vendor/tracing-tree/src/time.rs

   1 /// A type that can measure and format the current time.
   2 ///
   3 /// This trait is used by [HierarchicalLayer] to include a timestamp with each
   4 /// [Event] when it is logged.
   5 ///
   6 /// Notable default implementations of this trait are [LocalDateTime] and `()`.
   7 /// The former prints the current time as reported by [time's OffsetDateTime]
   8 /// (note that it requires a `time` feature to be enabled and may panic!
   9 /// make sure to check out the docs for the [LocalDateTime]),
  10 /// and the latter does not print the current time at all.
  11 ///
  12 /// Inspired by the [FormatTime] trait from [tracing-subscriber].
  13 ///
  14 /// [HierarchicalLayer]: crate::HierarchicalLayer
  15 /// [Event]: tracing_core::Event
  16 /// [time's OffsetDateTime]: time::OffsetDateTime
  17 /// [FormatTime]: tracing_subscriber::fmt::time::FormatTime
  18 /// [tracing-subscriber]: tracing_subscriber
  19 // NB:
  20 //   We can't use `tracing_subscriber::fmt::format::Writer`
  21 //   since it doesn't have a public constructor.
  22 pub trait FormatTime {
  23     fn format_time(&self, w: &mut impl std::fmt::Write) -> std::fmt::Result;
  24 }
  25
  26 ////////////////////////////////////////////////////////////////////////////////////////////////////
  27
  28 /// Default do-nothing time formatter.
  29 impl FormatTime for () {
  30     fn format_time(&self, _w: &mut impl std::fmt::Write) -> std::fmt::Result {
  31         Ok(())
  32     }
  33 }
  34
  35 ////////////////////////////////////////////////////////////////////////////////////////////////////
  36
  37 /// Retrieve and print the current wall-clock time in UTC timezone.
  38 #[cfg(feature = "time")]
  39 #[derive(Debug, Clone, Copy, Eq, PartialEq, Default)]
  40 pub struct UtcDateTime;
  41
  42 #[cfg(feature = "time")]
  43 impl FormatTime for UtcDateTime {
  44     fn format_time(&self, w: &mut impl std::fmt::Write) -> std::fmt::Result {
  45         let time = time::OffsetDateTime::now_utc();
  46         write!(w, "{} {}", time.date(), time.time())
  47     }
  48 }
  49
  50 ////////////////////////////////////////////////////////////////////////////////////////////////////
  51
  52 /// Retrieve and print the current wall-clock time.
  53 ///
  54 /// # Panics
  55 ///
  56 /// Panics if [time crate] cannot determine the local UTC offset.
  57 ///
  58 /// [time crate]: time
  59 // NB:
  60 //   Can't use `tracing_subscriber::fmt::time::SystemTime` since it uses
  61 //   private `datetime` module to format the actual time.
  62 #[cfg(feature = "time")]
  63 #[derive(Debug, Clone, Copy, Eq, PartialEq, Default)]
  64 pub struct LocalDateTime;
  65
  66 #[cfg(feature = "time")]
  67 impl FormatTime for LocalDateTime {
  68     fn format_time(&self, w: &mut impl std::fmt::Write) -> std::fmt::Result {
  69         let time = time::OffsetDateTime::now_local().expect("time offset cannot be determined");
  70         write!(w, "{}", time)
  71     }
  72 }
  73
  74 ////////////////////////////////////////////////////////////////////////////////////////////////////
  75
  76 /// Retrieve and print the relative elapsed wall-clock time since an epoch.
  77 ///
  78 /// The `Default` implementation for `Uptime` makes the epoch the current time.
  79 // NB: Copy-pasted from `tracing-subscriber::fmt::time::Uptime`.
  80 #[derive(Debug, Clone, Copy, Eq, PartialEq)]
  81 pub struct Uptime {
  82     epoch: std::time::Instant,
  83 }
  84
  85 impl Default for Uptime {
  86     fn default() -> Self {
  87         Uptime {
  88             epoch: std::time::Instant::now(),
  89         }
  90     }
  91 }
  92
  93 impl From<std::time::Instant> for Uptime {
  94     fn from(epoch: std::time::Instant) -> Self {
  95         Uptime { epoch }
  96     }
  97 }
  98
  99 impl FormatTime for Uptime {
 100     fn format_time(&self, w: &mut impl std::fmt::Write) -> std::fmt::Result {
 101         let e = self.epoch.elapsed();
 102         write!(w, "{:4}.{:06}s", e.as_secs(), e.subsec_micros())
 103     }
 104 }
 105
 106 ////////////////////////////////////////////////////////////////////////////////////////////////////
 107
 108 impl<'a, F> FormatTime for &'a F
 109 where
 110     F: FormatTime,
 111 {
 112     fn format_time(&self, w: &mut impl std::fmt::Write) -> std::fmt::Result {
 113         (*self).format_time(w)
 114     }
 115 }
 116
 117 // NB:
 118 //   Can't impl for `fn(&mut impl std::fmt::Write)` since impl trait is not allowed
 119 //   outside of function and inherent method return types for now.