147 lines
3.7 KiB
Go
147 lines
3.7 KiB
Go
package watch
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import "context"
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// DeepCopyable describes a type that implements the DeepCopy
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// method to get a copy of itself that is safe to pass around
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// without worrying about receivers modifying the original.
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type DeepCopyable[T any] interface {
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DeepCopy() T
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}
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// Map safely stores and retrieves values by validating that
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// there is a live watch for a key. InitWatch must be called
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// to associate a key with its cancel function before any
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// Set's are called.
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type Map[K comparable, V DeepCopyable[V]] struct {
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M map[K]watchedVal[V]
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}
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type watchedVal[V any] struct {
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Val *V
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// keeping cancel private has a beneficial side effect:
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// copying Map with copystructure.Copy will zero out
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// cancel, preventing it from being called by the
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// receiver of a proxy config snapshot.
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cancel context.CancelFunc
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}
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func NewMap[K comparable, V DeepCopyable[V]]() Map[K, V] {
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return Map[K, V]{M: make(map[K]watchedVal[V])}
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}
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// DeepCopy returns a copy of the Map that is safe to be passed
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// around without worrying about receivers modifying the original
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// or canceling its watches.
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func (m Map[K, V]) DeepCopy() Map[K, V] {
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dup := make(map[K]watchedVal[V], len(m.M))
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for k, v := range m.M {
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var val *V
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if v.Val != nil {
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dc := (*v.Val).DeepCopy()
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val = &dc
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}
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dup[k] = watchedVal[V]{Val: val}
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}
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return Map[K, V]{M: dup}
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}
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// InitWatch associates a cancel function with a key,
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// allowing Set to be called for the key. The cancel
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// function is allowed to be nil.
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//
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// Any existing data for a key will be cancelled and
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// overwritten.
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func (m Map[K, V]) InitWatch(key K, cancel func()) {
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if _, present := m.M[key]; present {
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m.CancelWatch(key)
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}
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m.M[key] = watchedVal[V]{
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cancel: cancel,
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}
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}
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// CancelWatch first calls the cancel function
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// associated with the key then deletes the key
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// from the map. No-op if key is not present.
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func (m Map[K, V]) CancelWatch(key K) {
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if entry, ok := m.M[key]; ok {
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if entry.cancel != nil {
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entry.cancel()
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}
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delete(m.M, key)
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}
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}
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// IsWatched returns true if InitWatch has been
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// called for key and has not been cancelled by
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// CancelWatch.
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func (m Map[K, V]) IsWatched(key K) bool {
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if _, present := m.M[key]; present {
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return true
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}
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return false
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}
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// Set stores V if K exists in the map.
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// No-op if the key never was initialized with InitWatch
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// or if the entry got cancelled by CancelWatch.
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func (m Map[K, V]) Set(key K, val V) bool {
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if entry, ok := m.M[key]; ok {
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entry.Val = &val
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m.M[key] = entry
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return true
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}
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return false
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}
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// Get returns the underlying value for a key.
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// If an entry has been set, returns (V, true).
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// Otherwise, returns the zero value (V, false).
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//
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// Note that even if InitWatch has been called
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// for a key, unless Set has been called this
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// function will return false.
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func (m Map[K, V]) Get(key K) (V, bool) {
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if entry, ok := m.M[key]; ok {
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if entry.Val != nil {
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return *entry.Val, true
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}
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}
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var empty V
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return empty, false
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}
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func (m Map[K, V]) Len() int {
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return len(m.M)
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}
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// ForEachKey iterates through the map, calling f
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// for each iteration. It is up to the caller to
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// Get the value and nil-check if required.
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// Stops iterating if f returns false.
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// Order of iteration is non-deterministic.
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func (m Map[K, V]) ForEachKey(f func(K) bool) {
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for k := range m.M {
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if ok := f(k); !ok {
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return
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}
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}
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}
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// ForEachKeyE iterates through the map, calling f
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// for each iteration. It is up to the caller to
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// Get the value and nil-check if required.
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// If a non-nil error is returned by f, iterating
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// stops and the error is returned.
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// Order of iteration is non-deterministic.
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func (m Map[K, V]) ForEachKeyE(f func(K) error) error {
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for k := range m.M {
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if err := f(k); err != nil {
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return err
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}
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}
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return nil
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}
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