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

   1 use crate::fmt;
   2 use crate::time::Duration;
   3
   4 pub use self::inner::Instant;
   5
   6 const NSEC_PER_SEC: u64 = 1_000_000_000;
   7 pub const UNIX_EPOCH: SystemTime = SystemTime { t: Timespec::zero() };
   8
   9 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
  10 pub struct SystemTime {
  11     pub(in crate::sys::unix) t: Timespec,
  12 }
  13
  14 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
  15 pub(in crate::sys::unix) struct Timespec {
  16     tv_sec: i64,
  17     tv_nsec: i64,
  18 }
  19
  20 impl SystemTime {
  21     #[cfg_attr(target_os = "horizon", allow(unused))]
  22     pub fn new(tv_sec: i64, tv_nsec: i64) -> SystemTime {
  23         SystemTime { t: Timespec::new(tv_sec, tv_nsec) }
  24     }
  25
  26     pub fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
  27         self.t.sub_timespec(&other.t)
  28     }
  29
  30     pub fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
  31         Some(SystemTime { t: self.t.checked_add_duration(other)? })
  32     }
  33
  34     pub fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
  35         Some(SystemTime { t: self.t.checked_sub_duration(other)? })
  36     }
  37 }
  38
  39 impl From<libc::timespec> for SystemTime {
  40     fn from(t: libc::timespec) -> SystemTime {
  41         SystemTime { t: Timespec::from(t) }
  42     }
  43 }
  44
  45 impl fmt::Debug for SystemTime {
  46     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  47         f.debug_struct("SystemTime")
  48             .field("tv_sec", &self.t.tv_sec)
  49             .field("tv_nsec", &self.t.tv_nsec)
  50             .finish()
  51     }
  52 }
  53
  54 impl Timespec {
  55     pub const fn zero() -> Timespec {
  56         Timespec { tv_sec: 0, tv_nsec: 0 }
  57     }
  58
  59     fn new(tv_sec: i64, tv_nsec: i64) -> Timespec {
  60         Timespec { tv_sec, tv_nsec }
  61     }
  62
  63     pub fn sub_timespec(&self, other: &Timespec) -> Result<Duration, Duration> {
  64         if self >= other {
  65             // NOTE(eddyb) two aspects of this `if`-`else` are required for LLVM
  66             // to optimize it into a branchless form (see also #75545):
  67             //
  68             // 1. `self.tv_sec - other.tv_sec` shows up as a common expression
  69             //    in both branches, i.e. the `else` must have its `- 1`
  70             //    subtraction after the common one, not interleaved with it
  71             //    (it used to be `self.tv_sec - 1 - other.tv_sec`)
  72             //
  73             // 2. the `Duration::new` call (or any other additional complexity)
  74             //    is outside of the `if`-`else`, not duplicated in both branches
  75             //
  76             // Ideally this code could be rearranged such that it more
  77             // directly expresses the lower-cost behavior we want from it.
  78             let (secs, nsec) = if self.tv_nsec >= other.tv_nsec {
  79                 ((self.tv_sec - other.tv_sec) as u64, (self.tv_nsec - other.tv_nsec) as u32)
  80             } else {
  81                 (
  82                     (self.tv_sec - other.tv_sec - 1) as u64,
  83                     self.tv_nsec as u32 + (NSEC_PER_SEC as u32) - other.tv_nsec as u32,
  84                 )
  85             };
  86
  87             Ok(Duration::new(secs, nsec))
  88         } else {
  89             match other.sub_timespec(self) {
  90                 Ok(d) => Err(d),
  91                 Err(d) => Ok(d),
  92             }
  93         }
  94     }
  95
  96     pub fn checked_add_duration(&self, other: &Duration) -> Option<Timespec> {
  97         let mut secs = other
  98             .as_secs()
  99             .try_into() // <- target type would be `i64`
 100             .ok()
 101             .and_then(|secs| self.tv_sec.checked_add(secs))?;
 102
 103         // Nano calculations can't overflow because nanos are <1B which fit
 104         // in a u32.
 105         let mut nsec = other.subsec_nanos() + self.tv_nsec as u32;
 106         if nsec >= NSEC_PER_SEC as u32 {
 107             nsec -= NSEC_PER_SEC as u32;
 108             secs = secs.checked_add(1)?;
 109         }
 110         Some(Timespec::new(secs, nsec as i64))
 111     }
 112
 113     pub fn checked_sub_duration(&self, other: &Duration) -> Option<Timespec> {
 114         let mut secs = other
 115             .as_secs()
 116             .try_into() // <- target type would be `i64`
 117             .ok()
 118             .and_then(|secs| self.tv_sec.checked_sub(secs))?;
 119
 120         // Similar to above, nanos can't overflow.
