NAME¶

std::basic_stringbuf::seekpos - std::basic_stringbuf::seekpos

Synopsis¶

protected:

virtual pos_type seekpos(pos_type sp,

std::ios_base::openmode which = std::ios_base::in | std::ios_base::out );

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¶

sp - stream position, such as one obtained by seekoff() or seekpos()
defines whether the input sequences, the output sequence, or both are
affected. It can be one or a combination of the following constants:
which -
Constant Explanation
in affect the input sequence
out affect the output sequence

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¶

// Run this code

#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);
}

Output:¶

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

See also¶

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