/src/Fast-DDS/include/fastrtps/utils/collections/ResourceLimitedVector.hpp

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// Copyright 2019 Proyectos y Sistemas de Mantenimiento SL (eProsima).
//
// 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.

/**
 * @file ResourceLimitedVector.hpp
 *
 */

#ifndef FASTRTPS_UTILS_COLLECTIONS_RESOURCELIMITEDVECTOR_HPP_
#define FASTRTPS_UTILS_COLLECTIONS_RESOURCELIMITEDVECTOR_HPP_

#include "ResourceLimitedContainerConfig.hpp"

#include <assert.h>
#include <algorithm>
#include <type_traits>
#include <vector>

namespace eprosima {
namespace fastrtps {

/**
 * Resource limited wrapper of std::vector.
 *
 * This template class holds an unordered collection of elements using a std::vector or a replacement.
 * It makes use of a \ref ResourceLimitedContainerConfig to setup the allocation behaviour regarding the number of
 * elements in the collection.
 *
 * It features linear increment of the capacity, initial preallocation, and maximum number of elements control.
 *
 * @tparam _Ty                 Element type.
 * @tparam _KeepOrderEnabler   Indicates if element order should be kept when removing items,
 *                             defaults to std::false_type.
 * @tparam _LimitsConfig       Type defining the resource limits configuration,
 *                             defaults to ResourceLimitedContainerConfig
 * @tparam _Alloc              Allocator to use on the underlying collection type, defaults to std::allocator<_Ty>.
 * @tparam _Collection         Type used to store the collection of items, defaults to std::vector<_Ty, _Alloc>.
 *
 * @ingroup UTILITIES_MODULE
 */
template <
    typename _Ty,
    typename _KeepOrderEnabler = std::false_type,
    typename _LimitsConfig = ResourceLimitedContainerConfig,
    typename _Alloc = std::allocator<_Ty>,
    typename _Collection = std::vector<_Ty, _Alloc>>
class ResourceLimitedVector
{
public:

    using configuration_type = _LimitsConfig;
    using collection_type = _Collection;
    using value_type = _Ty;
    using allocator_type = _Alloc;
    using pointer = typename collection_type::pointer;
    using const_pointer = typename collection_type::const_pointer;
    using reference = typename collection_type::reference;
    using const_reference = typename collection_type::const_reference;
    using size_type = typename collection_type::size_type;
    using difference_type = typename collection_type::difference_type;
    using iterator = typename collection_type::iterator;
    using const_iterator = typename collection_type::const_iterator;
    using reverse_iterator = typename collection_type::reverse_iterator;
    using const_reverse_iterator = typename collection_type::const_reverse_iterator;

    /**
     * Construct a ResourceLimitedVector.
     *
     * This constructor receives a \ref ResourceLimitedContainerConfig to setup the allocation behaviour regarding the
     * number of elements in the collection.
     *
     * The cfg parameter indicates the initial number to be reserved, the maximum number of items allowed,
     * and the capacity increment value.
     *
     * @param cfg     Resource limits configuration to use.
     * @param alloc   Allocator object. Forwarded to collection constructor.
     */
    ResourceLimitedVector(
            configuration_type cfg = configuration_type(),
            const allocator_type& alloc = allocator_type())
        : configuration_(cfg)
        , collection_(alloc)
    {
        collection_.reserve(cfg.initial);
    }

    ResourceLimitedVector(
            const ResourceLimitedVector& other)
        : configuration_(other.configuration_)
        , collection_(other.collection_.get_allocator())
    {
        collection_.reserve(other.collection_.capacity());
        collection_.assign(other.collection_.begin(), other.collection_.end());
    }

    virtual ~ResourceLimitedVector () = default;

    ResourceLimitedVector& operator = (
            const ResourceLimitedVector& other)
    {
        clear();
        for (const_reference item : other)
        {
            push_back(item);
        }

        assert(size() == other.size());
        return *this;
    }

    /**
     * Insert value before pos.
     *
     * @param pos   iterator before which the content will be inserted. pos may be the end() iterator.
     * @param value element value to insert.
     *
     * @return Iterator pointing to the inserted value. end() if insertion couldn't be done due to collection limits.
     */
    iterator insert(
            const_iterator pos,
            const value_type& value)
    {
        auto dist = std::distance(collection_.cbegin(), pos);
        if (!ensure_capacity())
        {
            return end();
        }

        return collection_.insert(collection_.cbegin() + dist, value);
    }

    /**
     * Insert value before pos.
     *
     * @param pos   iterator before which the content will be inserted. pos may be the end() iterator.
     * @param value element value to insert.
     *
     * @return Iterator pointing to the inserted value. end() if insertion couldn't be done due to collection limits.
     */
    iterator insert(
            const_iterator pos,
            value_type&& value)
    {
        auto dist = std::distance(collection_.cbegin(), pos);
        if (!ensure_capacity())
        {
            return end();
        }

        return collection_.insert(collection_.cbegin() + dist, std::move(value));
    }

    /**
     * Add element at the end.
     *
     * Adds a new element at the end of the vector, after its current last element.
     * The content of val is copied to the new element.
     *
     * @param val   Value to be copied to the new element.
     *
     * @return pointer to the new element, nullptr if resource limit is reached.
     */
    pointer push_back(
            const value_type& val)
    {
        return emplace_back(val);
    }

