8497c428e5
Having the primitive and module docs derived from the same source causes problems, primarily that they can't contain hyperlinks cross-referencing each other. This crates dedicated private modules in `std` to document the primitive types, then for all primitives that have a corresponding module, puts hyperlinks in moth the primitive docs and the module docs cross-linking each other. This should help clear up confusion when readers find themselves on the wrong page.
496 lines
15 KiB
Rust
496 lines
15 KiB
Rust
// Copyright 2012-2014 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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// FIXME: talk about offset, copy_memory, copy_nonoverlapping_memory
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//! Raw, unsafe pointers, `*const T`, and `*mut T`
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//!
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//! *[See also the pointer primitive types](../primitive.pointer.html).*
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#![stable(feature = "rust1", since = "1.0.0")]
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use mem;
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use clone::Clone;
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use intrinsics;
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use ops::Deref;
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use core::fmt;
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use option::Option::{self, Some, None};
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use marker::{PhantomData, Send, Sized, Sync};
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use nonzero::NonZero;
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use cmp::{PartialEq, Eq, Ord, PartialOrd};
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use cmp::Ordering::{self, Less, Equal, Greater};
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// FIXME #19649: intrinsic docs don't render, so these have no docs :(
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#[stable(feature = "rust1", since = "1.0.0")]
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pub use intrinsics::copy_nonoverlapping;
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#[stable(feature = "rust1", since = "1.0.0")]
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pub use intrinsics::copy;
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#[stable(feature = "rust1", since = "1.0.0")]
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pub use intrinsics::write_bytes;
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/// Creates a null raw pointer.
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///
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/// # Examples
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///
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/// ```
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/// use std::ptr;
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///
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/// let p: *const i32 = ptr::null();
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/// assert!(p.is_null());
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/// ```
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#[inline]
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn null<T>() -> *const T { 0 as *const T }
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/// Creates a null mutable raw pointer.
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///
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/// # Examples
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///
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/// ```
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/// use std::ptr;
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///
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/// let p: *mut i32 = ptr::null_mut();
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/// assert!(p.is_null());
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/// ```
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#[inline]
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn null_mut<T>() -> *mut T { 0 as *mut T }
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/// Swaps the values at two mutable locations of the same type, without
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/// deinitialising either. They may overlap, unlike `mem::swap` which is
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/// otherwise equivalent.
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///
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/// # Safety
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///
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/// This is only unsafe because it accepts a raw pointer.
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#[inline]
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#[stable(feature = "rust1", since = "1.0.0")]
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pub unsafe fn swap<T>(x: *mut T, y: *mut T) {
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// Give ourselves some scratch space to work with
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let mut tmp: T = mem::uninitialized();
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// Perform the swap
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copy_nonoverlapping(x, &mut tmp, 1);
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copy(y, x, 1); // `x` and `y` may overlap
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copy_nonoverlapping(&tmp, y, 1);
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// y and t now point to the same thing, but we need to completely forget `tmp`
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// because it's no longer relevant.
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mem::forget(tmp);
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}
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/// Replaces the value at `dest` with `src`, returning the old
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/// value, without dropping either.
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///
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/// # Safety
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///
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/// This is only unsafe because it accepts a raw pointer.
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/// Otherwise, this operation is identical to `mem::replace`.
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#[inline]
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#[stable(feature = "rust1", since = "1.0.0")]
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pub unsafe fn replace<T>(dest: *mut T, mut src: T) -> T {
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mem::swap(mem::transmute(dest), &mut src); // cannot overlap
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src
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}
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/// Reads the value from `src` without moving it. This leaves the
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/// memory in `src` unchanged.
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///
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/// # Safety
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///
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/// Beyond accepting a raw pointer, this is unsafe because it semantically
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/// moves the value out of `src` without preventing further usage of `src`.
