1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
use crate::iter::adapters::{
    zip::try_get_unchecked, TrustedRandomAccess, TrustedRandomAccessNoCoerce,
};
use crate::iter::{FusedIterator, TrustedLen};
use crate::mem::MaybeUninit;
use crate::mem::SizedTypeProperties;
use crate::num::NonZeroUsize;
use crate::ops::Try;
use crate::{array, ptr};

/// An iterator that copies the elements of an underlying iterator.
///
/// This `struct` is created by the [`copied`] method on [`Iterator`]. See its
/// documentation for more.
///
/// [`copied`]: Iterator::copied
/// [`Iterator`]: trait.Iterator.html
#[stable(feature = "iter_copied", since = "1.36.0")]
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[derive(Clone, Debug)]
pub struct Copied<I> {
    it: I,
}

impl<I> Copied<I> {
    pub(in crate::iter) fn new(it: I) -> Copied<I> {
        Copied { it }
    }
}

fn copy_fold<T: Copy, Acc>(mut f: impl FnMut(Acc, T) -> Acc) -> impl FnMut(Acc, &T) -> Acc {
    move |acc, &elt| f(acc, elt)
}

fn copy_try_fold<T: Copy, Acc, R>(mut f: impl FnMut(Acc, T) -> R) -> impl FnMut(Acc, &T) -> R {
    move |acc, &elt| f(acc, elt)
}

#[stable(feature = "iter_copied", since = "1.36.0")]
impl<'a, I, T: 'a> Iterator for Copied<I>
where
    I: Iterator<Item = &'a T>,
    T: Copy,
{
    type Item = T;

    fn next(&mut self) -> Option<T> {
        self.it.next().copied()
    }

    fn next_chunk<const N: usize>(
        &mut self,
    ) -> Result<[Self::Item; N], array::IntoIter<Self::Item, N>>
    where
        Self: Sized,
    {
        <I as SpecNextChunk<'_, N, T>>::spec_next_chunk(&mut self.it)
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        self.it.size_hint()
    }

    fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R
    where
        Self: Sized,
        F: FnMut(B, Self::Item) -> R,
        R: Try<Output = B>,
    {
        self.it.try_fold(init, copy_try_fold(f))
    }

    fn fold<Acc, F>(self, init: Acc, f: F) -> Acc
    where
        F: FnMut(Acc, Self::Item) -> Acc,
    {
        self.it.fold(init, copy_fold(f))
    }

    fn nth(&mut self, n: usize) -> Option<T> {
        self.it.nth(n).copied()
    }

    fn last(self) -> Option<T> {
        self.it.last().copied()
    }

    fn count(self) -> usize {
        self.it.count()
    }

    #[inline]
    fn advance_by(&mut self, n: usize) -> Result<(), NonZeroUsize> {
        self.it.advance_by(n)
    }

    unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> T
    where
        Self: TrustedRandomAccessNoCoerce,
    {
        // SAFETY: the caller must uphold the contract for
        // `Iterator::__iterator_get_unchecked`.
        *unsafe { try_get_unchecked(&mut self.it, idx) }
    }
}

#[stable(feature = "iter_copied", since = "1.36.0")]
impl<'a, I, T: 'a> DoubleEndedIterator for Copied<I>
where
    I: DoubleEndedIterator<Item = &'a T>,
    T: Copy,
{
    fn next_back(&mut self) -> Option<T> {
        self.it.next_back().copied()
    }

    fn try_rfold<B, F, R>(&mut self, init: B, f: F) -> R
    where
        Self: Sized,
        F: FnMut(B, Self::Item) -> R,
        R: Try<Output = B>,
    {
        self.it.try_rfold(init, copy_try_fold(f))
    }

    fn rfold<Acc, F>(self, init: Acc, f: F) -> Acc
    where
        F: FnMut(Acc, Self::Item) -> Acc,
    {
        self.it.rfold(init, copy_fold(f))
    }

    #[inline]
    fn advance_back_by(&mut self, n: usize) -> Result<(), NonZeroUsize> {
        self.it.advance_back_by(n)
    }
}

