[rustc.git] / library / alloc / src / vec / into_iter.rs

use crate::alloc::{Allocator, Global};
use crate::raw_vec::RawVec;
use core::fmt;
use core::intrinsics::arith_offset;
use core::iter::{FusedIterator, InPlaceIterable, SourceIter, TrustedLen, TrustedRandomAccess};
use core::marker::PhantomData;
use core::mem::{self};
use core::ptr::{self, NonNull};
use core::slice::{self};

/// An iterator that moves out of a vector.
///
/// This `struct` is created by the `into_iter` method on [`Vec`](super::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())
    }

    /// Drops remaining elements and relinquishes the backing allocation.
    ///
    /// This is roughly equivalent to the following, but more efficient
    ///
    /// ```
    /// # let mut into_iter = Vec::<u8>::with_capacity(10).into_iter();
    /// (&mut into_iter).for_each(core::mem::drop);
    /// unsafe { core::ptr::write(&mut into_iter, Vec::new().into_iter()); }
    /// ```
    pub(super) fn forget_allocation_drop_remaining(&mut self) {
        let remaining = self.as_raw_mut_slice();

        // overwrite the individual fields instead of creating a new
        // struct and then overwriting &mut self.
        // this creates less assembly
        self.cap = 0;
        self.buf = unsafe { NonNull::new_unchecked(RawVec::NEW.ptr()) };
        self.ptr = self.buf.as_ptr();
        self.end = self.buf.as_ptr();

        unsafe {
            ptr::drop_in_place(remaining);
        }
    }
}

#[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,
{
    const 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
    }
}

// internal helper trait for in-place iteration specialization.
#[rustc_specialization_trait]
pub(crate) trait AsIntoIter {
    type Item;
    fn as_into_iter(&mut self) -> &mut IntoIter<Self::Item>;
}

impl<T> AsIntoIter for IntoIter<T> {
    type Item = T;

