//

// Copyright (c) 2023 Dmitry Arkhipov (grisumbras@yandex.ru)

//

// Distributed under the Boost Software License, Version 1.0. (See accompanying

// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

//

// Official repository: https://github.com/boostorg/json

//

#ifndef BOOST_JSON_DETAIL_SBO_BUFFER_HPP

#define BOOST_JSON_DETAIL_SBO_BUFFER_HPP

#include <boost/json/detail/config.hpp>

#include <boost/json/detail/except.hpp>

#include <string>

#include <array>

namespace boost {

namespace json {

namespace detail {

template< std::size_t N >

class sbo_buffer

{

    struct size_ptr_pair

    {

        std::size_t size;

        char* ptr;

    };

    BOOST_STATIC_ASSERT( N >= sizeof(size_ptr_pair) );

    union {

        std::array<char, N> buffer_;

        std::size_t capacity_;

    };

    char* data_ = buffer_.data();

    std::size_t size_ = 0;

    bool

    is_small() const noexcept

    {

        return data_ == buffer_.data();

    }

    void

    dispose()

    {

        if( is_small() )

            return;

        delete[] data_;

#if defined(__GNUC__)

# pragma GCC diagnostic push

# pragma GCC diagnostic ignored "-Wmissing-field-initializers"

#endif

        buffer_ = {};

#if defined(__GNUC__)

# pragma GCC diagnostic pop

#endif

        data_ = buffer_.data();

    }

    static constexpr

    std::size_t

    max_size() noexcept

    {

        return BOOST_JSON_MAX_STRING_SIZE;

    }

public:

    sbo_buffer()

        : buffer_()

    {}

    sbo_buffer( sbo_buffer&& other ) noexcept

        : size_(other.size_)

    {

        if( other.is_small() )

        {

            buffer_ = other.buffer_;

            data_ = buffer_.data();

        }

        else

        {

            data_ = other.data_;

            other.data_ = other.buffer_.data();

        }

        BOOST_ASSERT( other.is_small() );

    }

    sbo_buffer&

    operator=( sbo_buffer&& other ) noexcept

    {

        if( &other == this )

            return this;

        if( other.is_small() )

        {

            buffer_ = other.buffer_;

            data_ = buffer_.data();

        }

        else

        {

            data_ = other.data_;

            other.data_ = other.buffer_.data();

        }

        size_ = other.size_;

        other.size_ = 0;

        return *this;

    }

    ~sbo_buffer()

    {

        if( !is_small() )

            delete[] data_;

    }

    std::size_t

    capacity() const noexcept

    {

        return is_small() ? buffer_.size() : capacity_;

    }

    void

    reset() noexcept

    {

        dispose();

        clear();

    }

    void

    clear()

    {

        size_ = 0;

    }

    void

    grow( std::size_t size )

    {

        if( !size )

            return;

        if( max_size() - size_ < size )

        {

            BOOST_STATIC_CONSTEXPR source_location loc = BOOST_CURRENT_LOCATION;

            detail::throw_system_error( error::number_too_large, &loc );

        }

        std::size_t const old_capacity = this->capacity();

        std::size_t new_capacity = size_ + size;

        // growth factor 2

        if( old_capacity <= max_size() - old_capacity ) // check for overflow

            new_capacity = (std::max)(old_capacity * 2, new_capacity);

        char* new_data = new char[new_capacity];

        std::memcpy(new_data, data_, size_);

        dispose();

        data_ = new_data;

        capacity_ = new_capacity;

    }

    char*

    append( char const* ptr, std::size_t size )

    {

        grow(size);

        if(BOOST_JSON_LIKELY( size ))

            std::memcpy( data_ + size_, ptr, size );

        size_ += size;

        return data_;

    }

    std::size_t

    size() noexcept

    {

        return size_;

    }

};

} // namespace detail

} // namespace json

} // namespace boost

#endif // BOOST_JSON_DETAIL_SBO_BUFFER_HPP