std::basic_spanbuf<CharT,Traits>:: seekoff

protected : pos_type seekoff ( off_type off, std:: ios_base :: seekdir dir, std:: ios_base :: openmode which = std:: ios_base :: in | std:: ios_base :: out ) override ;		(since C++23)

Repositions the next pointer to get and/or put area, if possible, to the position that corresponds to exactly off characters from beginning, end, or current position of the get and/or put area of the buffer.

Let n be the number of CharT elements in underlying buffer, or ​ 0 ​ when there is no underlying buffer, this function fails if

• the next pointer to the get and/or put area to reposition is null and the computed newoff (see below) is not zero, which may occur if there is no underlying buffer, or the * this is not opened in the mode required by which , or
• dir is std::ios_base::cur and both std::ios_base::in and std::ios_base::out are set in which , or
• the computed newoff is not representable in off_type , less than zero, or greater than n .

newoff is computed as below:

• If dir is std::ios_base::beg , newoff is off .
• If dir is std::ios_base::cur , newoff is
  • pptr ( ) - pbase ( ) + off if std::ios_base::out is set in which , or
  • gptr ( ) - eback ( ) + off if std::ios_base::in is set in which .
• If dir is std::ios_base::end , newoff is
  • pptr ( ) - pbase ( ) + off if std::ios_base::out but not std::ios_base::in is set in the open mode of * this ,
  • otherwise, off + n .

This function repositions the next pointer to get and/or put area to pbuf + newoff on success if std::ios_base::in and/or std::ios_base::out is correspondingly set in which , where pbuf is the pointer to the beginning of the underlying buffer, or the null pointer value if there is no underlying buffer.

Parameters

off	-	relative position to set the next pointer(s) to
dir	-	defines base position to apply the relative offset to. It can be one of the following constants: Constant Explanation beg the beginning of a stream end the ending of a stream cur the current position of stream position indicator
which	-	defines whether the input sequences, the output sequence, or both are affected. It can be one or a combination of the following constants: Constant Explanation in affect the input sequence out affect the output sequence

Return value

pos_type ( newoff ) on success, pos_type ( off_type ( - 1 ) ) on failure.

Example

This section is incomplete Reason: no example

See also

seekoff [virtual]	repositions the next pointer in the input sequence, output sequence, or both, using relative addressing (virtual protected member function of std::basic_stringbuf<CharT,Traits,Allocator> )
seekoff [virtual]	repositions the next pointer in the input sequence, output sequence, or both, using relative addressing (virtual protected member function of std::strstreambuf )