zx/
clock.rs

1// Copyright 2020 The Fuchsia Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5//! Type-safe bindings for Zircon clock objects.
6
7use crate::{
8    AsHandleRef, BootTimeline, ClockUpdate, Handle, HandleBased, HandleRef, Instant,
9    MonotonicTimeline, ObjectQuery, SyntheticTimeline, Timeline, Topic, object_get_info_single, ok,
10    sys,
11};
12use bitflags::bitflags;
13use std::mem::MaybeUninit;
14use std::ptr;
15use zx_status::Status;
16
17/// An object representing a kernel [clock], used to track the progress of time. A clock is a
18/// one-dimensional affine transformation of the [clock monotonic] reference timeline which may be
19/// atomically adjusted by a maintainer and observed by clients.
20///
21/// As essentially a subtype of `Handle`, it can be freely interconverted.
22///
23/// [clock]: https://fuchsia.dev/fuchsia-src/reference/kernel_objects/clock
24/// [clock monotonic]: https://fuchsia.dev/fuchsia-src/reference/syscalls/clock_get_monotonic.md
25#[derive(Debug, Eq, PartialEq, Ord, PartialOrd, Hash)]
26#[repr(transparent)]
27pub struct Clock<Reference = MonotonicTimeline, Output = SyntheticTimeline>(
28    Handle,
29    std::marker::PhantomData<(Reference, Output)>,
30);
31
32pub type SyntheticClock = Clock<MonotonicTimeline, SyntheticTimeline>;
33pub type SyntheticClockOnBoot = Clock<BootTimeline, SyntheticTimeline>;
34
35impl<Output: Timeline> Clock<MonotonicTimeline, Output> {
36    /// Create a new clock object with the provided arguments, with the monotonic clock as the
37    /// reference timeline. Wraps the [zx_clock_create] syscall.
38    ///
39    /// [zx_clock_create]: https://fuchsia.dev/fuchsia-src/reference/syscalls/clock_create
40    pub fn create(opts: ClockOpts, backstop: Option<Instant<Output>>) -> Result<Self, Status> {
41        let mut out = 0;
42        let status = match backstop {
43            Some(backstop) => {
44                // When using backstop time, use the API v1 args struct.
45                let args = sys::zx_clock_create_args_v1_t { backstop_time: backstop.into_nanos() };
46                unsafe {
47                    sys::zx_clock_create(
48                        sys::ZX_CLOCK_ARGS_VERSION_1 | opts.bits(),
49                        std::ptr::from_ref(&args).cast::<u8>(),
50                        &mut out,
51                    )
52                }
53            }
54            None => unsafe { sys::zx_clock_create(opts.bits(), ptr::null(), &mut out) },
55        };
56        ok(status)?;
57        unsafe { Ok(Self::from(Handle::from_raw(out))) }
58    }
59}
60
61impl<Output: Timeline> Clock<BootTimeline, Output> {
62    /// Create a new clock object with the provided arguments, with the boot clock as the reference
63    /// timeline. Wraps the [zx_clock_create] syscall.
64    ///
65    /// [zx_clock_create]: https://fuchsia.dev/fuchsia-src/reference/syscalls/clock_create
66    pub fn create(opts: ClockOpts, backstop: Option<Instant<Output>>) -> Result<Self, Status> {
67        let mut out = 0;
68        let opts = opts | ClockOpts::BOOT;
69        let status = match backstop {
70            Some(backstop) => {
71                // When using backstop time, use the API v1 args struct.
72                let args = sys::zx_clock_create_args_v1_t { backstop_time: backstop.into_nanos() };
73                unsafe {
74                    sys::zx_clock_create(
75                        sys::ZX_CLOCK_ARGS_VERSION_1 | opts.bits(),
76                        &args as *const _ as *const u8,
77                        &mut out,
78                    )
79                }
80            }
81            None => unsafe { sys::zx_clock_create(opts.bits(), ptr::null(), &mut out) },
82        };
83        ok(status)?;
84        unsafe { Ok(Self::from(Handle::from_raw(out))) }
85    }
86}
87
88impl<Reference: Timeline, Output: Timeline> Clock<Reference, Output> {
89    /// Perform a basic read of this clock. Wraps the [zx_clock_read] syscall. Requires
90    /// `ZX_RIGHT_READ` and that the clock has had an initial time established.
