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
|
// Copyright 2024 Huawei Cloud Computing Technology Co., Ltd.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef INCLUDED_SRC_OTHER_TOOLS_TRANSFORMED_RANGE_HPP
#define INCLUDED_SRC_OTHER_TOOLS_TRANSFORMED_RANGE_HPP
#include <cstddef>
#include <functional>
#include <iterator>
#include <type_traits>
#include <utility> // IWYU pragma: keep
#include <vector>
#include "gsl/gsl"
// TODO(modernize): Replace any use of this class by C++20's
// std::ranges/std::views (clang version >= 16.0.0)
/// \brief Transform iterable sequence "on the fly" invoking the given
/// transformation callback. If the callback throws an exception,
/// std::terminate is called.
/// \tparam TIterator Type of the iterator of the sequence to be
/// transformed.
/// \tparam Result Type of the transformation result.
template <typename TIterator, typename Result>
class TransformedRange final {
public:
using converter_t =
std::function<Result(typename TIterator::value_type const&)>;
class Iterator final {
public:
using value_type = std::remove_reference_t<Result>;
using pointer = value_type*;
using reference = value_type&;
using difference_type = std::ptrdiff_t;
using iterator_category = std::forward_iterator_tag;
Iterator() noexcept = default;
Iterator(TIterator Iterator, converter_t c) noexcept
: iterator_(std::move(Iterator)), c_(std::move(c)) {}
auto operator*() const noexcept -> decltype(auto) {
try {
return std::invoke(c_, *iterator_);
} catch (...) {
Ensures(false);
}
}
auto operator++() noexcept -> Iterator& {
++iterator_;
return *this;
}
[[nodiscard]] friend auto operator==(Iterator const& lhs,
Iterator const& rhs) noexcept
-> bool {
return lhs.iterator_ == rhs.iterator_;
}
[[nodiscard]] friend auto operator!=(Iterator const& lhs,
Iterator const& rhs) noexcept
-> bool {
return not(lhs == rhs);
}
private:
TIterator iterator_{};
converter_t c_{};
};
TransformedRange(TIterator begin, TIterator end, converter_t c) noexcept
: begin_{std::move(begin), std::move(c)},
end_{std::move(end), nullptr} {}
[[nodiscard]] auto begin() const noexcept -> Iterator { return begin_; }
[[nodiscard]] auto end() const noexcept -> Iterator { return end_; }
[[nodiscard]] auto size() const -> typename Iterator::difference_type {
return std::distance(begin_, end_);
}
[[nodiscard]] auto ToVector() const -> std::vector<Result> {
std::vector<Result> result;
result.reserve(gsl::narrow<std::size_t>(size()));
for (auto item : *this) {
result.emplace_back(std::move(item));
}
return result;
}
private:
Iterator const begin_;
Iterator const end_;
};
// User-defined deduction guide to help compiler dealing with generic lambdas
// and invokable objects.
template <typename TIterator,
typename Function,
typename IteratorValue = typename TIterator::value_type>
TransformedRange(TIterator, TIterator, Function)
-> TransformedRange<TIterator,
std::invoke_result_t<Function, IteratorValue>>;
#endif // INCLUDED_SRC_OTHER_TOOLS_TRANSFORMED_RANGE_HPP
|