    /**
     * Add element at the end.
     *
     * Adds a new element at the end of the vector, after its current last element.
     * The content of val is moved to the new element.
     *
     * @param val   Value to be moved to the new element.
     *
     * @return pointer to the new element, nullptr if resource limit is reached.
     */
    pointer push_back(
            value_type&& val)
    {
        if (!ensure_capacity())
        {
            // Indicate error by returning null pointer
            return nullptr;
        }

        // Move the element at the end of the collection
        collection_.push_back(std::move(val));

        // Return pointer to newly created element
        return &collection_.back();
    }

    /**
     * Construct and insert element at the end.
     *
     * Inserts a new element at the end of the vector, right after its current last element.
     * This new element is constructed in place using args as the arguments for its constructor.
     *
     * @param args   Arguments forwarded to construct the new element.
     *
     * @return pointer to the new element, nullptr if resource limit is reached.
     */
    template<typename ... Args>
    pointer emplace_back(
            Args&& ... args)
    {
        if (!ensure_capacity())
        {
            // Indicate error by returning null pointer
            return nullptr;
        }

        // Construct new element at the end of the collection
        collection_.emplace_back(args ...);

        // Return pointer to newly created element
        return &collection_.back();
    }

    /**
     * Remove element.
     *
     * Removes the first element in the vector that compares equal to val.
     * All iterators may become invalidated if this method returns true.
     *
     * @param val   Value to be compared.
     *
     * @return true if an element was removed, false otherwise.
     */
    bool remove(
            const value_type& val)
    {
        iterator it = std::find(collection_.begin(), collection_.end(), val);
        if (it != collection_.end())
        {
            do_remove(it);
            return true;
        }
        return false;
    }

    /**
     * Remove element.
     *
     * Removes the first element in the vector for which pred returns true.
     * All iterators may become invalidated if this method returns true.
     *
     * @param pred   Unary function that accepts an element in the range as argument and returns a value
     *               convertible to bool.
     *               The value returned indicates whether the element is considered a match in the context
     *               of this function.
     *               The function shall not modify its argument.
     *               This can either be a function pointer or a function object.
     *
     * @return true if an element was removed, false otherwise.
     */
    template<class UnaryPredicate>
    bool remove_if(
            UnaryPredicate pred)
    {
        iterator it = std::find_if(collection_.begin(), collection_.end(), pred);
        if (it != collection_.end())
        {
            do_remove(it);
            return true;
        }
        return false;
    }

    /**
     * Assign vector content.
     *
     * Assigns new contents to the vector, replacing its current contents, and modifying its size accordingly.
     *
     * @param first, last   Input iterators to the initial and final positions in a sequence.
     *                      The range used is [first,last), which includes all the elements between first and last,
     *                      including the element pointed by first but not the element pointed by last.
     *                      The function template argument InputIterator shall be an input iterator type that points
     *                      to elements of a type from which value_type objects can be constructed.
     *                      If the size of this range is greater than the maximum number of elements allowed on the
     *                      resource limits configuration, the elements exceeding that maximum will be silently
     *                      discarded.
     */
    template <class InputIterator>
    void assign(
            InputIterator first,
            InputIterator last)
    {
        size_type n = static_cast<size_type>(std::distance(first, last));
        n = (std::min)(n, configuration_.maximum);
        InputIterator value = first;
        std::advance(value, n);
        collection_.assign(first, value);
    }

    /**
     * Assign vector content.
     *
     * Assigns new contents to the vector, replacing its current contents, and modifying its size accordingly.
     *
     * @param n     New size for the container.
     *              Will be truncated if greater than the maximum allowed on the resource limits configuration.
     * @param val   Value to fill the container with.
     *              Each of the n elements in the container will be initialized to a copy of this value.
     */
    void assign(
            size_type n,
            const value_type& val)
    {
        n = (std::min)(n, configuration_.maximum);
        collection_.assign(n, val);
    }

    /**
     * Assign vector content.
     *
     * Assigns new contents to the vector, replacing its current contents, and modifying its size accordingly.
     *
     * @param il   An initializer_list object.
     *             The compiler will automatically construct such objects from initializer list declarators.
     *             Member type value_type is the type of the elements in the container.
     *             If the size of this list is greater than the maximum number of elements allowed on the
     *             resource limits configuration, the elements exceeding that maximum will be silently discarded.
     */
    void assign(
            std::initializer_list<value_type> il)
    {
        size_type n = (std::min)(il.size(), configuration_.maximum);
        collection_.assign(il.begin(), il.begin() + n);
    }

