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Diffstat (limited to 'src/libcore/ptr/non_null.rs')
| -rw-r--r-- | src/libcore/ptr/non_null.rs | 353 |
1 files changed, 0 insertions, 353 deletions
diff --git a/src/libcore/ptr/non_null.rs b/src/libcore/ptr/non_null.rs deleted file mode 100644 index 9f843a57099..00000000000 --- a/src/libcore/ptr/non_null.rs +++ /dev/null @@ -1,353 +0,0 @@ -use crate::cmp::Ordering; -use crate::convert::From; -use crate::fmt; -use crate::hash; -use crate::marker::Unsize; -use crate::mem; -use crate::ops::{CoerceUnsized, DispatchFromDyn}; -use crate::ptr::Unique; -use crate::slice::SliceIndex; - -/// `*mut T` but non-zero and covariant. -/// -/// This is often the correct thing to use when building data structures using -/// raw pointers, but is ultimately more dangerous to use because of its additional -/// properties. If you're not sure if you should use `NonNull<T>`, just use `*mut T`! -/// -/// Unlike `*mut T`, the pointer must always be non-null, even if the pointer -/// is never dereferenced. This is so that enums may use this forbidden value -/// as a discriminant -- `Option<NonNull<T>>` has the same size as `*mut T`. -/// However the pointer may still dangle if it isn't dereferenced. -/// -/// Unlike `*mut T`, `NonNull<T>` is covariant over `T`. If this is incorrect -/// for your use case, you should include some [`PhantomData`] in your type to -/// provide invariance, such as `PhantomData<Cell<T>>` or `PhantomData<&'a mut T>`. -/// Usually this won't be necessary; covariance is correct for most safe abstractions, -/// such as `Box`, `Rc`, `Arc`, `Vec`, and `LinkedList`. This is the case because they -/// provide a public API that follows the normal shared XOR mutable rules of Rust. -/// -/// Notice that `NonNull<T>` has a `From` instance for `&T`. However, this does -/// not change the fact that mutating through a (pointer derived from a) shared -/// reference is undefined behavior unless the mutation happens inside an -/// [`UnsafeCell<T>`]. The same goes for creating a mutable reference from a shared -/// reference. When using this `From` instance without an `UnsafeCell<T>`, -/// it is your responsibility to ensure that `as_mut` is never called, and `as_ptr` -/// is never used for mutation. -/// -/// [`PhantomData`]: ../marker/struct.PhantomData.html -/// [`UnsafeCell<T>`]: ../cell/struct.UnsafeCell.html -#[stable(feature = "nonnull", since = "1.25.0")] -#[repr(transparent)] -#[rustc_layout_scalar_valid_range_start(1)] -#[rustc_nonnull_optimization_guaranteed] -pub struct NonNull<T: ?Sized> { - pointer: *const T, -} - -/// `NonNull` pointers are not `Send` because the data they reference may be aliased. -// N.B., this impl is unnecessary, but should provide better error messages. -#[stable(feature = "nonnull", since = "1.25.0")] -impl<T: ?Sized> !Send for NonNull<T> {} - -/// `NonNull` pointers are not `Sync` because the data they reference may be aliased. -// N.B., this impl is unnecessary, but should provide better error messages. -#[stable(feature = "nonnull", since = "1.25.0")] -impl<T: ?Sized> !Sync for NonNull<T> {} - -impl<T: Sized> NonNull<T> { - /// Creates a new `NonNull` that is dangling, but well-aligned. - /// - /// This is useful for initializing types which lazily allocate, like - /// `Vec::new` does. - /// - /// Note that the pointer value may potentially represent a valid pointer to - /// a `T`, which means this must not be used as a "not yet initialized" - /// sentinel value. Types that lazily allocate must track initialization by - /// some other means. - #[stable(feature = "nonnull", since = "1.25.0")] - #[rustc_const_stable(feature = "const_nonnull_dangling", since = "1.32.0")] - #[inline] - pub const fn dangling() -> Self { - // SAFETY: mem::align_of() returns a non-zero usize which is then casted - // to a *mut T. Therefore, `ptr` is not null and the conditions for - // calling new_unchecked() are respected. - unsafe { - let ptr = mem::align_of::<T>() as *mut T; - NonNull::new_unchecked(ptr) - } - } -} - -impl<T: ?Sized> NonNull<T> { - /// Creates a new `NonNull`. - /// - /// # Safety - /// - /// `ptr` must be non-null. - #[stable(feature = "nonnull", since = "1.25.0")] - #[rustc_const_stable(feature = "const_nonnull_new_unchecked", since = "1.32.0")] - #[inline] - pub const unsafe fn new_unchecked(ptr: *mut T) -> Self { - // SAFETY: the caller