refactor: moved IntoIter into into_iter.rs

library/alloc/src/vec/into_iter.rs

@@ -0,0 +1,270 @@
+use crate::alloc::{Allocator, Global};
+use crate::raw_vec::RawVec;
+use core::marker::PhantomData;
+use core::intrinsics::{arith_offset};
+use core::mem::{self};
+use core::fmt;
+use core::ptr::{self, NonNull};
+use core::slice::{self};
+use core::iter::{
+    FusedIterator, InPlaceIterable, SourceIter, TrustedLen, TrustedRandomAccess,
+};
+
+/// An iterator that moves out of a vector.
+///
+/// This `struct` is created by the `into_iter` method on [`Vec`] (provided
+/// by the [`IntoIterator`] trait).
+///
+/// # Example
+///
+/// ```
+/// let v = vec![0, 1, 2];
+/// let iter: std::vec::IntoIter<_> = v.into_iter();
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct IntoIter<
+    T,
+    #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
+> {
+    pub(super) buf: NonNull<T>,
+    pub(super) phantom: PhantomData<T>,
+    pub(super) cap: usize,
+    pub(super) alloc: A,
+    pub(super) ptr: *const T,
+    pub(super) end: *const T,
+}
+
+#[stable(feature = "vec_intoiter_debug", since = "1.13.0")]
+impl<T: fmt::Debug, A: Allocator> fmt::Debug for IntoIter<T, A> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_tuple("IntoIter").field(&self.as_slice()).finish()
+    }
+}
+
+impl<T, A: Allocator> IntoIter<T, A> {
+    /// Returns the remaining items of this iterator as a slice.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let vec = vec!['a', 'b', 'c'];
+    /// let mut into_iter = vec.into_iter();
+    /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
+    /// let _ = into_iter.next().unwrap();
+    /// assert_eq!(into_iter.as_slice(), &['b', 'c']);
+    /// ```
+    #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
+    pub fn as_slice(&self) -> &[T] {
+        unsafe { slice::from_raw_parts(self.ptr, self.len()) }
+    }
+
+    /// Returns the remaining items of this iterator as a mutable slice.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let vec = vec!['a', 'b', 'c'];
+    /// let mut into_iter = vec.into_iter();
+    /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
+    /// into_iter.as_mut_slice()[2] = 'z';
+    /// assert_eq!(into_iter.next().unwrap(), 'a');
+    /// assert_eq!(into_iter.next().unwrap(), 'b');
+    /// assert_eq!(into_iter.next().unwrap(), 'z');
+    /// ```
+    #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
+    pub fn as_mut_slice(&mut self) -> &mut [T] {
+        unsafe { &mut *self.as_raw_mut_slice() }
+    }
+
+    /// Returns a reference to the underlying allocator.
+    #[unstable(feature = "allocator_api", issue = "32838")]
+    #[inline]
+    pub fn allocator(&self) -> &A {
+        &self.alloc
+    }
+
+    fn as_raw_mut_slice(&mut self) -> *mut [T] {
+        ptr::slice_from_raw_parts_mut(self.ptr as *mut T, self.len())
+    }
+
+    pub(super) fn drop_remaining(&mut self) {
+        unsafe {
+            ptr::drop_in_place(self.as_mut_slice());
+        }
+        self.ptr = self.end;
+    }
+
+    /// Relinquishes the backing allocation, equivalent to
+    /// `ptr::write(&mut self, Vec::new().into_iter())`
+    pub(super) fn forget_allocation(&mut self) {
+        self.cap = 0;
+        self.buf = unsafe { NonNull::new_unchecked(RawVec::NEW.ptr()) };
+        self.ptr = self.buf.as_ptr();
+        self.end = self.buf.as_ptr();
+    }
+}
+
+#[stable(feature = "vec_intoiter_as_ref", since = "1.46.0")]
+impl<T, A: Allocator> AsRef<[T]> for IntoIter<T, A> {
+    fn as_ref(&self) -> &[T] {
+        self.as_slice()
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl<T: Send, A: Allocator + Send> Send for IntoIter<T, A> {}
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl<T: Sync, A: Allocator> Sync for IntoIter<T, A> {}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T, A: Allocator> Iterator for IntoIter<T, A> {
+    type Item = T;
+
+    #[inline]
+    fn next(&mut self) -> Option<T> {
+        if self.ptr as *const _ == 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 = unsafe { arith_offset(self.ptr as *const i8, 1) as *mut T };
+
+            // Make up a value of this ZST.
