streambuf::seekoff


virtual protected member function
streampos seekoff ( streamoff off, ios_base::seekdir way, ios_base::openmode which = ios_base::in | ios_base::out );

Set internal position pointer to relative position

This member is called to set a new value for the position pointer in streambuf-derived objects. The public member function pubseekoff calls this protected member function to perform this action.

This is a virtual member function that shall be redefined in derived classes to behave as expected by setting the internal pointer specified by which to a position offset off characters relative to the direction way.

Its default behavior in streambuf is to do nothing and return the invalid position -1, but it is redefined in both standard derived classes, filebuf and stringbuf, to behave as expected specifically for each type of buffer (see filebuf::seekoff and stringbuf::seekoff).

Parameters

off
Offset value. This is relative to the way parameter.
It is a value of type streamoff.
way
Object of type ios_base::seekdir. It may take any of the following constant values:
valueoffset is relative to...
ios_base::begbeginning of the stream buffer
ios_base::curcurrent position in the stream buffer
ios_base::endend of the stream buffer
which
Determines which of the internal position pointers shall be modified, either the get pointer (input), the put pointer (output) or both. It is an object of type ios_base::openmode, that may take any combination of the following significant constant values:
valueposition pointer affected
ios_base::inModify get pointer position
ios_base::outModify put pointer position


Return Value

The new position value of the modified position pointer.
Errors are expected to be signaled by an invalid position value, like -1.

Basic template member declaration

( basic_streambuf<charT,traits> )
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typedef traits::pos_type pos_type;
typedef traits::off_type off_type;
pos_type seekoff (off_type off, ios_base::seekdir way, ios_base which = ios_base::in | ios_base::out );


See also

streambuf::pubseekoff Set internal position pointer to relative position (public member function)
streambuf::seekpos Set internal position pointer to absolute position (virtual protected member function)