variable_length_string.hpp

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//
// (c) Copyright 2017 DESY,ESS
//               2018 Eugen Wintersberger
//
// This file is part of h5cpp.
//
// This library is free software; you can redistribute it and/or modify it
// under the terms of the GNU Lesser General Public License as published
// by the Free Software Foundation; either version 2.1 of the License, or
// (at your option) any later version.
//
// This library is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty ofMERCHANTABILITY
// or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
// License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with this library; if not, write to the
// Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor
// Boston, MA  02110-1301 USA
// ===========================================================================
//
// Author: Eugen Wintersberger <eugen.wintersberger@gmail.com>
// Created on: Apr 4, 2019
//
#pragma once

#include <vector>
#include <string>
#include <algorithm>

namespace hdf5 {

template<typename CharT>
using VarLengthStringBuffer = std::vector<CharT*>;

template<typename T>
struct VarLengthStringTrait
{
    using BufferType = VarLengthStringBuffer<char>;
    using DataType = T;

    static BufferType to_buffer(const T &)
    {
      return BufferType();
    }

    static void from_buffer(const BufferType &, DataType &)
    { }
};

template<>
struct VarLengthStringTrait<std::string>
{
  using BufferType = VarLengthStringBuffer<char>;
  using DataType = std::string;


  static BufferType to_buffer(const DataType &data)
  {
    return BufferType{const_cast<char*>(data.c_str())};
  }

  static void from_buffer(const BufferType &buffer,DataType &data)
  {
    data = DataType(buffer[0],std::strlen(buffer[0]));
  }
};

template<>
struct VarLengthStringTrait<std::vector<std::string>>
{
  using BufferType = VarLengthStringBuffer<char>;
  using DataType = std::vector<std::string>;

  static BufferType to_buffer(const DataType &data)
  {
    BufferType buffer;
    std::transform(data.begin(),data.end(),std::back_inserter(buffer),
                   [](const std::string &str)
                   {
                    return const_cast<char*>(str.c_str());
                   });
    return buffer;
  }

  static void from_buffer(const BufferType &buffer,DataType &data)
  {
    std::transform(buffer.begin(),buffer.end(),data.begin(),
                   [](const char *ptr)
                   {
                     return std::string(ptr,std::strlen(ptr));
                   });
  }
};


}