From 40fbe9ba35116ccff04251f6c52d1607f3480c6f Mon Sep 17 00:00:00 2001
From: Lars Wirzenius <liw@liw.fi>
Date: Sat, 2 Apr 2022 15:48:23 +0300
Subject: feat: add data structures for accumulating time measurements

Sponsored-by: author
---
 src/accumulated_time.rs | 79 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)
 create mode 100644 src/accumulated_time.rs

(limited to 'src/accumulated_time.rs')

diff --git a/src/accumulated_time.rs b/src/accumulated_time.rs
new file mode 100644
index 0000000..e633a10
--- /dev/null
+++ b/src/accumulated_time.rs
@@ -0,0 +1,79 @@
+//! Measure accumulated time for various operations.
+
+use std::collections::HashMap;
+use std::hash::Hash;
+use std::sync::Mutex;
+use std::time::Instant;
+
+/// Accumulated times for different clocks.
+///
+/// The caller defines a clock type, usually an enum.
+/// `AccumulatedTime` accumulates time for each possible clock.
+/// Conceptually, every type of clock exists. If a type of clock
+/// doesn't ever get created, it measures at 0 accumulated time.
+#[derive(Debug)]
+pub struct AccumulatedTime<T> {
+    accumulated: Mutex<HashMap<T, ClockTime>>,
+}
+
+#[derive(Debug, Default)]
+struct ClockTime {
+    nanos: u128,
+    started: Option<Instant>,
+}
+
+impl<T: Eq + PartialEq + Hash + Copy> AccumulatedTime<T> {
+    /// Create a new accumulated time collector.
+    #[allow(clippy::new_without_default)]
+    pub fn new() -> Self {
+        Self {
+            accumulated: Mutex::new(HashMap::new()),
+        }
+    }
+
+    /// Start a new clock of a given type to measure a span of time.
+    ///
+    /// The clock's measured time is added to the accumulator when the
+    /// clock is stopped.
+    pub fn start(&mut self, clock: T) {
+        let mut map = self.accumulated.lock().unwrap();
+        let ct = map.entry(clock).or_insert_with(ClockTime::default);
+        assert!(ct.started.is_none());
+        ct.started = Some(Instant::now());
+    }
+
+    /// Stop a running clock.
+    ///
+    /// Its run time is added to the accumulated time for that kind of clock.
+    pub fn stop(&mut self, clock: T) {
+        let mut map = self.accumulated.lock().unwrap();
+        if let Some(mut ct) = map.get_mut(&clock) {
+            assert!(ct.started.is_some());
+            if let Some(started) = ct.started.take() {
+                ct.nanos += started.elapsed().as_nanos();
+                ct.started = None;
+            }
+        }
+    }
+
+    /// Return the accumulated time for a type of clock, as whole seconds.
+    pub fn secs(&self, clock: T) -> u128 {
+        self.nanos(clock) / 1_000_000_000u128
+    }
+
+    /// Return the accumulated time for a type of clock, as nanoseconds.
+    ///
+    /// This includes the time spent in a currently running clock.
+    pub fn nanos(&self, clock: T) -> u128 {
+        let map = self.accumulated.lock().unwrap();
+        if let Some(ct) = map.get(&clock) {
+            if let Some(started) = ct.started {
+                ct.nanos + started.elapsed().as_nanos()
+            } else {
+                ct.nanos
+            }
+        } else {
+            0
+        }
+    }
+}
-- 
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