openpgp: Add a macro to profile a block of code.

  - A macro to make profiling a few bits of code straightforward.

1 files changed, 54 insertions, 0 deletions

diff --git a/openpgp/src/macros.rs b/openpgp/src/macros.rs
index 6317a0fe..20aaa6e5 100644
--- a/openpgp/src/macros.rs
+++ b/openpgp/src/macros.rs
@@ -50,3 +50,57 @@ macro_rules! tracer {
         }
     }
 }
+
+
+/// A very simple profiling tool.
+///
+/// Note: don't ever profile code that has not been compiled in
+/// release mode.  There can be orders of magnitude difference in
+/// execution time between it and debug mode!
+///
+/// This macro measures the wall time it takes to execute the block.
+/// If the time is at least $ms_threshold (in milli-seconds), then it
+/// displays the output on stderr.  The output is prefixed with label,
+/// if it is provided.
+///
+/// ```
+/// let result = time_it!("Some code", 10, {
+///     // Some code.
+///     5
+/// });
+/// assert_eq!(result, 5);
+/// ```
+#[allow(unused_macros)]
+macro_rules! time_it {
+    ( $label:expr, $ms_threshold:expr, $body:expr ) => {{
+        use std::time::{SystemTime, Duration};
+
+        // We use drop so that code that uses non-local exits (e.g.,
+        // using break 'label) still works.
+        struct Timer {
+            start: SystemTime,
+        };
+        impl Drop for Timer {
+            fn drop(&mut self) {
+                let elapsed = self.start.elapsed();
+                if elapsed.clone().unwrap_or(Duration::from_millis($ms_threshold))
+                    >= Duration::from_millis($ms_threshold)
+                {
+                    if $label.len() > 0 {
+                        eprint!("{}:", $label);
+                    }
+                    eprintln!("{}:{}: {:?}", file!(), line!(), elapsed);
+                }
+            }
+        }
+
+        let _start = Timer { start: SystemTime::now() };
+        $body
+    }};
+    ( $label:expr, $body:expr ) => {
+        time_it!($label, 0, $body)
+    };
+    ( $body:expr ) => {
+        time_it!("", $body)
+    };
+}