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101 lines (85 loc) · 2.38 KB
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Copy pathlock.go
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101 lines (85 loc) · 2.38 KB
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/*
* Minio Cloud Storage, (C) 2016 Minio, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
// Package lock - implements filesystem locking wrappers around an
// open file descriptor.
package lock
import (
"errors"
"os"
"sync"
)
var (
// ErrAlreadyLocked is returned if the underlying fd is already locked.
ErrAlreadyLocked = errors.New("file already locked")
)
// RLockedFile represents a read locked file, implements a special
// closer which only closes the associated *os.File when the ref count.
// has reached zero, i.e when all the readers have given up their locks.
type RLockedFile struct {
*LockedFile
mutex sync.Mutex
refs int // Holds read lock refs.
}
// IsClosed - Check if the rlocked file is already closed.
func (r *RLockedFile) IsClosed() bool {
r.mutex.Lock()
defer r.mutex.Unlock()
return r.refs == 0
}
// IncLockRef - is used by called to indicate lock refs.
func (r *RLockedFile) IncLockRef() {
r.mutex.Lock()
r.refs++
r.mutex.Unlock()
}
// Close - this closer implements a special closer
// closes the underlying fd only when the refs
// reach zero.
func (r *RLockedFile) Close() (err error) {
r.mutex.Lock()
defer r.mutex.Unlock()
if r.refs == 0 {
return os.ErrInvalid
}
r.refs--
if r.refs == 0 {
err = r.File.Close()
}
return err
}
// Provides a new initialized read locked struct from *os.File
func newRLockedFile(lkFile *LockedFile) (*RLockedFile, error) {
if lkFile == nil {
return nil, os.ErrInvalid
}
return &RLockedFile{
LockedFile: lkFile,
refs: 1,
}, nil
}
// RLockedOpenFile - returns a wrapped read locked file, if the file
// doesn't exist at path returns an error.
func RLockedOpenFile(path string) (*RLockedFile, error) {
lkFile, err := LockedOpenFile(path, os.O_RDONLY, 0666)
if err != nil {
return nil, err
}
return newRLockedFile(lkFile)
}
// LockedFile represents a locked file
type LockedFile struct {
*os.File
}