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/// If `T` is not `Copy`, then care must be taken to ensure that the value at
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/// `src` is not used before the data is overwritten again (e.g. with `write`,
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/// `zero_memory`, or `copy_memory`). Note that `*src = foo` counts as a use
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/// because it will attempt to drop the value previously at `*src`.
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#[inline(always)]
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#[stable(feature = "rust1", since = "1.0.0")]
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pub unsafe fn read<T>(src: *const T) -> T {
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let mut tmp: T = mem::uninitialized();
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copy_nonoverlapping(src, &mut tmp, 1);
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tmp
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}
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/// Reads the value from `src` and nulls it out without dropping it.
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///
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/// # Safety
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///
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/// This is unsafe for the same reasons that `read` is unsafe.
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#[inline(always)]
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#[unstable(feature = "read_and_zero",
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reason = "may play a larger role in std::ptr future extensions")]
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pub unsafe fn read_and_zero<T>(dest: *mut T) -> T {
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// Copy the data out from `dest`:
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let tmp = read(&*dest);
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// Now zero out `dest`:
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write_bytes(dest, 0, 1);
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tmp
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}
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/// Variant of read_and_zero that writes the specific drop-flag byte
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/// (which may be more appropriate than zero).
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#[inline(always)]
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#[unstable(feature = "filling_drop",
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reason = "may play a larger role in std::ptr future extensions")]
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pub unsafe fn read_and_drop<T>(dest: *mut T) -> T {
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// Copy the data out from `dest`:
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let tmp = read(&*dest);
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// Now mark `dest` as dropped:
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write_bytes(dest, mem::POST_DROP_U8, 1);
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tmp
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}
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/// Overwrites a memory location with the given value without reading or
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/// dropping the old value.
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///
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/// # Safety
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///
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/// Beyond accepting a raw pointer, this operation is unsafe because it does
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/// not drop the contents of `dst`. This could leak allocations or resources,
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/// so care must be taken not to overwrite an object that should be dropped.
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///
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/// This is appropriate for initializing uninitialized memory, or overwriting
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/// memory that has previously been `read` from.
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#[inline]
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#[stable(feature = "rust1", since = "1.0.0")]
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pub unsafe fn write<T>(dst: *mut T, src: T) {
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intrinsics::move_val_init(&mut *dst, src)
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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#[lang = "const_ptr"]
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impl<T: ?Sized> *const T {
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/// Returns true if the pointer is null.
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn is_null(self) -> bool where T: Sized {
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self == 0 as *const T
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}
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/// Returns `None` if the pointer is null, or else returns a reference to
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/// the value wrapped in `Some`.
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///
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/// # Safety
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///
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/// While this method and its mutable counterpart are useful for
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/// null-safety, it is important to note that this is still an unsafe
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/// operation because the returned value could be pointing to invalid
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/// memory.
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#[unstable(feature = "ptr_as_ref",
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reason = "Option is not clearly the right return type, and we \
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may want to tie the return lifetime to a borrow of \
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the raw pointer")]
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#[inline]
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pub unsafe fn as_ref<'a>(&self) -> Option<&'a T> where T: Sized {
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if self.is_null() {
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None
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} else {
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Some(&**self)
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}
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}
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/// Calculates the offset from a pointer. `count` is in units of T; e.g. a
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/// `count` of 3 represents a pointer offset of `3 * sizeof::<T>()` bytes.
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///
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/// # Safety
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///
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/// Both the starting and resulting pointer must be either in bounds or one
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/// byte past the end of an allocated object. If either pointer is out of
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/// bounds or arithmetic overflow occurs then
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/// any further use of the returned value will result in undefined behavior.
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub unsafe fn offset(self, count: isize) -> *const T where T: Sized {
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intrinsics::offset(self, count)
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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#[lang = "mut_ptr"]
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impl<T: ?Sized> *mut T {
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/// Returns true if the pointer is null.
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn is_null(self) -> bool where T: Sized {
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self == 0 as *mut T
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}
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/// Returns `None` if the pointer is null, or else returns a reference to
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/// the value wrapped in `Some`.
