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std::basic_stringbuf::seekpos(3) | C++ Standard Libary | std::basic_stringbuf::seekpos(3) |
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)
2022.07.31 | http://cppreference.com |