virtual int_type pbackfail(int_type c = T::eof());
The protected virtual member function endeavors to put back an element into the input buffer, then make it the current
element (pointed to by the next pointer). If c
compares equal to T::
eof
()
, the element to push back is effectively the
one already in the stream before the current element. Otherwise, that element is replaced by x =
T::
to_char_type
(c)
. The function can put back an element in various ways:
x
, it can simply decrement the
next pointer for the input buffer.mode &
ios_base::
out
is nonzero), it can store x
into the putback position and decrement the next pointer for the
input buffer.If the function cannot succeed, it returns T::eof()
. Otherwise, it returns T::
not_eof
(c)
.