std::basic_stringbuf<CharT,Traits,Allocator>:: seekpos

Repositions std::basic_streambuf::gptr and/or std::basic_streambuf::pptr , if possible, to the position indicated by sp .

Effectively executes seekoff ( off_type ( sp ) , std:: ios_base :: beg , which ) .

Parameters

Return value

sp on success or pos_type ( off_type ( - 1 ) ) on failure.

Notes

seekpos() is called by std::basic_streambuf::pubseekpos() , which is called by the single-argument versions of std::basic_istream::seekg() and std::basic_ostream::seekp() .

Example

#include <sstream>
#include <iostream>
 
struct mybuf : std::stringbuf
{
    mybuf(const std::string& str) : std::stringbuf(str) {}
 
    pos_type seekpos(pos_type sp, std::ios_base::openmode which)
    {
        std::cout << "Before seekpos(" << sp << "), size of the get area is "
                  << egptr() - eback() << " with "
                  << egptr() - gptr() << " read positions available.\n";
 
        pos_type rc = std::stringbuf::seekpos(sp, which);
 
        std::cout << "seekpos() returns " << rc << ".\nAfter the call, "
                  << "size of the get area is "
                  << egptr() - eback() << " with "
                  << egptr() - gptr() << " read positions available.\n";
 
        return rc;
    }
};
 
int main()
{
    mybuf buf("12345");
    std::iostream stream(&buf);
    stream.seekg(2);
}

Before seekpos(2), size of the get area is 5 with 5 read positions available.
seekpos() returns 2.
After the call, size of the get area is 5 with 3 read positions available.

Defect reports

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

See also