library/std/src/sys/unix/time.rs

   1 use crate::cmp::Ordering;
   2 use crate::time::Duration;
   3
   4 use core::hash::{Hash, Hasher};
   5
   6 pub use self::inner::{Instant, SystemTime, UNIX_EPOCH};
   7 use crate::convert::TryInto;
   8
   9 const NSEC_PER_SEC: u64 = 1_000_000_000;
  10
  11 #[derive(Copy, Clone)]
  12 struct Timespec {
  13     t: libc::timespec,
  14 }
  15
  16 impl Timespec {
  17     const fn zero() -> Timespec {
  18         Timespec { t: libc::timespec { tv_sec: 0, tv_nsec: 0 } }
  19     }
  20
  21     fn sub_timespec(&self, other: &Timespec) -> Result<Duration, Duration> {
  22         if self >= other {
  23             // NOTE(eddyb) two aspects of this `if`-`else` are required for LLVM
  24             // to optimize it into a branchless form (see also #75545):
  25             //
  26             // 1. `self.t.tv_sec - other.t.tv_sec` shows up as a common expression
  27             //    in both branches, i.e. the `else` must have its `- 1`
  28             //    subtraction after the common one, not interleaved with it
  29             //    (it used to be `self.t.tv_sec - 1 - other.t.tv_sec`)
  30             //
  31             // 2. the `Duration::new` call (or any other additional complexity)
  32             //    is outside of the `if`-`else`, not duplicated in both branches
  33             //
  34             // Ideally this code could be rearranged such that it more
  35             // directly expresses the lower-cost behavior we want from it.
  36             let (secs, nsec) = if self.t.tv_nsec >= other.t.tv_nsec {
  37                 ((self.t.tv_sec - other.t.tv_sec) as u64, (self.t.tv_nsec - other.t.tv_nsec) as u32)
  38             } else {
  39                 (
  40                     (self.t.tv_sec - other.t.tv_sec - 1) as u64,
  41                     self.t.tv_nsec as u32 + (NSEC_PER_SEC as u32) - other.t.tv_nsec as u32,
  42                 )
  43             };
  44
  45             Ok(Duration::new(secs, nsec))
  46         } else {
  47             match other.sub_timespec(self) {
  48                 Ok(d) => Err(d),
  49                 Err(d) => Ok(d),
  50             }
  51         }
  52     }
  53
  54     fn checked_add_duration(&self, other: &Duration) -> Option<Timespec> {
  55         let mut secs = other
  56             .as_secs()
  57             .try_into() // <- target type would be `libc::time_t`
  58             .ok()
  59             .and_then(|secs| self.t.tv_sec.checked_add(secs))?;
  60
  61         // Nano calculations can't overflow because nanos are <1B which fit
  62         // in a u32.
  63         let mut nsec = other.subsec_nanos() + self.t.tv_nsec as u32;
  64         if nsec >= NSEC_PER_SEC as u32 {
  65             nsec -= NSEC_PER_SEC as u32;
  66             secs = secs.checked_add(1)?;
  67         }
  68         Some(Timespec { t: libc::timespec { tv_sec: secs, tv_nsec: nsec as _ } })
  69     }
  70
  71     fn checked_sub_duration(&self, other: &Duration) -> Option<Timespec> {
  72         let mut secs = other
  73             .as_secs()
  74             .try_into() // <- target type would be `libc::time_t`
  75             .ok()
  76             .and_then(|secs| self.t.tv_sec.checked_sub(secs))?;
  77
  78         // Similar to above, nanos can't overflow.
