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

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.

[edit] Parameters

[edit] Return value

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

[edit] Example

[edit] See also

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