91    ///
92    /// [zx_clock_read]: https://fuchsia.dev/fuchsia-src/reference/syscalls/clock_read
93    pub fn read(&self) -> Result<Instant<Output>, Status> {
94        let mut now = 0;
95        let status = unsafe { sys::zx_clock_read(self.raw_handle(), &mut now) };
96        ok(status)?;
97        Ok(Instant::<Output>::from_nanos(now))
98    }
99
100    /// Perform a basic read of a mapped clock. Wraps the [zx_clock_read_mapped] syscall.
101    ///
102    /// # Safety
103    ///
104    /// |zx_clock_get_details_mapped| must only be called using a |clock_addr| which is the address
105    /// of a clock's state currently mapped into the caller's address space using
106    /// |zx_vmar_map_clock|.  Attempting to get_details from any other address, or from a clock
107    /// mapping which has been unmapped (completely or partially) will result in undefined behavior.
108    ///
109    /// [zx_clock_read]: https://fuchsia.dev/fuchsia-src/reference/syscalls/clock_read_mapped
110    pub unsafe fn read_mapped(clock_addr: usize) -> Result<Instant<Output>, Status> {
111        let mut now = 0;
112        let status = unsafe {
113            // SAFETY: see function docs above.
114            sys::zx_clock_read_mapped(clock_addr as *const u8, &mut now)
115        };
116        ok(status)?;
117        Ok(Instant::<Output>::from_nanos(now))
118    }
119
120    /// Get low level details of this clock's current status. Wraps the
121    /// [zx_clock_get_details] syscall. Requires `ZX_RIGHT_READ`.
122    ///
123    /// [zx_clock_get_details]: https://fuchsia.dev/fuchsia-src/reference/syscalls/clock_get_details
124    pub fn get_details(&self) -> Result<ClockDetails<Reference, Output>, Status> {
125        let mut out_details = MaybeUninit::<sys::zx_clock_details_v1_t>::uninit();
126        let status = unsafe {
127            sys::zx_clock_get_details(
128                self.raw_handle(),
129                sys::ZX_CLOCK_ARGS_VERSION_1,
130                out_details.as_mut_ptr().cast::<u8>(),
131            )
132        };
133        ok(status)?;
134        let out_details = unsafe { out_details.assume_init() };
135        Ok(out_details.into())
136    }
137
138    /// Get low level details of a mapped clock's current status. Wraps the
139    /// [zx_clock_get_details_mapped] syscall.
140    ///
141    /// # Safety
142    ///
143    /// |zx_clock_get_details_mapped| must only be called using a |clock_addr| which is the address
144    /// of a clock's state currently mapped into the caller's address space using
145    /// |zx_vmar_map_clock|.  Attempting to get_details from any other address, or from a clock
146    /// mapping which has been unmapped (completely or partially) will result in undefined behavior.
147    ///
148    /// [zx_clock_get_details_mapped]: https://fuchsia.dev/fuchsia-src/reference/syscalls/clock_get_details_mapped
149    pub unsafe fn get_details_mapped(
150        clock_addr: usize,
151    ) -> Result<ClockDetails<Reference, Output>, Status> {
152        let mut out_details = MaybeUninit::<sys::zx_clock_details_v1_t>::uninit();
153        let status = unsafe {
154            // SAFETY: see safety notes in the function docs above.
155            sys::zx_clock_get_details_mapped(
156                clock_addr as *const u8,
157                sys::ZX_CLOCK_ARGS_VERSION_1,
158                out_details.as_mut_ptr().cast::<u8>(),
159            )
160        };
161        ok(status)?;
162        let out_details = unsafe { out_details.assume_init() };
163        Ok(out_details.into())
164    }
165
166    // Returns the memory size for the memory region used to store clock details.
