src/libstd/sys/windows/time.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use cmp::Ordering;
  12 use fmt;
  13 use mem;
  14 use sync::Once;
  15 use sys::c;
  16 use sys::cvt;
  17 use sys_common::mul_div_u64;
  18 use time::Duration;
  19
  20 const NANOS_PER_SEC: u64 = 1_000_000_000;
  21 const INTERVALS_PER_SEC: u64 = NANOS_PER_SEC / 100;
  22
  23 #[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Debug)]
  24 pub struct Instant {
  25     t: c::LARGE_INTEGER,
  26 }
  27
  28 #[derive(Copy, Clone)]
  29 pub struct SystemTime {
  30     t: c::FILETIME,
  31 }
  32
  33 const INTERVALS_TO_UNIX_EPOCH: u64 = 11_644_473_600 * INTERVALS_PER_SEC;
  34
  35 pub const UNIX_EPOCH: SystemTime = SystemTime {
  36     t: c::FILETIME {
  37         dwLowDateTime: INTERVALS_TO_UNIX_EPOCH as u32,
  38         dwHighDateTime: (INTERVALS_TO_UNIX_EPOCH >> 32) as u32,
  39     },
  40 };
  41
  42 impl Instant {
  43     pub fn now() -> Instant {
  44         let mut t = Instant { t: 0 };
  45         cvt(unsafe {
  46             c::QueryPerformanceCounter(&mut t.t)
  47         }).unwrap();
  48         t
  49     }
  50
  51     pub fn sub_instant(&self, other: &Instant) -> Duration {
  52         // Values which are +- 1 need to be considered as basically the same
  53         // units in time due to various measurement oddities, according to
  54         // Windows [1]
  55         //
  56         // [1]:
  57         // https://msdn.microsoft.com/en-us/library/windows/desktop
  58         //                           /dn553408%28v=vs.85%29.aspx#guidance
  59         if other.t > self.t && other.t - self.t == 1 {
  60             return Duration::new(0, 0)
  61         }
  62         let diff = (self.t as u64).checked_sub(other.t as u64)
  63                                   .expect("specified instant was later than \
  64                                            self");
  65         let nanos = mul_div_u64(diff, NANOS_PER_SEC, frequency() as u64);
  66         Duration::new(nanos / NANOS_PER_SEC, (nanos % NANOS_PER_SEC) as u32)
  67     }
  68
  69     pub fn add_duration(&self, other: &Duration) -> Instant {
  70         let freq = frequency() as u64;
  71         let t = other.as_secs().checked_mul(freq).and_then(|i| {
  72             (self.t as u64).checked_add(i)
  73         }).and_then(|i| {
  74             i.checked_add(mul_div_u64(other.subsec_nanos() as u64, freq,
  75                                       NANOS_PER_SEC))
  76         }).expect("overflow when adding duration to time");
  77         Instant {
  78             t: t as c::LARGE_INTEGER,
  79         }
  80     }
  81
  82     pub fn sub_duration(&self, other: &Duration) -> Instant {
  83         let freq = frequency() as u64;
  84         let t = other.as_secs().checked_mul(freq).and_then(|i| {
  85             (self.t as u64).checked_sub(i)
  86         }).and_then(|i| {
  87             i.checked_sub(mul_div_u64(other.subsec_nanos() as u64, freq,
  88                                       NANOS_PER_SEC))
  89         }).expect("overflow when subtracting duration from time");
  90         Instant {
  91             t: t as c::LARGE_INTEGER,
  92         }
  93     }
  94 }
  95
  96 impl SystemTime {
  97     pub fn now() -> SystemTime {
  98         unsafe {
  99             let mut t: SystemTime = mem::zeroed();
 100             c::GetSystemTimeAsFileTime(&mut t.t);
 101             return t
 102         }
 103     }
 104
 105     fn from_intervals(intervals: i64) -> SystemTime {
 106         SystemTime {
 107             t: c::FILETIME {
 108                 dwLowDateTime: intervals as c::DWORD,
 109                 dwHighDateTime: (intervals >> 32) as c::DWORD,
 110             }
 111         }
 112     }
 113
 114     fn intervals(&self) -> i64 {
 115         (self.t.dwLowDateTime as i64) | ((self.t.dwHighDateTime as i64) << 32)
 116     }
 117
 118     pub fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
 119         let me = self.intervals();
 120         let other = other.intervals();
 121         if me >= other {
 122             Ok(intervals2dur((me - other) as u64))
 123         } else {
 124             Err(intervals2dur((other - me) as u64))
 125         }
 126     }
 127
 128     pub fn add_duration(&self, other: &Duration) -> SystemTime {
 129         let intervals = self.intervals().checked_add(dur2intervals(other))
 130                             .expect("overflow when adding duration to time");
 131         SystemTime::from_intervals(intervals)
 132     }
 133
 134     pub fn sub_duration(&self, other: &Duration) -> SystemTime {
 135         let intervals = self.intervals().checked_sub(dur2intervals(other))
 136                             .expect("overflow when subtracting from time");
 137         SystemTime::from_intervals(intervals)
 138     }
 139 }
 140
 141 impl PartialEq for SystemTime {
 142     fn eq(&self, other: &SystemTime) -> bool {
 143         self.intervals() == other.intervals()
 144     }
 145 }
 146
 147 impl Eq for SystemTime {}
 148
 149 impl PartialOrd for SystemTime {
 150     fn partial_cmp(&self, other: &SystemTime) -> Option<Ordering> {
 151         Some(self.cmp(other))
 152     }
 153 }
 154
 155 impl Ord for SystemTime {
 156     fn cmp(&self, other: &SystemTime) -> Ordering {
 157         self.intervals().cmp(&other.intervals())
 158     }
 159 }
 160
 161 impl fmt::Debug for SystemTime {
 162     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 163         f.debug_struct("SystemTime")
 164          .field("intervals", &self.intervals())
 165          .finish()
 166     }
 167 }
 168
 169 fn dur2intervals(d: &Duration) -> i64 {
 170     d.as_secs().checked_mul(INTERVALS_PER_SEC).and_then(|i| {
 171         i.checked_add(d.subsec_nanos() as u64 / 100)
 172     }).expect("overflow when converting duration to intervals") as i64
 173 }
 174
 175 fn intervals2dur(intervals: u64) -> Duration {
 176     Duration::new(intervals / INTERVALS_PER_SEC,
 177                   ((intervals % INTERVALS_PER_SEC) * 100) as u32)
 178 }
 179
 180 fn frequency() -> c::LARGE_INTEGER {
 181     static mut FREQUENCY: c::LARGE_INTEGER = 0;
 182     static ONCE: Once = Once::new();
 183
 184     unsafe {
 185         ONCE.call_once(|| {
 186             cvt(c::QueryPerformanceFrequency(&mut FREQUENCY)).unwrap();
 187         });
 188         FREQUENCY
 189     }
 190 }