diff options
| -rw-r--r-- | src/libcore/slice.rs | 86 |
1 files changed, 41 insertions, 45 deletions
diff --git a/src/libcore/slice.rs b/src/libcore/slice.rs index 7bed0ef6daa..38e66c5a3d6 100644 --- a/src/libcore/slice.rs +++ b/src/libcore/slice.rs @@ -625,6 +625,36 @@ impl<'a, T> IntoIterator for &'a mut [T] { } } +#[inline(always)] +fn size_from_ptr<T>(_: *const T) -> usize { + mem::size_of::<T>() +} + + +// Use macro to be generic over const/mut +macro_rules! slice_offset { + ($ptr:expr, $by:expr) => {{ + let ptr = $ptr; + if size_from_ptr(ptr) == 0 { + transmute(ptr as usize + $by) + } else { + ptr.offset($by) + } + }}; +} + +macro_rules! slice_ref { + ($ptr:expr) => {{ + let ptr = $ptr; + if size_from_ptr(ptr) == 0 { + // Use a non-null pointer value + &mut *(1 as *mut _) + } else { + transmute(ptr) + } + }}; +} + // The shared definition of the `Iter` and `IterMut` iterators macro_rules! iterator { (struct $name:ident -> $ptr:ty, $elem:ty) => { @@ -641,20 +671,9 @@ macro_rules! iterator { if self.ptr == self.end { None } else { - if mem::size_of::<T>() == 0 { - // purposefully don't use 'ptr.offset' because for - // vectors with 0-size elements this would return the - // same pointer. - self.ptr = transmute(self.ptr as usize + 1); - - // Use a non-null pointer value - Some(&mut *(1 as *mut _)) - } else { - let old = self.ptr; - self.ptr = self.ptr.offset(1); - - Some(transmute(old)) - } + let old = self.ptr; + self.ptr = slice_offset!(self.ptr, 1); + Some(slice_ref!(old)) } } } @@ -695,17 +714,8 @@ macro_rules! iterator { if self.end == self.ptr { None } else { - if mem::size_of::<T>() == 0 { - // See above for why 'ptr.offset' isn't used - self.end = transmute(self.end as usize - 1); - - // Use a non-null pointer value - Some(&mut *(1 as *mut _)) - } else { - self.end = self.end.offset(-1); - - Some(transmute(self.end)) - } + self.end = slice_offset!(self.end, -1); + Some(slice_ref!(self.end)) } } } @@ -805,16 +815,9 @@ impl<'a, T> Iter<'a, T> { // Helper function for Iter::nth fn iter_nth(&mut self, n: usize) -> Option<&'a T> { match self.as_slice().get(n) { - Some(elem_ref) => if mem::size_of::<T>() == 0 { - unsafe { - self.ptr = transmute((elem_ref as *const _) as usize + 1); - Some(& *(1 as *const _)) - } - } else { - unsafe { - self.ptr = (elem_ref as *const _).offset(1); - Some(elem_ref) - } + Some(elem_ref) => unsafe { + self.ptr = slice_offset!(elem_ref as *const _, 1); + Some(slice_ref!(elem_ref)) }, None => { self.ptr = self.end; @@ -955,16 +958,9 @@ impl<'a, T> IterMut<'a, T> { // Helper function for IterMut::nth fn iter_nth(&mut self, n: usize) -> Option<&'a mut T> { match make_mut_slice!(T => &'a mut [T]: self.ptr, self.end).get_mut(n) { - Some(elem_ref) => if mem::size_of::<T>() == 0 { - unsafe { - self.ptr = transmute((elem_ref as *mut _) as usize + 1); - Some(&mut *(1 as *mut _)) - } - } else { - unsafe { - self.ptr = (elem_ref as *mut _).offset(1); - Some(elem_ref) - } + Some(elem_ref) => unsafe { + self.ptr = slice_offset!(elem_ref as *mut _, 1); + Some(slice_ref!(elem_ref)) }, None => { self.ptr = self.end; |