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() | ||||||
| which | - | defines whether the input sequences, the output sequence, or both are affected. It can be one or a combination of the following constants:
|
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);
}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
invokes seekpos() (public member function of std::basic_streambuf) | |
| [virtual] | repositions the next pointer in the input sequence, output sequence, or both, using relative addressing (virtual protected member function) |
| [virtual] | repositions the file position, using absolute addressing (virtual protected member function of std::basic_filebuf) |
| [virtual] | repositions the next pointer in the input sequence, output sequence, or both using absolute addressing (virtual protected member function of std::strstreambuf) |
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