 121         let mut nsec = self.tv_nsec as i32 - other.subsec_nanos() as i32;
 122         if nsec < 0 {
 123             nsec += NSEC_PER_SEC as i32;
 124             secs = secs.checked_sub(1)?;
 125         }
 126         Some(Timespec::new(secs, nsec as i64))
 127     }
 128
 129     #[allow(dead_code)]
 130     pub fn to_timespec(&self) -> Option<libc::timespec> {
 131         Some(libc::timespec {
 132             tv_sec: self.tv_sec.try_into().ok()?,
 133             tv_nsec: self.tv_nsec.try_into().ok()?,
 134         })
 135     }
 136 }
 137
 138 impl From<libc::timespec> for Timespec {
 139     fn from(t: libc::timespec) -> Timespec {
 140         Timespec::new(t.tv_sec as i64, t.tv_nsec as i64)
 141     }
 142 }
 143
 144 #[cfg(any(target_os = "macos", target_os = "ios"))]
 145 mod inner {
 146     use crate::sync::atomic::{AtomicU64, Ordering};
 147     use crate::sys::cvt;
 148     use crate::sys_common::mul_div_u64;
 149     use crate::time::Duration;
 150
 151     use super::{SystemTime, Timespec, NSEC_PER_SEC};
 152
 153     #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
 154     pub struct Instant {
 155         t: u64,
 156     }
 157
 158     #[repr(C)]
 159     #[derive(Copy, Clone)]
 160     struct mach_timebase_info {
 161         numer: u32,
 162         denom: u32,
 163     }
 164     type mach_timebase_info_t = *mut mach_timebase_info;
 165     type kern_return_t = libc::c_int;
 166
 167     impl Instant {
 168         pub fn now() -> Instant {
 169             extern "C" {
 170                 fn mach_absolute_time() -> u64;
 171             }
 172             Instant { t: unsafe { mach_absolute_time() } }
 173         }
 174
 175         pub fn checked_sub_instant(&self, other: &Instant) -> Option<Duration> {
 176             let diff = self.t.checked_sub(other.t)?;
 177             let info = info();
 178             let nanos = mul_div_u64(diff, info.numer as u64, info.denom as u64);
 179             Some(Duration::new(nanos / NSEC_PER_SEC, (nanos % NSEC_PER_SEC) as u32))
 180         }
 181
 182         pub fn checked_add_duration(&self, other: &Duration) -> Option<Instant> {
 183             Some(Instant { t: self.t.checked_add(checked_dur2intervals(other)?)? })
 184         }
 185
 186         pub fn checked_sub_duration(&self, other: &Duration) -> Option<Instant> {
 187             Some(Instant { t: self.t.checked_sub(checked_dur2intervals(other)?)? })
 188         }
 189     }
 190
 191     impl SystemTime {
 192         pub fn now() -> SystemTime {
 193             use crate::ptr;
 194
 195             let mut s = libc::timeval { tv_sec: 0, tv_usec: 0 };
 196             cvt(unsafe { libc::gettimeofday(&mut s, ptr::null_mut()) }).unwrap();
 197             return SystemTime::from(s);
 198         }
 199     }
 200
 201     impl From<libc::timeval> for Timespec {
 202         fn from(t: libc::timeval) -> Timespec {
 203             Timespec::new(t.tv_sec as i64, 1000 * t.tv_usec as i64)
 204         }
 205     }
 206
 207     impl From<libc::timeval> for SystemTime {
 208         fn from(t: libc::timeval) -> SystemTime {
 209             SystemTime { t: Timespec::from(t) }
 210         }
 211     }
 212
 213     fn checked_dur2intervals(dur: &Duration) -> Option<u64> {
 214         let nanos =
 215             dur.as_secs().checked_mul(NSEC_PER_SEC)?.checked_add(dur.subsec_nanos() as u64)?;
 216         let info = info();
 217         Some(mul_div_u64(nanos, info.denom as u64, info.numer as u64))
 218     }
 219
 220     fn info() -> mach_timebase_info {
 221         // INFO_BITS conceptually is an `Option<mach_timebase_info>`. We can do
 222         // this in 64 bits because we know 0 is never a valid value for the
 223         // `denom` field.
 224         //
 225         // Encoding this as a single `AtomicU64` allows us to use `Relaxed`
 226         // operations, as we are only interested in the effects on a single
 227         // memory location.
 228         static INFO_BITS: AtomicU64 = AtomicU64::new(0);
 229
 230         // If a previous thread has initialized `INFO_BITS`, use it.
