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// Copyright 2013 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.
#![allow(missing_doc)]
#![experimental]
//! Contains struct definitions for the layout of compiler built-in types.
//!
//! They can be used as targets of transmutes in unsafe code for manipulating
//! the raw representations directly.
//!
//! Their definition should always match the ABI defined in `rustc::back::abi`.
use mem;
/// The representation of a Rust managed box
pub struct Box<T> {
pub ref_count: uint,
pub drop_glue: fn(ptr: *mut u8),
pub prev: *mut Box<T>,
pub next: *mut Box<T>,
pub data: T,
}
/// The representation of a Rust slice
pub struct Slice<T> {
pub data: *T,
pub len: uint,
}
/// The representation of a Rust closure
pub struct Closure {
pub code: *(),
pub env: *(),
}
/// The representation of a Rust procedure (`proc()`)
pub struct Procedure {
pub code: *(),
pub env: *(),
}
/// The representation of a Rust trait object.
///
/// This struct does not have a `Repr` implementation
/// because there is no way to refer to all trait objects generically.
pub struct TraitObject {
pub vtable: *(),
pub data: *(),
}
/// This trait is meant to map equivalences between raw structs and their
/// corresponding rust values.
pub trait Repr<T> {
/// This function "unwraps" a rust value (without consuming it) into its raw
/// struct representation. This can be used to read/write different values
/// for the struct. This is a safe method because by default it does not
/// enable write-access to the fields of the return value in safe code.
#[inline]
fn repr(&self) -> T { unsafe { mem::transmute_copy(self) } }
}
impl<'a, T> Repr<Slice<T>> for &'a [T] {}
impl<'a> Repr<Slice<u8>> for &'a str {}
#[cfg(test)]
mod tests {
use super::*;
use mem;
#[test]
fn synthesize_closure() {
unsafe {
let x = 10;
let f: |int| -> int = |y| x + y;
assert_eq!(f(20), 30);
let original_closure: Closure = mem::transmute(f);
let actual_function_pointer = original_closure.code;
let environment = original_closure.env;
let new_closure = Closure {
code: actual_function_pointer,
env: environment
};
let new_f: |int| -> int = mem::transmute(new_closure);
assert_eq!(new_f(20), 30);
}
}
}
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