167    pub fn get_mapped_size(clock: &Clock<Reference, Output>) -> Result<usize, Status> {
168        Ok(object_get_info_single::<MappedSizeQuery>(clock.as_handle_ref())?)
169    }
170
171    /// Make adjustments to this clock. Wraps the [zx_clock_update] syscall. Requires
172    /// `ZX_RIGHT_WRITE`.
173    ///
174    /// [zx_clock_update]: https://fuchsia.dev/fuchsia-src/reference/syscalls/clock_update
175    pub fn update(&self, update: impl Into<ClockUpdate<Reference, Output>>) -> Result<(), Status> {
176        let update = update.into();
177        let options = update.options();
178        let args = update.args();
179        let status = unsafe {
180            sys::zx_clock_update(self.raw_handle(), options, std::ptr::from_ref(&args).cast::<u8>())
181        };
182        ok(status)?;
183        Ok(())
184    }
185
186    /// Convert this clock to one on a generic synthetic timeline, erasing any user-defined
187    /// timeline.
188    pub fn downcast<NewReference: Timeline>(self) -> Clock<NewReference, SyntheticTimeline> {
189        Clock(self.0, std::marker::PhantomData)
190    }
191}
192
193impl<Reference: Timeline> Clock<Reference, SyntheticTimeline> {
194    /// Cast a "base" clock to one with a user-defined timeline that will carry the timeline for
195    /// all transformations and reads.
196    pub fn cast<NewReference: Timeline, UserTimeline: Timeline>(
197        self,
198    ) -> Clock<NewReference, UserTimeline> {
199        Clock(self.0, std::marker::PhantomData)
200    }
201}
202
203impl<Reference: Timeline, Output: Timeline> AsHandleRef for Clock<Reference, Output> {
204    fn as_handle_ref(&self) -> HandleRef<'_> {
205        self.0.as_handle_ref()
206    }
207}
208
209impl<Reference: Timeline, Output: Timeline> From<Handle> for Clock<Reference, Output> {
210    fn from(handle: Handle) -> Self {
211        Clock(handle, std::marker::PhantomData)
212    }
213}
214
215impl<Reference: Timeline, Output: Timeline> From<Clock<Reference, Output>> for Handle {
216    fn from(x: Clock<Reference, Output>) -> Handle {
217        x.0
218    }
219}
220
221impl<Reference: Timeline, Output: Timeline> HandleBased for Clock<Reference, Output> {}
222
223struct MappedSizeQuery;
224unsafe impl ObjectQuery for MappedSizeQuery {
225    const TOPIC: Topic = Topic::CLOCK_MAPPED_SIZE;
226    type InfoTy = usize;
227}
228
229bitflags! {
230    #[repr(transparent)]
231    #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
232    pub struct ClockOpts: u64 {
233        /// When set, creates a clock object which is guaranteed to never run backwards. Monotonic
234        /// clocks must always move forward.
235        const MONOTONIC = sys::ZX_CLOCK_OPT_MONOTONIC;
236
237        /// When set, creates a clock which is guaranteed to never jump either forwards or
238        /// backwards. Continuous clocks may only be maintained using frequency adjustments and are,
239        /// by definition, also monotonic.
240        const CONTINUOUS = sys::ZX_CLOCK_OPT_CONTINUOUS | Self::MONOTONIC.bits();
241
242        /// When set, creates a clock that is automatically started and is initially a clone of
243        /// clock monotonic. Users may still update the clock within the limits defined by the
244        /// other options, the handle rights, and the backstop time of the clock.
245        const AUTO_START = sys::ZX_CLOCK_OPT_AUTO_START;
246
247        /// When set, creates a clock object that uses the boot timeline as its reference timeline.
248        const BOOT = sys::ZX_CLOCK_OPT_BOOT;
249
250        /// When set, creates a clock whose state may be mapped into a VMAR, allowing the state to
251        /// be used with calls to |zx_clock_read_mapped| and |zx_clock_get_details_mapped|.
