src/libcore/any.rs - third_party/rust - Git at Google

 // Copyright 2013-2014 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.

 //! This module implements the `Any` trait, which enables dynamic typing
 //! of any `'static` type through runtime reflection.
 //!
 //! `Any` itself can be used to get a `TypeId`, and has more features when used
 //! as a trait object. As `&Any` (a borrowed trait object), it has the `is` and
 //! `downcast_ref` methods, to test if the contained value is of a given type,
 //! and to get a reference to the inner value as a type. As `&mut Any`, there
 //! is also the `downcast_mut` method, for getting a mutable reference to the
 //! inner value. `Box<Any>` adds the `downcast` method, which attempts to
 //! convert to a `Box<T>`. See the [`Box`] documentation for the full details.
 //!
 //! Note that &Any is limited to testing whether a value is of a specified
 //! concrete type, and cannot be used to test whether a type implements a trait.
 //!
 //! [`Box`]: ../../std/boxed/struct.Box.html
 //!
 //! # Examples
 //!
 //! Consider a situation where we want to log out a value passed to a function.
 //! We know the value we're working on implements Debug, but we don't know its
 //! concrete type.  We want to give special treatment to certain types: in this
 //! case printing out the length of String values prior to their value.
 //! We don't know the concrete type of our value at compile time, so we need to
 //! use runtime reflection instead.
 //!
 //! ```rust
 //! use std::fmt::Debug;
 //! use std::any::Any;
 //!
 //! // Logger function for any type that implements Debug.
 //! fn log<T: Any + Debug>(value: &T) {
 //!     let value_any = value as &Any;
 //!
 //!     // try to convert our value to a String.  If successful, we want to
 //!     // output the String's length as well as its value.  If not, it's a
 //!     // different type: just print it out unadorned.
 //!     match value_any.downcast_ref::<String>() {
 //!         Some(as_string) => {
 //!             println!("String ({}): {}", as_string.len(), as_string);
 //!         }
 //!         None => {
 //!             println!("{:?}", value);
 //!         }
 //!     }
 //! }
 //!
 //! // This function wants to log its parameter out prior to doing work with it.
 //! fn do_work<T: Any + Debug>(value: &T) {
 //!     log(value);
 //!     // ...do some other work
 //! }
 //!
 //! fn main() {
 //!     let my_string = "Hello World".to_string();
 //!     do_work(&my_string);
 //!
 //!     let my_i8: i8 = 100;
 //!     do_work(&my_i8);
 //! }
 //! ```

 #![stable(feature = "rust1", since = "1.0.0")]

 use fmt;
 use marker::Send;
 use mem::transmute;
 use option::Option::{self, Some, None};
 use raw::TraitObject;
 use intrinsics;
 use marker::{Reflect, Sized};

 ///////////////////////////////////////////////////////////////////////////////
 // Any trait
 ///////////////////////////////////////////////////////////////////////////////

 /// A type to emulate dynamic typing.
 ///
 /// Most types implement `Any`. However, any type which contains a non-`'static` reference does not.
 /// See the [module-level documentation][mod] for more details.
 ///
 /// [mod]: index.html
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait Any: Reflect + 'static {
     /// Gets the `TypeId` of `self`.
     ///
     /// # Examples
     ///
     /// ```
     /// #![feature(get_type_id)]
     ///
     /// use std::any::{Any, TypeId};
     ///
     /// fn is_string(s: &Any) -> bool {
     ///     TypeId::of::<String>() == s.get_type_id()
     /// }
     ///
     /// fn main() {
     ///     assert_eq!(is_string(&0), false);
     ///     assert_eq!(is_string(&"cookie monster".to_owned()), true);
     /// }
     /// ```
     #[unstable(feature = "get_type_id",
                reason = "this method will likely be replaced by an associated static",
                issue = "27745")]
     fn get_type_id(&self) -> TypeId;
 }

 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: Reflect + 'static + ?Sized > Any for T {
     fn get_type_id(&self) -> TypeId { TypeId::of::<T>() }
 }

 ///////////////////////////////////////////////////////////////////////////////
 // Extension methods for Any trait objects.
 ///////////////////////////////////////////////////////////////////////////////

 #[stable(feature = "rust1", since = "1.0.0")]
 impl fmt::Debug for Any {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.pad("Any")
     }
 }

