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