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
//! High resolution hardware timer based task scheduling
//!
//! Although FreeRTOS provides software timers, these timers have a few
//! limitations:
//!
//! - Maximum resolution is equal to RTOS tick period
//! - Timer callbacks are dispatched from a low-priority task
//!
//! EspTimer is a set of APIs that provides one-shot and periodic timers,
//! microsecond time resolution, and 52-bit range.

use core::num::NonZeroU32;
use core::time::Duration;
use core::{ffi, ptr};

extern crate alloc;
use alloc::boxed::Box;
use alloc::sync::Arc;

use esp_idf_hal::task::asynch::Notification;

use crate::sys::*;

use ::log::debug;

#[cfg(esp_idf_esp_timer_supports_isr_dispatch_method)]
pub use isr::*;

use crate::handle::RawHandle;

struct UnsafeCallback<'a>(*mut Box<dyn FnMut() + Send + 'a>);

impl<'a> UnsafeCallback<'a> {
    fn from(boxed: &mut Box<dyn FnMut() + Send + 'a>) -> Self {
        Self(boxed)
    }

    unsafe fn from_ptr(ptr: *mut ffi::c_void) -> Self {
        Self(ptr as *mut _)
    }

    fn as_ptr(&self) -> *mut ffi::c_void {
        self.0 as *mut _
    }

    unsafe fn call(&self) {
        let reference = self.0.as_mut().unwrap();

        (reference)();
    }
}

pub struct EspTimer<'a> {
    handle: esp_timer_handle_t,
    _callback: Box<dyn FnMut() + Send + 'a>,
}

impl<'a> EspTimer<'a> {
    pub fn is_scheduled(&self) -> Result<bool, EspError> {
        Ok(unsafe { esp_timer_is_active(self.handle) })
    }

    pub fn cancel(&self) -> Result<bool, EspError> {
        let res = unsafe { esp_timer_stop(self.handle) };

        Ok(res != ESP_OK)
    }

    pub fn after(&self, duration: Duration) -> Result<(), EspError> {
        self.cancel()?;

        esp!(unsafe { esp_timer_start_once(self.handle, duration.as_micros() as _) })?;

        Ok(())
    }

    pub fn every(&self, duration: Duration) -> Result<(), EspError> {
        self.cancel()?;

        esp!(unsafe { esp_timer_start_periodic(self.handle, duration.as_micros() as _) })?;

        Ok(())
    }

    extern "C" fn handle(arg: *mut ffi::c_void) {
        if crate::hal::interrupt::active() {
            #[cfg(esp_idf_esp_timer_supports_isr_dispatch_method)]
            {
                let signaled = crate::hal::interrupt::with_isr_yield_signal(move || unsafe {
                    UnsafeCallback::from_ptr(arg).call();
                });

                if signaled {
                    unsafe {
                        crate::sys::esp_timer_isr_dispatch_need_yield();
                    }
                }
            }

            #[cfg(not(esp_idf_esp_timer_supports_isr_dispatch_method))]
            {
                unreachable!();
            }
        } else {
            unsafe {
                UnsafeCallback::from_ptr(arg).call();
            }
        }
    }
}

unsafe impl<'a> Send for EspTimer<'a> {}

impl<'a> Drop for EspTimer<'a> {
    fn drop(&mut self) {
        self.cancel().unwrap();

        while unsafe { esp_timer_delete(self.handle) } != ESP_OK {
            // Timer is still running, busy-loop
        }

        debug!("Timer dropped");
    }
}

impl<'a> RawHandle for EspTimer<'a> {
    type Handle = esp_timer_handle_t;

    fn handle(&self) -> Self::Handle {
        self.handle
    }
}

pub struct EspAsyncTimer {
    timer: EspTimer<'static>,
    notification: Arc<Notification>,
}

impl EspAsyncTimer {
    pub async fn after(&mut self, duration: Duration) -> Result<(), EspError> {
        self.timer.cancel()?;

        self.notification.reset();
        self.timer.after(duration)?;

        self.notification.wait().await;

        Ok(())
    }

    pub fn every(&mut self, duration: Duration) -> Result<&'_ mut Self, EspError> {
        self.timer.cancel()?;

        self.notification.reset();
        self.timer.every(duration)?;

        Ok(self)
    }

    pub async fn tick(&mut self) -> Result<(), EspError> {
        self.notification.wait().await;