252        const MAPPABLE = sys::ZX_CLOCK_OPT_MAPPABLE;
253    }
254}
255
256/// Fine grained details of a [`Clock`] object.
257#[derive(Debug, Clone, PartialEq, Eq)]
258pub struct ClockDetails<Reference = MonotonicTimeline, Output = SyntheticTimeline> {
259    /// The minimum time the clock can ever be set to.
260    pub backstop: Instant<Output>,
261
262    /// The current ticks to clock transformation.
263    pub ticks_to_synthetic: ClockTransformation<Reference, Output>,
264
265    /// The current clock monotonic to clock transformation.
266    pub reference_to_synthetic: ClockTransformation<Reference, Output>,
267
268    /// The current symmetric error estimate (if any) for the clock, measured in nanoseconds.
269    pub error_bounds: u64,
270
271    /// An observation of the system tick counter which was taken during the observation of the
272    /// clock.
273    pub query_ticks: sys::zx_ticks_t,
274
275    /// The last time the clock's value was updated as defined by the clock monotonic reference
276    /// timeline.
277    pub last_value_update_ticks: sys::zx_ticks_t,
278
279    /// The last time the clock's rate adjustment was updated as defined by the clock monotonic
280    /// reference timeline.
281    pub last_rate_adjust_update_ticks: sys::zx_ticks_t,
282
283    /// The last time the clock's error bounds were updated as defined by the clock monotonic
284    /// reference timeline.
285    pub last_error_bounds_update_ticks: sys::zx_ticks_t,
286
287    /// The generation nonce.
288    pub generation_counter: u32,
289}
290
291impl<Reference: Timeline, Output: Timeline> From<sys::zx_clock_details_v1_t>
292    for ClockDetails<Reference, Output>
293{
294    fn from(details: sys::zx_clock_details_v1_t) -> Self {
295        ClockDetails {
296            backstop: Instant::from_nanos(details.backstop_time),
297            ticks_to_synthetic: details.reference_ticks_to_synthetic.into(),
298            reference_to_synthetic: details.reference_to_synthetic.into(),
299            error_bounds: details.error_bound,
300            query_ticks: details.query_ticks,
301            last_value_update_ticks: details.last_value_update_ticks,
302            last_rate_adjust_update_ticks: details.last_rate_adjust_update_ticks,
303            last_error_bounds_update_ticks: details.last_error_bounds_update_ticks,
304            generation_counter: details.generation_counter,
305        }
306    }
307}
308
309/// A one-dimensional affine transformation that maps points from the reference timeline to the
310/// clock timeline. See [clock transformations].
311///
312/// [clock transformations]: https://fuchsia.dev/fuchsia-src/concepts/kernel/clock_transformations
313#[derive(Debug, Clone, Eq, PartialEq)]
314pub struct ClockTransformation<Reference = MonotonicTimeline, Output = SyntheticTimeline> {
315    /// The offset on the reference timeline, measured in reference clock ticks.
316    pub reference_offset: Instant<Reference>,
317    /// The offset on the clock timeline, measured in clock ticks (typically normalized to
318    /// nanoseconds).
319    pub synthetic_offset: Instant<Output>,
320    /// The ratio of the reference to clock rate.
321    pub rate: sys::zx_clock_rate_t,
322}
323
324impl<Reference: Timeline, Output: Timeline> From<sys::zx_clock_transformation_t>
325    for ClockTransformation<Reference, Output>
326{
327    fn from(ct: sys::zx_clock_transformation_t) -> Self {
328        ClockTransformation {
329            reference_offset: Instant::<Reference>::from_nanos(ct.reference_offset),
330            synthetic_offset: Instant::<Output>::from_nanos(ct.synthetic_offset),
331            rate: ct.rate,
332        }
333    }
334}
335
336// Apply affine transformation to convert the reference time "r" to the
337// synthetic time "c".
