Geodata: Cleanup unneeded shared matchers (weakly referenced in map) (#6139)

https://github.com/XTLS/Xray-core/pull/6139#issuecomment-4525195265

common/utils/weak_cache.go

@@ -0,0 +1,45 @@
+package utils
+
+import (
+	"runtime"
+	"sync"
+	"weak"
+)
+
+// WeakCacheMap is a map that holds weak references to values.
+// Use for shared expensive objects and automatic cleanup when no longer used.
+// This object can be GC and no goroutine is used for cleanup.
+type WeakCacheMap[K comparable, V any] struct {
+	mu sync.Mutex
+	m  map[K]weak.Pointer[V]
+}
+
+func NewWeakCacheMap[K comparable, V any]() *WeakCacheMap[K, V] {
+	return &WeakCacheMap[K, V]{
+		m: make(map[K]weak.Pointer[V]),
+	}
+}
+
+func (c *WeakCacheMap[K, V]) Load(key K) (value *V, ok bool) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	weakPtr := c.m[key].Value()
+	if weakPtr != nil {
+		return weakPtr, true
+	}
+	return nil, false
+}
+
+func (c *WeakCacheMap[K, V]) Store(key K, value *V) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	weakPtr := weak.Make(value)
+	c.m[key] = weakPtr
+	runtime.AddCleanup(value, func(struct{}) {
+		c.mu.Lock()
+		defer c.mu.Unlock()
+		if c.m[key] == weakPtr {
+			delete(c.m, key)
+		}
+	}, struct{}{})
+}