        Ok(())
    }
}

impl embedded_hal_async::delay::DelayNs for EspAsyncTimer {
    async fn delay_ns(&mut self, ns: u32) {
        EspAsyncTimer::after(self, Duration::from_micros(ns as _))
            .await
            .unwrap();
    }

    async fn delay_ms(&mut self, ms: u32) {
        EspAsyncTimer::after(self, Duration::from_millis(ms as _))
            .await
            .unwrap();
    }
}

pub trait EspTimerServiceType {
    fn is_isr() -> bool;
}

#[derive(Clone, Debug)]
pub struct Task;

impl EspTimerServiceType for Task {
    fn is_isr() -> bool {
        false
    }
}

pub struct EspTimerService<T>(T)
where
    T: EspTimerServiceType;

impl<T> EspTimerService<T>
where
    T: EspTimerServiceType,
{
    pub fn now(&self) -> Duration {
        Duration::from_micros(unsafe { esp_timer_get_time() as _ })
    }

    pub fn timer<F>(&self, callback: F) -> Result<EspTimer<'static>, EspError>
    where
        F: FnMut() + Send + 'static,
    {
        self.internal_timer(callback)
    }

    pub fn timer_async(&self) -> Result<EspAsyncTimer, EspError> {
        let notification = Arc::new(Notification::new());

        let timer = {
            let notification = Arc::downgrade(&notification);

            self.timer(move || {
                if let Some(notification) = notification.upgrade() {
                    notification.notify(NonZeroU32::new(1).unwrap());
                }
            })?
        };

        Ok(EspAsyncTimer {
            timer,
            notification,
        })
    }

    /// # Safety
    ///
    /// This method - in contrast to method `timer` - allows the user to pass
    /// a non-static callback/closure. This enables users to borrow
    /// - in the closure - variables that live on the stack - or more generally - in the same
    ///   scope where the service is created.
    ///
    /// HOWEVER: care should be taken NOT to call `core::mem::forget()` on the service,
    /// as that would immediately lead to an UB (crash).
    /// Also note that forgetting the service might happen with `Rc` and `Arc`
    /// when circular references are introduced: https://github.com/rust-lang/rust/issues/24456
    ///
    /// The reason is that the closure is actually sent to a hidden ESP IDF thread.
    /// This means that if the service is forgotten, Rust is free to e.g. unwind the stack
    /// and the closure now owned by this other thread will end up with references to variables that no longer exist.
    ///
    /// The destructor of the service takes care - prior to the service being dropped and e.g.
    /// the stack being unwind - to remove the closure from the hidden thread and destroy it.
    /// Unfortunately, when the service is forgotten, the un-subscription does not happen
    /// and invalid references are left dangling.
    ///
    /// This "local borrowing" will only be possible to express in a safe way once/if `!Leak` types
    /// are introduced to Rust (i.e. the impossibility to "forget" a type and thus not call its destructor).
    pub unsafe fn timer_nonstatic<'a, F>(&self, callback: F) -> Result<EspTimer<'a>, EspError>
    where
        F: FnMut() + Send + 'a,
    {
        self.internal_timer(callback)
    }

    fn internal_timer<'a, F>(&self, callback: F) -> Result<EspTimer<'a>, EspError>
    where
        F: FnMut() + Send + 'a,
    {
        let mut handle: esp_timer_handle_t = ptr::null_mut();

        let boxed_callback: Box<dyn FnMut() + Send + 'a> = Box::new(callback);

        let mut callback = Box::new(boxed_callback);
        let unsafe_callback = UnsafeCallback::from(&mut callback);

        #[cfg(esp_idf_esp_timer_supports_isr_dispatch_method)]
        let dispatch_method = if T::is_isr() {
            esp_timer_dispatch_t_ESP_TIMER_ISR
        } else {
            esp_timer_dispatch_t_ESP_TIMER_TASK
        };

        #[cfg(not(esp_idf_esp_timer_supports_isr_dispatch_method))]
        let dispatch_method = esp_timer_dispatch_t_ESP_TIMER_TASK;

        esp!(unsafe {
            esp_timer_create(
                &esp_timer_create_args_t {
                    callback: Some(EspTimer::handle),
                    name: b"rust\0" as *const _ as *const _, // TODO
                    arg: unsafe_callback.as_ptr(),
                    dispatch_method,
                    skip_unhandled_events: false, // TODO
                },
                &mut handle as *mut _,
            )
        })?;

        Ok(EspTimer {
            handle,
            _callback: callback,
        })
    }
}

pub type EspTaskTimerService = EspTimerService<Task>;

impl EspTimerService<Task> {
    pub fn new() -> Result<Self, EspError> {
        Ok(Self(Task))
    }
}

impl<T> Clone for EspTimerService<T>
where
    T: EspTimerServiceType + Clone,
{
    fn clone(&self) -> Self {
        Self(self.0.clone())
    }
}

