mirror of https://github.com/status-im/consul.git
109 lines
2.6 KiB
Go
109 lines
2.6 KiB
Go
package watch
|
|
|
|
import "context"
|
|
|
|
// Map safely stores and retrieves values by validating that
|
|
// there is a live watch for a key. InitWatch must be called
|
|
// to associate a key with its cancel function before any
|
|
// Set's are called.
|
|
type Map[K comparable, V any] struct {
|
|
M map[K]watchedVal[V]
|
|
}
|
|
|
|
type watchedVal[V any] struct {
|
|
Val *V
|
|
|
|
// keeping cancel private has a beneficial side effect:
|
|
// copying Map with copystructure.Copy will zero out
|
|
// cancel, preventing it from being called by the
|
|
// receiver of a proxy config snapshot.
|
|
cancel context.CancelFunc
|
|
}
|
|
|
|
func NewMap[K comparable, V any]() Map[K, V] {
|
|
return Map[K, V]{M: make(map[K]watchedVal[V])}
|
|
}
|
|
|
|
// InitWatch associates a cancel function with a key,
|
|
// allowing Set to be called for the key. The cancel
|
|
// function is allowed to be nil.
|
|
//
|
|
// Any existing data for a key will be cancelled and
|
|
// overwritten.
|
|
func (m Map[K, V]) InitWatch(key K, cancel func()) {
|
|
if _, present := m.M[key]; present {
|
|
m.CancelWatch(key)
|
|
}
|
|
m.M[key] = watchedVal[V]{
|
|
cancel: cancel,
|
|
}
|
|
}
|
|
|
|
// CancelWatch first calls the cancel function
|
|
// associated with the key then deletes the key
|
|
// from the map. No-op if key is not present.
|
|
func (m Map[K, V]) CancelWatch(key K) {
|
|
if entry, ok := m.M[key]; ok {
|
|
if entry.cancel != nil {
|
|
entry.cancel()
|
|
}
|
|
delete(m.M, key)
|
|
}
|
|
}
|
|
|
|
// IsWatched returns true if InitWatch has been
|
|
// called for key and has not been cancelled by
|
|
// CancelWatch.
|
|
func (m Map[K, V]) IsWatched(key K) bool {
|
|
if _, present := m.M[key]; present {
|
|
return true
|
|
}
|
|
return false
|
|
}
|
|
|
|
// Set stores V if K exists in the map.
|
|
// No-op if the key never was initialized with InitWatch
|
|
// or if the entry got cancelled by CancelWatch.
|
|
func (m Map[K, V]) Set(key K, val V) bool {
|
|
if entry, ok := m.M[key]; ok {
|
|
entry.Val = &val
|
|
m.M[key] = entry
|
|
return true
|
|
}
|
|
return false
|
|
}
|
|
|
|
// Get returns the underlying value for a key.
|
|
// If an entry has been set, returns (V, true).
|
|
// Otherwise, returns the zero value (V, false).
|
|
//
|
|
// Note that even if InitWatch has been called
|
|
// for a key, unless Set has been called this
|
|
// function will return false.
|
|
func (m Map[K, V]) Get(key K) (V, bool) {
|
|
if entry, ok := m.M[key]; ok {
|
|
if entry.Val != nil {
|
|
return *entry.Val, true
|
|
}
|
|
}
|
|
var empty V
|
|
return empty, false
|
|
}
|
|
|
|
func (m Map[K, V]) Len() int {
|
|
return len(m.M)
|
|
}
|
|
|
|
// ForEachKey iterates through the map, calling f
|
|
// for each iteration. It is up to the caller to
|
|
// Get the value and nil-check if required.
|
|
// Stops iterating if f returns false.
|
|
// Order of iteration is non-deterministic.
|
|
func (m Map[K, V]) ForEachKey(f func(K) bool) {
|
|
for k := range m.M {
|
|
if ok := f(k); !ok {
|
|
return
|
|
}
|
|
}
|
|
}
|