manuzhang commented on code in PR #905: URL: https://github.com/apache/iceberg-cpp/pull/905#discussion_r3921822734
########## src/iceberg/test/iterator_test.cc: ########## @@ -0,0 +1,117 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you 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. + */ + +#include "iceberg/util/iterator.h" + +#include <memory> +#include <optional> +#include <type_traits> +#include <vector> + +#include <gtest/gtest.h> + +#include "iceberg/test/matchers.h" + +namespace iceberg { +namespace { + +class CopyOnly { + public: + explicit CopyOnly(int value) : value_(value) {} + + CopyOnly(const CopyOnly&) = default; + CopyOnly& operator=(const CopyOnly&) = default; + CopyOnly(CopyOnly&&) = delete; + CopyOnly& operator=(CopyOnly&&) = delete; + + int value() const { return value_; } + + private: + int value_; +}; + +static_assert(std::is_copy_constructible_v<CopyOnly>); +static_assert(!std::is_move_constructible_v<CopyOnly>); + +class CopyOnlyIterator final : public Iterator<CopyOnly> { + public: + Result<std::optional<CopyOnly>> Next() override { + if (next_ == 3) { + return Result<std::optional<CopyOnly>>(std::in_place, std::nullopt); + } + return Result<std::optional<CopyOnly>>(std::in_place, std::in_place, next_++); + } + + private: + int next_ = 0; +}; + +class MoveOnlyIterator final : public Iterator<std::unique_ptr<int>> { + public: + Result<std::optional<std::unique_ptr<int>>> Next() override { + if (next_ == 3) { + return Result<std::optional<std::unique_ptr<int>>>(std::in_place, + std::nullopt); + } + return Result<std::optional<std::unique_ptr<int>>>( + std::in_place, std::in_place, std::make_unique<int>(next_++)); + } + + private: + int next_ = 0; +}; + +class FailingIterator final : public Iterator<int> { + public: + Result<std::optional<int>> Next() override { return Invalid("iteration failed"); } +}; + +TEST(IteratorTest, ToVectorSupportsCopyOnlyValues) { + CopyOnlyIterator iterator; + + ICEBERG_UNWRAP_OR_FAIL(auto values, iterator.ToVector()); + + ASSERT_EQ(values.size(), 3); + EXPECT_EQ(values[0].value(), 0); + EXPECT_EQ(values[1].value(), 1); + EXPECT_EQ(values[2].value(), 2); +} + +TEST(IteratorTest, ToVectorSupportsMoveOnlyValues) { + MoveOnlyIterator iterator; + + ICEBERG_UNWRAP_OR_FAIL(auto values, iterator.ToVector()); + + ASSERT_EQ(values.size(), 3); + EXPECT_EQ(*values[0], 0); + EXPECT_EQ(*values[1], 1); + EXPECT_EQ(*values[2], 2); +} + +TEST(IteratorTest, ToVectorPropagatesErrors) { + FailingIterator iterator; + + auto result = iterator.ToVector(); + + EXPECT_THAT(result, IsError(ErrorKind::kInvalid)); + EXPECT_THAT(result, HasErrorMessage("iteration failed")); +} Review Comment: Updated FailingIterator to yield two values before failing. The test consumes the first value directly, then calls ToVector(), which consumes another value before verifying that the iterator error is propagated. ########## src/iceberg/util/iterator.h: ########## @@ -0,0 +1,93 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you 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. + */ + +#pragma once + +/// \file iceberg/util/iterator.h +/// \brief Pull-based iterator interface for fallible, lazily produced values. + +#include <deque> +#include <optional> +#include <type_traits> +#include <utility> +#include <vector> + +#include "iceberg/result.h" +#include "iceberg/util/macros.h" Review Comment: Removed the unused iceberg/util/macros.h include from the public header. ########## src/iceberg/util/iterator.h: ########## @@ -0,0 +1,93 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you 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. + */ + +#pragma once + +/// \file iceberg/util/iterator.h +/// \brief Pull-based iterator interface for fallible, lazily produced values. + +#include <deque> +#include <optional> +#include <type_traits> +#include <utility> +#include <vector> + +#include "iceberg/result.h" +#include "iceberg/util/macros.h" + +namespace iceberg { + +/// \brief A pull-based iterator whose reads may fail. +/// +/// Iterator implementations own any resources needed to produce values. Destroying an +/// iterator releases those resources, including when iteration stops before reaching the +/// end. Iterators are not thread-safe unless an implementation explicitly says otherwise. +/// +/// \tparam T Value returned by the iterator. +template <typename T> +class Iterator { + public: + virtual ~Iterator() = default; + + Iterator() = default; + Iterator(const Iterator&) = delete; + Iterator& operator=(const Iterator&) = delete; + + /// \brief Return the next value, or std::nullopt when the iterator is exhausted. + virtual Result<std::optional<T>> Next() = 0; + + /// \brief Consume the remaining values into a vector. + Result<std::vector<T>> ToVector() { + if constexpr (!std::is_move_constructible_v<T>) { + static_assert(std::is_copy_constructible_v<T>, + "Iterator::ToVector requires T to be move- or copy-constructible"); + + // A vector cannot grow portably when T has an explicitly deleted move + // constructor. Stage copy-only values in a deque, then use vector's + // forward-range constructor to allocate the final storage once. Review Comment: Reworded the comment to explain that deque staging avoids copying previously collected values during growth and lets the final vector allocate once. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
