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std::fpos

From cppreference.com
< cpp‎ | io
Defined in header <ios>
template< class State >
class fpos;

Specializations of the class template std::fpos identify absolute positions in a stream or in a file. Each object of type fpos holds the byte position in the stream (typically as a private member of type std::streamoff) and the current shift state, a value of type State (typically std::mbstate_t).

The following specializations of std::fpos are provided:

Type Definition
streampos std::fpos<std::char_traits<char>::state_type>
wstreampos std::fpos<std::char_traits<wchar_t>::state_type>

In addition, std::u16streampos and std::u32streampos are provided as implementation-defined types that satisfy the requirements of pos_type

(since C++11)

[edit] Member functions

gets/sets the value of the shift state
(public member function)

In addition, the following member functions and operators must be provided, although it's unspecified if they are members or non-member.

  • A constructor that accepts an argument of type int.
  • A constructor that accepts an argument of type std::streamoff. This constructor must also accept the special value std::streamoff(-1): the std::fpos constructed in this manner is returned by some stream operations to indicate errors.
  • A conversion operator that converts fpos to std::streamoff with the value equal to the offset from std::fpos(0).
  • operator== that compares two objects of type std::fpos and returns a value of type convertible to bool
  • operator!= that compares two objects of type std::fpos and returns a value of type convertible to bool
  • operator- and operator-= which can subtract std::streamoff from an std::fpos
  • operator- which can subtract two objects of type std::fpos producing an std::streamoff

[edit] Notes

Some of the I/O streams member functions return and manipulate objects of member typedef pos_type. For streams, these member typedefs are provided by the template parameter Traits, which defaults to std::char_traits, which define their pos_types to be instantiations of std::fpos. User-defined pos_types (e.g. in a custom Traits type) are required to satisfy the pos_type type requirements.

[edit] See also

represents relative file/stream position (offset from fpos), sufficient to represent any file size
(typedef)
returns the output position indicator
(public member function of std::basic_ostream) [edit]
sets the output position indicator
(public member function of std::basic_ostream) [edit]
gets the file position indicator
(function) [edit]