include/paimon/compare.h

// Licensed to the Apache Software Foundation (ASF) under one
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// 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
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// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

// Adapted from Apache Arrow
// https://github.com/apache/arrow/blob/apache-arrow-17.0.0/cpp/src/arrow/util/compare.h

#pragma once

#include <memory>
#include <type_traits>
#include <utility>

#include "paimon/macros.h"
#include "paimon/type_fwd.h"

namespace paimon::util {

/// CRTP helper for declaring equality comparison. Defines operator== and operator!=
template <typename T>
class PAIMON_EXPORT EqualityComparable {
 public:
    ~EqualityComparable() {
        static_assert(
            std::is_same_v<decltype(std::declval<const T>().Equals(std::declval<const T>())), bool>,
            "EqualityComparable depends on the method T::Equals(const T&) const");
    }

    template <typename... Extra>
    bool Equals(const std::shared_ptr<T>& other, Extra&&... extra) const {
        if (other == nullptr) {
            return false;
        }
        return cast().Equals(*other, std::forward<Extra>(extra)...);
    }

    struct PtrsEqual {
        bool operator()(const std::shared_ptr<T>& l, const std::shared_ptr<T>& r) const {
            return l->Equals(r);
        }
    };

    bool operator==(const T& other) const {
        return cast().Equals(other);
    }
    bool operator!=(const T& other) const {
        return !(cast() == other);
    }

 private:
    const T& cast() const {
        return static_cast<const T&>(*this);
    }
};

}  // namespace paimon::util