99b8a4f234
Summary: Skiplist ReverseIterator and Distance Approximation Test Plan: manual Reviewers: florijan, buda Reviewed By: buda Subscribers: pullbot, florijan, buda Differential Revision: https://phabricator.memgraph.io/D44
91 lines
2.1 KiB
C++
91 lines
2.1 KiB
C++
#pragma once
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#include <utility>
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#include "utils/assert.hpp"
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#include <ext/aligned_buffer.h>
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/**
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* @class Placeholder
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*
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* @brief
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* Placeholder is used to allocate memory for an object on heap providing
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* methods for setting and getting the object and making sure that the
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* object is initialized.
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*
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* @tparam T type of object to be wrapped in the placeholder
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*/
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template <class T>
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class Placeholder {
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public:
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Placeholder() = default;
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Placeholder(Placeholder &) = delete;
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Placeholder(Placeholder &&) = delete;
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/**
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* The destructor automatically calls the wrapped objects destructor.
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*/
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~Placeholder() {
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if (initialized) get().~T();
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};
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/**
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* @return returns true if object is set in memory otherwise false.
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*/
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bool is_initialized() { return initialized; }
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T &get() noexcept {
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runtime_assert(initialized, "Placeholder object not initialized");
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return *data._M_ptr();
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}
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/**
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* @return const reference to object.
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*/
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const T &get() const noexcept {
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runtime_assert(initialized, "Placeholder object not initialized");
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return *data._M_ptr();
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}
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/**
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* Sets item in allocated memory and sets the initialized flag.
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*
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* @param T& item reference to the item initialized in allocated memory
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*/
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void set(const T &item) {
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new (data._M_addr()) T(item);
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initialized = true;
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}
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/**
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* Moves item to allocated memory and sets initialized flag.1
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*
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* @param T&& rvalue reference to the item which is moved to allocated memory
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*/
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void set(T &&item) {
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new (data._M_addr()) T(std::move(item));
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initialized = true;
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}
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/**
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* Emplaces item to allocated memory and calls the Constructor with specified
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* arguments.
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*
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* @tparam Args type of arguments to be passed to the objects constructor.
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* @param Parameters passed to the objects constructor.
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*/
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template <class... Args>
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void emplace(Args &&... args) {
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new (data._M_addr()) T(args...);
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initialized = true;
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}
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private:
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// libstd aligned buffer struct
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__gnu_cxx::__aligned_buffer<T> data;
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bool initialized = false;
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};
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