    fn as_into_iter(&mut self) -> &mut IntoIter<Self::Item> {
        self
    }
}
Commit	Line	Data
5869c6ff XL	1	use crate::alloc::{Allocator, Global};
	2	use crate::raw_vec::RawVec;
	3	use core::fmt;
	4	use core::intrinsics::arith_offset;
	5	use core::iter::{FusedIterator, InPlaceIterable, SourceIter, TrustedLen, TrustedRandomAccess};
	6	use core::marker::PhantomData;
	7	use core::mem::{self};
	8	use core::ptr::{self, NonNull};
	9	use core::slice::{self};
	10
	11	/// An iterator that moves out of a vector.
	12	///
	13	/// This `struct` is created by the `into_iter` method on [`Vec`](super::Vec)
	14	/// (provided by the [`IntoIterator`] trait).
	15	///
	16	/// # Example
	17	///
	18	/// ```
	19	/// let v = vec![0, 1, 2];
	20	/// let iter: std::vec::IntoIter<_> = v.into_iter();
	21	/// ```
	22	#[stable(feature = "rust1", since = "1.0.0")]
	23	pub struct IntoIter<
	24	T,
	25	#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
	26	> {
	27	pub(super) buf: NonNull<T>,
	28	pub(super) phantom: PhantomData<T>,
	29	pub(super) cap: usize,
	30	pub(super) alloc: A,
	31	pub(super) ptr: *const T,
	32	pub(super) end: *const T,
	33	}
	34
	35	#[stable(feature = "vec_intoiter_debug", since = "1.13.0")]
	36	impl<T: fmt::Debug, A: Allocator> fmt::Debug for IntoIter<T, A> {
	37	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	38	f.debug_tuple("IntoIter").field(&self.as_slice()).finish()
	39	}
	40	}
	41
	42	impl<T, A: Allocator> IntoIter<T, A> {
	43	/// Returns the remaining items of this iterator as a slice.
	44	///
	45	/// # Examples
	46	///
	47	/// ```
	48	/// let vec = vec!['a', 'b', 'c'];
	49	/// let mut into_iter = vec.into_iter();
	50	/// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
	51	/// let _ = into_iter.next().unwrap();
	52	/// assert_eq!(into_iter.as_slice(), &['b', 'c']);
	53	/// ```
	54	#[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
	55	pub fn as_slice(&self) -> &[T] {
	56	unsafe { slice::from_raw_parts(self.ptr, self.len()) }
	57	}
	58
	59	/// Returns the remaining items of this iterator as a mutable slice.
	60	///
	61	/// # Examples
	62	///
	63	/// ```
	64	/// let vec = vec!['a', 'b', 'c'];
65	/// let mut into_iter = vec.into_iter();
66	/// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
67	/// into_iter.as_mut_slice()[2] = 'z';
68	/// assert_eq!(into_iter.next().unwrap(), 'a');
69	/// assert_eq!(into_iter.next().unwrap(), 'b');
70	/// assert_eq!(into_iter.next().unwrap(), 'z');
71	/// ```
72	#[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
73	pub fn as_mut_slice(&mut self) -> &mut [T] {
74	unsafe { &mut *self.as_raw_mut_slice() }
75	}
76
77	/// Returns a reference to the underlying allocator.
78	#[unstable(feature = "allocator_api", issue = "32838")]
79	#[inline]
80	pub fn allocator(&self) -> &A {
81	&self.alloc
82	}
83
84	fn as_raw_mut_slice(&mut self) -> *mut [T] {
85	ptr::slice_from_raw_parts_mut(self.ptr as *mut T, self.len())
86	}
87
36d6ef2b XL	88	/// Drops remaining elements and relinquishes the backing allocation.
	89	///
	90	/// This is roughly equivalent to the following, but more efficient
	91	///
	92	/// ```
	93	/// # let mut into_iter = Vec::<u8>::with_capacity(10).into_iter();
	94	/// (&mut into_iter).for_each(core::mem::drop);
	95	/// unsafe { core::ptr::write(&mut into_iter, Vec::new().into_iter()); }
	96	/// ```
	97	pub(super) fn forget_allocation_drop_remaining(&mut self) {
	98	let remaining = self.as_raw_mut_slice();
5869c6ff	99
36d6ef2b XL	100	// overwrite the individual fields instead of creating a new
	101	// struct and then overwriting &mut self.
	102	// this creates less assembly
5869c6ff XL	103	self.cap = 0;
	104	self.buf = unsafe { NonNull::new_unchecked(RawVec::NEW.ptr()) };
	105	self.ptr = self.buf.as_ptr();
	106	self.end = self.buf.as_ptr();
36d6ef2b XL	107
	108	unsafe {
	109	ptr::drop_in_place(remaining);
	110	}
5869c6ff XL	111	}
	112	}
	113
	114	#[stable(feature = "vec_intoiter_as_ref", since = "1.46.0")]
	115	impl<T, A: Allocator> AsRef<[T]> for IntoIter<T, A> {
	116	fn as_ref(&self) -> &[T] {
	117	self.as_slice()
	118	}
	119	}
	120
	121	#[stable(feature = "rust1", since = "1.0.0")]
	122	unsafe impl<T: Send, A: Allocator + Send> Send for IntoIter<T, A> {}
	123	#[stable(feature = "rust1", since = "1.0.0")]
	124	unsafe impl<T: Sync, A: Allocator> Sync for IntoIter<T, A> {}
	125
	126	#[stable(feature = "rust1", since = "1.0.0")]
	127	impl<T, A: Allocator> Iterator for IntoIter<T, A> {
	128	type Item = T;
	129
	130	#[inline]
	131	fn next(&mut self) -> Option<T> {
	132	if self.ptr as *const _ == self.end {
	133	None
	134	} else if mem::size_of::<T>() == 0 {
	135	// purposefully don't use 'ptr.offset' because for
	136	// vectors with 0-size elements this would return the
	137	// same pointer.
