[PATCH] Coverity issue 434132

Hi all,
  the attached patch tries to address Coverity Scan issue 434132 -
(Improper use of negative value (REVERSE_NEGATIVE).

This is done by moving the check to the StoreIOBuffer constructor,
making it more consitently enforced. It also changes the type of a
data field from unsigned int to bool.

What do you think?

--
    /kinkie