ceph-csi/vendor/github.com/ceph/go-ceph/internal/callbacks/callbacks.go

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package callbacks
import (
"sync"
)
// The logic of this file is largely adapted from:
// https://github.com/golang/go/wiki/cgo#function-variables
//
// Also helpful:
// https://eli.thegreenplace.net/2019/passing-callbacks-and-pointers-to-cgo/
// Callbacks provides a tracker for data that is to be passed between Go
// and C callback functions. The Go callback/object may not be passed
// by a pointer to C code and so instead integer IDs into an internal
// map are used.
// Typically the item being added will either be a callback function or
// a data structure containing a callback function. It is up to the caller
// to control and validate what "callbacks" get used.
type Callbacks struct {
mutex sync.RWMutex
cmap map[uintptr]interface{}
lastID uintptr
}
// New returns a new callbacks tracker.
func New() *Callbacks {
return &Callbacks{cmap: make(map[uintptr]interface{})}
}
// getID returns a unique ID.
// NOTE: cb.mutex must be locked already!
func (cb *Callbacks) getID() uintptr {
for exists := true; exists; {
cb.lastID++
// Sanity check for the very unlikely case of an integer overflow in long
// running processes.
_, exists = cb.cmap[cb.lastID]
}
return cb.lastID
}
// Add a callback/object to the tracker and return a new ID
// for the object.
func (cb *Callbacks) Add(v interface{}) uintptr {
cb.mutex.Lock()
defer cb.mutex.Unlock()
id := cb.getID()
cb.cmap[id] = v
return id
}
// Remove a callback/object given it's ID.
func (cb *Callbacks) Remove(id uintptr) {
cb.mutex.Lock()
defer cb.mutex.Unlock()
delete(cb.cmap, id)
}
// Lookup returns a mapped callback/object given an ID.
func (cb *Callbacks) Lookup(id uintptr) interface{} {
cb.mutex.RLock()
defer cb.mutex.RUnlock()
return cb.cmap[id]
}