risingwave_common/array/
iterator.rs

1// Copyright 2025 RisingWave Labs
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15use std::iter::TrustedLen;
16
17use super::Array;
18
19pub struct ArrayIterator<'a, A: Array> {
20    data: &'a A,
21    pos: usize,
22}
23
24impl<'a, A: Array> ArrayIterator<'a, A> {
25    pub fn new(data: &'a A) -> Self {
26        Self { data, pos: 0 }
27    }
28}
29
30impl<'a, A: Array> Iterator for ArrayIterator<'a, A> {
31    type Item = Option<A::RefItem<'a>>;
32
33    fn next(&mut self) -> Option<Self::Item> {
34        if self.pos >= self.data.len() {
35            None
36        } else {
37            // SAFETY: bounds check is done by `self.pos < self.data.len()`.
38            let item = unsafe { self.data.value_at_unchecked(self.pos) };
39            self.pos += 1;
40            Some(item)
41        }
42    }
43
44    fn size_hint(&self) -> (usize, Option<usize>) {
45        let size = self.data.len() - self.pos;
46        (size, Some(size))
47    }
48}
49
50impl<A: Array> ExactSizeIterator for ArrayIterator<'_, A> {}
51unsafe impl<A: Array> TrustedLen for ArrayIterator<'_, A> {}
52
53#[cfg(test)]
54mod tests {
55    use paste::paste;
56
57    use super::*;
58    use crate::array::{ArrayBuilder, ArrayImpl};
59    use crate::for_all_variants;
60
61    macro_rules! test_trusted_len {
62        ($( { $data_type:ident, $variant_name:ident, $suffix_name:ident, $scalar:ty, $scalar_ref:ty, $array:ty, $builder:ty } ),*) => {
63            $(
64                paste! {
65                    #[test]
66                    fn [<test_trusted_len_for_ $suffix_name _array>]() {
67                        let mut builder = $builder::new(5);
68                        for _ in 0..5 {
69                            builder.append_null();
70                        }
71                        let array = builder.finish();
72                        let mut iter = array.iter();
73
74                        assert_eq!(iter.size_hint(), (5, Some(5))); iter.next();
75                        assert_eq!(iter.size_hint(), (4, Some(4))); iter.next();
76                        assert_eq!(iter.size_hint(), (3, Some(3))); iter.nth(0);
77                        assert_eq!(iter.size_hint(), (2, Some(2))); iter.nth(1);
78                        assert_eq!(iter.size_hint(), (0, Some(0)));
79
80                        let array_impl = ArrayImpl::from(array);
81                        let mut iter = array_impl.iter();
82
83                        assert_eq!(iter.size_hint(), (5, Some(5))); iter.next();
84                        assert_eq!(iter.size_hint(), (4, Some(4))); iter.next();
85                        assert_eq!(iter.size_hint(), (3, Some(3))); iter.nth(0);
86                        assert_eq!(iter.size_hint(), (2, Some(2))); iter.nth(1);
87                        assert_eq!(iter.size_hint(), (0, Some(0)));
88                    }
89                }
90            )*
91        };
92    }
93
94    for_all_variants! { test_trusted_len }
95}
risingwave_common/array/iterator.rs

risingwave_common/array/
iterator.rs
