cpp/io/basic streambuf/uflow

Ensures that at least one character is available in the input area by updating the pointers to the input area (if needed). On success returns the value of that character and advances the value of the get pointer by one character. On failure returns.

The function may update, and  pointers to define the location of newly loaded data (if any). On failure, the function ensures that either or.

The base class version of the function calls underflow and increments gptr.

Parameters
(none)

Return value
The value of the character that was pointed to by the get pointer before it was advanced by one, or otherwise.

The base class version of the function returns the value returned by underflow.

Note
The public functions of std call this function only if or.

The custom streambuf classes that do not use the get area and do not set the get area pointers in basic_streambuf are required to override this function.