Add ExactSizeIterator impls for Hash{Map, Set, Table}

This commit also changes the return types of all `size_hint()` impls
in these files from (uint, Option<uint>) to (usize, Option<usize>).

src/libstd/collections/hash/map.rs

@@ -20,7 +20,7 @@ use cmp::{max, Eq, PartialEq};
 use default::Default;
 use fmt::{self, Show};
 use hash::{self, Hash, SipHasher};
-use iter::{self, Iterator, IteratorExt, FromIterator, Extend, Map};
+use iter::{self, Iterator, ExactSizeIterator, IteratorExt, FromIterator, Extend, Map};
 use marker::Sized;
 use mem::{self, replace};
 use num::{Int, UnsignedInt};
@@ -1384,7 +1384,11 @@ impl<'a, K, V> Iterator for Iter<'a, K, V> {
     type Item = (&'a K, &'a V);
 
     #[inline] fn next(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next() }
-    #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
+    #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
+}
+#[stable]
+impl<'a, K, V> ExactSizeIterator for Iter<'a, K, V> {
+    #[inline] fn len(&self) -> usize { self.inner.len() }
 }
 
 #[stable]
@@ -1392,7 +1396,11 @@ impl<'a, K, V> Iterator for IterMut<'a, K, V> {
     type Item = (&'a K, &'a mut V);
 
     #[inline] fn next(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next() }
-    #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
+    #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
+}
+#[stable]
+impl<'a, K, V> ExactSizeIterator for IterMut<'a, K, V> {
+    #[inline] fn len(&self) -> usize { self.inner.len() }
 }
 
 #[stable]
@@ -1400,7 +1408,11 @@ impl<K, V> Iterator for IntoIter<K, V> {
     type Item = (K, V);
 
     #[inline] fn next(&mut self) -> Option<(K, V)> { self.inner.next() }
-    #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
+    #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
+}
+#[stable]
+impl<K, V> ExactSizeIterator for IntoIter<K, V> {
+    #[inline] fn len(&self) -> usize { self.inner.len() }
 }
 
 #[stable]
@@ -1408,7 +1420,11 @@ impl<'a, K, V> Iterator for Keys<'a, K, V> {
     type Item = &'a K;
 
     #[inline] fn next(&mut self) -> Option<(&'a K)> { self.inner.next() }
-    #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
+    #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
+}
+#[stable]
+impl<'a, K, V> ExactSizeIterator for Keys<'a, K, V> {
+    #[inline] fn len(&self) -> usize { self.inner.len() }
 }
 
 #[stable]
@@ -1416,21 +1432,23 @@ impl<'a, K, V> Iterator for Values<'a, K, V> {
     type Item = &'a V;
 
     #[inline] fn next(&mut self) -> Option<(&'a V)> { self.inner.next() }
-    #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
+    #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
+}
+#[stable]
+impl<'a, K, V> ExactSizeIterator for Values<'a, K, V> {
+    #[inline] fn len(&self) -> usize { self.inner.len() }
 }
 
 #[stable]
-impl<'a, K: 'a, V: 'a> Iterator for Drain<'a, K, V> {
+impl<'a, K, V> Iterator for Drain<'a, K, V> {
     type Item = (K, V);
 
-    #[inline]
-    fn next(&mut self) -> Option<(K, V)> {
-        self.inner.next()
-    }
-    #[inline]
-    fn size_hint(&self) -> (uint, Option<uint>) {
-        self.inner.size_hint()
-    }
+    #[inline] fn next(&mut self) -> Option<(K, V)> { self.inner.next() }
+    #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
+}
+#[stable]
+impl<'a, K, V> ExactSizeIterator for Drain<'a, K, V> {
+    #[inline] fn len(&self) -> usize { self.inner.len() }
 }
 
 #[unstable = "matches collection reform v2 specification, waiting for dust to settle"]
@@ -2135,6 +2153,19 @@ mod test_map {
         assert_eq!(iter.size_hint(), (3, Some(3)));
     }
 
