()`.
    #[doc(alias = "g_thread_pool_stop_unused_threads")]
    pub fn stop_unused_threads() {
        unsafe {
            ffi::g_thread_pool_stop_unused_threads();
        }
    }

    /// 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
    /// [`stop_unused_threads()`][Self::stop_unused_threads()] on a regular timeout,
    /// except this is done on a per thread basis.
    ///
    /// By setting `interval` to 0, idle threads will not be stopped.
    ///
    /// The default value is 15000 (15 seconds).
    /// ## `interval`
    /// the maximum `interval` (in milliseconds)
    ///  a thread can be idle
    #[doc(alias = "g_thread_pool_set_max_idle_time")]
    pub fn set_max_idle_time(max_idle_time: u32) {
        unsafe { ffi::g_thread_pool_set_max_idle_time(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.
    ///
    /// If this function returns 0, threads waiting in the thread
    /// pool for new work are not stopped.
    ///
    /// # Returns
    ///
    /// the maximum `interval` (milliseconds) to wait
    ///  for new tasks in the thread pool before stopping the
    ///  thread
    #[doc(alias = "g_thread_pool_get_max_idle_time")]
    #[doc(alias = "get_max_idle_time")]
    pub fn max_idle_time() -> u32 {
        unsafe { ffi::g_thread_pool_get_max_idle_time() }
    }
}

impl Drop for ThreadPool {
    #[inline]
    fn drop(&mut self) {
        unsafe {
            ffi::g_thread_pool_free(self.0.as_ptr(), ffi::GFALSE, ffi::GTRUE);
        }
    }
}

unsafe extern "C" fn spawn_func(func: ffi::gpointer, _data: ffi::gpointer) {
    let func: Box<Box<dyn FnOnce()>> = Box::from_raw(func as *mut _);
    func()
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_push() {
        use std::sync::mpsc;

        let p = ThreadPool::exclusive(1).unwrap();
        let (sender, receiver) = mpsc::channel();

        let handle = p
            .push(move || {
                sender.send(true).unwrap();
                123
            })
            .unwrap();

        assert_eq!(handle.join().unwrap(), 123);
        assert_eq!(receiver.recv(), Ok(true));
    }

    #[test]
    fn test_push_future() {
        let c = crate::MainContext::new();
        let p = ThreadPool::shared(None).unwrap();

        let fut = p.push_future(|| true).unwrap();

        let res = c.block_on(fut);
        assert!(res.unwrap());
    }
}