164 lines
4.7 KiB
Rust
164 lines
4.7 KiB
Rust
// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! Unsafe casting functions
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use sys;
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use unstable;
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pub mod rusti {
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#[abi = "rust-intrinsic"]
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#[link_name = "rusti"]
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pub extern "rust-intrinsic" {
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fn forget<T>(+x: T);
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fn transmute<T,U>(e: T) -> U;
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}
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}
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/// Casts the value at `src` to U. The two types must have the same length.
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pub unsafe fn transmute_copy<T, U>(src: &T) -> U {
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let mut dest: U = unstable::intrinsics::init();
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{
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let dest_ptr: *mut u8 = rusti::transmute(&mut dest);
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let src_ptr: *u8 = rusti::transmute(src);
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unstable::intrinsics::memmove64(dest_ptr,
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src_ptr,
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sys::size_of::<U>() as u64);
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}
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dest
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}
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/**
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* Move a thing into the void
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*
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* The forget function will take ownership of the provided value but neglect
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* to run any required cleanup or memory-management operations on it. This
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* can be used for various acts of magick, particularly when using
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* reinterpret_cast on pointer types.
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*/
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#[inline(always)]
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pub unsafe fn forget<T>(thing: T) { rusti::forget(thing); }
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/**
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* Force-increment the reference count on a shared box. If used
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* carelessly, this can leak the box. Use this in conjunction with transmute
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* and/or reinterpret_cast when such calls would otherwise scramble a box's
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* reference count
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*/
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pub unsafe fn bump_box_refcount<T>(t: @T) { forget(t); }
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/**
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* Transform a value of one type into a value of another type.
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* Both types must have the same size and alignment.
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*
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* # Example
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*
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* assert!(transmute("L") == ~[76u8, 0u8]);
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*/
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#[inline(always)]
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pub unsafe fn transmute<L, G>(thing: L) -> G {
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rusti::transmute(thing)
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}
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/// Coerce an immutable reference to be mutable.
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#[inline(always)]
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pub unsafe fn transmute_mut<'a,T>(ptr: &'a T) -> &'a mut T { transmute(ptr) }
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/// Coerce a mutable reference to be immutable.
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#[inline(always)]
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pub unsafe fn transmute_immut<'a,T>(ptr: &'a mut T) -> &'a T {
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transmute(ptr)
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}
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/// Coerce a borrowed pointer to have an arbitrary associated region.
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#[inline(always)]
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pub unsafe fn transmute_region<'a,'b,T>(ptr: &'a T) -> &'b T {
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transmute(ptr)
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}
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/// Coerce an immutable reference to be mutable.
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#[inline(always)]
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pub unsafe fn transmute_mut_unsafe<T>(ptr: *const T) -> *mut T {
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transmute(ptr)
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}
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/// Coerce an immutable reference to be mutable.
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#[inline(always)]
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pub unsafe fn transmute_immut_unsafe<T>(ptr: *const T) -> *T {
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transmute(ptr)
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}
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/// Coerce a borrowed mutable pointer to have an arbitrary associated region.
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#[inline(always)]
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pub unsafe fn transmute_mut_region<'a,'b,T>(ptr: &'a mut T) -> &'b mut T {
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transmute(ptr)
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}
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/// Transforms lifetime of the second pointer to match the first.
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#[inline(always)]
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pub unsafe fn copy_lifetime<'a,S,T>(_ptr: &'a S, ptr: &T) -> &'a T {
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transmute_region(ptr)
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}
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/// Transforms lifetime of the second pointer to match the first.
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#[inline(always)]
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pub unsafe fn copy_lifetime_vec<'a,S,T>(_ptr: &'a [S], ptr: &T) -> &'a T {
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transmute_region(ptr)
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}
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/****************************************************************************
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* Tests
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****************************************************************************/
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#[cfg(test)]
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mod tests {
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use cast::{bump_box_refcount, transmute};
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#[test]
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fn test_transmute_copy() {
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assert!(1u == unsafe { ::cast::transmute_copy(&1) });
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}
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#[test]
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fn test_bump_box_refcount() {
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unsafe {
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let box = @~"box box box"; // refcount 1
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bump_box_refcount(box); // refcount 2
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let ptr: *int = transmute(box); // refcount 2
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let _box1: @~str = ::cast::transmute_copy(&ptr);
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let _box2: @~str = ::cast::transmute_copy(&ptr);
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assert!(*_box1 == ~"box box box");
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assert!(*_box2 == ~"box box box");
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// Will destroy _box1 and _box2. Without the bump, this would
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// use-after-free. With too many bumps, it would leak.
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}
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}
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#[test]
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fn test_transmute() {
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use managed::raw::BoxRepr;
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unsafe {
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let x = @100u8;
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let x: *BoxRepr = transmute(x);
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assert!((*x).data == 100);
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let _x: @int = transmute(x);
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}
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}
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#[test]
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fn test_transmute2() {
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unsafe {
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assert!(~[76u8, 0u8] == transmute(~"L"));
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}
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}
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}
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