libcollections

1 files changed, 265 insertions, 0 deletions

diff --git a/libcollections/borrow.rs b/libcollections/borrow.rs
new file mode 100644
index 0000000..6ca0db6
--- /dev/null
+++ b/libcollections/borrow.rs
@@ -0,0 +1,265 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! A module for working with borrowed data.
+
+#![stable(feature = "rust1", since = "1.0.0")]
+
+use core::clone::Clone;
+use core::cmp::{Eq, Ord, Ordering, PartialEq, PartialOrd};
+use core::convert::AsRef;
+use core::hash::{Hash, Hasher};
+use core::marker::Sized;
+use core::ops::Deref;
+use core::option::Option;
+
+use fmt;
+
+use self::Cow::*;
+
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use core::borrow::{Borrow, BorrowMut};
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, B: ?Sized> Borrow<B> for Cow<'a, B>
+    where B: ToOwned,
+          <B as ToOwned>::Owned: 'a
+{
+    fn borrow(&self) -> &B {
+        &**self
+    }
+}
+
+/// A generalization of `Clone` to borrowed data.
+///
+/// Some types make it possible to go from borrowed to owned, usually by
+/// implementing the `Clone` trait. But `Clone` works only for going from `&T`
+/// to `T`. The `ToOwned` trait generalizes `Clone` to construct owned data
+/// from any borrow of a given type.
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait ToOwned {
+    #[stable(feature = "rust1", since = "1.0.0")]
+    type Owned: Borrow<Self>;
+
+    /// Creates owned data from borrowed data, usually by cloning.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let s = "a"; // &str
+    /// let ss = s.to_owned(); // String
+    ///
+    /// let v = &[1, 2]; // slice
+    /// let vv = v.to_owned(); // Vec
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    fn to_owned(&self) -> Self::Owned;
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> ToOwned for T where T: Clone {
+    type Owned = T;
+    fn to_owned(&self) -> T {
+        self.clone()
+    }
+}
+
+/// A clone-on-write smart pointer.
+///
+/// The type `Cow` is a smart pointer providing clone-on-write functionality: it
+/// can enclose and provide immutable access to borrowed data, and clone the
+/// data lazily when mutation or ownership is required. The type is designed to
+/// work with general borrowed data via the `Borrow` trait.
+///
+/// `Cow` implements `Deref`, which means that you can call
+/// non-mutating methods directly on the data it encloses. If mutation
+/// is desired, `to_mut` will obtain a mutable reference to an owned
+/// value, cloning if necessary.
+///
+/// # Examples
+///
+/// ```
+/// use std::borrow::Cow;
+///
+/// # #[allow(dead_code)]
+/// fn abs_all(input: &mut Cow<[i32]>) {
+///     for i in 0..input.len() {
+///         let v = input[i];
+///         if v < 0 {
+///             // clones into a vector the first time (if not already owned)
+///             input.to_mut()[i] = -v;
+///         }
+///     }
+/// }
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+pub enum Cow<'a, B: ?Sized + 'a>
+    where B: ToOwned
+{
+    /// Borrowed data.
+    #[stable(feature = "rust1", since = "1.0.0")]
+    Borrowed(#[stable(feature = "rust1", since = "1.0.0")] &'a B),
+
+    /// Owned data.
+    #[stable(feature = "rust1", since = "1.0.0")]
+    Owned(
+        #[stable(feature = "rust1", since = "1.0.0")] <B as ToOwned>::Owned
+    ),
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, B: ?Sized> Clone for Cow<'a, B> where B: ToOwned {
+    fn clone(&self) -> Cow<'a, B> {
+        match *self {
+            Borrowed(b) => Borrowed(b),
+            Owned(ref o) => {
+                let b: &B = o.borrow();
+                Owned(b.to_owned())
+            }
+        }
+    }
+}
+
+impl<'a, B: ?Sized> Cow<'a, B> where B: ToOwned {
+    /// Acquires a mutable reference to the owned form of the data.
+    ///
+    /// Clones the data if it is not already owned.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::borrow::Cow;
+    ///
+    /// let mut cow: Cow<[_]> = Cow::Owned(vec![1, 2, 3]);
+    ///
+    /// let hello = cow.to_mut();
+    ///
+    /// assert_eq!(hello, &[1, 2, 3]);
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn to_mut(&mut self) -> &mut <B as ToOwned>::Owned {
+        match *self {
+            Borrowed(borrowed) => {
+                *self = Owned(borrowed.to_owned());
+                self.to_mut()
+            }
+            Owned(ref mut owned) => owned,
+        }
+    }
+
+    /// Extracts the owned data.
+    ///
+    /// Clones the data if it is not already owned.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::borrow::Cow;
+    ///
+    /// let cow: Cow<[_]> = Cow::Owned(vec![1, 2, 3]);
+    ///
+    /// let hello = cow.into_owned();
+    ///
+    /// assert_eq!(vec![1, 2, 3], hello);
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn into_owned(self) -> <B as ToOwned>::Owned {
+        match self {
+            Borrowed(borrowed) => borrowed.to_owned(),
+            Owned(owned) => owned,
+        }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, B: ?Sized> Deref for Cow<'a, B> where B: ToOwned {
+    type Target = B;
+
+    fn deref(&self) -> &B {
+        match *self {
+            Borrowed(borrowed) => borrowed,
+            Owned(ref owned) => owned.borrow(),
+        }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, B: ?Sized> Eq for Cow<'a, B> where B: Eq + ToOwned {}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, B: ?Sized> Ord for Cow<'a, B> where B: Ord + ToOwned {
+    #[inline]
+    fn cmp(&self, other: &Cow<'a, B>) -> Ordering {
+        Ord::cmp(&**self, &**other)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, 'b, B: ?Sized, C: ?Sized> PartialEq<Cow<'b, C>> for Cow<'a, B>
+    where B: PartialEq<C> + ToOwned,
+          C: ToOwned
+{
+    #[inline]
+    fn eq(&self, other: &Cow<'b, C>) -> bool {
+        PartialEq::eq(&**self, &**other)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, B: ?Sized> PartialOrd for Cow<'a, B> where B: PartialOrd + ToOwned {
+    #[inline]
+    fn partial_cmp(&self, other: &Cow<'a, B>) -> Option<Ordering> {
+        PartialOrd::partial_cmp(&**self, &**other)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, B: ?Sized> fmt::Debug for Cow<'a, B>
+    where B: fmt::Debug + ToOwned,
+          <B as ToOwned>::Owned: fmt::Debug
+{
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            Borrowed(ref b) => fmt::Debug::fmt(b, f),
+            Owned(ref o) => fmt::Debug::fmt(o, f),
+        }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, B: ?Sized> fmt::Display for Cow<'a, B>
+    where B: fmt::Display + ToOwned,
+          <B as ToOwned>::Owned: fmt::Display
+{
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            Borrowed(ref b) => fmt::Display::fmt(b, f),
+            Owned(ref o) => fmt::Display::fmt(o, f),
+        }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, B: ?Sized> Hash for Cow<'a, B> where B: Hash + ToOwned {
+    #[inline]
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        Hash::hash(&**self, state)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+#[allow(deprecated)]
+impl<'a, T: ?Sized + ToOwned> AsRef<T> for Cow<'a, T> {
+    fn as_ref(&self) -> &T {
+        self
+    }
+}