namespace std {
template <class charT, class traits = char_traits<charT>>
class basic_ifstream
: public basic_istream<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;
// [ifstream.cons], constructors
basic_ifstream();
explicit basic_ifstream(const char* s,
ios_base::openmode mode = ios_base::in);
explicit basic_ifstream(const string& s,
ios_base::openmode mode = ios_base::in);
basic_ifstream(const basic_ifstream& rhs) = delete;
basic_ifstream(basic_ifstream&& rhs);
// [ifstream.assign], assign and swap
basic_ifstream& operator=(const basic_ifstream& rhs) = delete;
basic_ifstream& operator=(basic_ifstream&& rhs);
void swap(basic_ifstream& rhs);
// [ifstream.members], members
basic_filebuf<charT, traits>* rdbuf() const;
bool is_open() const;
void open(const char* s, ios_base::openmode mode = ios_base::in);
void open(const string& s, ios_base::openmode mode = ios_base::in);
void close();
private:
basic_filebuf<charT, traits> sb; // exposition only
};
template <class charT, class traits>
void swap(basic_ifstream<charT, traits>& x,
basic_ifstream<charT, traits>& y);
}
The class basic_ifstream<charT, traits> supports reading from 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:
sb, the filebuf object.
Effects: Constructs an object of class basic_ifstream<charT, traits>, initializing the base class with basic_istream(&sb) and initializing sb with basic_filebuf<charT, traits>()) ([istream.cons], [filebuf.cons]).
explicit basic_ifstream(const char* s,
ios_base::openmode mode = ios_base::in);
Effects: Constructs an object of class basic_ifstream, initializing the base class with basic_istream(&sb) and initializing sb with basic_filebuf<charT, traits>()) ([istream.cons], [filebuf.cons]), then calls rdbuf()->open(s, mode | ios_base::in). If that function returns a null pointer, calls setstate(failbit).
explicit basic_ifstream(const string& s,
ios_base::openmode mode = ios_base::in);
Effects: The same as basic_ifstream(s.c_str(), mode).
basic_ifstream(basic_ifstream&& rhs);
Effects: Move constructs from the rvalue rhs. This is accomplished by move constructing the base class, and the contained basic_filebuf. Next basic_istream<charT, traits>::set_rdbuf(&sb) is called to install the contained basic_filebuf.
basic_ifstream& operator=(basic_ifstream&& rhs);
Effects: Move assigns the base and members of *this from the base and corresponding members of rhs.
Returns: *this.
void swap(basic_ifstream& rhs);
Effects: Exchanges the state of *this and rhs by calling basic_istream<charT, traits>::swap(rhs) and sb.swap(rhs.sb).
template <class charT, class traits>
void swap(basic_ifstream<charT, traits>& x,
basic_ifstream<charT, traits>& y);
Effects: As if by x.swap(y).
basic_filebuf<charT, traits>* rdbuf() const;
Returns: const_cast<basic_filebuf<charT, traits>*>(&sb).
Returns: rdbuf()->is_open().
void open(const char* s, ios_base::openmode mode = ios_base::in);
Effects: Calls rdbuf()->open(s, mode | ios_base::in). If that function does not return a null pointer calls clear(), otherwise calls setstate(failbit) (which may throw ios_base::failure) ([iostate.flags]).
void open(const string& s, ios_base::openmode mode = ios_base::in);
Effects: Calls open(s.c_str(), mode).
Effects: Calls rdbuf()->close() and, if that function returns a null pointer, calls setstate(failbit) (which may throw ios_base::failure) ([iostate.flags]).