#[cfg(esp_idf_esp_timer_supports_isr_dispatch_method)]
mod isr {
    use crate::sys::EspError;

    #[derive(Clone, Debug)]
    pub struct ISR;

    impl super::EspTimerServiceType for ISR {
        fn is_isr() -> bool {
            true
        }
    }

    pub type EspISRTimerService = super::EspTimerService<ISR>;

    impl EspISRTimerService {
        /// # Safety
        /// TODO
        pub unsafe fn new() -> Result<Self, EspError> {
            Ok(Self(ISR))
        }
    }
}

#[cfg(feature = "embassy-time-driver")]
pub mod embassy_time_driver {
    use core::cell::UnsafeCell;

    use heapless::Vec;

    use ::embassy_time_driver::{AlarmHandle, Driver};

    use crate::hal::task::CriticalSection;

    use crate::sys::*;

    use crate::timer::*;

    struct Alarm {
        timer: Option<EspTimer<'static>>,
        #[allow(clippy::type_complexity)]
        callback: Option<(fn(*mut ()), *mut ())>,
    }

    struct EspDriver<const MAX_ALARMS: usize = 16> {
        alarms: UnsafeCell<Vec<Alarm, MAX_ALARMS>>,
        cs: CriticalSection,
    }

    impl<const MAX_ALARMS: usize> EspDriver<MAX_ALARMS> {
        const fn new() -> Self {
            Self {
                alarms: UnsafeCell::new(Vec::new()),
                cs: CriticalSection::new(),
            }
        }

        fn call(&self, id: u8) {
            let callback = {
                let _guard = self.cs.enter();

                let alarm = self.alarm(id);

                alarm.callback
            };

            if let Some((func, arg)) = callback {
                func(arg)
            }
        }

        #[allow(clippy::mut_from_ref)]
        fn alarm(&self, id: u8) -> &mut Alarm {
            &mut unsafe { self.alarms.get().as_mut() }.unwrap()[id as usize]
        }
    }

    unsafe impl<const MAX_ALARMS: usize> Send for EspDriver<MAX_ALARMS> {}
    unsafe impl<const MAX_ALARMS: usize> Sync for EspDriver<MAX_ALARMS> {}

    impl<const MAX_ALARMS: usize> Driver for EspDriver<MAX_ALARMS> {
        fn now(&self) -> u64 {
            unsafe { esp_timer_get_time() as _ }
        }

        unsafe fn allocate_alarm(&self) -> Option<AlarmHandle> {
            let id = {
                let _guard = self.cs.enter();

                let id = self.alarms.get().as_mut().unwrap().len();

                if id < MAX_ALARMS {
                    self.alarms
                        .get()
                        .as_mut()
                        .unwrap()
                        .push(Alarm {
                            timer: None,
                            callback: None,
                        })
                        .unwrap_or_else(|_| unreachable!());

                    id as u8
                } else {
                    return None;
                }
            };

            let service = EspTimerService::<Task>::new().unwrap();

            // Driver is always statically allocated, so this is safe
            let static_self: &'static Self = core::mem::transmute(self);

            self.alarm(id).timer = Some(service.timer(move || static_self.call(id)).unwrap());

            Some(AlarmHandle::new(id))
        }

        fn set_alarm_callback(&self, handle: AlarmHandle, callback: fn(*mut ()), ctx: *mut ()) {
            let _guard = self.cs.enter();

            let alarm = self.alarm(handle.id());

            alarm.callback = Some((callback, ctx));
        }

        fn set_alarm(&self, handle: AlarmHandle, timestamp: u64) -> bool {
            let alarm = self.alarm(handle.id());

            let now = self.now();

            if now < timestamp {
                alarm
                    .timer
                    .as_mut()
                    .unwrap()
                    .after(Duration::from_micros(timestamp - now))
                    .unwrap();
                true
            } else {
                false
            }
        }
    }

    pub type LinkWorkaround = [*mut (); 4];

    static mut __INTERNAL_REFERENCE: LinkWorkaround = [
        _embassy_time_now as *mut _,
        _embassy_time_allocate_alarm as *mut _,
        _embassy_time_set_alarm_callback as *mut _,
        _embassy_time_set_alarm as *mut _,
    ];

    pub fn link() -> LinkWorkaround {
        unsafe { __INTERNAL_REFERENCE }
    }

    ::embassy_time_driver::time_driver_impl!(static DRIVER: EspDriver = EspDriver::new());
}