Implement Display trait (solana-labs#6929)

measure/src/measure.rs

@@ -1,14 +1,16 @@
 use solana_sdk::timing::duration_as_ns;
-use std::time::Instant;
+use std::{fmt, time::Instant};
 
 pub struct Measure {
+    name: &'static str,
     start: Instant,
     duration: u64,
 }
 
 impl Measure {
-    pub fn start(_name: &'static str) -> Self {
+    pub fn start(name: &'static str) -> Self {
         Self {
+            name,
             start: Instant::now(),
             duration: 0,
         }
@@ -31,6 +33,22 @@ impl Measure {
     }
 }
 
+impl fmt::Display for Measure {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        if self.duration == 0 {
+            write!(f, "{} running", self.name)
+        } else if self.as_us() < 1 {
+            write!(f, "{} took {}ns", self.name, self.duration)
+        } else if self.as_ms() < 1 {
+            write!(f, "{} took {}us", self.name, self.as_us())
+        } else if self.as_s() < 1. {
+            write!(f, "{} took {}ms", self.name, self.as_ms())
+        } else {
+            write!(f, "{} took {:.1}s", self.name, self.as_s())
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -46,4 +64,38 @@ mod tests {
         assert!(measure.as_ms() >= 990 && measure.as_ms() <= 1_010);
         assert!(measure.as_us() >= 999_000 && measure.as_us() <= 1_010_000);
     }
+
+    #[test]
+    fn test_measure_display() {
+        let measure = Measure {
+            name: "test_ns",
+            start: Instant::now(),
+            duration: 1,
+        };
+        assert_eq!(format!("{}", measure), "test_ns took 1ns");
+
+        let measure = Measure {
+            name: "test_us",
+            start: Instant::now(),
+            duration: 1000,
+        };
+        assert_eq!(format!("{}", measure), "test_us took 1us");
+
+        let measure = Measure {
+            name: "test_ms",
+            start: Instant::now(),
+            duration: 1000 * 1000,
+        };
+        assert_eq!(format!("{}", measure), "test_ms took 1ms");
+
+        let measure = Measure {
+            name: "test_s",
+            start: Instant::now(),
+            duration: 1000 * 1000 * 1000,
+        };
+        assert_eq!(format!("{}", measure), "test_s took 1.0s");
+
+        let measure = Measure::start("test_not_stopped");
+        assert_eq!(format!("{}", measure), "test_not_stopped running");
+    }
 }