 // Ensure that the result of e.g. joining a thread can be printed and
 // hence used with `unwrap`. May eventually no longer be needed if
 // dispatch works with upcasting.
 #[stable(feature = "rust1", since = "1.0.0")]
 impl fmt::Debug for Any + Send {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.pad("Any")
     }
 }

 impl Any {
     /// Returns true if the boxed type is the same as `T`.
     ///
     /// # Examples
     ///
     /// ```
     /// use std::any::Any;
     ///
     /// fn is_string(s: &Any) {
     ///     if s.is::<String>() {
     ///         println!("It's a string!");
     ///     } else {
     ///         println!("Not a string...");
     ///     }
     /// }
     ///
     /// fn main() {
     ///     is_string(&0);
     ///     is_string(&"cookie monster".to_owned());
     /// }
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn is<T: Any>(&self) -> bool {
         // Get TypeId of the type this function is instantiated with
         let t = TypeId::of::<T>();

         // Get TypeId of the type in the trait object
         let boxed = self.get_type_id();

         // Compare both TypeIds on equality
         t == boxed
     }

     /// Returns some reference to the boxed value if it is of type `T`, or
     /// `None` if it isn't.
     ///
     /// # Examples
     ///
     /// ```
     /// use std::any::Any;
     ///
     /// fn print_if_string(s: &Any) {
     ///     if let Some(string) = s.downcast_ref::<String>() {
     ///         println!("It's a string({}): '{}'", string.len(), string);
     ///     } else {
     ///         println!("Not a string...");
     ///     }
     /// }
     ///
     /// fn main() {
     ///     print_if_string(&0);
     ///     print_if_string(&"cookie monster".to_owned());
     /// }
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn downcast_ref<T: Any>(&self) -> Option<&T> {
         if self.is::<T>() {
             unsafe {
                 // Get the raw representation of the trait object
                 let to: TraitObject = transmute(self);

                 // Extract the data pointer
                 Some(&*(to.data as *const T))
             }
         } else {
             None
         }
     }

     /// Returns some mutable reference to the boxed value if it is of type `T`, or
     /// `None` if it isn't.
     ///
     /// # Examples
     ///
     /// ```
     /// use std::any::Any;
     ///
     /// fn modify_if_u32(s: &mut Any) {
     ///     if let Some(num) = s.downcast_mut::<u32>() {
     ///         *num = 42;
     ///     }
     /// }
     ///
     /// fn main() {
     ///     let mut x = 10u32;
     ///     let mut s = "starlord".to_owned();
     ///
     ///     modify_if_u32(&mut x);
     ///     modify_if_u32(&mut s);
     ///
     ///     assert_eq!(x, 42);
     ///     assert_eq!(&s, "starlord");
     /// }
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn downcast_mut<T: Any>(&mut self) -> Option<&mut T> {
         if self.is::<T>() {
             unsafe {
                 // Get the raw representation of the trait object
                 let to: TraitObject = transmute(self);

                 // Extract the data pointer
                 Some(&mut *(to.data as *const T as *mut T))
             }
         } else {
             None
         }
     }
 }

 impl Any+Send {
     /// Forwards to the method defined on the type `Any`.
     ///
     /// # Examples
     ///
     /// ```
     /// use std::any::Any;
     ///
     /// fn is_string(s: &(Any + Send)) {
     ///     if s.is::<String>() {
     ///         println!("It's a string!");
     ///     } else {
     ///         println!("Not a string...");
     ///     }
     /// }
     ///
     /// fn main() {
     ///     is_string(&0);
     ///     is_string(&"cookie monster".to_owned());
     /// }
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn is<T: Any>(&self) -> bool {
         Any::is::<T>(self)
     }

     /// Forwards to the method defined on the type `Any`.
     ///
     /// # Examples
     ///
     /// ```
     /// use std::any::Any;
     ///
     /// fn print_if_string(s: &(Any + Send)) {
     ///     if let Some(string) = s.downcast_ref::<String>() {
     ///         println!("It's a string({}): '{}'", string.len(), string);
     ///     } else {
     ///         println!("Not a string...");
     ///     }
     /// }
     ///
     /// fn main() {
     ///     print_if_string(&0);
     ///     print_if_string(&"cookie monster".to_owned());
     /// }
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn downcast_ref<T: Any>(&self) -> Option<&T> {
         Any::downcast_ref::<T>(self)
     }

