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use crate::cmp::Ordering;
use crate::convert::TryInto;
use crate::fmt;
use crate::mem;
use crate::sys::c;
use crate::time::Duration;
use core::hash::{Hash, Hasher};
const NANOS_PER_SEC: u64 = 1_000_000_000;
const INTERVALS_PER_SEC: u64 = NANOS_PER_SEC / 100;
#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Debug, Hash)]
pub struct Instant {
// This duration is relative to an arbitrary microsecond epoch
// from the winapi QueryPerformanceCounter function.
t: Duration,
}
#[derive(Copy, Clone)]
pub struct SystemTime {
t: c::FILETIME,
}
const INTERVALS_TO_UNIX_EPOCH: u64 = 11_644_473_600 * INTERVALS_PER_SEC;
pub const UNIX_EPOCH: SystemTime = SystemTime {
t: c::FILETIME {
dwLowDateTime: INTERVALS_TO_UNIX_EPOCH as u32,
dwHighDateTime: (INTERVALS_TO_UNIX_EPOCH >> 32) as u32,
},
};
impl Instant {
pub fn now() -> Instant {
// High precision timing on windows operates in "Performance Counter"
// units, as returned by the WINAPI QueryPerformanceCounter function.
// These relate to seconds by a factor of QueryPerformanceFrequency.
// In order to keep unit conversions out of normal interval math, we
// measure in QPC units and immediately convert to nanoseconds.
perf_counter::PerformanceCounterInstant::now().into()
}
pub fn actually_monotonic() -> bool {
false
}
pub const fn zero() -> Instant {
Instant { t: Duration::from_secs(0) }
}
pub fn checked_sub_instant(&self, other: &Instant) -> Option<Duration> {
// On windows there's a threshold below which we consider two timestamps
// equivalent due to measurement error. For more details + doc link,
// check the docs on epsilon.
let epsilon = perf_counter::PerformanceCounterInstant::epsilon();
if other.t > self.t && other.t - self.t <= epsilon {
Some(Duration::new(0, 0))
} else {
self.t.checked_sub(other.t)
}
}
pub fn checked_add_duration(&self, other: &Duration) -> Option<Instant> {
Some(Instant { t: self.t.checked_add(*other)? })
}
pub fn checked_sub_duration(&self, other: &Duration) -> Option<Instant> {
Some(Instant { t: self.t.checked_sub(*other)? })
}
}
impl SystemTime {
pub fn now() -> SystemTime {
unsafe {
let mut t: SystemTime = mem::zeroed();
c::GetSystemTimeAsFileTime(&mut t.t);
t
}
}
fn from_intervals(intervals: i64) -> SystemTime {
SystemTime {
t: c::FILETIME {
dwLowDateTime: intervals as c::DWORD,
dwHighDateTime: (intervals >> 32) as c::DWORD,
},
}
}
fn intervals(&self) -> i64 {
(self.t.dwLowDateTime as i64) | ((self.t.dwHighDateTime as i64) << 32)
}
pub fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
let me = self.intervals();
let other = other.intervals();
if me >= other {
Ok(intervals2dur((me - other) as u64))
} else {
Err(intervals2dur((other - me) as u64))
}
}
pub fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
let intervals = self.intervals().checked_add(checked_dur2intervals(other)?)?;
Some(SystemTime::from_intervals(intervals))
}
pub fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
let intervals = self.intervals().checked_sub(checked_dur2intervals(other)?)?;
Some(SystemTime::from_intervals(intervals))
}
}
impl PartialEq for SystemTime {
fn eq(&self, other: &SystemTime) -> bool {
self.intervals() == other.intervals()
}
}
impl Eq for SystemTime {}
impl PartialOrd for SystemTime {
fn partial_cmp(&self, other: &SystemTime) -> Option<Ordering> {
Some(self.cmp(other))
}
}
impl Ord for SystemTime {
fn cmp(&self, other: &SystemTime) -> Ordering {
self.intervals().cmp(&other.intervals())
}
}
impl fmt::Debug for SystemTime {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("SystemTime").field("intervals", &self.intervals()).finish()
}
}
impl From<c::FILETIME> for SystemTime {
fn from(t: c::FILETIME) -> SystemTime {
SystemTime { t }
}
}
impl Hash for SystemTime {
fn hash<H: Hasher>(&self, state: &mut H) {
self.intervals().hash(state)
}
}
fn checked_dur2intervals(dur: &Duration) -> Option<i64> {
dur.as_secs()
.checked_mul(INTERVALS_PER_SEC)?
.checked_add(dur.subsec_nanos() as u64 / 100)?
.try_into()
.ok()
}
fn intervals2dur(intervals: u64) -> Duration {
Duration::new(intervals / INTERVALS_PER_SEC, ((intervals % INTERVALS_PER_SEC) * 100) as u32)
}
mod perf_counter {
use super::NANOS_PER_SEC;
use crate::sync::atomic::{AtomicUsize, Ordering::SeqCst};
use crate::sys::c;
use crate::sys::cvt;
use crate::sys_common::mul_div_u64;
use crate::time::Duration;
pub struct PerformanceCounterInstant {
ts: c::LARGE_INTEGER,
}
impl PerformanceCounterInstant {
pub fn now() -> Self {
Self { ts: query() }
}
// Per microsoft docs, the margin of error for cross-thread time comparisons
// using QueryPerformanceCounter is 1 "tick" -- defined as 1/frequency().
// Reference: https://docs.microsoft.com/en-us/windows/desktop/SysInfo
// /acquiring-high-resolution-time-stamps
pub fn epsilon() -> Duration {
let epsilon = NANOS_PER_SEC / (frequency() as u64);
Duration::from_nanos(epsilon)
}
}
impl From<PerformanceCounterInstant> for super::Instant {
fn from(other: PerformanceCounterInstant) -> Self {
let freq = frequency() as u64;
let instant_nsec = mul_div_u64(other.ts as u64, NANOS_PER_SEC, freq);
Self { t: Duration::from_nanos(instant_nsec) }
}
}
fn frequency() -> c::LARGE_INTEGER {
static mut FREQUENCY: c::LARGE_INTEGER = 0;
static STATE: AtomicUsize = AtomicUsize::new(0);
unsafe {
// If a previous thread has filled in this global state, use that.
if STATE.load(SeqCst) == 2 {
return FREQUENCY;
}
// ... otherwise learn for ourselves ...
let mut frequency = 0;
cvt(c::QueryPerformanceFrequency(&mut frequency)).unwrap();
// ... and attempt to be the one thread that stores it globally for
// all other threads
if STATE.compare_exchange(0, 1, SeqCst, SeqCst).is_ok() {
FREQUENCY = frequency;
STATE.store(2, SeqCst);
}
frequency
}
}
fn query() -> c::LARGE_INTEGER {
let mut qpc_value: c::LARGE_INTEGER = 0;
cvt(unsafe { c::QueryPerformanceCounter(&mut qpc_value) }).unwrap();
qpc_value
}
}
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