basic_teebuf.hpp

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 * SUPPORT OPEN SCIENCE!  If you use OpenMD or its source code in your
 * research, please cite the appropriate papers when you publish your
 * work.  Good starting points are:
 *
 * [1] Meineke, et al., J. Comp. Chem. 26, 252-271 (2005).
 * [2] Fennell & Gezelter, J. Chem. Phys. 124, 234104 (2006).
 * [3] Sun, Lin & Gezelter, J. Chem. Phys. 128, 234107 (2008).
 * [4] Vardeman, Stocker & Gezelter, J. Chem. Theory Comput. 7, 834 (2011).
 * [5] Kuang & Gezelter, Mol. Phys., 110, 691-701 (2012).
 * [6] Lamichhane, Gezelter & Newman, J. Chem. Phys. 141, 134109 (2014).
 * [7] Lamichhane, Newman & Gezelter, J. Chem. Phys. 141, 134110 (2014).
 * [8] Bhattarai, Newman & Gezelter, Phys. Rev. B 99, 094106 (2019).
 */
 
#ifndef UTILS_MULTISTREAMBUF_HPP
#define UTILS_MULTISTREAMBUF_HPP
 
#include <streambuf>
#include <vector>
 
namespace OpenMD {
 
  /**
   * @class basic_teebuf basic_teebuf.hpp "utils/basic_teebuf.hpp"
   * @brief As a subclass of basic_streambuf,  basic_teebuf can operate on
   * multiple stream simultaneously.
   * @code
   *    std::ofstream file1("file1");
   *    std::ofstream file2("file22");
   *    std::vector<std::streambuf*> buffers;
   *    buffers.push_back(file1.rdbuf());
   *    buffers.push_back(file2.rdbuf());
   *    teebuf tmp(buffers.begin(), buffers.end());
   *    std::ostream myOs(&tmp);
   *    myOs << "hello world";
   * @endcode
   */
  template<class CharT, class Traits = std::char_traits<CharT>>
  class basic_teebuf : public std::basic_streambuf<CharT, Traits> {
  public:
    using streambuf_type = std::basic_streambuf<CharT, Traits>;
    using traits_type    = Traits;
    using char_type      = CharT;
    using int_type       = typename traits_type::int_type;
 
    template<typename ForwardIterator>
    basic_teebuf(ForwardIterator begin, ForwardIterator end) :
        buffers_(begin, end) {}
 
  protected:
    int_type overflow(int_type c = traits_type::eof()) {
      // avoid writing eof to stream
      if (c == traits_type::eof()) { return traits_type::eof(); }
 
      typename std::vector<streambuf_type*>::iterator
          iter;  // typename is needed since it's a dependant name
      for (iter = buffers_.begin(); iter != buffers_.end(); ++iter) {
        if ((*iter)->sputc(c) == traits_type::eof()) {
          return traits_type::eof();
        }
      }
 
      return traits_type::not_eof(c);
    }
 
    int sync() {
      // flush buffer, checking return for eof.
      if (traits_type::eq_int_type(overflow(traits_type::eof()),
                                   traits_type::eof())) {
        return -1;
      }
 
      // flush streams
      typename std::vector<streambuf_type*>::iterator iter;
      for (iter = buffers_.begin(); iter != buffers_.end(); ++iter) {
        if ((*iter)->pubsync() == -1) { return -1; }
      }
 
      return 0;
    }
 
  private:
    std::vector<streambuf_type*> buffers_;
  };
 
  using TeeBuf = basic_teebuf<char>;
}  // namespace OpenMD
 
#endif