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|
//! `GenericArray` iterator implementation.
use super::{ArrayLength, GenericArray};
use core::iter::FusedIterator;
use core::mem::ManuallyDrop;
use core::{cmp, fmt, mem, ptr};
/// An iterator that moves out of a `GenericArray`
pub struct GenericArrayIter<T, N: ArrayLength<T>> {
// Invariants: index <= index_back <= N
// Only values in array[index..index_back] are alive at any given time.
// Values from array[..index] and array[index_back..] are already moved/dropped.
array: ManuallyDrop<GenericArray<T, N>>,
index: usize,
index_back: usize,
}
#[cfg(test)]
mod test {
use super::*;
fn send<I: Send>(_iter: I) {}
#[test]
fn test_send_iter() {
send(GenericArray::from([1, 2, 3, 4]).into_iter());
}
}
impl<T, N> GenericArrayIter<T, N>
where
N: ArrayLength<T>,
{
/// Returns the remaining items of this iterator as a slice
#[inline]
pub fn as_slice(&self) -> &[T] {
&self.array.as_slice()[self.index..self.index_back]
}
/// Returns the remaining items of this iterator as a mutable slice
#[inline]
pub fn as_mut_slice(&mut self) -> &mut [T] {
&mut self.array.as_mut_slice()[self.index..self.index_back]
}
}
impl<T, N> IntoIterator for GenericArray<T, N>
where
N: ArrayLength<T>,
{
type Item = T;
type IntoIter = GenericArrayIter<T, N>;
fn into_iter(self) -> Self::IntoIter {
GenericArrayIter {
array: ManuallyDrop::new(self),
index: 0,
index_back: N::USIZE,
}
}
}
// Based on work in rust-lang/rust#49000
impl<T: fmt::Debug, N> fmt::Debug for GenericArrayIter<T, N>
where
N: ArrayLength<T>,
{
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.debug_tuple("GenericArrayIter")
.field(&self.as_slice())
.finish()
}
}
impl<T, N> Drop for GenericArrayIter<T, N>
where
N: ArrayLength<T>,
{
#[inline]
fn drop(&mut self) {
if mem::needs_drop::<T>() {
// Drop values that are still alive.
for p in self.as_mut_slice() {
unsafe {
ptr::drop_in_place(p);
}
}
}
}
}
// Based on work in rust-lang/rust#49000
impl<T: Clone, N> Clone for GenericArrayIter<T, N>
where
N: ArrayLength<T>,
{
fn clone(&self) -> Self {
// This places all cloned elements at the start of the new array iterator,
// not at their original indices.
let mut array = unsafe { ptr::read(&self.array) };
let mut index_back = 0;
for (dst, src) in array.as_mut_slice().into_iter().zip(self.as_slice()) {
unsafe { ptr::write(dst, src.clone()) };
index_back += 1;
}
GenericArrayIter {
array,
index: 0,
index_back,
}
}
}
impl<T, N> Iterator for GenericArrayIter<T, N>
where
N: ArrayLength<T>,
{
type Item = T;
#[inline]
fn next(&mut self) -> Option<T> {
if self.index < self.index_back {
let p = unsafe { Some(ptr::read(self.array.get_unchecked(self.index))) };
self.index += 1;
p
} else {
None
}
}
fn fold<B, F>(mut self, init: B, mut f: F) -> B
where
F: FnMut(B, Self::Item) -> B,
{
let ret = unsafe {
let GenericArrayIter {
ref array,
ref mut index,
index_back,
} = self;
let remaining = &array[*index..index_back];
remaining.iter().fold(init, |acc, src| {
let value = ptr::read(src);
*index += 1;
f(acc, value)
})
};
// ensure the drop happens here after iteration
drop(self);
ret
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let len = self.len();
(len, Some(len))
}
#[inline]
fn count(self) -> usize {
self.len()
}
fn nth(&mut self, n: usize) -> Option<T> {
// First consume values prior to the nth.
let ndrop = cmp::min(n, self.len());
for p in &mut self.array[self.index..self.index + ndrop] {
self.index += 1;
unsafe {
ptr::drop_in_place(p);
}
}
self.next()
}
#[inline]
fn last(mut self) -> Option<T> {
// Note, everything else will correctly drop first as `self` leaves scope.
self.next_back()
}
}
impl<T, N> DoubleEndedIterator for GenericArrayIter<T, N>
where
N: ArrayLength<T>,
{
fn next_back(&mut self) -> Option<T> {
if self.index < self.index_back {
self.index_back -= 1;
unsafe { Some(ptr::read(self.array.get_unchecked(self.index_back))) }
} else {
None
}
}
fn rfold<B, F>(mut self, init: B, mut f: F) -> B
where
F: FnMut(B, Self::Item) -> B,
{
let ret = unsafe {
let GenericArrayIter {
ref array,
index,
ref mut index_back,
} = self;
let remaining = &array[index..*index_back];
remaining.iter().rfold(init, |acc, src| {
let value = ptr::read(src);
*index_back -= 1;
f(acc, value)
})
};
// ensure the drop happens here after iteration
drop(self);
ret
}
}
impl<T, N> ExactSizeIterator for GenericArrayIter<T, N>
where
N: ArrayLength<T>,
{
fn len(&self) -> usize {
self.index_back - self.index
}
}
impl<T, N> FusedIterator for GenericArrayIter<T, N> where N: ArrayLength<T> {}
// TODO: Implement `TrustedLen` when stabilized
|