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///
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/// # Safety
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///
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/// While this method and its mutable counterpart are useful for
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/// null-safety, it is important to note that this is still an unsafe
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/// operation because the returned value could be pointing to invalid
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/// memory.
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#[unstable(feature = "ptr_as_ref",
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reason = "Option is not clearly the right return type, and we \
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may want to tie the return lifetime to a borrow of \
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the raw pointer")]
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#[inline]
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pub unsafe fn as_ref<'a>(&self) -> Option<&'a T> where T: Sized {
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if self.is_null() {
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None
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} else {
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Some(&**self)
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}
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}
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/// Calculates the offset from a pointer. `count` is in units of T; e.g. a
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/// `count` of 3 represents a pointer offset of `3 * sizeof::<T>()` bytes.
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///
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/// # Safety
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///
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/// The offset must be in-bounds of the object, or one-byte-past-the-end.
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/// Otherwise `offset` invokes Undefined Behaviour, regardless of whether
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/// the pointer is used.
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub unsafe fn offset(self, count: isize) -> *mut T where T: Sized {
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intrinsics::offset(self, count) as *mut T
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}
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/// Returns `None` if the pointer is null, or else returns a mutable
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/// reference to the value wrapped in `Some`.
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///
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/// # Safety
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///
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/// As with `as_ref`, this is unsafe because it cannot verify the validity
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/// of the returned pointer.
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#[unstable(feature = "ptr_as_ref",
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reason = "return value does not necessarily convey all possible \
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information")]
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#[inline]
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pub unsafe fn as_mut<'a>(&self) -> Option<&'a mut T> where T: Sized {
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if self.is_null() {
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None
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} else {
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Some(&mut **self)
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}
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}
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}
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// Equality for pointers
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: ?Sized> PartialEq for *const T {
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#[inline]
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fn eq(&self, other: &*const T) -> bool { *self == *other }
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: ?Sized> Eq for *const T {}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: ?Sized> PartialEq for *mut T {
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#[inline]
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fn eq(&self, other: &*mut T) -> bool { *self == *other }
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: ?Sized> Eq for *mut T {}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: ?Sized> Clone for *const T {
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#[inline]
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fn clone(&self) -> *const T {
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*self
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: ?Sized> Clone for *mut T {
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#[inline]
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fn clone(&self) -> *mut T {
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*self
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}
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}
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// Equality for extern "C" fn pointers
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mod externfnpointers {
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use mem;
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use cmp::PartialEq;
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<_R> PartialEq for extern "C" fn() -> _R {
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#[inline]
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fn eq(&self, other: &extern "C" fn() -> _R) -> bool {
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let self_: *const () = unsafe { mem::transmute(*self) };
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let other_: *const () = unsafe { mem::transmute(*other) };
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self_ == other_
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}
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}
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macro_rules! fnptreq {
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($($p:ident),*) => {
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<_R,$($p),*> PartialEq for extern "C" fn($($p),*) -> _R {
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#[inline]
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fn eq(&self, other: &extern "C" fn($($p),*) -> _R) -> bool {
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let self_: *const () = unsafe { mem::transmute(*self) };
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let other_: *const () = unsafe { mem::transmute(*other) };
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self_ == other_
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}
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}
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}
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}
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fnptreq! { A }
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fnptreq! { A,B }
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fnptreq! { A,B,C }
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fnptreq! { A,B,C,D }
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fnptreq! { A,B,C,D,E }
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}
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// Comparison for pointers
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: ?Sized> Ord for *const T {
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#[inline]
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fn cmp(&self, other: &*const T) -> Ordering {
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if self < other {
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Less
