feat: add lambda transformation functions target (#16507)

internal/config/lambda/target/lazyinit.go

@@ -0,0 +1,51 @@
+// Copyright (c) 2015-2023 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package target
+
+import (
+	"sync"
+	"sync/atomic"
+)
+
+// Inspired from Golang sync.Once but it is only marked
+// initialized when the provided function returns nil.
+
+type lazyInit struct {
+	done uint32
+	m    sync.Mutex
+}
+
+func (l *lazyInit) Do(f func() error) error {
+	if atomic.LoadUint32(&l.done) == 0 {
+		return l.doSlow(f)
+	}
+	return nil
+}
+
+func (l *lazyInit) doSlow(f func() error) error {
+	l.m.Lock()
+	defer l.m.Unlock()
+	if atomic.LoadUint32(&l.done) == 0 {
+		if err := f(); err != nil {
+			return err
+		}
+		// Mark as done only when f() is successful
+		atomic.StoreUint32(&l.done, 1)
+	}
+	return nil
+}