must guarantee that `ptr` is non-null. - unsafe { NonNull { pointer: ptr as _ } } - } - - /// Creates a new `NonNull` if `ptr` is non-null. - #[stable(feature = "nonnull", since = "1.25.0")] - #[inline] - pub fn new(ptr: *mut T) -> Option<Self> { - if !ptr.is_null() { - // SAFETY: The pointer is already checked and is not null - Some(unsafe { Self::new_unchecked(ptr) }) - } else { - None - } - } - - /// Acquires the underlying `*mut` pointer. - #[stable(feature = "nonnull", since = "1.25.0")] - #[rustc_const_stable(feature = "const_nonnull_as_ptr", since = "1.32.0")] - #[inline] - pub const fn as_ptr(self) -> *mut T { - self.pointer as *mut T - } - - /// Dereferences the content. - /// - /// The resulting lifetime is bound to self so this behaves "as if" - /// it were actually an instance of T that is getting borrowed. If a longer - /// (unbound) lifetime is needed, use `&*my_ptr.as_ptr()`. - #[stable(feature = "nonnull", since = "1.25.0")] - #[inline] - pub unsafe fn as_ref(&self) -> &T { - // SAFETY: the caller must guarantee that `self` meets all the - // requirements for a reference. - unsafe { &*self.as_ptr() } - } - - /// Mutably dereferences the content. - /// - /// The resulting lifetime is bound to self so this behaves "as if" - /// it were actually an instance of T that is getting borrowed. If a longer - /// (unbound) lifetime is needed, use `&mut *my_ptr.as_ptr()`. - #[stable(feature = "nonnull", since = "1.25.0")] - #[inline] - pub unsafe fn as_mut(&mut self) -> &mut T { - // SAFETY: the caller must guarantee that `self` meets all the - // requirements for a mutable reference. - unsafe { &mut *self.as_ptr() } - } - - /// Casts to a pointer of another type. - #[stable(feature = "nonnull_cast", since = "1.27.0")] - #[rustc_const_stable(feature = "const_nonnull_cast", since = "1.32.0")] - #[inline] - pub const fn cast<U>(self) -> NonNull<U> { - // SAFETY: `self` is a `NonNull` pointer which is necessarily non-null - unsafe { NonNull::new_unchecked(self.as_ptr() as *mut U) } - } -} - -impl<T> NonNull<[T]> { - /// Creates a non-null raw slice from a thin pointer and a length. - /// - /// The `len` argument is the number of **elements**, not the number of bytes. - /// - /// This function is safe, but dereferencing the return value is unsafe. - /// See the documentation of [`slice::from_raw_parts`] for slice safety requirements. - /// - /// [`slice::from_raw_parts`]: ../../std/slice/fn.from_raw_parts.html - /// - /// # Examples - /// - /// ```rust - /// #![feature(nonnull_slice_from_raw_parts)] - /// - /// use std::ptr::NonNull; - /// - /// // create a slice pointer when starting out with a pointer to the first element - /// let mut x = [5, 6, 7]; - /// let nonnull_pointer = NonNull::new(x.as_mut_ptr()).unwrap(); - /// let slice = NonNull::slice_from_raw_parts(nonnull_pointer, 3); - /// assert_eq!(unsafe { slice.as_ref()[2] }, 7); - /// ``` - /// - /// (Note that this example artificially demonstrates a use of this method, - /// but `let slice = NonNull::from(&x[..]);` would be a better way to write code like this.) - #[unstable(feature = "nonnull_slice_from_raw_parts", issue = "71941")] - #[rustc_const_unstable(feature = "const_nonnull_slice_from_raw_parts", issue = "71941")] - #[inline] - pub const fn slice_from_raw_parts(data: NonNull<T>, len: usize) -> Self { - // SAFETY: `data` is a `NonNull` pointer which is necessarily non-null - unsafe { Self::new_unchecked(super::slice_from_raw_parts_mut(data.as_ptr(), len)) } - } - - /// Returns the length of a non-null raw slice. - /// - /// The returned value is the number of **elements**, not the number of bytes. - /// - /// This function is safe, even when the non-null raw slice cannot be dereferenced to a slice - /// because the pointer does not have a valid address. - /// - /// # Examples - /// - /// ```rust - /// #![feature(slice_ptr_len, nonnull_slice_from_raw_parts)] - /// use std::ptr::NonNull; - /// - /// let slice: NonNull<[i8]> = NonNull::slice_from_raw_parts(NonNull::dangling(), 3); - /// assert_eq!(slice.len(), 3); - /// ``` - #[unstable(feature = "slice_ptr_len", issue = "71146")] - #[rustc_const_unstable(feature = "const_slice_ptr_len", issue = "71146")] - #[inline] - pub const fn len(self) -> usize { - self.as_ptr().len() - } - - /// Returns a non-null pointer to the slice's buffer. - /// - /// # Examples - /// - /// ```rust - /// #![feature(slice_ptr_get, nonnull_slice_from_raw_parts)] - /// use std::ptr::NonNull; - /// - /// let slice: NonNull<[i8]> = NonNull::slice_from_raw_parts(NonNull::dangling(), 3); - /// assert_eq!