27 Input/output library [input.output]

27.9 File-based streams [file.streams]

27.9.4 Class template basic_ofstream [ofstream]

namespace std {
  template <class charT, class traits = char_traits<charT>>
  class basic_ofstream
    : public basic_ostream<charT, traits> {
  public:
    using char_type   = charT;
    using int_type    = typename traits::int_type;
    using pos_type    = typename traits::pos_type;
    using off_type    = typename traits::off_type;
    using traits_type = traits;

    // [ofstream.cons], constructors
    basic_ofstream();
    explicit basic_ofstream(const char* s,
                            ios_base::openmode mode = ios_base::out);
    explicit basic_ofstream(const string& s,
                            ios_base::openmode mode = ios_base::out);
    basic_ofstream(const basic_ofstream& rhs) = delete;
    basic_ofstream(basic_ofstream&& rhs);

    // [ofstream.assign], assign and swap
    basic_ofstream& operator=(const basic_ofstream& rhs) = delete;
    basic_ofstream& operator=(basic_ofstream&& rhs);
    void swap(basic_ofstream& rhs);

    // [ofstream.members], members
    basic_filebuf<charT, traits>* rdbuf() const;

    bool is_open() const;
    void open(const char* s, ios_base::openmode mode = ios_base::out);
    void open(const string& s, ios_base::openmode mode = ios_base::out);
    void close();
  private:
    basic_filebuf<charT, traits> sb; // exposition only
  };

  template <class charT, class traits>
    void swap(basic_ofstream<charT, traits>& x,
              basic_ofstream<charT, traits>& y);
}
1

The class basic_ofstream<charT, traits> supports writing to named files. It uses a basic_filebuf<charT, traits> object to control the associated sequence. For the sake of exposition, the maintained data is presented here as:

  • (1.1)

    sb, the filebuf object.

27.9.4.1 basic_ofstream constructors [ofstream.cons]

basic_ofstream();

1

Effects: Constructs an object of class basic_ofstream<charT, traits>, initializing the base class with basic_ostream(&sb) and initializing sb with basic_filebuf<charT, traits>()) ([ostream.cons], [filebuf.cons]).

explicit basic_ofstream(const char* s, ios_base::openmode mode = ios_base::out);

2

Effects: Constructs an object of class basic_ofstream<charT, traits>, initializing the base class with basic_ostream(&sb) and initializing sb with basic_filebuf<charT, traits>()) ([ostream.cons], [filebuf.cons]), then calls rdbuf()->open(s, mode | ios_base::out). If that function returns a null pointer, calls setstate(failbit).

explicit basic_ofstream(const string& s, ios_base::openmode mode = ios_base::out);

3

Effects: The same as basic_ofstream(s.c_str(), mode).

basic_ofstream(basic_ofstream&& rhs);

4

Effects: Move constructs from the rvalue rhs. This is accomplished by move constructing the base class, and the contained basic_filebuf. Next basic_ostream<charT, traits>::set_rdbuf(&sb) is called to install the contained basic_filebuf.

27.9.4.2 Assign and swap [ofstream.assign]

basic_ofstream& operator=(basic_ofstream&& rhs);

1

Effects: Move assigns the base and members of *this from the base and corresponding members of rhs.

2

Returns: *this.

void swap(basic_ofstream& rhs);

3

Effects: Exchanges the state of *this and rhs by calling basic_ostream<charT, traits>::swap(rhs) and sb.swap(rhs.sb).

template <class charT, class traits> void swap(basic_ofstream<charT, traits>& x, basic_ofstream<charT, traits>& y);

4

Effects: As if by x.swap(y).

27.9.4.3 Member functions [ofstream.members]

basic_filebuf<charT, traits>* rdbuf() const;

1

Returns: const_cast<basic_filebuf<charT, traits>*>(&sb).

bool is_open() const;

2

Returns: rdbuf()->is_open().

void open(const char* s, ios_base::openmode mode = ios_base::out);

3

Effects: Calls rdbuf()->open(s, mode | ios_base::out). If that function does not return a null pointer calls clear(), otherwise calls setstate(failbit) (which may throw ios_base::failure) ([iostate.flags]).

void close();

4

Effects: Calls rdbuf()->close() and, if that function fails (returns a null pointer), calls setstate(failbit) (which may throw ios_base::failure) ([iostate.flags]).

void open(const string& s, ios_base::openmode mode = ios_base::out);

5

Effects: Calls open(s.c_str(), mode).