  79         let mut nsec = self.t.tv_nsec as i32 - other.subsec_nanos() as i32;
  80         if nsec < 0 {
  81             nsec += NSEC_PER_SEC as i32;
  82             secs = secs.checked_sub(1)?;
  83         }
  84         Some(Timespec { t: libc::timespec { tv_sec: secs, tv_nsec: nsec as _ } })
  85     }
  86 }
  87
  88 impl PartialEq for Timespec {
  89     fn eq(&self, other: &Timespec) -> bool {
  90         self.t.tv_sec == other.t.tv_sec && self.t.tv_nsec == other.t.tv_nsec
  91     }
  92 }
  93
  94 impl Eq for Timespec {}
  95
  96 impl PartialOrd for Timespec {
  97     fn partial_cmp(&self, other: &Timespec) -> Option<Ordering> {
  98         Some(self.cmp(other))
  99     }
 100 }
 101
 102 impl Ord for Timespec {
 103     fn cmp(&self, other: &Timespec) -> Ordering {
 104         let me = (self.t.tv_sec, self.t.tv_nsec);
 105         let other = (other.t.tv_sec, other.t.tv_nsec);
 106         me.cmp(&other)
 107     }
 108 }
 109
 110 impl Hash for Timespec {
 111     fn hash<H: Hasher>(&self, state: &mut H) {
 112         self.t.tv_sec.hash(state);
 113         self.t.tv_nsec.hash(state);
 114     }
 115 }
 116
 117 #[cfg(any(target_os = "macos", target_os = "ios"))]
 118 mod inner {
 119     use crate::fmt;
 120     use crate::sync::atomic::{AtomicU64, Ordering};
 121     use crate::sys::cvt;
 122     use crate::sys_common::mul_div_u64;
 123     use crate::time::Duration;
 124
 125     use super::Timespec;
 126     use super::NSEC_PER_SEC;
 127
 128     #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
 129     pub struct Instant {
 130         t: u64,
 131     }
 132
 133     #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 134     pub struct SystemTime {
 135         t: Timespec,
 136     }
 137
 138     pub const UNIX_EPOCH: SystemTime = SystemTime { t: Timespec::zero() };
 139
 140     #[repr(C)]
 141     #[derive(Copy, Clone)]
 142     struct mach_timebase_info {
 143         numer: u32,
 144         denom: u32,
 145     }
 146     type mach_timebase_info_t = *mut mach_timebase_info;
 147     type kern_return_t = libc::c_int;
 148
 149     impl Instant {
 150         pub fn now() -> Instant {
 151             extern "C" {
 152                 fn mach_absolute_time() -> u64;
 153             }
 154             Instant { t: unsafe { mach_absolute_time() } }
 155         }
 156
 157         pub const fn zero() -> Instant {
 158             Instant { t: 0 }
 159         }
 160
 161         pub fn actually_monotonic() -> bool {
 162             true
 163         }
 164
 165         pub fn checked_sub_instant(&self, other: &Instant) -> Option<Duration> {
 166             let diff = self.t.checked_sub(other.t)?;
 167             let info = info();
 168             let nanos = mul_div_u64(diff, info.numer as u64, info.denom as u64);
 169             Some(Duration::new(nanos / NSEC_PER_SEC, (nanos % NSEC_PER_SEC) as u32))
 170         }
 171
 172         pub fn checked_add_duration(&self, other: &Duration) -> Option<Instant> {
 173             Some(Instant { t: self.t.checked_add(checked_dur2intervals(other)?)? })
 174         }
 175
 176         pub fn checked_sub_duration(&self, other: &Duration) -> Option<Instant> {
 177             Some(Instant { t: self.t.checked_sub(checked_dur2intervals(other)?)? })
 178         }
 179     }
 180
 181     impl SystemTime {
 182         pub fn now() -> SystemTime {
 183             use crate::ptr;
 184
 185             let mut s = libc::timeval { tv_sec: 0, tv_usec: 0 };
 186             cvt(unsafe { libc::gettimeofday(&mut s, ptr::null_mut()) }).unwrap();
 187             return SystemTime::from(s);
 188         }
 189
 190         pub fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
 191             self.t.sub_timespec(&other.t)
 192         }
 193
 194         pub fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
 195             Some(SystemTime { t: self.t.checked_add_duration(other)? })
 196         }
 197
 198         pub fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
 199             Some(SystemTime { t: self.t.checked_sub_duration(other)? })
 200         }
 201     }
 202
 203     impl From<libc::timeval> for SystemTime {
 204         fn from(t: libc::timeval) -> SystemTime {
 205             SystemTime::from(libc::timespec {
 206                 tv_sec: t.tv_sec,
 207                 tv_nsec: (t.tv_usec * 1000) as libc::c_long,
 208             })
 209         }
 210     }
 211
 212     impl From<libc::timespec> for SystemTime {
 213         fn from(t: libc::timespec) -> SystemTime {
 214             SystemTime { t: Timespec { t } }
 215         }
 216     }
 217
 218     impl fmt::Debug for SystemTime {
 219         fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 220             f.debug_struct("SystemTime")
 221                 .field("tv_sec", &self.t.t.tv_sec)
 222                 .field("tv_nsec", &self.t.t.tv_nsec)
 223                 .finish()
 224         }
 225     }
 226
 227     fn checked_dur2intervals(dur: &Duration) -> Option<u64> {
 228         let nanos =
 229             dur.as_secs().checked_mul(NSEC_PER_SEC)?.checked_add(dur.subsec_nanos() as u64)?;
 230         let info = info();
 231         Some(mul_div_u64(nanos, info.denom as u64, info.numer as u64))
 232     }
 233
 234     fn info() -> mach_timebase_info {
 235         // INFO_BITS conceptually is an `Option<mach_timebase_info>`. We can do
 236         // this in 64 bits because we know 0 is never a valid value for the
 237         // `denom` field.
 238         //
 239         // Encoding this as a single `AtomicU64` allows us to use `Relaxed`
 240         // operations, as we are only interested in the effects on a single
 241         // memory location.
