Add into_keys and into_values to AHashMap (#136)

* Add into_keys and into_values

Signed-off-by: Tom Kaitchuck <Tom.Kaitchuck@gmail.com>

src/hash_map.rs

@@ -1,5 +1,6 @@
 use std::borrow::Borrow;
 use std::collections::{hash_map, HashMap};
+use std::collections::hash_map::{IntoKeys, IntoValues};
 use std::fmt::{self, Debug};
 use std::hash::{BuildHasher, Hash};
 use std::iter::FromIterator;
@@ -181,6 +182,68 @@ where
         self.0.insert(k, v)
     }
 
+    /// Creates a consuming iterator visiting all the keys in arbitrary order.
+    /// The map cannot be used after calling this.
+    /// The iterator element type is `K`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::collections::HashMap;
+    ///
+    /// let map = HashMap::from([
+    ///     ("a", 1),
+    ///     ("b", 2),
+    ///     ("c", 3),
+    /// ]);
+    ///
+    /// let mut vec: Vec<&str> = map.into_keys().collect();
+    /// // The `IntoKeys` iterator produces keys in arbitrary order, so the
+    /// // keys must be sorted to test them against a sorted array.
+    /// vec.sort_unstable();
+    /// assert_eq!(vec, ["a", "b", "c"]);
+    /// ```
+    ///
+    /// # Performance
+    ///
+    /// In the current implementation, iterating over keys takes O(capacity) time
+    /// instead of O(len) because it internally visits empty buckets too.
+    #[inline]
+    pub fn into_keys(self) -> IntoKeys<K, V> {
+        self.0.into_keys()
+    }
+
+    /// Creates a consuming iterator visiting all the values in arbitrary order.
+    /// The map cannot be used after calling this.
+    /// The iterator element type is `V`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::collections::HashMap;
+    ///
+    /// let map = HashMap::from([
+    ///     ("a", 1),
+    ///     ("b", 2),
+    ///     ("c", 3),
+    /// ]);
+    ///
+    /// let mut vec: Vec<i32> = map.into_values().collect();
+    /// // The `IntoValues` iterator produces values in arbitrary order, so
+    /// // the values must be sorted to test them against a sorted array.
+    /// vec.sort_unstable();
+    /// assert_eq!(vec, [1, 2, 3]);
+    /// ```
+    ///
+    /// # Performance
+    ///
+    /// In the current implementation, iterating over values takes O(capacity) time
+    /// instead of O(len) because it internally visits empty buckets too.
+    #[inline]
+    pub fn into_values(self) -> IntoValues<K, V> {
+        self.0.into_values()
+    }
+
     /// Removes a key from the map, returning the value at the key if the key
     /// was previously in the map.
     ///