rw_iter_util/
lib.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
15pub trait ZipEqFast<B: IntoIterator>: ExactSizeIterator + Sized
16where
17    B::IntoIter: ExactSizeIterator,
18{
19    /// A specialized version of `zip_eq` for [`ExactSizeIterator`].
20    ///
21    /// It's a separate trait because Rust doesn't support specialization yet.
22    /// See [tracking issue for specialization (RFC 1210)](https://github.com/rust-lang/rust/issues/31844).
23    #[expect(clippy::disallowed_methods)]
24    fn zip_eq_fast(self, other: B) -> impl ExactSizeIterator<Item = (Self::Item, B::Item)> {
25        let other = other.into_iter();
26        assert_eq!(self.len(), other.len());
27        self.zip(other)
28    }
29}
30
31impl<A: ExactSizeIterator, B: IntoIterator> ZipEqFast<B> for A where B::IntoIter: ExactSizeIterator {}
32
33pub trait ZipEqDebug<B: IntoIterator>: itertools::Itertools + Sized {
34    /// Use `zip_eq` when `debug_assertions` is enabled, otherwise use `zip`.
35    ///
36    /// It's because `zip_eq` has a very large overhead of checking each item in the iterators.
37    #[expect(clippy::disallowed_methods)]
38    fn zip_eq_debug(self, other: B) -> impl Iterator<Item = (Self::Item, B::Item)> {
39        #[cfg(debug_assertions)]
40        return self.zip_eq(other);
41        #[cfg(not(debug_assertions))]
42        return self.zip(other);
43    }
44}
45
46impl<A: itertools::Itertools + Sized, B: IntoIterator> ZipEqDebug<B> for A {}
47
48pub fn zip_eq_fast<A, B>(a: A, b: B) -> impl Iterator<Item = (A::Item, B::Item)>
49where
50    A: IntoIterator,
51    B: IntoIterator,
52    A::IntoIter: ExactSizeIterator,
53    B::IntoIter: ExactSizeIterator,
54{
55    a.into_iter().zip_eq_fast(b)
56}
rw_iter_util/lib.rs

rw_iter_util/
lib.rs
