getbyte

/*
 * call-seq:
 *   strio.getc   -> fixnum or nil
 *
 * See IO#getc.
 */
static VALUE
strio_getc(self)
    VALUE self;
{
    struct StringIO *ptr = readable(StringIO(self));
    int c;
    if (ptr->pos >= RSTRING(ptr->string)->len) {
        ptr->flags |= STRIO_EOF;
        return Qnil;
    }
    c = RSTRING(ptr->string)->ptr[ptr->pos++];
    return CHR2FIX(c);
}