    /**
     * Wrappers to other basic vector methods.
     * Please refer to https://en.cppreference.com/w/cpp/container/vector
     */
    ///@{
    reference at(
            size_type pos)
    {
        return collection_.at(pos);
    }

    const_reference at(
            size_type pos) const
    {
        return collection_.at(pos);
    }

    reference operator [](
            size_type pos)
    {
        return collection_[pos];
    }

    const_reference operator [](
            size_type pos) const
    {
        return collection_[pos];
    }

    reference front()
    {
        return collection_.front();
    }

    const_reference front() const
    {
        return collection_.front();
    }

    reference back()
    {
        return collection_.back();
    }

    const_reference back() const
    {
        return collection_.back();
    }

    iterator begin() noexcept
    {
        return collection_.begin();
    }

    const_iterator begin() const noexcept
    {
        return collection_.begin();
    }

    const_iterator cbegin() const noexcept
    {
        return collection_.cbegin();
    }

    iterator end() noexcept
    {
        return collection_.end();
    }

    const_iterator end() const noexcept
    {
        return collection_.end();
    }

    const_iterator cend() const noexcept
    {
        return collection_.cend();
    }

    reverse_iterator rbegin() noexcept
    {
        return collection_.rbegin();
    }

    const_reverse_iterator rbegin() const noexcept
    {
        return collection_.rbegin();
    }

    const_reverse_iterator crbegin() const noexcept
    {
        return collection_.crbegin();
    }

    reverse_iterator rend() noexcept
    {
        return collection_.rend();
    }

    const_reverse_iterator rend() const noexcept
    {
        return collection_.rend();
    }

    const_reverse_iterator crend() const noexcept
    {
        return collection_.crend();
    }

    bool empty() const noexcept
    {
        return collection_.empty();
    }

    size_type size() const noexcept
    {
        return collection_.size();
    }

    size_type capacity() const noexcept
    {
        return collection_.capacity();
    }

    size_type max_size() const noexcept
    {
        return (std::min)(configuration_.maximum, collection_.max_size());
    }

    void clear()
    {
        collection_.clear();
    }

    iterator erase(
            const_iterator pos)
    {
        return collection_.erase(pos);
    }

    iterator erase(
            const_iterator first,
            const_iterator last)
    {
        return collection_.erase(first, last);
    }

    void pop_back()
    {
        collection_.pop_back();
    }

    value_type* data()
    {
        return collection_.data();
    }

    const value_type* data() const
    {
        return collection_.data();
    }

    ///@}

    /**
     * Const cast to underlying collection.
     *
     * Useful to easy integration on old APIs where a traditional container was used.
     *
     * @return const reference to the underlying collection.
     */
    operator const collection_type& () const noexcept
    {
        return collection_;
    }

protected:

    configuration_type configuration_;
    collection_type collection_;

    /**
     * Make room for one item.
     *
     * Tries to ensure that a new item can be added to the container.
     *
     * @return true if there is room for a new item, false if resource limit is reached.
     */
    bool ensure_capacity()
    {
        size_type size = collection_.size();
        size_type cap = collection_.capacity();
        if (size == cap)
        {
            // collection is full, check resource limit
            if (cap < configuration_.maximum)
            {
                // increase collection capacity
                assert(configuration_.increment > 0);
                cap += configuration_.increment;
                cap = (std::min)(cap, configuration_.maximum);
                collection_.reserve(cap);
            }
            else
            {
                return false;
            }
        }

        return true;
    }

    /**
     * Remove element.
     *
     * Removes the element pointed to by it.
     * All iterators may become invalidated.
     * This version doesn't keep the order of insertion, optimizing the number of copies performed.
     *
     * @param it   Iterator pointing to the item to be removed.
     */
    template <typename Enabler = _KeepOrderEnabler>
    typename std::enable_if<!Enabler::value, void>::type do_remove(
            iterator it)
    {
        // Copy last element into the element being removed
        if (it != --collection_.end())
        {
            *it = std::move(collection_.back());
        }

        // Then drop last element
        collection_.pop_back();
    }

    /**
     * Remove element.
     *
     * Removes the element pointed to by it.
     * All iterators may become invalidated.
     * This version keeps the order of insertion, so when removing an item different from the last one,
     * part of the collection will be copied.
     *
     * @param it   Iterator pointing to the item to be removed.
     */
    template <typename Enabler = _KeepOrderEnabler>
    typename std::enable_if<Enabler::value, void>::type do_remove(
            iterator it)
    {
        collection_.erase(it);
    }

};

}  // namespace fastrtps
}  // namespace eprosima

#endif /* FASTRTPS_UTILS_COLLECTIONS_RESOURCELIMITEDVECTOR_HPP_ */

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Created: 2022-08-24 06:19