1 files changed, 21 insertions, 1 deletions
diff --git a/src/lib.rs b/src/lib.rs
index 9c030d0..2d34b1c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -44,7 +44,7 @@
 #![forbid(unsafe_code)]
 #![warn(missing_docs)]
 
-use std::{collections::HashMap, num::NonZeroUsize};
+use std::{collections::HashMap, iter::FusedIterator, num::NonZeroUsize};
 
 use crossbeam_channel::{Receiver, Select, Sender, TryRecvError};
 
@@ -295,6 +295,26 @@ where
             }
         }
     }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let (lower, upper) = self.iter.size_hint();
+        let inflight = self.inflight();
+        (
+            lower.saturating_add(inflight),
+            upper.and_then(|i| i.checked_add(inflight)),
+        )
+    }
+}
+
+impl<I, B> FusedIterator for ParallelMap<I, B> where I: FusedIterator {}
+
+impl<I, B> ExactSizeIterator for ParallelMap<I, B>
+where
+    I: ExactSizeIterator,
+{
+    fn len(&self) -> usize {
+        self.iter.len() + self.inflight()
+    }
 }
 
 /// Calls a given closure when the thread unwinds due to a panic.