c++ - Difficulty overloading operator<< for file handling class -

i have to:

define file_handle class constructor takes string argument (file name), opens file in constructor, , closes in destructor.

as understand it, class used provide raii , trying implement class using file* basic data structure goal make file* smart pointer:

filehandler.h:

// class cfile_handler based on file* class cfile_handler { public:     cfile_handler();                                           // default constructor        cfile_handler(const std::string& filename,                 // constructor                   const std::string& mode);          ~cfile_handler ();                                          // destructor      // modifying member function     void open_file(const std::string& filename,                     const std::string& mode);  protected:     typedef file* ptr;  private:     cfile_handler(const cfile_handler&);                        // prevent copy creation     cfile_handler& operator= (const cfile_handler&);            // prevent copy assignment      ptr c_style_stream;                                         // data member }; 

filehandler.cpp:

// class cfile_handler member implementations // default constuctor cfile_handler::cfile_handler() {  }  // constructor cfile_handler::cfile_handler(const std::string& filename, const std::string& mode = "r")     : c_style_stream( fopen( filename.c_str(), mode.c_str() ) )  {  }  // destructor cfile_handler::~cfile_handler() {     if (c_style_stream) fclose(c_style_stream); }  // modifying member functions void cfile_handler::open_file(const std::string& filename, const std::string& mode) {     c_style_stream = ( fopen( filename.c_str(), mode.c_str() ) ); } 

however, i'm having difficulties in overloading i/o operators<< / >>, can't figure out how implement either of them.

how overload operator<< such class works iostream objects?

edit:

as proposed @lokiastari, better strategy inherit istream , define own streambuf.

could give example or directions implementation of streambuf handles file*?

---

what want provide is:

cfile_handler fh("filename.txt", "r");  std::string file_text; fh >> file_text; 

or:

cfile_handler fh("filename.txt", "w");  fh << "write file"; 

you can derive types of std::streams using std::streambuf handle file*

#include <iostream> #include <stdio.h>  class outputfilepointerstream: public std::ostream {     class outputfilepointerstreambuf: public std::streambuf     {         file*   buffer;         public:             outputfilepointerstreambuf(std::string const& filename)             {                 buffer  = fopen(filename.c_str(), "w");             }             ~outputfilepointerstreambuf()             {                 fclose(buffer);             }             virtual std::streamsize xsputn(const char* s, std::streamsize n) override             {                 static char format[30];                 sprintf(format, "%%.%lds", n);                 fprintf(buffer, format, s);                 return n;             }     };     outputfilepointerstreambuf       buffer;     public:         outputfilepointerstream(std::string const& filename)             : std::ostream(nullptr)             , buffer(filename)         {             rdbuf(&buffer);         } };  int main() {     outputfilepointerstream      filestream("test");      filestream << "testing: " << 5 << "><\n";     filestream << "line again\n"; }