	138	self.ptr = unsafe { arith_offset(self.ptr as const i8, 1) as mut T };
	139
	140	// Make up a value of this ZST.
	141	Some(unsafe { mem::zeroed() })
	142	} else {
	143	let old = self.ptr;
	144	self.ptr = unsafe { self.ptr.offset(1) };
	145
	146	Some(unsafe { ptr::read(old) })
	147	}
	148	}
	149
	150	#[inline]
	151	fn size_hint(&self) -> (usize, Option<usize>) {
	152	let exact = if mem::size_of::<T>() == 0 {
	153	(self.end as usize).wrapping_sub(self.ptr as usize)
	154	} else {
	155	unsafe { self.end.offset_from(self.ptr) as usize }
	156	};
	157	(exact, Some(exact))
	158	}
	159
	160	#[inline]
	161	fn count(self) -> usize {
	162	self.len()
	163	}
	164
	165	unsafe fn __iterator_get_unchecked(&mut self, i: usize) -> Self::Item
	166	where
	167	Self: TrustedRandomAccess,
	168	{
	169	// SAFETY: the caller must guarantee that `i` is in bounds of the
	170	// `Vec<T>`, so `i` cannot overflow an `isize`, and the `self.ptr.add(i)`
	171	// is guaranteed to pointer to an element of the `Vec<T>` and
	172	// thus guaranteed to be valid to dereference.
	173	//
	174	// Also note the implementation of `Self: TrustedRandomAccess` requires
175	// that `T: Copy` so reading elements from the buffer doesn't invalidate
176	// them for `Drop`.
177	unsafe {
178	if mem::size_of::<T>() == 0 { mem::zeroed() } else { ptr::read(self.ptr.add(i)) }
179	}
180	}
181	}
182
183	#[stable(feature = "rust1", since = "1.0.0")]
184	impl<T, A: Allocator> DoubleEndedIterator for IntoIter<T, A> {
185	#[inline]
186	fn next_back(&mut self) -> Option<T> {
187	if self.end == self.ptr {
188	None
189	} else if mem::size_of::<T>() == 0 {
190	// See above for why 'ptr.offset' isn't used
191	self.end = unsafe { arith_offset(self.end as const i8, -1) as mut T };
192
193	// Make up a value of this ZST.
194	Some(unsafe { mem::zeroed() })
195	} else {
196	self.end = unsafe { self.end.offset(-1) };
197
198	Some(unsafe { ptr::read(self.end) })
199	}
200	}
201	}
202
203	#[stable(feature = "rust1", since = "1.0.0")]
204	impl<T, A: Allocator> ExactSizeIterator for IntoIter<T, A> {
205	fn is_empty(&self) -> bool {
206	self.ptr == self.end
207	}
208	}
209
210	#[stable(feature = "fused", since = "1.26.0")]
211	impl<T, A: Allocator> FusedIterator for IntoIter<T, A> {}
212
213	#[unstable(feature = "trusted_len", issue = "37572")]
214	unsafe impl<T, A: Allocator> TrustedLen for IntoIter<T, A> {}
215
216	#[doc(hidden)]
217	#[unstable(issue = "none", feature = "std_internals")]
218	// T: Copy as approximation for !Drop since get_unchecked does not advance self.ptr
219	// and thus we can't implement drop-handling
220	unsafe impl<T, A: Allocator> TrustedRandomAccess for IntoIter<T, A>
221	where
222	T: Copy,
223	{
6a06907d	224	const MAY_HAVE_SIDE_EFFECT: bool = false;
5869c6ff XL	225	}
	226
	227	#[stable(feature = "vec_into_iter_clone", since = "1.8.0")]
	228	impl<T: Clone, A: Allocator + Clone> Clone for IntoIter<T, A> {
	229	#[cfg(not(test))]
	230	fn clone(&self) -> Self {
	231	self.as_slice().to_vec_in(self.alloc.clone()).into_iter()
	232	}
	233	#[cfg(test)]
	234	fn clone(&self) -> Self {
	235	crate::slice::to_vec(self.as_slice(), self.alloc.clone()).into_iter()
	236	}
	237	}
	238
	239	#[stable(feature = "rust1", since = "1.0.0")]
	240	unsafe impl<#[may_dangle] T, A: Allocator> Drop for IntoIter<T, A> {
	241	fn drop(&mut self) {
	242	struct DropGuard<'a, T, A: Allocator>(&'a mut IntoIter<T, A>);
	243
	244	impl<T, A: Allocator> Drop for DropGuard<'_, T, A> {
	245	fn drop(&mut self) {
	246	unsafe {
	247	// `IntoIter::alloc` is not used anymore after this
	248	let alloc = ptr::read(&self.0.alloc);
	249	// RawVec handles deallocation
	250	let _ = RawVec::from_raw_parts_in(self.0.buf.as_ptr(), self.0.cap, alloc);
	251	}
	252	}
	253	}
	254
	255	let guard = DropGuard(self);
	256	// destroy the remaining elements
	257	unsafe {
	258	ptr::drop_in_place(guard.0.as_raw_mut_slice());
	259	}
	260	// now `guard` will be dropped and do the rest
	261	}
	262	}
	263
	264	#[unstable(issue = "none", feature = "inplace_iteration")]
	265	unsafe impl<T, A: Allocator> InPlaceIterable for IntoIter<T, A> {}
	266
	267	#[unstable(issue = "none", feature = "inplace_iteration")]
	268	unsafe impl<T, A: Allocator> SourceIter for IntoIter<T, A> {
	269	type Source = Self;
	270
	271	#[inline]
	272	unsafe fn as_inner(&mut self) -> &mut Self::Source {
	273	self
	274	}
	275	}
	276
	277	// internal helper trait for in-place iteration specialization.
	278	#[rustc_specialization_trait]
	279	pub(crate) trait AsIntoIter {
	280	type Item;
	281	fn as_into_iter(&mut self) -> &mut IntoIter<Self::Item>;
	282	}
	283
	284	impl<T> AsIntoIter for IntoIter<T> {
	285	type Item = T;
	286
	287	fn as_into_iter(&mut self) -> &mut IntoIter<Self::Item> {
	288	self
289	}
290	}