Pushes back one character (passed as a parameter) onto strio such
that a subsequent buffered read will
return it. Pushing back behind the beginning of the buffer string is not possible. Nothing will be
done if such an attempt is made. In other case, there is no limitation for
multiple pushbacks.
/*
* call-seq:
* strio.ungetc(integer) -> nil
*
* Pushes back one character (passed as a parameter) onto *strio*
* such that a subsequent buffered read will return it. Pushing back
* behind the beginning of the buffer string is not possible. Nothing
* will be done if such an attempt is made.
* In other case, there is no limitation for multiple pushbacks.
*/
static VALUE
strio_ungetc(self, ch)
VALUE self, ch;
{
struct StringIO *ptr = readable(StringIO(self));
int cc = NUM2INT(ch);
long len, pos = ptr->pos;
if (cc != EOF && pos > 0) {
if ((len = RSTRING(ptr->string)->len) < pos-- ||
(unsigned char)RSTRING(ptr->string)->ptr[pos] !=
(unsigned char)cc) {
strio_extend(ptr, pos, 1);
RSTRING(ptr->string)->ptr[pos] = cc;
OBJ_INFECT(ptr->string, self);
}
--ptr->pos;
ptr->flags &= ~STRIO_EOF;
}
return Qnil;
}