 242         static INFO_BITS: AtomicU64 = AtomicU64::new(0);
 243
 244         // If a previous thread has initialized `INFO_BITS`, use it.
 245         let info_bits = INFO_BITS.load(Ordering::Relaxed);
 246         if info_bits != 0 {
 247             return info_from_bits(info_bits);
 248         }
 249
 250         // ... otherwise learn for ourselves ...
 251         extern "C" {
 252             fn mach_timebase_info(info: mach_timebase_info_t) -> kern_return_t;
 253         }
 254
 255         let mut info = info_from_bits(0);
 256         unsafe {
 257             mach_timebase_info(&mut info);
 258         }
 259         INFO_BITS.store(info_to_bits(info), Ordering::Relaxed);
 260         info
 261     }
 262
 263     #[inline]
 264     fn info_to_bits(info: mach_timebase_info) -> u64 {
 265         ((info.denom as u64) << 32) | (info.numer as u64)
 266     }
 267
 268     #[inline]
 269     fn info_from_bits(bits: u64) -> mach_timebase_info {
 270         mach_timebase_info { numer: bits as u32, denom: (bits >> 32) as u32 }
 271     }
 272 }
 273
 274 #[cfg(not(any(target_os = "macos", target_os = "ios")))]
 275 mod inner {
 276     use crate::fmt;
 277     use crate::sys::cvt;
 278     use crate::time::Duration;
 279
 280     use super::Timespec;
 281
 282     #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 283     pub struct Instant {
 284         t: Timespec,
 285     }
 286
 287     #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 288     pub struct SystemTime {
 289         t: Timespec,
 290     }
 291
 292     pub const UNIX_EPOCH: SystemTime = SystemTime { t: Timespec::zero() };
 293
 294     impl Instant {
 295         pub fn now() -> Instant {
 296             Instant { t: now(libc::CLOCK_MONOTONIC) }
 297         }
 298
 299         pub const fn zero() -> Instant {
 300             Instant { t: Timespec::zero() }
 301         }
 302
 303         pub fn actually_monotonic() -> bool {
 304             (cfg!(target_os = "linux") && cfg!(target_arch = "x86_64"))
 305                 || (cfg!(target_os = "linux") && cfg!(target_arch = "x86"))
 306                 || cfg!(target_os = "fuchsia")
 307         }
 308
 309         pub fn checked_sub_instant(&self, other: &Instant) -> Option<Duration> {
 310             self.t.sub_timespec(&other.t).ok()
 311         }
 312
 313         pub fn checked_add_duration(&self, other: &Duration) -> Option<Instant> {
 314             Some(Instant { t: self.t.checked_add_duration(other)? })
 315         }
 316
 317         pub fn checked_sub_duration(&self, other: &Duration) -> Option<Instant> {
 318             Some(Instant { t: self.t.checked_sub_duration(other)? })
 319         }
 320     }
 321
 322     impl fmt::Debug for Instant {
 323         fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 324             f.debug_struct("Instant")
 325                 .field("tv_sec", &self.t.t.tv_sec)
 326                 .field("tv_nsec", &self.t.t.tv_nsec)
 327                 .finish()
 328         }
 329     }
 330
 331     impl SystemTime {
 332         pub fn now() -> SystemTime {
 333             SystemTime { t: now(libc::CLOCK_REALTIME) }
 334         }
 335
 336         pub fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
 337             self.t.sub_timespec(&other.t)
 338         }
 339
 340         pub fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
 341             Some(SystemTime { t: self.t.checked_add_duration(other)? })
 342         }
 343
 344         pub fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
 345             Some(SystemTime { t: self.t.checked_sub_duration(other)? })
 346         }
 347     }
 348
 349     impl From<libc::timespec> for SystemTime {
 350         fn from(t: libc::timespec) -> SystemTime {
 351             SystemTime { t: Timespec { t } }
 352         }
 353     }
 354
 355     impl fmt::Debug for SystemTime {
 356         fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 357             f.debug_struct("SystemTime")
 358                 .field("tv_sec", &self.t.t.tv_sec)
 359                 .field("tv_nsec", &self.t.t.tv_nsec)
 360                 .finish()
 361         }
 362     }
 363
 364     #[cfg(not(any(target_os = "dragonfly", target_os = "espidf")))]
 365     pub type clock_t = libc::c_int;
 366     #[cfg(any(target_os = "dragonfly", target_os = "espidf"))]
 367     pub type clock_t = libc::c_ulong;
 368
 369     fn now(clock: clock_t) -> Timespec {
 370         let mut t = Timespec { t: libc::timespec { tv_sec: 0, tv_nsec: 0 } };
 371         cvt(unsafe { libc::clock_gettime(clock, &mut t.t) }).unwrap();
 372         t
 373     }
 374 }