+            Some(unsafe { mem::zeroed() })
+        } else {
+            let old = self.ptr;
+            self.ptr = unsafe { self.ptr.offset(1) };
+
+            Some(unsafe { ptr::read(old) })
+        }
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let exact = if mem::size_of::<T>() == 0 {
+            (self.end as usize).wrapping_sub(self.ptr as usize)
+        } else {
+            unsafe { self.end.offset_from(self.ptr) as usize }
+        };
+        (exact, Some(exact))
+    }
+
+    #[inline]
+    fn count(self) -> usize {
+        self.len()
+    }
+
+    unsafe fn __iterator_get_unchecked(&mut self, i: usize) -> Self::Item
+        where
+            Self: TrustedRandomAccess,
+    {
+        // SAFETY: the caller must guarantee that `i` is in bounds of the
+        // `Vec<T>`, so `i` cannot overflow an `isize`, and the `self.ptr.add(i)`
+        // is guaranteed to pointer to an element of the `Vec<T>` and
+        // thus guaranteed to be valid to dereference.
+        //
+        // Also note the implementation of `Self: TrustedRandomAccess` requires
+        // that `T: Copy` so reading elements from the buffer doesn't invalidate
+        // them for `Drop`.
+        unsafe {
+            if mem::size_of::<T>() == 0 { mem::zeroed() } else { ptr::read(self.ptr.add(i)) }
+        }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T, A: Allocator> DoubleEndedIterator for IntoIter<T, A> {
+    #[inline]
+    fn next_back(&mut self) -> Option<T> {
+        if self.end == self.ptr {
+            None
+        } else if mem::size_of::<T>() == 0 {
+            // See above for why 'ptr.offset' isn't used
+            self.end = unsafe { arith_offset(self.end as *const i8, -1) as *mut T };
+
+            // Make up a value of this ZST.
+            Some(unsafe { mem::zeroed() })
+        } else {
+            self.end = unsafe { self.end.offset(-1) };
+
+            Some(unsafe { ptr::read(self.end) })
+        }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T, A: Allocator> ExactSizeIterator for IntoIter<T, A> {
+    fn is_empty(&self) -> bool {
+        self.ptr == self.end
+    }
+}
+
+#[stable(feature = "fused", since = "1.26.0")]
+impl<T, A: Allocator> FusedIterator for IntoIter<T, A> {}
+
+#[unstable(feature = "trusted_len", issue = "37572")]
+unsafe impl<T, A: Allocator> TrustedLen for IntoIter<T, A> {}
+
+#[doc(hidden)]
+#[unstable(issue = "none", feature = "std_internals")]
+// T: Copy as approximation for !Drop since get_unchecked does not advance self.ptr
+// and thus we can't implement drop-handling
+unsafe impl<T, A: Allocator> TrustedRandomAccess for IntoIter<T, A>
+    where
+        T: Copy,
+{
+    fn may_have_side_effect() -> bool {
+        false
+    }
+}
+
+#[stable(feature = "vec_into_iter_clone", since = "1.8.0")]
+impl<T: Clone, A: Allocator + Clone> Clone for IntoIter<T, A> {
+    #[cfg(not(test))]
+    fn clone(&self) -> Self {
+        self.as_slice().to_vec_in(self.alloc.clone()).into_iter()
+    }
+    #[cfg(test)]
+    fn clone(&self) -> Self {
+        crate::slice::to_vec(self.as_slice(), self.alloc.clone()).into_iter()
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl<#[may_dangle] T, A: Allocator> Drop for IntoIter<T, A> {
+    fn drop(&mut self) {
+        struct DropGuard<'a, T, A: Allocator>(&'a mut IntoIter<T, A>);
+
+        impl<T, A: Allocator> Drop for DropGuard<'_, T, A> {
+            fn drop(&mut self) {
+                unsafe {
+                    // `IntoIter::alloc` is not used anymore after this
+                    let alloc = ptr::read(&self.0.alloc);
+                    // RawVec handles deallocation
+                    let _ = RawVec::from_raw_parts_in(self.0.buf.as_ptr(), self.0.cap, alloc);
+                }
+            }
+        }
+
+        let guard = DropGuard(self);
+        // destroy the remaining elements
+        unsafe {
+            ptr::drop_in_place(guard.0.as_raw_mut_slice());
+        }
+        // now `guard` will be dropped and do the rest
+    }
+}
+
+#[unstable(issue = "none", feature = "inplace_iteration")]
+unsafe impl<T, A: Allocator> InPlaceIterable for IntoIter<T, A> {}
+
+#[unstable(issue = "none", feature = "inplace_iteration")]
+unsafe impl<T, A: Allocator> SourceIter for IntoIter<T, A> {
+    type Source = Self;
+
+    #[inline]
+    unsafe fn as_inner(&mut self) -> &mut Self::Source {
+        self
+    }
+}