+    #[test]
+    fn test_iter_len() {
+        let xs = [(1i, 1i), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
+
+        let map: HashMap<int, int> = xs.iter().map(|&x| x).collect();
+
+        let mut iter = map.iter();
+
+        for _ in iter.by_ref().take(3) {}
+
+        assert_eq!(iter.len(), 3);
+    }
+
     #[test]
     fn test_mut_size_hint() {
         let xs = [(1i, 1i), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
@@ -2148,6 +2179,19 @@ mod test_map {
         assert_eq!(iter.size_hint(), (3, Some(3)));
     }
 
+    #[test]
+    fn test_iter_mut_len() {
+        let xs = [(1i, 1i), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
+
+        let mut map: HashMap<int, int> = xs.iter().map(|&x| x).collect();
+
+        let mut iter = map.iter_mut();
+
+        for _ in iter.by_ref().take(3) {}
+
+        assert_eq!(iter.len(), 3);
+    }
+
     #[test]
     fn test_index() {
         let mut map: HashMap<int, int> = HashMap::new();

src/libstd/collections/hash/set.rs

@@ -18,7 +18,7 @@ use default::Default;
 use fmt::Show;
 use fmt;
 use hash::{self, Hash};
-use iter::{Iterator, IteratorExt, FromIterator, Map, Chain, Extend};
+use iter::{Iterator, ExactSizeIterator, IteratorExt, FromIterator, Map, Chain, Extend};
 use ops::{BitOr, BitAnd, BitXor, Sub};
 use option::Option::{Some, None, self};
 
@@ -837,7 +837,11 @@ impl<'a, K> Iterator for Iter<'a, K> {
     type Item = &'a K;
 
     fn next(&mut self) -> Option<&'a K> { self.iter.next() }
-    fn size_hint(&self) -> (uint, Option<uint>) { self.iter.size_hint() }
+    fn size_hint(&self) -> (usize, Option<usize>) { self.iter.size_hint() }
+}
+#[stable]
+impl<'a, K> ExactSizeIterator for Iter<'a, K> {
+    fn len(&self) -> usize { self.iter.len() }
 }
 
 #[stable]
@@ -845,15 +849,23 @@ impl<K> Iterator for IntoIter<K> {
     type Item = K;
 
     fn next(&mut self) -> Option<K> { self.iter.next() }
-    fn size_hint(&self) -> (uint, Option<uint>) { self.iter.size_hint() }
+    fn size_hint(&self) -> (usize, Option<usize>) { self.iter.size_hint() }
+}
+#[stable]
+impl<K> ExactSizeIterator for IntoIter<K> {
+    fn len(&self) -> usize { self.iter.len() }
 }
 
 #[stable]
-impl<'a, K: 'a> Iterator for Drain<'a, K> {
+impl<'a, K> Iterator for Drain<'a, K> {
     type Item = K;
 
     fn next(&mut self) -> Option<K> { self.iter.next() }
-    fn size_hint(&self) -> (uint, Option<uint>) { self.iter.size_hint() }
+    fn size_hint(&self) -> (usize, Option<usize>) { self.iter.size_hint() }
+}
+#[stable]
+impl<'a, K> ExactSizeIterator for Drain<'a, K> {
+    fn len(&self) -> usize { self.iter.len() }
 }
 
 #[stable]
@@ -875,7 +887,7 @@ impl<'a, T, S, H> Iterator for Intersection<'a, T, S>
         }
     }
 
-    fn size_hint(&self) -> (uint, Option<uint>) {
+    fn size_hint(&self) -> (usize, Option<usize>) {
         let (_, upper) = self.iter.size_hint();
         (0, upper)
     }
@@ -900,7 +912,7 @@ impl<'a, T, S, H> Iterator for Difference<'a, T, S>
         }
     }
 
