diff options
Diffstat (limited to 'src/libcore/ptr.rs')
| -rw-r--r-- | src/libcore/ptr.rs | 76 |
1 files changed, 76 insertions, 0 deletions
diff --git a/src/libcore/ptr.rs b/src/libcore/ptr.rs index d2830a6d00c..04480fc5d31 100644 --- a/src/libcore/ptr.rs +++ b/src/libcore/ptr.rs @@ -500,6 +500,44 @@ impl<T: ?Sized> *const T { intrinsics::arith_offset(self, count) } } + + /// Calculates the distance between two pointers. The returned value is in + /// units of T: the distance in bytes is divided by `mem::size_of::<T>()`. + /// + /// If the address different between the two pointers ia not a multiple of + /// `mem::size_of::<T>()` then the result of the division is rounded towards + /// zero. + /// + /// This function returns `None` if `T` is a zero-sized typed. + /// + /// # Examples + /// + /// Basic usage: + /// + /// ``` + /// #![feature(offset_to)] + /// + /// fn main() { + /// let a = [0; 5]; + /// let ptr1: *const i32 = &a[1]; + /// let ptr2: *const i32 = &a[3]; + /// assert_eq!(ptr1.offset_to(ptr2), Some(2)); + /// assert_eq!(ptr2.offset_to(ptr1), Some(-2)); + /// assert_eq!(unsafe { ptr1.offset(2) }, ptr2); + /// assert_eq!(unsafe { ptr2.offset(-2) }, ptr1); + /// } + /// ``` + #[unstable(feature = "offset_to", issue = "41079")] + #[inline] + pub fn offset_to(self, other: *const T) -> Option<isize> where T: Sized { + let size = mem::size_of::<T>(); + if size == 0 { + None + } else { + let diff = (other as isize).wrapping_sub(self as isize); + Some(diff / size as isize) + } + } } #[lang = "mut_ptr"] @@ -653,6 +691,44 @@ impl<T: ?Sized> *mut T { Some(&mut *self) } } + + /// Calculates the distance between two pointers. The returned value is in + /// units of T: the distance in bytes is divided by `mem::size_of::<T>()`. + /// + /// If the address different between the two pointers ia not a multiple of + /// `mem::size_of::<T>()` then the result of the division is rounded towards + /// zero. + /// + /// This function returns `None` if `T` is a zero-sized typed. + /// + /// # Examples + /// + /// Basic usage: + /// + /// ``` + /// #![feature(offset_to)] + /// + /// fn main() { + /// let mut a = [0; 5]; + /// let ptr1: *mut i32 = &mut a[1]; + /// let ptr2: *mut i32 = &mut a[3]; + /// assert_eq!(ptr1.offset_to(ptr2), Some(2)); + /// assert_eq!(ptr2.offset_to(ptr1), Some(-2)); + /// assert_eq!(unsafe { ptr1.offset(2) }, ptr2); + /// assert_eq!(unsafe { ptr2.offset(-2) }, ptr1); + /// } + /// ``` + #[unstable(feature = "offset_to", issue = "41079")] + #[inline] + pub fn offset_to(self, other: *const T) -> Option<isize> where T: Sized { + let size = mem::size_of::<T>(); + if size == 0 { + None + } else { + let diff = (other as isize).wrapping_sub(self as isize); + Some(diff / size as isize) + } + } } // Equality for pointers |