#[stable(feature = "iter_copied", since = "1.36.0")]
impl<'a, I, T: 'a> ExactSizeIterator for Copied<I>
where
    I: ExactSizeIterator<Item = &'a T>,
    T: Copy,
{
    fn len(&self) -> usize {
        self.it.len()
    }

    fn is_empty(&self) -> bool {
        self.it.is_empty()
    }
}

#[stable(feature = "iter_copied", since = "1.36.0")]
impl<'a, I, T: 'a> FusedIterator for Copied<I>
where
    I: FusedIterator<Item = &'a T>,
    T: Copy,
{
}

#[doc(hidden)]
#[unstable(feature = "trusted_random_access", issue = "none")]
unsafe impl<I> TrustedRandomAccess for Copied<I> where I: TrustedRandomAccess {}

#[doc(hidden)]
#[unstable(feature = "trusted_random_access", issue = "none")]
unsafe impl<I> TrustedRandomAccessNoCoerce for Copied<I>
where
    I: TrustedRandomAccessNoCoerce,
{
    const MAY_HAVE_SIDE_EFFECT: bool = I::MAY_HAVE_SIDE_EFFECT;
}

#[stable(feature = "iter_copied", since = "1.36.0")]
unsafe impl<'a, I, T: 'a> TrustedLen for Copied<I>
where
    I: TrustedLen<Item = &'a T>,
    T: Copy,
{
}

trait SpecNextChunk<'a, const N: usize, T: 'a>: Iterator<Item = &'a T>
where
    T: Copy,
{
    fn spec_next_chunk(&mut self) -> Result<[T; N], array::IntoIter<T, N>>;
}

impl<'a, const N: usize, I, T: 'a> SpecNextChunk<'a, N, T> for I
where
    I: Iterator<Item = &'a T>,
    T: Copy,
{
    default fn spec_next_chunk(&mut self) -> Result<[T; N], array::IntoIter<T, N>> {
        array::iter_next_chunk(&mut self.map(|e| *e))
    }
}

impl<'a, const N: usize, T: 'a> SpecNextChunk<'a, N, T> for crate::slice::Iter<'a, T>
where
    T: Copy,
{
    fn spec_next_chunk(&mut self) -> Result<[T; N], array::IntoIter<T, N>> {
        let mut raw_array = MaybeUninit::uninit_array();

        let len = self.len();

        if T::IS_ZST {
            if len < N {
                let _ = self.advance_by(len);
                // SAFETY: ZSTs can be conjured ex nihilo; only the amount has to be correct
                return Err(unsafe { array::IntoIter::new_unchecked(raw_array, 0..len) });
            }

            let _ = self.advance_by(N);
            // SAFETY: ditto
            return Ok(unsafe { MaybeUninit::array_assume_init(raw_array) });
        }

        if len < N {
            // SAFETY: `len` indicates that this many elements are available and we just checked that
            // it fits into the array.
            unsafe {
                ptr::copy_nonoverlapping(
                    self.as_ref().as_ptr(),
                    raw_array.as_mut_ptr() as *mut T,
                    len,
                );
                let _ = self.advance_by(len);
                return Err(array::IntoIter::new_unchecked(raw_array, 0..len));
            }
        }

        // SAFETY: `len` is larger than the array size. Copy a fixed amount here to fully initialize
        // the array.
        unsafe {
            ptr::copy_nonoverlapping(self.as_ref().as_ptr(), raw_array.as_mut_ptr() as *mut T, N);
            let _ = self.advance_by(N);
            Ok(MaybeUninit::array_assume_init(raw_array))
        }
    }
}

#[stable(feature = "default_iters", since = "1.70.0")]
impl<I: Default> Default for Copied<I> {
    /// Creates a `Copied` iterator from the default value of `I`
    /// ```
    /// # use core::slice;
    /// # use core::iter::Copied;
    /// let iter: Copied<slice::Iter<'_, u8>> = Default::default();
    /// assert_eq!(iter.len(), 0);
    /// ```
    fn default() -> Self {
        Self::new(Default::default())
    }
}
This documentation is an old archive. Please see https://rust.docs.kernel.org instead.