LoanableCollection.hpp

// Copyright 2020 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.

 
#ifndef FASTDDS_DDS_CORE__LOANABLECOLLECTION_HPP
#define FASTDDS_DDS_CORE__LOANABLECOLLECTION_HPP
 
#include <cstdint>
 
namespace eprosima {
namespace fastdds {
namespace dds {

class LoanableCollection
{
public:
 
    using size_type = int32_t;
    using element_type = void*;

    const element_type* buffer() const
    {
        return elements_;
    }

    bool has_ownership() const
    {
        return has_ownership_;
    }

    size_type maximum() const
    {
        return maximum_;
    }

    size_type length() const
    {
        return length_;
    }

    bool length(
            size_type new_length)
    {
        if (new_length < 0)
        {
            return false;
        }
 
        if (new_length <= maximum_)
        {
            length_ = new_length;
            return true;
        }
 
        if (!has_ownership_)
        {
            return false;
        }
 
        resize(new_length);
        length_ = new_length;
        return true;
    }

    bool loan(
            element_type* buffer,
            size_type new_maximum,
            size_type new_length)
    {
        if (has_ownership_ && maximum_ > 0)
        {
            return false;
        }
 
        if ((nullptr == buffer) || (new_maximum < new_length) || (new_maximum < 1))
        {
            return false;
        }
 
        maximum_ = new_maximum;
        length_ = new_length;
        elements_ = buffer;
        has_ownership_ = false;
        return true;
    }

    element_type* unloan(
            size_type& maximum,
            size_type& length)
    {
        if (has_ownership_)
        {
            return nullptr;
        }
 
        element_type* ret_val = elements_;
        maximum = maximum_;
        length = length_;
 
        maximum_ = 0;
        length_ = 0;
        elements_ = nullptr;
        has_ownership_ = true;
 
        return ret_val;
    }

    element_type* unloan()
    {
        size_type max, len;
        return unloan(max, len);
    }
 
protected:

    LoanableCollection() = default;
 
    virtual void resize(
            size_type new_length) = 0;
 
    size_type maximum_ = 0;
    size_type length_ = 0;
    element_type* elements_ = nullptr;
    bool has_ownership_ = true;
};
 
} // namespace dds
} // namespace fastdds
} // namespace eprosima
 
#endif // FASTDDS_DDS_CORE__LOANABLECOLLECTION_HPP