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DESCRIPTION

The CreateInterruptSet function extends an IST. When calling it, pass the member set ID and the set member number in parentSet and parentMember to uniquely identify which leaf member is to become the parent member. Pass the number of child members to create in setSize. Pass a pointer to a variable of type InterruptSetID in setID. CreateInterruptSet returns noErr if the creation process succeeded, and the variable pointed to by setID contains the member set ID of the new set's child members.

The options parameter operates in these ways to modify the default interrupt dispatching behavior:

• Option kReturnToParentWhenComplete modifies the behavior for successful interrupt completion. Any time a child in a set with this option returns kIsrIsComplete, the dispatcher reinvokes the parent's transversal ISR. A parent can thus reevaluate its children's interrupt requests and can have another child serviced immediately instead of having to traverse the entire interrupt tree again.
• Option kReturnToParentWhenNotComplete modifies the behavior for unsuccessful interrupt completion. Any time a child in a set with this option returns kIsrIsNotComplete, the dispatcher reinvokes the parent's transversal ISR. The parent can then invoke another child to try to service the interrupt request. This process is repeated until one of the children members returns kIsrIsComplete or the parent returns kIsrIsNotComplete. In the latter case, the dispatcher continues traversing the tree between the parent and the root, looking for an ISR to satisfy the interrupt request. If the root is reached, the interrupt request is treated as spurious.
• If no options are set, the dispatcher traverses the tree toward the root, looking for an IST member's interrupt set that has options set, until it arrives at the root.

EXECUTION CONTEXT

CreateInterruptSet may be called only from task level, not from secondary or hardware interrupt level.

RESULT CODES

noErr	0	No error
paramErr	-50	Bad parameter
memFullErr	-108	Not enough room in heap