     /// Forwards to the method defined on the type `Any`.
     ///
     /// # Examples
     ///
     /// ```
     /// use std::any::Any;
     ///
     /// fn modify_if_u32(s: &mut (Any+ Send)) {
     ///     if let Some(num) = s.downcast_mut::<u32>() {
     ///         *num = 42;
     ///     }
     /// }
     ///
     /// fn main() {
     ///     let mut x = 10u32;
     ///     let mut s = "starlord".to_owned();
     ///
     ///     modify_if_u32(&mut x);
     ///     modify_if_u32(&mut s);
     ///
     ///     assert_eq!(x, 42);
     ///     assert_eq!(&s, "starlord");
     /// }
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn downcast_mut<T: Any>(&mut self) -> Option<&mut T> {
         Any::downcast_mut::<T>(self)
     }
 }


 ///////////////////////////////////////////////////////////////////////////////
 // TypeID and its methods
 ///////////////////////////////////////////////////////////////////////////////

 /// A `TypeId` represents a globally unique identifier for a type.
 ///
 /// Each `TypeId` is an opaque object which does not allow inspection of what's
 /// inside but does allow basic operations such as cloning, comparison,
 /// printing, and showing.
 ///
 /// A `TypeId` is currently only available for types which ascribe to `'static`,
 /// but this limitation may be removed in the future.
 #[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct TypeId {
     t: u64,
 }

 impl TypeId {
     /// Returns the `TypeId` of the type this generic function has been
     /// instantiated with.
     ///
     /// # Examples
     ///
     /// ```
     /// #![feature(get_type_id)]
     ///
     /// use std::any::{Any, TypeId};
     ///
     /// fn is_string(s: &Any) -> bool {
     ///     TypeId::of::<String>() == s.get_type_id()
     /// }
     ///
     /// fn main() {
     ///     assert_eq!(is_string(&0), false);
     ///     assert_eq!(is_string(&"cookie monster".to_owned()), true);
     /// }
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn of<T: ?Sized + Reflect + 'static>() -> TypeId {
         TypeId {
             t: unsafe { intrinsics::type_id::<T>() },
         }
     }
 }
	// Copyright 2013-2014 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.

	//! This module implements the `Any` trait, which enables dynamic typing
	//! of any `'static` type through runtime reflection.
	//!
	//! `Any` itself can be used to get a `TypeId`, and has more features when used
	//! as a trait object. As `&Any` (a borrowed trait object), it has the `is` and
	//! `downcast_ref` methods, to test if the contained value is of a given type,
	//! and to get a reference to the inner value as a type. As `&mut Any`, there
	//! is also the `downcast_mut` method, for getting a mutable reference to the
	//! inner value. `Box<Any>` adds the `downcast` method, which attempts to
	//! convert to a `Box<T>`. See the [`Box`] documentation for the full details.
	//!
	//! Note that &Any is limited to testing whether a value is of a specified
	//! concrete type, and cannot be used to test whether a type implements a trait.
	//!
	//! [`Box`]: ../../std/boxed/struct.Box.html
	//!
	//! # Examples
	//!
	//! Consider a situation where we want to log out a value passed to a function.
	//! We know the value we're working on implements Debug, but we don't know its
	//! concrete type. We want to give special treatment to certain types: in this
	//! case printing out the length of String values prior to their value.
	//! We don't know the concrete type of our value at compile time, so we need to
	//! use runtime reflection instead.
	//!
	//! ```rust
	//! use std::fmt::Debug;
	//! use std::any::Any;
	//!
	//! // Logger function for any type that implements Debug.
	//! fn log<T: Any + Debug>(value: &T) {
	//! let value_any = value as &Any;
	//!
	//! // try to convert our value to a String. If successful, we want to
	//! // output the String's length as well as its value. If not, it's a
	//! // different type: just print it out unadorned.
	//! match value_any.downcast_ref::<String>() {
	//! Some(as_string) => {
	//! println!("String ({}): {}", as_string.len(), as_string);
	//! }
	//! None => {
	//! println!("{:?}", value);
	//! }
	//! }
	//! }
	//!
	//! // This function wants to log its parameter out prior to doing work with it.
	//! fn do_work<T: Any + Debug>(value: &T) {
	//! log(value);
	//! // ...do some other work
	//! }
	//!
	//! fn main() {
	//! let my_string = "Hello World".to_string();
	//! do_work(&my_string);
	//!
	//! let my_i8: i8 = 100;
	//! do_work(&my_i8);
	//! }
	//! ```

