mirror of
https://github.com/SerenityOS/serenity.git
synced 2026-11-07 12:38:38 -10:00
Timothy Flynn
0edcd19615
There are actually a couple of issues here: 1. We are not properly perfect-forwarding the iterable to the Enumerator member. We are using the class template as the constructor type, but we would actually have to do something like this to achieve perfect forwarding: template <typname Iter = Iterable> Enumerator(Iter&&) 2. The begin / end methods on Enumerator (although they return by const- ref) are making copies during for-each loops. The compiler basically generates this when we call enumerate: for (auto it = Enumerator::begin(); it != Enumerator::end(); ++it) The creation of `it` above actually creates a copy of the returned Enumerator instance. To avoid all of this, let's create an intermediate structure to act as the enumerated iterator. This structure does not hold the iterable and thus is fine to copy. We can then let the compiler handle forwarding the iterable to the Enumerator.
92 lines
2.4 KiB
C++
92 lines
2.4 KiB
C++
/*
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* Copyright (c) 2024, Dan Klishch <[email protected]>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <LibTest/TestCase.h>
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#include <AK/Enumerate.h>
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#include <AK/Span.h>
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#include <AK/Vector.h>
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struct IndexAndValue {
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size_t index;
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int value;
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bool operator==(IndexAndValue const&) const = default;
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};
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TEST_CASE(enumerate)
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{
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{
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Vector<IndexAndValue> result;
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for (auto [i, value] : enumerate(Vector { 1, 2, 3, 4 })) {
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result.append({ i, value });
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}
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EXPECT_EQ(result, (Vector<IndexAndValue> { { 0, 1 }, { 1, 2 }, { 2, 3 }, { 3, 4 } }));
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}
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{
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Vector<IndexAndValue> result;
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Vector<int> values = { 9, 8, 7, 6 };
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for (auto [i, value] : enumerate(values)) {
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static_assert(SameAs<decltype(value), int&>);
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result.append({ i, value });
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value = static_cast<int>(i);
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}
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EXPECT_EQ(result, (Vector<IndexAndValue> { { 0, 9 }, { 1, 8 }, { 2, 7 }, { 3, 6 } }));
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EXPECT_EQ(values, (Vector<int> { 0, 1, 2, 3 }));
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}
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{
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Vector<IndexAndValue> result;
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Vector<int> const& values = { 9, 8, 7, 6 };
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for (auto [i, value] : enumerate(values)) {
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static_assert(SameAs<decltype(value), int const&>);
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result.append({ i, value });
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}
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EXPECT_EQ(result, (Vector<IndexAndValue> { { 0, 9 }, { 1, 8 }, { 2, 7 }, { 3, 6 } }));
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}
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}
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class CopyCounter {
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public:
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static inline size_t copy_count = 0;
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CopyCounter() = default;
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CopyCounter(CopyCounter const&) { ++copy_count; }
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CopyCounter(CopyCounter&&) { }
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auto begin() const { return m_vec.begin(); }
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auto end() const { return m_vec.end(); }
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private:
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Vector<int> m_vec { 1, 2, 3, 4 };
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};
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TEST_CASE(do_not_copy)
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{
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{
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Vector<IndexAndValue> result;
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CopyCounter::copy_count = 0;
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CopyCounter counter {};
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for (auto [i, value] : enumerate(counter))
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result.append({ i, value });
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EXPECT_EQ(result, (Vector<IndexAndValue> { { 0, 1 }, { 1, 2 }, { 2, 3 }, { 3, 4 } }));
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EXPECT_EQ(CopyCounter::copy_count, 0uz);
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}
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{
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Vector<IndexAndValue> result;
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CopyCounter::copy_count = 0;
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for (auto [i, value] : enumerate(CopyCounter {}))
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result.append({ i, value });
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EXPECT_EQ(result, (Vector<IndexAndValue> { { 0, 1 }, { 1, 2 }, { 2, 3 }, { 3, 4 } }));
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EXPECT_EQ(CopyCounter::copy_count, 0uz);
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}
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}
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