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use crate::sys;
use libc::c_void;
use std::marker::PhantomData;
use std::mem;
use crate::TimerSubsystem;
impl TimerSubsystem {
/// Constructs a new timer using the boxed closure `callback`.
///
/// The timer is started immediately, it will be cancelled either:
///
/// * when the timer is dropped
/// * or when the callback returns a non-positive continuation interval
///
/// The callback is run in a thread that is created and managed internally
/// by SDL2 from C. The callback *must* not panic!
#[must_use = "if unused the Timer will be dropped immediately"]
#[doc(alias = "SDL_AddTimer")]
pub fn add_timer<'b, 'c>(&'b self, delay: u32, callback: TimerCallback<'c>) -> Timer<'b, 'c> {
unsafe {
let callback = Box::new(callback);
let timer_id = sys::SDL_AddTimer(
delay,
Some(c_timer_callback),
mem::transmute_copy(&callback),
);
Timer {
callback: Some(callback),
raw: timer_id,
_marker: PhantomData,
}
}
}
/// Gets the number of milliseconds elapsed since the timer subsystem was initialized.
///
/// It's recommended that you use another library for timekeeping, such as `time`.
///
/// This function is not recommended in upstream SDL2 as of 2.0.18 and internally
/// calls the 64-bit variant and masks the result.
#[doc(alias = "SDL_GetTicks")]
pub fn ticks(&self) -> u32 {
// This is thread-safe as long as the ticks subsystem is inited, and
// tying this to `TimerSubsystem` ensures the timer subsystem can
// safely make calls into the ticks subsystem without invoking a
// thread-unsafe `SDL_TicksInit()`.
//
// This binding is offered for completeness but is debatably a relic.
unsafe { sys::SDL_GetTicks() }
}
/// Gets the number of milliseconds elapsed since the timer subsystem was initialized.
///
/// It's recommended that you use another library for timekeeping, such as `time`.
#[doc(alias = "SDL_GetTicks64")]
pub fn ticks64(&self) -> u64 {
// This is thread-safe as long as the ticks subsystem is inited, and
// tying this to `TimerSubsystem` ensures the timer subsystem can
// safely make calls into the ticks subsystem without invoking a
// thread-unsafe `SDL_TicksInit()`.
//
// This binding is offered for completeness but is debatably a relic.
unsafe { sys::SDL_GetTicks64() }
}
/// Sleeps the current thread for the specified amount of milliseconds.
///
/// It's recommended that you use `std::thread::sleep()` instead.
#[doc(alias = "SDL_Delay")]
pub fn delay(&self, ms: u32) {
// This is thread-safe as long as the ticks subsystem is inited, and
// tying this to `TimerSubsystem` ensures the timer subsystem can
// safely make calls into the ticks subsystem without invoking a
// thread-unsafe `SDL_TicksInit()`.
//
// This binding is offered for completeness but is debatably a relic.
unsafe { sys::SDL_Delay(ms) }
}
#[doc(alias = "SDL_GetPerformanceCounter")]
pub fn performance_counter(&self) -> u64 {
unsafe { sys::SDL_GetPerformanceCounter() }
}
#[doc(alias = "SDL_GetPerformanceFrequency")]
pub fn performance_frequency(&self) -> u64 {
unsafe { sys::SDL_GetPerformanceFrequency() }
}
}
pub type TimerCallback<'a> = Box<dyn FnMut() -> u32 + 'a + Send>;
pub struct Timer<'b, 'a> {
callback: Option<Box<TimerCallback<'a>>>,
raw: sys::SDL_TimerID,
_marker: PhantomData<&'b ()>,
}
impl<'b, 'a> Timer<'b, 'a> {
/// Returns the closure as a trait-object and cancels the timer
/// by consuming it...
pub fn into_inner(mut self) -> TimerCallback<'a> {
*self.callback.take().unwrap()
}
}
impl<'b, 'a> Drop for Timer<'b, 'a> {
#[inline]
#[doc(alias = "SDL_RemoveTimer")]
fn drop(&mut self) {
// SDL_RemoveTimer returns SDL_FALSE if the timer wasn't found (impossible),
// or the timer has been cancelled via the callback (possible).
// The timer being cancelled isn't an issue, so we ignore the result.
unsafe { sys::SDL_RemoveTimer(self.raw) };
}
}
extern "C" fn c_timer_callback(_interval: u32, param: *mut c_void) -> u32 {
// FIXME: This is UB if the callback panics! (But will realistically
// crash on stack underflow.)
//
// I tried using `std::panic::catch_unwind()` here and it compiled but
// would not catch. Maybe wait for `c_unwind` to stabilize? Then the behavior
// will automatically abort the process when panicking over an `extern "C"`
// function.
let f = param as *mut TimerCallback<'_>;
unsafe { (*f)() }
}
#[cfg(not(target_os = "macos"))]
#[cfg(test)]
mod test {
use std::sync::{Arc, Mutex};
use std::time::Duration;
#[test]
fn test_timer() {
test_timer_runs_multiple_times();
test_timer_runs_at_least_once();
test_timer_can_be_recreated();
}
fn test_timer_runs_multiple_times() {
let sdl_context = crate::sdl::init().unwrap();
let timer_subsystem = sdl_context.timer().unwrap();
let local_num = Arc::new(Mutex::new(0));
let timer_num = local_num.clone();
let _timer = timer_subsystem.add_timer(
20,
Box::new(|| {
// increment up to 10 times (0 -> 9)
// tick again in 100ms after each increment
//
let mut num = timer_num.lock().unwrap();
if *num < 9 {
*num += 1;
20
} else {
0
}
}),
);
// tick the timer at least 10 times w/ 200ms of "buffer"
::std::thread::sleep(Duration::from_millis(250));
let num = local_num.lock().unwrap(); // read the number back
assert_eq!(*num, 9); // it should have incremented at least 10 times...
}
fn test_timer_runs_at_least_once() {
let sdl_context = crate::sdl::init().unwrap();
let timer_subsystem = sdl_context.timer().unwrap();
let local_flag = Arc::new(Mutex::new(false));
let timer_flag = local_flag.clone();
let _timer = timer_subsystem.add_timer(
20,
Box::new(|| {
let mut flag = timer_flag.lock().unwrap();
*flag = true;
0
}),
);
::std::thread::sleep(Duration::from_millis(50));
let flag = local_flag.lock().unwrap();
assert_eq!(*flag, true);
}
fn test_timer_can_be_recreated() {
let sdl_context = crate::sdl::init().unwrap();
let timer_subsystem = sdl_context.timer().unwrap();
let local_num = Arc::new(Mutex::new(0));
let timer_num = local_num.clone();
// run the timer once and reclaim its closure
let timer_1 = timer_subsystem.add_timer(
20,
Box::new(move || {
let mut num = timer_num.lock().unwrap();
*num += 1; // increment the number
0 // do not run timer again
}),
);
// reclaim closure after timer runs
::std::thread::sleep(Duration::from_millis(50));
let closure = timer_1.into_inner();
// create a second timer and increment again
let _timer_2 = timer_subsystem.add_timer(20, closure);
::std::thread::sleep(Duration::from_millis(50));
// check that timer was incremented twice
let num = local_num.lock().unwrap();
assert_eq!(*num, 2);
}
}