	#![stable(feature = "rust1", since = "1.0.0")]

	use fmt;
	use marker::Send;
	use mem::transmute;
	use option::Option::{self, Some, None};
	use raw::TraitObject;
	use intrinsics;
	use marker::{Reflect, Sized};

	///////////////////////////////////////////////////////////////////////////////
	// Any trait
	///////////////////////////////////////////////////////////////////////////////

	/// A type to emulate dynamic typing.
	///
	/// Most types implement `Any`. However, any type which contains a non-`'static` reference does not.
	/// See the [module-level documentation][mod] for more details.
	///
	/// [mod]: index.html
	#[stable(feature = "rust1", since = "1.0.0")]
	pub trait Any: Reflect + 'static {
	/// Gets the `TypeId` of `self`.
	///
	/// # Examples
	///
	/// ```
	/// #![feature(get_type_id)]
	///
	/// use std::any::{Any, TypeId};
	///
	/// fn is_string(s: &Any) -> bool {
	/// TypeId::of::<String>() == s.get_type_id()
	/// }
	///
	/// fn main() {
	/// assert_eq!(is_string(&0), false);
	/// assert_eq!(is_string(&"cookie monster".to_owned()), true);
	/// }
	/// ```
	#[unstable(feature = "get_type_id",
	reason = "this method will likely be replaced by an associated static",
	issue = "27745")]
	fn get_type_id(&self) -> TypeId;
	}

	#[stable(feature = "rust1", since = "1.0.0")]
	impl<T: Reflect + 'static + ?Sized > Any for T {
	fn get_type_id(&self) -> TypeId { TypeId::of::<T>() }
	}

	///////////////////////////////////////////////////////////////////////////////
	// Extension methods for Any trait objects.
	///////////////////////////////////////////////////////////////////////////////

	#[stable(feature = "rust1", since = "1.0.0")]
	impl fmt::Debug for Any {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
	f.pad("Any")
	}
	}

	// Ensure that the result of e.g. joining a thread can be printed and
	// hence used with `unwrap`. May eventually no longer be needed if
	// dispatch works with upcasting.
	#[stable(feature = "rust1", since = "1.0.0")]
	impl fmt::Debug for Any + Send {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
	f.pad("Any")
	}
	}

	impl Any {
	/// Returns true if the boxed type is the same as `T`.
	///
	/// # Examples
	///
	/// ```
	/// use std::any::Any;
	///
	/// fn is_string(s: &Any) {
	/// if s.is::<String>() {
	/// println!("It's a string!");
	/// } else {
	/// println!("Not a string...");
	/// }
	/// }
	///
	/// fn main() {
	/// is_string(&0);
	/// is_string(&"cookie monster".to_owned());
	/// }
	/// ```
	#[stable(feature = "rust1", since = "1.0.0")]
	#[inline]
	pub fn is<T: Any>(&self) -> bool {
	// Get TypeId of the type this function is instantiated with
	let t = TypeId::of::<T>();

	// Get TypeId of the type in the trait object
	let boxed = self.get_type_id();

	// Compare both TypeIds on equality
	t == boxed
	}

	/// Returns some reference to the boxed value if it is of type `T`, or
	/// `None` if it isn't.
	///
	/// # Examples
	///
	/// ```
	/// use std::any::Any;
	///
	/// fn print_if_string(s: &Any) {
	/// if let Some(string) = s.downcast_ref::<String>() {
	/// println!("It's a string({}): '{}'", string.len(), string);
	/// } else {
	/// println!("Not a string...");
	/// }
	/// }
	///
	/// fn main() {
	/// print_if_string(&0);
	/// print_if_string(&"cookie monster".to_owned());
	/// }
	/// ```
	#[stable(feature = "rust1", since = "1.0.0")]
	#[inline]
	pub fn downcast_ref<T: Any>(&self) -> Option<&T> {
	if self.is::<T>() {
	unsafe {
	// Get the raw representation of the trait object
	let to: TraitObject = transmute(self);

	// Extract the data pointer
	Some(&(to.data as const T))
	}
	} else {
	None
	}
	}

