wings/events/pool.go

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package events
import (
"github.com/gammazero/workerpool"
"reflect"
)
type CallbackPool struct {
callbacks []*func(Event)
pool *workerpool.WorkerPool
}
// Pushes a new callback into the array of listeners for the pool.
func (cp *CallbackPool) Add(callback *func(Event)) {
if cp.index(reflect.ValueOf(callback)) < 0 {
cp.callbacks = append(cp.callbacks, callback)
}
}
// Removes a callback from the array of registered callbacks if it exists.
func (cp *CallbackPool) Remove(callback *func(Event)) {
i := cp.index(reflect.ValueOf(callback))
// If i < 0 it means there was no index found for the given callback, meaning it was
// never registered or was already unregistered from the listeners. Also double check
// that we didn't somehow escape the length of the topic callback (not sure how that
// would happen, but lets avoid a panic condition).
if i < 0 || i >= len(cp.callbacks) {
return
}
// We can assume that the topic still exists at this point since we acquire an exclusive
// lock on the process, and the "e.index" function cannot return a value >= 0 if there is
// no topic already existing.
cp.callbacks = append(cp.callbacks[:i], cp.callbacks[i+1:]...)
}
// Finds the index of a given callback in the topic by comparing all of the registered callback
// pointers to the passed function. This function does not aquire a lock as it should only be called
// within the confines of a function that has already acquired a lock for the duration of the lookup.
func (cp *CallbackPool) index(v reflect.Value) int {
for i, handler := range cp.callbacks {
if reflect.ValueOf(handler).Pointer() == v.Pointer() {
return i
}
}
return -1
}