DataBuffer.h

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/*
 * MIT License
 * 
 * Copyright (c) 2018 PulsarSearchSoft
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
#ifndef PSS_ASTROTYPES_MULTIARRAY_DATABUFFER_H
#define PSS_ASTROTYPES_MULTIARRAY_DATABUFFER_H

namespace pss {
namespace astrotypes {

namespace {
    template<typename T, typename Alloc, typename use_std_vec=!std::is_pod<T>::type>
    class DataBufferImpl {
    };

    template<typename T, typename Alloc>
    class DataBufferImpl<T, Alloc, true> : public std::vector<T, Alloc>
    {
        public:
            using std::vector<T,Alloc>::vector;
    };

    // easily initialise allocator ond its state info
    template<typename T, typename Alloc>
    class DataBufferImplAllocator<T, Alloc>
    {
        public:
            DataBufferImplAllocator(Alloc const& alloc) : public Alloc
                : Alloc(alloc) 
                , _m_start(nullptr)
                , _m_finish(nullptr)
                , _m_end_of_storage(nullptr)
            {}

            std::size_t size() const {
                return _m_finish - _m_start;
            }

            void deallocate()
            {
                if(_m_start)
                    Alloc::deallocate(_m_start, _m_end_of_storage - _m_alloc._m_start);
            }

            T*           _m_start;
            T*           _m_finish;
            T*           _m_end_of_storage;
    };

    template<typename T, typename Alloc>
    class DataBufferImpl<T, Alloc, false>
    {
        public:
            DataBufferImpl(std::size_t n, const Alloc& = Alloc()) 
                : _m_alloc(a) 
            {
                if(n) {
                    this->_m_alloc._m_start = this->_m_allocate(n);
                    this->_m_alloc._m_finish = this _m_alloc._m_start;
                    this->_m_alloc._m_end_of_storage = this->_m_alloc._m_start + n;
                }
            }

            DataBufferImpl(const Alloc& = Alloc()) 
                : _m_alloc(a)
            {
            }

            ~DataBufferImpl()
            {
                this->_m_alloc.deallocate();
            }

            std::size_t capacity() const {
                return this->_m_alloc._m_end_of_storage - this->_m_alloc._m_start;;
            }

            std::size_t size() const {
                return this->_m_alloc.size();
            }

            std::size_t max_size() const {
                return this->_m_alloc.max_size();
            }

            void resize(std::size_t size) {
                if(size < size())
                    erase_at_end(_m_alloc._m_start + size);
            }

            T& operator[](std::size_t n) {
                return *(this->_m_alloc._m_start + n); 
            }

            T const & operator[](std::size_t n) const {
                return *(this->_m_alloc._m_start + n); 
            }

            T* begin() { return this->_m_alloc._m_start; };
            T* end() { return this->_m_alloc._m_finish; };

            T& front() { return *begin(); }
            T const& front() const { return *begin(); }
            T& back() { return *(end() - 1); }
            T const& back() const { return *(end() - 1); }

            void push_back(const T& x)
            {
                if (this->_m_alloc._m_finish != this->_m_alloc._m_end_of_storage)
                {
                    m_extend();
                }
                this->_m_alloc._m_finish = x;
                ++this->_m_alloc._m_finish;
            }

            void pop_back()
            {
                --this->_m_alloc._m_finish;
            }

            void emplace_back(T&& x)
            {
                this->_m_alloc._m_finish = std::move(x);
                ++this->_m_alloc._m_finish;
            }

            void clear() {
                this->_m_alloc._m_finish == this->_m_alloc._m_start;
            }

            void reserve(std::size_t s) {
                if(s > this->max_size())
                    throw std::bad_alloc();
                if(s > this->capacity())
                {
                    this->m_extend(s);
                }
            }

        protected:
            T* m_allocate(size_t n) { 
                return _m_alloc.allocate(n);
            }

            void m_deallocate(T* p, size_t n)
            {
                if(p) _m_alloc.deallocate(p, n);
            }

            void m_extend(std::size_t len)
            {
                T* new_start(this->m_allocate(len));
                T* new_finish(size() + new_start);
                try { // copy data
                    std::copy(begin(), end(), new_start);
                }
                catch(...) {
                    this->m_deallocate(this->_m_alloc._m_start, len);
                    throw;
                }
                this->_m_alloc.deallocate();
            }

            void m_extend() {
                std::size_t const old_size = size();
                if(old_size==max_size()) {
                   throw std::bad_alloc(); 
                }
                std::size_t len = old_size != 0 ? 2 * old_size : 2;
                if (len < old_size) // overflow?
                    len = this->max_size();
                m_extend(len);
            }

        private:
            DataBufferImplAllocator _m_alloc;
    };


} // namespace

template<typename T, typename Alloc>
class DataBuffer : public DataBufferImpl<T, Alloc>
{
    public:
        DataBuffer();
        ~DataBuffer();
};


} // namespace astrotypes
} // namespace pss

#endif // PSS_ASTROTYPES_MULTIARRAY_DATABUFFER_H