1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126

//! [![github]](https://github.com/dtolnay/dyn-clone) [![crates-io]](https://crates.io/crates/dyn-clone) [![docs-rs]](https://docs.rs/dyn-clone)
//!
//! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
//! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust
//! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logoColor=white&logo=data:image/svg+xml;base64,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
//!
//! <br>
//!
//! This crate provides a [`DynClone`] trait that can be used in trait objects,
//! and a [`clone_box`] function that can clone any sized or dynamically sized
//! implementation of `DynClone`. Types that implement the standard library's
//! [`std::clone::Clone`] trait are automatically usable by a `DynClone` trait
//! object.
//! 
//! [`DynClone`]: trait.DynClone.html
//! [`clone_box`]: fn.clone_box.html
//! [`std::clone::Clone`]: https://doc.rust-lang.org/std/clone/trait.Clone.html
//! 
//! # Example
//! 
//! ```
//! use dyn_clone::DynClone;
//!
//! trait MyTrait: DynClone {
//!     fn recite(&self);
//! }
//! 
//! impl MyTrait for String {
//!     fn recite(&self) {
//!         println!("{} ♫", self);
//!     }
//! }
//! 
//! fn main() {
//!     let line = "The slithy structs did gyre and gimble the namespace";
//! 
//!     // Build a trait object holding a String.
//!     // This requires String to implement MyTrait and std::clone::Clone.
//!     let x: Box<dyn MyTrait> = Box::new(String::from(line));
//! 
//!     x.recite();
//! 
//!     // The type of x2 is a Box<dyn MyTrait> cloned from x.
//!     let x2 = dyn_clone::clone_box(&*x);
//! 
//!     x2.recite();
//! }
//! ```
//!
//! This crate includes a macro for concisely implementing `impl
//! std::clone::Clone for Box<dyn MyTrait>` in terms of `dyn_clone::clone_box`.
//!
//! ```
//! # use dyn_clone::DynClone;
//! #
//! // As before.
//! trait MyTrait: DynClone {
//!     /* ... */
//! }
//!
//! dyn_clone::clone_trait_object!(MyTrait);
//!
//! // Now data structures containing Box<dyn MyTrait> can derive Clone:
//! #[derive(Clone)]
//! struct Container {
//!     trait_object: Box<dyn MyTrait>,
//! }
//! ```

#![doc(html_root_url = "https://docs.rs/dyn_clone/1.0.2")]
#![no_std]

extern crate alloc;

#[macro_use]
mod macros;

#[doc(hidden)]
pub mod private {
    pub use alloc::boxed::Box;
    pub use core::clone::Clone;
}

/// This trait is implemented by any type that implements [`std::clone::Clone`].
///
/// [`std::clone::Clone`]: https://doc.rust-lang.org/std/clone/trait.Clone.html
pub trait DynClone {
    // Not public API
    #[doc(hidden)]
    unsafe fn clone_box(&self) -> *mut ();
}

use alloc::boxed::Box;

pub fn clone<T>(t: &T) -> T
where
    T: DynClone,
{
    unsafe {
        *Box::from_raw(<T as DynClone>::clone_box(t) as *mut T)
    }
}

pub fn clone_box<T>(t: &T) -> Box<T>
where
    T: ?Sized + DynClone,
{
    let mut fat_ptr = t as *const T;
    unsafe {
        let data_ptr = &mut fat_ptr as *mut *const T as *mut *mut ();
        assert_eq!(*data_ptr as *const (), t as *const T as *const ());
        *data_ptr = <T as DynClone>::clone_box(t);
    }
    unsafe {
        Box::from_raw(fat_ptr as *mut T)
    }
}

impl<T> DynClone for T
where
    T: core::clone::Clone,
{
    unsafe fn clone_box(&self) -> *mut () {
        Box::into_raw(Box::new(self.clone())) as *mut ()
    }
}