Repositionsstd::basic_streambuf::gptr and/orstd::basic_streambuf::pptr, if possible, to the position indicated bysp.

Ifstd::ios_base::in is set inwhich, attempts to repositiongptr() (the next pointer in the get area). Ifstd::ios_base::out is set inwhich, attempts to repositionpptr() (the next pointer in the put area). If neither bit is set inwhich, the operation fails.

Each next pointer is repositioned as follows:

• If the next pointer is null, the operation fails.
• Otherwise, the new offsetnewoff (of typeoff_type) is determined by callingsp.offset(). Ifnewoff is negative, out of bounds of the buffer, or invalid, the operation fails.
• Otherwise, the next pointer is assigned as if bygptr()= eback()+ newoff orpptr()= pbase()+ newoff.

[edit]Parameters

[edit]Return value

The resultant offset converted topos_type on success orpos_type(off_type(-1)) on failure.

[edit]Notes

seekpos() is called bystd::basic_streambuf::pubseekpos(), which is called by the single-argument versions ofstd::basic_istream::seekg() andstd::basic_ostream::seekp().

[edit]Example

#include <cstring>#include <iostream>#include <strstream> struct mybuf:std::strstreambuf{    mybuf(constchar* str):std::strstreambuf(str,std::strlen(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::strstreambuf::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.

[edit]Defect reports

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

[edit]See also

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