Use wait_while for Condvar in Queue to simplify code.

src/cargo/util/queue.rs

@@ -1,6 +1,6 @@
 use std::collections::VecDeque;
 use std::sync::{Condvar, Mutex};
-use std::time::{Duration, Instant};
+use std::time::Duration;
 
 /// A simple, threadsafe, queue of items of type `T`
 ///
@@ -40,41 +40,30 @@ impl<T> Queue<T> {
 
     /// Pushes an item onto the queue, blocking if the queue is full.
     pub fn push_bounded(&self, item: T) {
-        let mut state = self.state.lock().unwrap();
-        loop {
-            if state.items.len() >= self.bound {
-                state = self.bounded_cv.wait(state).unwrap();
-            } else {
-                state.items.push_back(item);
-                self.popper_cv.notify_one();
-                break;
-            }
-        }
+        let locked_state = self.state.lock().unwrap();
+        let mut state = self
+            .bounded_cv
+            .wait_while(locked_state, |s| s.items.len() >= self.bound)
+            .unwrap();
+        state.items.push_back(item);
+        self.popper_cv.notify_one();
     }
 
     pub fn pop(&self, timeout: Duration) -> Option<T> {
-        let mut state = self.state.lock().unwrap();
-        let now = Instant::now();
-        while state.items.is_empty() {
-            let elapsed = now.elapsed();
-            if elapsed >= timeout {
-                break;
-            }
-            let (lock, result) = self
-                .popper_cv
-                .wait_timeout(state, timeout - elapsed)
-                .unwrap();
-            state = lock;
-            if result.timed_out() {
-                break;
+        let (mut state, result) = self
+            .popper_cv
+            .wait_timeout_while(self.state.lock().unwrap(), timeout, |s| s.items.is_empty())
+            .unwrap();
+        if result.timed_out() {
+            None
+        } else {
+            let value = state.items.pop_front()?;
+            if state.items.len() < self.bound {
+                // Assumes threads cannot be canceled.
+                self.bounded_cv.notify_one();
             }
+            Some(value)
         }
-        let value = state.items.pop_front()?;
-        if state.items.len() < self.bound {
-            // Assumes threads cannot be canceled.
-            self.bounded_cv.notify_one();
-        }
-        Some(value)
     }
 
     pub fn try_pop_all(&self) -> Vec<T> {