	/// Returns some mutable reference to the boxed value if it is of type `T`, or
	/// `None` if it isn't.
	///
	/// # Examples
	///
	/// ```
	/// use std::any::Any;
	///
	/// fn modify_if_u32(s: &mut Any) {
	/// if let Some(num) = s.downcast_mut::<u32>() {
	/// *num = 42;
	/// }
	/// }
	///
	/// fn main() {
	/// let mut x = 10u32;
	/// let mut s = "starlord".to_owned();
	///
	/// modify_if_u32(&mut x);
	/// modify_if_u32(&mut s);
	///
	/// assert_eq!(x, 42);
	/// assert_eq!(&s, "starlord");
	/// }
	/// ```
	#[stable(feature = "rust1", since = "1.0.0")]
	#[inline]
	pub fn downcast_mut<T: Any>(&mut self) -> Option<&mut T> {
	if self.is::<T>() {
	unsafe {
	// Get the raw representation of the trait object
	let to: TraitObject = transmute(self);

	// Extract the data pointer
	Some(&mut (to.data as const T as *mut T))
	}
	} else {
	None
	}
	}
	}

	impl Any+Send {
	/// Forwards to the method defined on the type `Any`.
	///
	/// # Examples
	///
	/// ```
	/// use std::any::Any;
	///
	/// fn is_string(s: &(Any + Send)) {
	/// if s.is::<String>() {
	/// println!("It's a string!");
	/// } else {
	/// println!("Not a string...");
	/// }
	/// }
	///
	/// fn main() {
	/// is_string(&0);
	/// is_string(&"cookie monster".to_owned());
	/// }
	/// ```
	#[stable(feature = "rust1", since = "1.0.0")]
	#[inline]
	pub fn is<T: Any>(&self) -> bool {
	Any::is::<T>(self)
	}

	/// Forwards to the method defined on the type `Any`.
	///
	/// # Examples
	///
	/// ```
	/// use std::any::Any;
	///
	/// fn print_if_string(s: &(Any + Send)) {
	/// if let Some(string) = s.downcast_ref::<String>() {
	/// println!("It's a string({}): '{}'", string.len(), string);
	/// } else {
	/// println!("Not a string...");
	/// }
	/// }
	///
	/// fn main() {
	/// print_if_string(&0);
	/// print_if_string(&"cookie monster".to_owned());
	/// }
	/// ```
	#[stable(feature = "rust1", since = "1.0.0")]
	#[inline]
	pub fn downcast_ref<T: Any>(&self) -> Option<&T> {
	Any::downcast_ref::<T>(self)
	}

	/// Forwards to the method defined on the type `Any`.
	///
	/// # Examples
	///
	/// ```
	/// use std::any::Any;
	///
	/// fn modify_if_u32(s: &mut (Any+ Send)) {
	/// if let Some(num) = s.downcast_mut::<u32>() {
	/// *num = 42;
	/// }
	/// }
	///
	/// fn main() {
	/// let mut x = 10u32;
	/// let mut s = "starlord".to_owned();
	///
	/// modify_if_u32(&mut x);
	/// modify_if_u32(&mut s);
	///
	/// assert_eq!(x, 42);
	/// assert_eq!(&s, "starlord");
	/// }
	/// ```
	#[stable(feature = "rust1", since = "1.0.0")]
	#[inline]
	pub fn downcast_mut<T: Any>(&mut self) -> Option<&mut T> {
	Any::downcast_mut::<T>(self)
	}
	}


	///////////////////////////////////////////////////////////////////////////////
	// TypeID and its methods
	///////////////////////////////////////////////////////////////////////////////

	/// A `TypeId` represents a globally unique identifier for a type.
	///
	/// Each `TypeId` is an opaque object which does not allow inspection of what's
	/// inside but does allow basic operations such as cloning, comparison,
	/// printing, and showing.
	///
	/// A `TypeId` is currently only available for types which ascribe to `'static`,
	/// but this limitation may be removed in the future.
	#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
	#[stable(feature = "rust1", since = "1.0.0")]
	pub struct TypeId {
	t: u64,
	}

	impl TypeId {
	/// Returns the `TypeId` of the type this generic function has been
	/// instantiated with.
	///
	/// # Examples
	///
	/// ```
	/// #![feature(get_type_id)]
	///
	/// use std::any::{Any, TypeId};
	///
	/// fn is_string(s: &Any) -> bool {
	/// TypeId::of::<String>() == s.get_type_id()
	/// }
	///
	/// fn main() {
	/// assert_eq!(is_string(&0), false);
	/// assert_eq!(is_string(&"cookie monster".to_owned()), true);
	/// }
	/// ```
	#[stable(feature = "rust1", since = "1.0.0")]
	pub fn of<T: ?Sized + Reflect + 'static>() -> TypeId {
	TypeId {
	t: unsafe { intrinsics::type_id::<T>() },
	}
	}
	}