338//
339// All values are widened to i128 before calculations and the end result is
340// converted back to a i64. If "c" is a larger number than would fit in an i64,
341// the result saturates when cast to i64.
342//
343// # Panics
344// If `r_rate` is zero, this function will panic.
345fn transform_clock(r: i64, r_offset: i64, c_offset: i64, r_rate: u32, c_rate: u32) -> i64 {
346    assert!(r_rate != 0, "r_rate may not be zero");
347    let r = r as i128;
348    let r_offset = r_offset as i128;
349    let c_offset = c_offset as i128;
350    let r_rate = r_rate as i128;
351    let c_rate = c_rate as i128;
352    let c = (((r - r_offset) * c_rate) / r_rate) + c_offset;
353    c.try_into().unwrap_or_else(|_| if c.is_positive() { i64::MAX } else { i64::MIN })
354}
355
356/// [Clock
357/// transformations](https://fuchsia.dev/fuchsia-src/concepts/kernel/clock_transformations)
358/// can be applied to convert a time from a reference time to a synthetic time.
359///
360/// The inverse transformation can be applied to convert a synthetic time back
361/// to the reference time.
362impl<Reference: Timeline + Copy, Output: Timeline + Copy> ClockTransformation<Reference, Output> {
363    /// Apply the transformation to convert a time from the reference timeline
364    /// to the output timeline.
365    ///
366    /// # Panics
367    /// If the reference clock rate is zero, this function will panic.
368    pub fn apply(&self, time: Instant<Reference>) -> Instant<Output> {
369        let c = transform_clock(
370            time.into_nanos(),
371            self.reference_offset.into_nanos(),
372            self.synthetic_offset.into_nanos(),
373            self.rate.reference_ticks,
374            self.rate.synthetic_ticks,
375        );
376
377        Instant::from_nanos(c)
378    }
379
380    /// Apply the transformation to convert a time from the output timeline
381    /// to the reference timeline.
382    ///
383    /// # Panics
384    /// If the output clock rate is zero, this function will panic.
385    pub fn apply_inverse(&self, time: Instant<Output>) -> Instant<Reference> {
386        let r = transform_clock(
387            time.into_nanos(),
388            self.synthetic_offset.into_nanos(),
389            self.reference_offset.into_nanos(),
390            self.rate.synthetic_ticks,
391            self.rate.reference_ticks,
392        );
393
394        Instant::from_nanos(r as i64)
395    }
396}
397
398#[cfg(test)]
399mod tests {
400    use super::*;
401    use crate::{MonotonicInstant, SyntheticInstant};
402    use assert_matches::assert_matches;
403
404    #[test]
405    fn create_clocks() {
406        assert_matches!(SyntheticClock::create(ClockOpts::empty(), None), Ok(_));
407        assert_matches!(SyntheticClock::create(ClockOpts::MONOTONIC, None), Ok(_));
408        assert_matches!(SyntheticClock::create(ClockOpts::CONTINUOUS, None), Ok(_));
409        assert_matches!(
410            SyntheticClock::create(ClockOpts::AUTO_START | ClockOpts::MONOTONIC, None),
411            Ok(_)
412        );
413        assert_matches!(
414            SyntheticClock::create(ClockOpts::AUTO_START | ClockOpts::CONTINUOUS, None),
415            Ok(_)
416        );
417
418        // Now with backstop.
419        let backstop = Some(SyntheticInstant::from_nanos(5500));
420        assert_matches!(SyntheticClock::create(ClockOpts::MONOTONIC, backstop), Ok(_));
421        assert_matches!(SyntheticClock::create(ClockOpts::CONTINUOUS, backstop), Ok(_));
422        assert_matches!(
423            SyntheticClock::create(ClockOpts::AUTO_START | ClockOpts::MONOTONIC, backstop),
424            Ok(_)
425        );
426        assert_matches!(
427            SyntheticClock::create(ClockOpts::AUTO_START | ClockOpts::CONTINUOUS, backstop),
428            Ok(_)
429        );
430    }
431
432    #[test]
433    fn read_time() {
434        let clock =
435            SyntheticClock::create(ClockOpts::MONOTONIC, None).expect("failed to create clock");
436        assert_matches!(clock.read(), Ok(_));
437    }
438
439    #[test]
440    fn get_clock_details() {
441        // No backstop.