-    fn size_hint(&self) -> (uint, Option<uint>) {
+    fn size_hint(&self) -> (usize, Option<usize>) {
         let (_, upper) = self.iter.size_hint();
         (0, upper)
     }
@@ -915,7 +927,7 @@ impl<'a, T, S, H> Iterator for SymmetricDifference<'a, T, S>
     type Item = &'a T;
 
     fn next(&mut self) -> Option<&'a T> { self.iter.next() }
-    fn size_hint(&self) -> (uint, Option<uint>) { self.iter.size_hint() }
+    fn size_hint(&self) -> (usize, Option<usize>) { self.iter.size_hint() }
 }
 
 #[stable]
@@ -927,7 +939,7 @@ impl<'a, T, S, H> Iterator for Union<'a, T, S>
     type Item = &'a T;
 
     fn next(&mut self) -> Option<&'a T> { self.iter.next() }
-    fn size_hint(&self) -> (uint, Option<uint>) { self.iter.size_hint() }
+    fn size_hint(&self) -> (usize, Option<usize>) { self.iter.size_hint() }
 }
 
 #[cfg(test)]

src/libstd/collections/hash/table.rs

@@ -15,7 +15,7 @@ use self::BucketState::*;
 use clone::Clone;
 use cmp;
 use hash::{Hash, Hasher};
-use iter::{Iterator, count};
+use iter::{Iterator, ExactSizeIterator, count};
 use marker::{Copy, Sized, self};
 use mem::{min_align_of, size_of};
 use mem;
@@ -838,10 +838,13 @@ impl<'a, K, V> Iterator for Iter<'a, K, V> {
         })
     }
 
-    fn size_hint(&self) -> (uint, Option<uint>) {
+    fn size_hint(&self) -> (usize, Option<usize>) {
         (self.elems_left, Some(self.elems_left))
     }
 }
+impl<'a, K, V> ExactSizeIterator for Iter<'a, K, V> {
+    fn len(&self) -> usize { self.elems_left }
+}
 
 impl<'a, K, V> Iterator for IterMut<'a, K, V> {
     type Item = (&'a K, &'a mut V);
@@ -856,10 +859,13 @@ impl<'a, K, V> Iterator for IterMut<'a, K, V> {
         })
     }
 
-    fn size_hint(&self) -> (uint, Option<uint>) {
+    fn size_hint(&self) -> (usize, Option<usize>) {
         (self.elems_left, Some(self.elems_left))
     }
 }
+impl<'a, K, V> ExactSizeIterator for IterMut<'a, K, V> {
+    fn len(&self) -> usize { self.elems_left }
+}
 
 impl<K, V> Iterator for IntoIter<K, V> {
     type Item = (SafeHash, K, V);
@@ -879,13 +885,16 @@ impl<K, V> Iterator for IntoIter<K, V> {
         })
     }
 
-    fn size_hint(&self) -> (uint, Option<uint>) {
+    fn size_hint(&self) -> (usize, Option<usize>) {
         let size = self.table.size();
         (size, Some(size))
     }
 }
+impl<K, V> ExactSizeIterator for IntoIter<K, V> {
+    fn len(&self) -> usize { self.table.size() }
+}
 
-impl<'a, K: 'a, V: 'a> Iterator for Drain<'a, K, V> {
+impl<'a, K, V> Iterator for Drain<'a, K, V> {
     type Item = (SafeHash, K, V);
 
     #[inline]
@@ -904,11 +913,14 @@ impl<'a, K: 'a, V: 'a> Iterator for Drain<'a, K, V> {
         })
     }
 
-    fn size_hint(&self) -> (uint, Option<uint>) {
+    fn size_hint(&self) -> (usize, Option<usize>) {
         let size = self.table.size();
         (size, Some(size))
     }
 }
+impl<'a, K, V> ExactSizeIterator for Drain<'a, K, V> {
+    fn len(&self) -> usize { self.table.size() }
+}
 
 #[unsafe_destructor]
 impl<'a, K: 'a, V: 'a> Drop for Drain<'a, K, V> {