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} else if self == other {
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Equal
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} else {
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Greater
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}
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: ?Sized> PartialOrd for *const T {
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#[inline]
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fn partial_cmp(&self, other: &*const T) -> Option<Ordering> {
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Some(self.cmp(other))
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}
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#[inline]
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fn lt(&self, other: &*const T) -> bool { *self < *other }
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#[inline]
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fn le(&self, other: &*const T) -> bool { *self <= *other }
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#[inline]
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fn gt(&self, other: &*const T) -> bool { *self > *other }
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#[inline]
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fn ge(&self, other: &*const T) -> bool { *self >= *other }
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: ?Sized> Ord for *mut T {
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#[inline]
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fn cmp(&self, other: &*mut T) -> Ordering {
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if self < other {
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Less
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} else if self == other {
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Equal
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} else {
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Greater
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}
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: ?Sized> PartialOrd for *mut T {
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#[inline]
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fn partial_cmp(&self, other: &*mut T) -> Option<Ordering> {
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Some(self.cmp(other))
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}
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#[inline]
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fn lt(&self, other: &*mut T) -> bool { *self < *other }
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#[inline]
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fn le(&self, other: &*mut T) -> bool { *self <= *other }
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#[inline]
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fn gt(&self, other: &*mut T) -> bool { *self > *other }
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#[inline]
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fn ge(&self, other: &*mut T) -> bool { *self >= *other }
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}
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/// A wrapper around a raw `*mut T` that indicates that the possessor
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/// of this wrapper owns the referent. This in turn implies that the
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/// `Unique<T>` is `Send`/`Sync` if `T` is `Send`/`Sync`, unlike a raw
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/// `*mut T` (which conveys no particular ownership semantics). It
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/// also implies that the referent of the pointer should not be
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/// modified without a unique path to the `Unique` reference. Useful
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/// for building abstractions like `Vec<T>` or `Box<T>`, which
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/// internally use raw pointers to manage the memory that they own.
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#[unstable(feature = "unique", reason = "needs an RFC to flesh out design")]
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pub struct Unique<T: ?Sized> {
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pointer: NonZero<*const T>,
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// NOTE: this marker has no consequences for variance, but is necessary
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// for dropck to understand that we logically own a `T`.
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//
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// For details, see:
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// https://github.com/rust-lang/rfcs/blob/master/text/0769-sound-generic-drop.md#phantom-data
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_marker: PhantomData<T>,
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}
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/// `Unique` pointers are `Send` if `T` is `Send` because the data they
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/// reference is unaliased. Note that this aliasing invariant is
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/// unenforced by the type system; the abstraction using the
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/// `Unique` must enforce it.
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#[unstable(feature = "unique")]
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unsafe impl<T: Send + ?Sized> Send for Unique<T> { }
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/// `Unique` pointers are `Sync` if `T` is `Sync` because the data they
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/// reference is unaliased. Note that this aliasing invariant is
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/// unenforced by the type system; the abstraction using the
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/// `Unique` must enforce it.
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#[unstable(feature = "unique")]
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unsafe impl<T: Sync + ?Sized> Sync for Unique<T> { }
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#[unstable(feature = "unique")]
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impl<T: ?Sized> Unique<T> {
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/// Creates a new `Unique`.
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pub unsafe fn new(ptr: *mut T) -> Unique<T> {
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Unique { pointer: NonZero::new(ptr), _marker: PhantomData }
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}
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/// Dereferences the content.
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pub unsafe fn get(&self) -> &T {
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&**self.pointer
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}
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/// Mutably dereferences the content.
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pub unsafe fn get_mut(&mut self) -> &mut T {
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&mut ***self
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}
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}
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#[unstable(feature = "unique")]
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impl<T:?Sized> Deref for Unique<T> {
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type Target = *mut T;
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#[inline]
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fn deref<'a>(&'a self) -> &'a *mut T {
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unsafe { mem::transmute(&*self.pointer) }
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T> fmt::Pointer for Unique<T> {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
|
|
fmt::Pointer::fmt(&*self.pointer, f)
|
|
}
|
|
}
|