442        let clock =
443            SyntheticClock::create(ClockOpts::MONOTONIC, None).expect("failed to create clock");
444        let details = clock.get_details().expect("failed to get details");
445        assert_eq!(details.backstop, SyntheticInstant::from_nanos(0));
446
447        // With backstop.
448        let clock =
449            SyntheticClock::create(ClockOpts::MONOTONIC, Some(SyntheticInstant::from_nanos(5500)))
450                .expect("failed to create clock");
451        let details = clock.get_details().expect("failed to get details");
452        assert_eq!(details.backstop, SyntheticInstant::from_nanos(5500));
453    }
454
455    #[test]
456    fn update_clock() {
457        let clock =
458            SyntheticClock::create(ClockOpts::MONOTONIC, None).expect("failed to create clock");
459        let before_details = clock.get_details().expect("failed to get details");
460        assert_eq!(before_details.last_value_update_ticks, 0);
461        assert_eq!(before_details.last_rate_adjust_update_ticks, 0);
462        assert_eq!(before_details.last_error_bounds_update_ticks, 0);
463
464        // Update all properties.
465        clock
466            .update(
467                ClockUpdate::builder()
468                    .absolute_value(
469                        MonotonicInstant::from_nanos(999),
470                        SyntheticInstant::from_nanos(42),
471                    )
472                    .rate_adjust(52)
473                    .error_bounds(52),
474            )
475            .expect("failed to update clock");
476        let after_details = clock.get_details().expect("failed to get details");
477        assert!(before_details.generation_counter < after_details.generation_counter);
478        assert!(after_details.last_value_update_ticks > before_details.last_value_update_ticks);
479        assert_eq!(
480            after_details.last_value_update_ticks,
481            after_details.last_rate_adjust_update_ticks
482        );
483        assert_eq!(
484            after_details.last_value_update_ticks,
485            after_details.last_error_bounds_update_ticks
486        );
487        assert_eq!(after_details.error_bounds, 52);
488        assert_eq!(after_details.ticks_to_synthetic.synthetic_offset.into_nanos(), 42);
489        assert_eq!(after_details.reference_to_synthetic.reference_offset.into_nanos(), 999);
490        assert_eq!(after_details.reference_to_synthetic.synthetic_offset.into_nanos(), 42);
491
492        let before_details = after_details;
493
494        // Update only one property.
495        clock.update(ClockUpdate::builder().error_bounds(100)).expect("failed to update clock");
496        let after_details = clock.get_details().expect("failed to get details");
497        assert!(before_details.generation_counter < after_details.generation_counter);
498        assert!(
499            after_details.last_error_bounds_update_ticks > before_details.last_value_update_ticks
500        );
501        assert!(
502            after_details.last_error_bounds_update_ticks
503                > after_details.last_rate_adjust_update_ticks
504        );
505        assert_eq!(
506            after_details.last_rate_adjust_update_ticks,
507            after_details.last_value_update_ticks
508        );
509        assert_eq!(after_details.error_bounds, 100);
510        assert_eq!(after_details.ticks_to_synthetic.synthetic_offset.into_nanos(), 42);
511        assert_eq!(after_details.reference_to_synthetic.synthetic_offset.into_nanos(), 42);
512    }
513
514    #[test]
515    fn clock_identity_transformation_roundtrip() {
516        let t_0 = MonotonicInstant::ZERO;
517        // Identity clock transformation
518        let xform = ClockTransformation {
519            reference_offset: MonotonicInstant::from_nanos(0),
520            synthetic_offset: SyntheticInstant::from_nanos(0),
521            rate: sys::zx_clock_rate_t { synthetic_ticks: 1, reference_ticks: 1 },
522        };
523
524        // Transformation roundtrip should be equivalent with the identity transformation.
