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//! Source of time abstraction.
//!
//! By default, `std::time::Instant::now()` is used. However, when the
//! `test-util` feature flag is enabled, the values returned for `now()` are
//! configurable.
cfg_not_test_util! {
use crate::time::Instant;
#[derive(Debug, Clone)]
pub(crate) struct Clock {}
pub(crate) fn now() -> Instant {
Instant::from_std(std::time::Instant::now())
}
impl Clock {
pub(crate) fn new() -> Clock {
Clock {}
}
pub(crate) fn now(&self) -> Instant {
now()
}
pub(crate) fn enter<F, R>(&self, f: F) -> R
where
F: FnOnce() -> R,
{
f()
}
}
}
cfg_test_util! {
use crate::time::{Duration, Instant};
use std::cell::Cell;
use std::sync::{Arc, Mutex};
/// A handle to a source of time.
#[derive(Debug, Clone)]
pub(crate) struct Clock {
inner: Arc<Inner>,
}
#[derive(Debug)]
struct Inner {
/// Instant at which the clock was created
start: std::time::Instant,
/// Current, "frozen" time as an offset from `start`.
frozen: Mutex<Option<Duration>>,
}
thread_local! {
/// Thread-local tracking the current clock
static CLOCK: Cell<Option<*const Clock>> = Cell::new(None)
}
/// Pause time
///
/// The current value of `Instant::now()` is saved and all subsequent calls
/// to `Instant::now()` will return the saved value. This is useful for
/// running tests that are dependent on time.
///
/// # Panics
///
/// Panics if time is already frozen or if called from outside of the Tokio
/// runtime.
pub fn pause() {
CLOCK.with(|cell| {
let ptr = match cell.get() {
Some(ptr) => ptr,
None => panic!("time cannot be frozen from outside the Tokio runtime"),
};
let clock = unsafe { &*ptr };
let mut frozen = clock.inner.frozen.lock().unwrap();
if frozen.is_some() {
panic!("time is already frozen");
}
*frozen = Some(clock.inner.start.elapsed());
})
}
/// Resume time
///
/// Clears the saved `Instant::now()` value. Subsequent calls to
/// `Instant::now()` will return the value returned by the system call.
///
/// # Panics
///
/// Panics if time is not frozen or if called from outside of the Tokio
/// runtime.
pub fn resume() {
CLOCK.with(|cell| {
let ptr = match cell.get() {
Some(ptr) => ptr,
None => panic!("time cannot be frozen from outside the Tokio runtime"),
};
let clock = unsafe { &*ptr };
let mut frozen = clock.inner.frozen.lock().unwrap();
if frozen.is_none() {
panic!("time is not frozen");
}
*frozen = None;
})
}
/// Advance time
///
/// Increments the saved `Instant::now()` value by `duration`. Subsequent
/// calls to `Instant::now()` will return the result of the increment.
///
/// # Panics
///
/// Panics if time is not frozen or if called from outside of the Tokio
/// runtime.
pub async fn advance(duration: Duration) {
CLOCK.with(|cell| {
let ptr = match cell.get() {
Some(ptr) => ptr,
None => panic!("time cannot be frozen from outside the Tokio runtime"),
};
let clock = unsafe { &*ptr };
clock.advance(duration);
});
crate::task::yield_now().await;
}
/// Return the current instant, factoring in frozen time.
pub(crate) fn now() -> Instant {
CLOCK.with(|cell| {
Instant::from_std(match cell.get() {
Some(ptr) => {
let clock = unsafe { &*ptr };
if let Some(frozen) = *clock.inner.frozen.lock().unwrap() {
clock.inner.start + frozen
} else {
std::time::Instant::now()
}
}
None => std::time::Instant::now(),
})
})
}
impl Clock {
/// Return a new `Clock` instance that uses the current execution context's
/// source of time.
pub(crate) fn new() -> Clock {
Clock {
inner: Arc::new(Inner {
start: std::time::Instant::now(),
frozen: Mutex::new(None),
}),
}
}
// TODO: delete this. Some tests rely on this
#[cfg(all(test, not(loom)))]
/// Return a new `Clock` instance that uses the current execution context's
/// source of time.
pub(crate) fn new_frozen() -> Clock {
Clock {
inner: Arc::new(Inner {
start: std::time::Instant::now(),
frozen: Mutex::new(Some(Duration::from_millis(0))),
}),
}
}
pub(crate) fn advance(&self, duration: Duration) {
let mut frozen = self.inner.frozen.lock().unwrap();
if let Some(ref mut elapsed) = *frozen {
*elapsed += duration;
} else {
panic!("time is not frozen");
}
}
// TODO: delete this as well
#[cfg(all(test, not(loom)))]
pub(crate) fn advanced(&self) -> Duration {
self.inner.frozen.lock().unwrap().unwrap()
}
pub(crate) fn now(&self) -> Instant {
Instant::from_std(if let Some(frozen) = *self.inner.frozen.lock().unwrap() {
self.inner.start + frozen
} else {
std::time::Instant::now()
})
}
/// Set the clock as the default source of time for the duration of the
/// closure
pub(crate) fn enter<F, R>(&self, f: F) -> R
where
F: FnOnce() -> R,
{
CLOCK.with(|cell| {
assert!(
cell.get().is_none(),
"default clock already set for execution context"
);
// Ensure that the clock is removed from the thread-local context
// when leaving the scope. This handles cases that involve panicking.
struct Reset<'a>(&'a Cell<Option<*const Clock>>);
impl Drop for Reset<'_> {
fn drop(&mut self) {
self.0.set(None);
}
}
let _reset = Reset(cell);
cell.set(Some(self as *const Clock));
f()
})
}
}
}