1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! A unique pointer type.
16 use core::clone::Clone;
17 use core::cmp::{PartialEq, PartialOrd, Eq, Ord, Ordering};
18 use core::default::Default;
20 use core::hash::{self, Hash};
21 use core::marker::Sized;
23 use core::option::Option;
24 use core::ptr::Unique;
25 use core::raw::TraitObject;
26 use core::result::Result;
27 use core::result::Result::{Ok, Err};
28 use core::ops::{Deref, DerefMut};
30 /// A value that represents the global exchange heap. This is the default
31 /// place that the `box` keyword allocates into when no place is supplied.
33 /// The following two examples are equivalent:
36 /// use std::boxed::HEAP;
39 /// # impl Bar { fn new(_a: int) { } }
40 /// let foo = box(HEAP) Bar::new(2);
41 /// let foo = box Bar::new(2);
43 #[lang = "exchange_heap"]
44 #[experimental = "may be renamed; uncertain about custom allocator design"]
45 pub static HEAP: () = ();
47 /// A type that represents a uniquely-owned value.
50 pub struct Box<T>(Unique<T>);
54 /// Moves `x` into a freshly allocated box on the global exchange heap.
56 pub fn new(x: T) -> Box<T> {
62 impl<T: Default> Default for Box<T> {
64 fn default() -> Box<T> { box Default::default() }
68 impl<T> Default for Box<[T]> {
70 fn default() -> Box<[T]> { box [] }
74 impl<T: Clone> Clone for Box<T> {
75 /// Returns a copy of the owned box.
77 fn clone(&self) -> Box<T> { box {(**self).clone()} }
79 /// Performs copy-assignment from `source` by reusing the existing allocation.
81 fn clone_from(&mut self, source: &Box<T>) {
82 (**self).clone_from(&(**source));
87 impl<T: ?Sized + PartialEq> PartialEq for Box<T> {
89 fn eq(&self, other: &Box<T>) -> bool { PartialEq::eq(&**self, &**other) }
91 fn ne(&self, other: &Box<T>) -> bool { PartialEq::ne(&**self, &**other) }
94 impl<T: ?Sized + PartialOrd> PartialOrd for Box<T> {
96 fn partial_cmp(&self, other: &Box<T>) -> Option<Ordering> {
97 PartialOrd::partial_cmp(&**self, &**other)
100 fn lt(&self, other: &Box<T>) -> bool { PartialOrd::lt(&**self, &**other) }
102 fn le(&self, other: &Box<T>) -> bool { PartialOrd::le(&**self, &**other) }
104 fn ge(&self, other: &Box<T>) -> bool { PartialOrd::ge(&**self, &**other) }
106 fn gt(&self, other: &Box<T>) -> bool { PartialOrd::gt(&**self, &**other) }
109 impl<T: ?Sized + Ord> Ord for Box<T> {
111 fn cmp(&self, other: &Box<T>) -> Ordering {
112 Ord::cmp(&**self, &**other)
116 impl<T: ?Sized + Eq> Eq for Box<T> {}
118 impl<S: hash::Writer, T: ?Sized + Hash<S>> Hash<S> for Box<T> {
120 fn hash(&self, state: &mut S) {
121 (**self).hash(state);
125 /// Extension methods for an owning `Any` trait object.
126 #[unstable = "post-DST and coherence changes, this will not be a trait but \
127 rather a direct `impl` on `Box<Any>`"]
129 /// Returns the boxed value if it is of type `T`, or
130 /// `Err(Self)` if it isn't.
132 fn downcast<T: 'static>(self) -> Result<Box<T>, Self>;
135 impl BoxAny for Box<Any> {
137 #[unstable = "method may be renamed with respect to other downcasting \
139 fn downcast<T: 'static>(self) -> Result<Box<T>, Box<Any>> {
142 // Get the raw representation of the trait object
143 let to: TraitObject =
144 mem::transmute::<Box<Any>, TraitObject>(self);
146 // Extract the data pointer
147 Ok(mem::transmute(to.data))
155 impl<T: ?Sized + fmt::Show> fmt::Show for Box<T> {
156 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
157 write!(f, "Box({:?})", &**self)
161 impl<T: ?Sized + fmt::String> fmt::String for Box<T> {
162 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
163 fmt::String::fmt(&**self, f)
167 impl fmt::Show for Box<Any> {
168 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
174 impl<T: ?Sized> Deref for Box<T> {
177 fn deref(&self) -> &T { &**self }
181 impl<T: ?Sized> DerefMut for Box<T> {
182 fn deref_mut(&mut self) -> &mut T { &mut **self }
188 fn test_owned_clone() {
190 let b: Box<int> = a.clone();
196 let a = box 8u as Box<Any>;
197 let b = box Test as Box<Any>;
199 match a.downcast::<uint>() {
200 Ok(a) => { assert!(a == box 8u); }
203 match b.downcast::<Test>() {
204 Ok(a) => { assert!(a == box Test); }
208 let a = box 8u as Box<Any>;
209 let b = box Test as Box<Any>;
211 assert!(a.downcast::<Box<Test>>().is_err());
212 assert!(b.downcast::<Box<uint>>().is_err());
217 let a = box 8u as Box<Any>;
218 let b = box Test as Box<Any>;
219 let a_str = a.to_str();
220 let b_str = b.to_str();
221 assert_eq!(a_str, "Box<Any>");
222 assert_eq!(b_str, "Box<Any>");
225 let b = &Test as &Any;
226 let s = format!("{}", a);
227 assert_eq!(s, "&Any");
228 let s = format!("{}", b);
229 assert_eq!(s, "&Any");
234 fn homura<T: Deref<Target=i32>>(_: T) { }