Set position of internal position pointer.
  Sets an absolute new position (sp) in the stream for the position pointers specified by parameter which.

Parameters.

pos

New position for the position pointer.
This is an object of class streampos.

which

Determines which of the internal position pointers shall be modified, either in, out or both. It is an object of type ios_base::openmode that may take any combination of the following significant constant values:

• ios_base::in Modify input position.
• ios_base::out Modify output position.

Return Value.
  The new position value of the modified position pointer.
  In case of error the value returned is an invalid position.

Basic template member declaration ( basic_stringbuf<charT,traits,Allocator> ):

typedef traits::pos_type pos_type; pos_type seekpos (pos_type sp, ios_base which = ios_base::in | ios_base::out );

See also.
  streambuf::pubseekpos, seekoff
  stringbuf class