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/// A type that can measure and format the current time.
///
/// This trait is used by [HierarchicalLayer] to include a timestamp with each
/// [Event] when it is logged.
///
/// Notable default implementations of this trait are [LocalDateTime] and `()`.
/// The former prints the current time as reported by [time's OffsetDateTime]
/// (note that it requires a `time` feature to be enabled and may panic!
/// make sure to check out the docs for the [LocalDateTime]),
/// and the latter does not print the current time at all.
///
/// Inspired by the [FormatTime] trait from [tracing-subscriber].
///
/// [HierarchicalLayer]: crate::HierarchicalLayer
/// [Event]: tracing_core::Event
/// [time's OffsetDateTime]: time::OffsetDateTime
/// [FormatTime]: tracing_subscriber::fmt::time::FormatTime
/// [tracing-subscriber]: tracing_subscriber
// NB:
// We can't use `tracing_subscriber::fmt::format::Writer`
// since it doesn't have a public constructor.
pub trait FormatTime {
fn format_time(&self, w: &mut impl std::fmt::Write) -> std::fmt::Result;
}
////////////////////////////////////////////////////////////////////////////////////////////////////
/// Default do-nothing time formatter.
impl FormatTime for () {
fn format_time(&self, _w: &mut impl std::fmt::Write) -> std::fmt::Result {
Ok(())
}
}
////////////////////////////////////////////////////////////////////////////////////////////////////
/// Retrieve and print the current wall-clock time in UTC timezone.
#[cfg(feature = "time")]
#[derive(Debug, Clone, Copy, Eq, PartialEq, Default)]
pub struct UtcDateTime;
#[cfg(feature = "time")]
impl FormatTime for UtcDateTime {
fn format_time(&self, w: &mut impl std::fmt::Write) -> std::fmt::Result {
let time = time::OffsetDateTime::now_utc();
write!(w, "{} {}", time.date(), time.time())
}
}
////////////////////////////////////////////////////////////////////////////////////////////////////
/// Retrieve and print the current wall-clock time.
///
/// # Panics
///
/// Panics if [time crate] cannot determine the local UTC offset.
///
/// [time crate]: time
// NB:
// Can't use `tracing_subscriber::fmt::time::SystemTime` since it uses
// private `datetime` module to format the actual time.
#[cfg(feature = "time")]
#[derive(Debug, Clone, Copy, Eq, PartialEq, Default)]
pub struct LocalDateTime;
#[cfg(feature = "time")]
impl FormatTime for LocalDateTime {
fn format_time(&self, w: &mut impl std::fmt::Write) -> std::fmt::Result {
let time = time::OffsetDateTime::now_local().expect("time offset cannot be determined");
write!(w, "{}", time)
}
}
////////////////////////////////////////////////////////////////////////////////////////////////////
/// Retrieve and print the relative elapsed wall-clock time since an epoch.
///
/// The `Default` implementation for `Uptime` makes the epoch the current time.
// NB: Copy-pasted from `tracing-subscriber::fmt::time::Uptime`.
#[derive(Debug, Clone, Copy, Eq, PartialEq)]
pub struct Uptime {
epoch: std::time::Instant,
}
impl Default for Uptime {
fn default() -> Self {
Uptime {
epoch: std::time::Instant::now(),
}
}
}
impl From<std::time::Instant> for Uptime {
fn from(epoch: std::time::Instant) -> Self {
Uptime { epoch }
}
}
impl FormatTime for Uptime {
fn format_time(&self, w: &mut impl std::fmt::Write) -> std::fmt::Result {
let e = self.epoch.elapsed();
write!(w, "{:4}.{:06}s", e.as_secs(), e.subsec_micros())
}
}
////////////////////////////////////////////////////////////////////////////////////////////////////
impl<'a, F> FormatTime for &'a F
where
F: FormatTime,
{
fn format_time(&self, w: &mut impl std::fmt::Write) -> std::fmt::Result {
(*self).format_time(w)
}
}
// NB:
// Can't impl for `fn(&mut impl std::fmt::Write)` since impl trait is not allowed
// outside of function and inherent method return types for now.
|