525        let transformed_time = xform.apply(t_0);
526        let original_time = xform.apply_inverse(transformed_time);
527        assert_eq!(t_0, original_time);
528    }
529
530    #[test]
531    fn clock_trivial_transformation() {
532        let t_0 = MonotonicInstant::ZERO;
533        // Identity clock transformation
534        let xform = ClockTransformation {
535            reference_offset: MonotonicInstant::from_nanos(3),
536            synthetic_offset: SyntheticInstant::from_nanos(2),
537            rate: sys::zx_clock_rate_t { synthetic_ticks: 6, reference_ticks: 2 },
538        };
539
540        let utc_time = xform.apply(t_0);
541        let monotonic_time = xform.apply_inverse(utc_time);
542        // Verify that the math is correct.
543        assert_eq!(3 * (t_0.into_nanos() - 3) + 2, utc_time.into_nanos());
544
545        // Transformation roundtrip should be equivalent.
546        assert_eq!(t_0, monotonic_time);
547    }
548
549    #[test]
550    fn clock_transformation_roundtrip() {
551        let t_0 = MonotonicInstant::ZERO;
552        // Arbitrary clock transformation
553        let xform = ClockTransformation {
554            reference_offset: MonotonicInstant::from_nanos(196980085208),
555            synthetic_offset: SyntheticInstant::from_nanos(1616900096031887801),
556            rate: sys::zx_clock_rate_t { synthetic_ticks: 999980, reference_ticks: 1000000 },
557        };
558
559        // Transformation roundtrip should be equivalent modulo rounding error.
560        let transformed_time = xform.apply(t_0);
561        let original_time = xform.apply_inverse(transformed_time);
562        let roundtrip_diff = t_0 - original_time;
563        assert!(roundtrip_diff.into_nanos().abs() <= 1);
564    }
565
566    #[test]
567    fn clock_trailing_transformation_roundtrip() {
568        let t_0 = MonotonicInstant::ZERO;
569        // Arbitrary clock transformation where the synthetic clock is trailing behind the
570        // reference clock.
571        let xform = ClockTransformation {
572            reference_offset: MonotonicInstant::from_nanos(1616900096031887801),
573            synthetic_offset: SyntheticInstant::from_nanos(196980085208),
574            rate: sys::zx_clock_rate_t { synthetic_ticks: 1000000, reference_ticks: 999980 },
575        };
576
577        // Transformation roundtrip should be equivalent modulo rounding error.
578        let transformed_time = xform.apply(t_0);
579        let original_time = xform.apply_inverse(transformed_time);
580        let roundtrip_diff = t_0 - original_time;
581        assert!(roundtrip_diff.into_nanos().abs() <= 1);
582    }
583
584    #[test]
585    fn clock_saturating_transformations() {
586        let t_0 = MonotonicInstant::from_nanos(i64::MAX);
587        // Clock transformation which will positively overflow t_0
588        let xform = ClockTransformation {
589            reference_offset: MonotonicInstant::from_nanos(0),
590            synthetic_offset: SyntheticInstant::from_nanos(1),
591            rate: sys::zx_clock_rate_t { synthetic_ticks: 1, reference_ticks: 1 },
592        };
593
594        // Applying the transformation will lead to saturation
595        let time = xform.apply(t_0).into_nanos();
596        assert_eq!(time, i64::MAX);
597
598        let t_0 = MonotonicInstant::from_nanos(i64::MIN);
599        // Clock transformation which will negatively overflow t_0
600        let xform = ClockTransformation {
601            reference_offset: MonotonicInstant::from_nanos(1),
602            synthetic_offset: SyntheticInstant::from_nanos(0),
603            rate: sys::zx_clock_rate_t { synthetic_ticks: 1, reference_ticks: 1 },
604        };
605
606        // Applying the transformation will lead to saturation
607        let time = xform.apply(t_0).into_nanos();
608        assert_eq!(time, i64::MIN);
609    }
610}
zx/clock.rs

zx/
clock.rs