(slice.as_non_null_ptr(), NonNull::new(1 as *mut i8).unwrap()); - /// ``` - #[inline] - #[unstable(feature = "slice_ptr_get", issue = "74265")] - #[rustc_const_unstable(feature = "slice_ptr_get", issue = "74265")] - pub const fn as_non_null_ptr(self) -> NonNull<T> { - // SAFETY: We know `self` is non-null. - unsafe { NonNull::new_unchecked(self.as_ptr().as_mut_ptr()) } - } - - /// Returns a raw pointer to an element or subslice, without doing bounds - /// checking. - /// - /// Calling this method with an out-of-bounds index or when `self` is not dereferencable - /// is *[undefined behavior]* even if the resulting pointer is not used. - /// - /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html - /// - /// # Examples - /// - /// ``` - /// #![feature(slice_ptr_get, nonnull_slice_from_raw_parts)] - /// use std::ptr::NonNull; - /// - /// let x = &mut [1, 2, 4]; - /// let x = NonNull::slice_from_raw_parts(NonNull::new(x.as_mut_ptr()).unwrap(), x.len()); - /// - /// unsafe { - /// assert_eq!(x.get_unchecked_mut(1).as_ptr(), x.as_non_null_ptr().as_ptr().add(1)); - /// } - /// ``` - #[unstable(feature = "slice_ptr_get", issue = "74265")] - #[inline] - pub unsafe fn get_unchecked_mut<I>(self, index: I) -> NonNull<I::Output> - where - I: SliceIndex<[T]>, - { - // SAFETY: the caller ensures that `self` is dereferencable and `index` in-bounds. - // As a consequence, the resulting pointer cannot be NULL. - unsafe { NonNull::new_unchecked(self.as_ptr().get_unchecked_mut(index)) } - } -} - -#[stable(feature = "nonnull", since = "1.25.0")] -impl<T: ?Sized> Clone for NonNull<T> { - #[inline] - fn clone(&self) -> Self { - *self - } -} - -#[stable(feature = "nonnull", since = "1.25.0")] -impl<T: ?Sized> Copy for NonNull<T> {} - -#[unstable(feature = "coerce_unsized", issue = "27732")] -impl<T: ?Sized, U: ?Sized> CoerceUnsized<NonNull<U>> for NonNull<T> where T: Unsize<U> {} - -#[unstable(feature = "dispatch_from_dyn", issue = "none")] -impl<T: ?Sized, U: ?Sized> DispatchFromDyn<NonNull<U>> for NonNull<T> where T: Unsize<U> {} - -#[stable(feature = "nonnull", since = "1.25.0")] -impl<T: ?Sized> fmt::Debug for NonNull<T> { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - fmt::Pointer::fmt(&self.as_ptr(), f) - } -} - -#[stable(feature = "nonnull", since = "1.25.0")] -impl<T: ?Sized> fmt::Pointer for NonNull<T> { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - fmt::Pointer::fmt(&self.as_ptr(), f) - } -} - -#[stable(feature = "nonnull", since = "1.25.0")] -impl<T: ?Sized> Eq for NonNull<T> {} - -#[stable(feature = "nonnull", since = "1.25.0")] -impl<T: ?Sized> PartialEq for NonNull<T> { - #[inline] - fn eq(&self, other: &Self) -> bool { - self.as_ptr() == other.as_ptr() - } -} - -#[stable(feature = "nonnull", since = "1.25.0")] -impl<T: ?Sized> Ord for NonNull<T> { - #[inline] - fn cmp(&self, other: &Self) -> Ordering { - self.as_ptr().cmp(&other.as_ptr()) - } -} - -#[stable(feature = "nonnull", since = "1.25.0")] -impl<T: ?Sized> PartialOrd for NonNull<T> { - #[inline] - fn partial_cmp(&self, other: &Self) -> Option<Ordering> { - self.as_ptr().partial_cmp(&other.as_ptr()) - } -} - -#[stable(feature = "nonnull", since = "1.25.0")] -impl<T: ?Sized> hash::Hash for NonNull<T> { - #[inline] - fn hash<H: hash::Hasher>(&self, state: &mut H) { - self.as_ptr().hash(state) - } -} - -#[unstable(feature = "ptr_internals", issue = "none")] -impl<T: ?Sized> From<Unique<T>> for NonNull<T> { - #[inline] - fn from(unique: Unique<T>) -> Self { - // SAFETY: A Unique pointer cannot be null, so the conditions for - // new_unchecked() are respected. - unsafe { NonNull::new_unchecked(unique.as_ptr()) } - } -} - -#[stable(feature = "nonnull", since = "1.25.0")] -impl<T: ?Sized> From<&mut T> for NonNull<T> { - #[inline] - fn from(reference: &mut T) -> Self { - // SAFETY: A mutable reference cannot be null. - unsafe { NonNull { pointer: reference as *mut T } } - } -} - -#[stable(feature = "nonnull", since = "1.25.0")] -impl<T: ?Sized> From<&T> for NonNull<T> { - #[inline] - fn from(reference: &T) -> Self { - // SAFETY: A reference cannot be null, so the conditions for - // new_unchecked() are respected. - unsafe { NonNull { pointer: reference as *const T } } - } -} |