IoSchedulerJobFunc
typealias IoSchedulerJobFunc = (cancellable: Cancellable?, <Error class: unknown class>?) -> Boolean
I/O Job function.
Long-running jobs should periodically check the @cancellable to see if they have been cancelled.
param
cancellable
optional #GCancellable object, null to ignore.param
data
data passed to the callback functionreturn true if this function should be called again to complete the job, false if the job is complete (or cancelled)