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
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
//! Readiness event types.
use fmt;
use ;
use Duration;
/// A readiness event source that can be polled for events.
///
/// # Implementing event source
///
/// The trait has two generic parameters: `ES` and `E`. `ES` must implement
/// [`event::Sink`], this should always be a generic parameter to ensure that
/// any event sink can be used with the event source. `E` should also remain
/// generic but a trait bound `From<MyError>` should be added, this way [`poll`]
/// can return a single error from multiple event sources. The example below
/// shows how this works.
///
/// [`event::Sink`]: Sink
/// [`poll`]: crate::poll
///
/// ```
/// use std::time::Duration;
///
/// use gaea::{event, Event, poll};
///
/// /// Our event source that implements `event::Source`.
/// struct MyEventSource(Vec<Event>);
///
/// /// The error returned by our even source implementation.
/// struct SourceError;
///
/// impl<ES, E> event::Source<ES, E> for MyEventSource
/// where ES: event::Sink, // We keep the event sink generic to support all
/// // kinds of event sinks.
/// E: From<SourceError>, // We add this bound to allow use to convert
/// // `SourceError` into the generic error `E`.
/// {
/// fn max_timeout(&self) -> Option<Duration> {
/// if !self.0.is_empty() {
/// // If we have an event ready we don't want to block.
/// Some(Duration::from_millis(0))
/// } else {
/// // If we don't have any events we don't have a preference about
/// // blocking times.
/// None
/// }
/// }
///
/// fn poll(&mut self, event_sink: &mut ES) -> Result<(), E> {
/// match poll_events(event_sink) {
/// Ok(()) => Ok(()),
/// // We need explicitly call `into()` to convert our error into
/// // the generic error. Note that this isn't required when using
/// // `?` (the try operator).
/// Err(err) => Err(err.into()),
/// }
/// }
/// }
/// # fn poll_events<ES>(_event_sink: &mut ES) -> Result<(), SourceError> { Ok(()) }
///
/// #[derive(Debug)]
/// struct MyError;
///
/// // Implementing `From` for `MyError` allows us to use it as an error in our call
/// // to poll below.
/// impl From<SourceError> for MyError {
/// fn from(_err: SourceError) -> MyError {
/// MyError
/// }
/// }
///
/// # fn main() -> Result<(), MyError> {
/// // Now we can use our event source with `MyError` as error type.
/// let mut my_source = MyEventSource(Vec::new());
/// let mut events = Vec::new();
/// poll(&mut [&mut my_source], &mut events, None)
/// # }
/// ```
/// An event sink to which events can be added.
///
/// `event::Sink` is passed as an argument to [`poll`] and will be used to
/// receive any new readiness events received since the last poll. Usually, a
/// single `event::Sink` is created and reused on each call to [`poll`].
///
/// See [`poll`] for more documentation on polling.
///
/// [`poll`]: crate::poll
///
/// # Why a trait?
///
/// A possible question that might arise is: "why is this a trait and not a
/// concrete type?" The answer is flexibility. Previously it was a vector, but
/// most users actually have there own data structure with runnable processes,
/// green threads, `Future`s, etc. This meant that `event::Sink` was often an
/// intermediate storage used to receive events only to mark processes as
/// runnable and run them later.
///
/// Using a trait removes the need for this intermediate storage and allows
/// users to direct mark processes as runnable inside there own data structure.
///
/// # Examples
///
/// An implementation of `event::Sink` for an array.
///
/// ```
/// # fn main() -> Result<(), ()> {
/// use gaea::{event, Event, Queue, Ready, poll};
///
/// const EVENTS_SIZE: usize = 32;
///
/// /// Our `event::Sink` implementation.
/// struct MyEvents([Option<Event>; EVENTS_SIZE]);
///
/// impl event::Sink for MyEvents {
/// fn capacity_left(&self) -> event::Capacity {
/// let limit = self.0.iter().position(Option::is_some).unwrap_or(EVENTS_SIZE);
/// event::Capacity::Limited(limit)
/// }
///
/// fn add(&mut self, event: Event) {
/// let index = self.0.iter().position(Option::is_none).unwrap();
/// self.0[index] = Some(event);
/// }
/// }
///
/// // An event source, with some events.
/// let mut queue = Queue::new();
/// let event1 = Event::new(event::Id(0), Ready::READABLE);
/// queue.add(event1);
/// let event2 = Event::new(event::Id(1), Ready::WRITABLE);
/// queue.add(event2);
///
/// // Poll the source.
/// let mut events = MyEvents([None; EVENTS_SIZE]);
/// poll(&mut [&mut queue], &mut events, None)?;
/// assert_eq!(events.0[0], Some(event1));
/// assert_eq!(events.0[1], Some(event2));
/// # Ok(())
/// # }
/// ```
/// The capacity left in the [event sink].
///
/// If the event source can grow it should use `Growable`. If there is some kind
/// of capacity limit `Limited` should be used.
///
/// [event sink]: Sink
/// A readiness event.
///
/// `Event` is a [readiness state] paired with an [id]. Events are returned by
/// [`poll`].
///
/// For more documentation on polling and events, see [`poll`].
///
/// [readiness state]: Ready
/// [id]: Id
/// [`poll`]: crate::poll
///
/// # Examples
///
/// ```
/// use gaea::{event, Event, Ready};
///
/// let my_event = Event::new(event::Id(0), Ready::READABLE | Ready::WRITABLE);
///
/// assert_eq!(my_event.id(), event::Id(0));
/// assert_eq!(my_event.readiness(), Ready::READABLE | Ready::WRITABLE);
/// ```
/// Identifier of an event.
///
/// This is used to associate a readiness notification with an event handle.
///
/// See [`poll`] for more documentation on polling.
///
/// [`poll`]: crate::poll
///
/// # Uniqueness of `Id`
///
/// `Id` does not have to be unique, it is purely a tool for the user to
/// associate an `Event` with an event handle. It is advised for example to use
/// the same `Id` for say a `TcpStream` and any related timeout or deadline for
/// the same connection. The `Id` is effectively opaque to any readiness event
/// sources.
;
/// A set of readiness event kinds.
///
/// `Ready` is a set of operation descriptors indicating which kind of operation
/// is ready to be performed. For example, `Ready::READABLE` indicates that the
/// associated `Evented` handle is ready to perform a read operation.
///
/// `Ready` values can be combined together using the various bitwise operators,
/// see examples below.
///
/// For high level documentation on polling and readiness, see [`poll`].
///
/// [`poll`]: crate::poll
///
/// # Examples
///
/// ```
/// use gaea::Ready;
///
/// let ready = Ready::READABLE | Ready::WRITABLE;
///
/// assert!(ready.is_readable());
/// assert!(ready.is_writable());
/// assert!(!ready.is_error());
/// ```
;
const READABLE: u8 = 1;
const WRITABLE: u8 = 1 << 1;
const ERROR: u8 = 1 << 2;
const TIMER: u8 = 1 << 3;
const HUP: u8 = 1 << 4;