initial import

core/syncx/limit.go

@@ -0,0 +1,42 @@
+package syncx
+
+import (
+	"errors"
+
+	"zero/core/lang"
+)
+
+var ErrReturn = errors.New("discarding limited token, resource pool is full, someone returned multiple times")
+
+type Limit struct {
+	pool chan lang.PlaceholderType
+}
+
+func NewLimit(n int) Limit {
+	return Limit{
+		pool: make(chan lang.PlaceholderType, n),
+	}
+}
+
+func (l Limit) Borrow() {
+	l.pool <- lang.Placeholder
+}
+
+// Return returns the borrowed resource, returns error only if returned more than borrowed.
+func (l Limit) Return() error {
+	select {
+	case <-l.pool:
+		return nil
+	default:
+		return ErrReturn
+	}
+}
+
+func (l Limit) TryBorrow() bool {
+	select {
+	case l.pool <- lang.Placeholder:
+		return true
+	default:
+		return false
+	}
+}