github.com/minio/minio@v0.0.0-20240328213742-3f72439b8a27/internal/config/lambda/target/lazyinit.go (about)

     1  // Copyright (c) 2015-2023 MinIO, Inc.
     2  //
     3  // This file is part of MinIO Object Storage stack
     4  //
     5  // This program is free software: you can redistribute it and/or modify
     6  // it under the terms of the GNU Affero General Public License as published by
     7  // the Free Software Foundation, either version 3 of the License, or
     8  // (at your option) any later version.
     9  //
    10  // This program is distributed in the hope that it will be useful
    11  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    12  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    13  // GNU Affero General Public License for more details.
    14  //
    15  // You should have received a copy of the GNU Affero General Public License
    16  // along with this program.  If not, see <http://www.gnu.org/licenses/>.
    17  
    18  package target
    19  
    20  import (
    21  	"sync"
    22  	"sync/atomic"
    23  )
    24  
    25  // Inspired from Golang sync.Once but it is only marked
    26  // initialized when the provided function returns nil.
    27  
    28  type lazyInit struct {
    29  	done uint32
    30  	m    sync.Mutex
    31  }
    32  
    33  func (l *lazyInit) Do(f func() error) error {
    34  	if atomic.LoadUint32(&l.done) == 0 {
    35  		return l.doSlow(f)
    36  	}
    37  	return nil
    38  }
    39  
    40  func (l *lazyInit) doSlow(f func() error) error {
    41  	l.m.Lock()
    42  	defer l.m.Unlock()
    43  	if atomic.LoadUint32(&l.done) == 0 {
    44  		if err := f(); err != nil {
    45  			return err
    46  		}
    47  		// Mark as done only when f() is successful
    48  		atomic.StoreUint32(&l.done, 1)
    49  	}
    50  	return nil
    51  }