 231         let info_bits = INFO_BITS.load(Ordering::Relaxed);
 232         if info_bits != 0 {
 233             return info_from_bits(info_bits);
 234         }
 235
 236         // ... otherwise learn for ourselves ...
 237         extern "C" {
 238             fn mach_timebase_info(info: mach_timebase_info_t) -> kern_return_t;
 239         }
 240
 241         let mut info = info_from_bits(0);
 242         unsafe {
 243             mach_timebase_info(&mut info);
 244         }
 245         INFO_BITS.store(info_to_bits(info), Ordering::Relaxed);
 246         info
 247     }
 248
 249     #[inline]
 250     fn info_to_bits(info: mach_timebase_info) -> u64 {
 251         ((info.denom as u64) << 32) | (info.numer as u64)
 252     }
 253
 254     #[inline]
 255     fn info_from_bits(bits: u64) -> mach_timebase_info {
 256         mach_timebase_info { numer: bits as u32, denom: (bits >> 32) as u32 }
 257     }
 258 }
 259
 260 #[cfg(not(any(target_os = "macos", target_os = "ios")))]
 261 mod inner {
 262     use crate::fmt;
 263     use crate::mem::MaybeUninit;
 264     use crate::sys::cvt;
 265     use crate::time::Duration;
 266
 267     use super::{SystemTime, Timespec};
 268
 269     #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 270     pub struct Instant {
 271         t: Timespec,
 272     }
 273
 274     impl Instant {
 275         pub fn now() -> Instant {
 276             Instant { t: Timespec::now(libc::CLOCK_MONOTONIC) }
 277         }
 278
 279         pub fn checked_sub_instant(&self, other: &Instant) -> Option<Duration> {
 280             self.t.sub_timespec(&other.t).ok()
 281         }
 282
 283         pub fn checked_add_duration(&self, other: &Duration) -> Option<Instant> {
 284             Some(Instant { t: self.t.checked_add_duration(other)? })
 285         }
 286
 287         pub fn checked_sub_duration(&self, other: &Duration) -> Option<Instant> {
 288             Some(Instant { t: self.t.checked_sub_duration(other)? })
 289         }
 290     }
 291
 292     impl fmt::Debug for Instant {
 293         fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 294             f.debug_struct("Instant")
 295                 .field("tv_sec", &self.t.tv_sec)
 296                 .field("tv_nsec", &self.t.tv_nsec)
 297                 .finish()
 298         }
 299     }
 300
 301     impl SystemTime {
 302         pub fn now() -> SystemTime {
 303             SystemTime { t: Timespec::now(libc::CLOCK_REALTIME) }
 304         }
 305     }
 306
 307     #[cfg(not(any(target_os = "dragonfly", target_os = "espidf", target_os = "horizon")))]
 308     pub type clock_t = libc::c_int;
 309     #[cfg(any(target_os = "dragonfly", target_os = "espidf", target_os = "horizon"))]
 310     pub type clock_t = libc::c_ulong;
 311
 312     impl Timespec {
 313         pub fn now(clock: clock_t) -> Timespec {
 314             // Try to use 64-bit time in preparation for Y2038.
 315             #[cfg(all(target_os = "linux", target_env = "gnu", target_pointer_width = "32"))]
 316             {
 317                 use crate::sys::weak::weak;
 318
 319                 // __clock_gettime64 was added to 32-bit arches in glibc 2.34,
 320                 // and it handles both vDSO calls and ENOSYS fallbacks itself.
 321                 weak!(fn __clock_gettime64(libc::clockid_t, *mut __timespec64) -> libc::c_int);
 322
 323                 #[repr(C)]
 324                 struct __timespec64 {
 325                     tv_sec: i64,
 326                     #[cfg(target_endian = "big")]
 327                     _padding: i32,
 328                     tv_nsec: i32,
 329                     #[cfg(target_endian = "little")]
 330                     _padding: i32,
 331                 }
 332
 333                 if let Some(clock_gettime64) = __clock_gettime64.get() {
 334                     let mut t = MaybeUninit::uninit();
 335                     cvt(unsafe { clock_gettime64(clock, t.as_mut_ptr()) }).unwrap();
 336                     let t = unsafe { t.assume_init() };
 337                     return Timespec { tv_sec: t.tv_sec, tv_nsec: t.tv_nsec as i64 };
 338                 }
 339             }
 340
 341             let mut t = MaybeUninit::uninit();
 342             cvt(unsafe { libc::clock_gettime(clock, t.as_mut_ptr()) }).unwrap();
 343             Timespec::from(unsafe { t.assume_init() })
 344         }
 345     }
 346 }