Implement `shrink_to` method on collections

1 files changed, 30 insertions, 0 deletions

diff --git a/src/libstd/ffi/os_str.rs b/src/libstd/ffi/os_str.rs
index 3959e8533be..7520121a8c2 100644
--- a/src/libstd/ffi/os_str.rs
+++ b/src/libstd/ffi/os_str.rs
@@ -295,6 +295,36 @@ impl OsString {
         self.inner.shrink_to_fit()
     }
 
+    /// Shrinks the capacity of the `OsString` with a lower bound.
+    ///
+    /// The capacity will remain at least as large as both the length
+    /// and the supplied value.
+    ///
+    /// Panics if the current capacity is smaller than the supplied
+    /// minimum capacity.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(shrink_to)]
+    /// use std::ffi::OsString;
+    ///
+    /// let mut s = OsString::from("foo");
+    ///
+    /// s.reserve(100);
+    /// assert!(s.capacity() >= 100);
+    ///
+    /// s.shrink_to(10);
+    /// assert!(s.capacity() >= 10);
+    /// s.shrink_to(0);
+    /// assert!(s.capacity() >= 3);
+    /// ```
+    #[inline]
+    #[unstable(feature = "shrink_to", reason = "new API", issue="0")]
+    pub fn shrink_to(&mut self, min_capacity: usize) {
+        self.inner.shrink_to(min_capacity)
+    }
+
     /// Converts this `OsString` into a boxed [`OsStr`].
     ///
     /// [`OsStr`]: struct.OsStr.html