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std::basic_streambuf<CharT,Traits>::pubseekoff, std::basic_streambuf<CharT,Traits>::seekoff

pos_type pubseekoff( off_type off, std::ios_base::seekdir dir,
                     std::ios_base::openmode which = ios_base::in | ios_base::out );

(1)

protected:
virtual pos_type seekoff( off_type off, std::ios_base::seekdir dir,
                          std::ios_base::openmode which = ios_base::in | ios_base::out );

(2)

Sets the position indicator of the input and/or output sequence relative to some other position.

1) Calls seekoff(off, dir, which) of the most derived class.

2) The base class version of this function has no effect. The derived classes may override this function to allow relative positioning of the position indicator.

Parameters

off - relative position to set the position indicator to.

dir

defines base position to apply the relative offset to. It can be one of the following constants:

Constant	Explanation
`beg`	the beginning of a stream
`end`	the ending of a stream
`cur`	the current position of stream position indicator

which

defines which of the input and/or output sequences to affect. It can be one or a combination of the following constants:

Constant	Explanation
`in`	affect the input sequence
`out`	affect the output sequence

Note

Not all combinations of parameters may be valid, see the derived versions of seekoff for details.

Return value

1) The return value of seekoff(off, dir, which)

2) The resulting absolute position as defined by the position indicator. The base class version returns pos_type(off_type(-1)).

Example

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 55	C++98	the base class version of `seekoff` returned an undefined invalid stream position	returns `pos_type(off_type(-1))`

pubseekpos	invokes `seekpos()` (public member function)
seekoff [virtual]	repositions the file position, using relative addressing (virtual protected member function of `std::basic_filebuf<CharT,Traits>`)
seekoff [virtual]	repositions the next pointer in the input sequence, output sequence, or both, using relative addressing (virtual protected member function of `std::basic_stringbuf<CharT,Traits,Allocator>`)
seekoff [virtual]	repositions the next pointer in the input sequence, output sequence, or both, using relative addressing (virtual protected member function of `std::strstreambuf`)