mirror of https://go.googlesource.com/go
71 lines
1.8 KiB
Go
71 lines
1.8 KiB
Go
// Copyright 2022 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package os
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// File locking support for Plan 9. This uses fdMutex from the
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// internal/poll package.
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// incref adds a reference to the file. It returns an error if the file
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// is already closed. This method is on File so that we can incorporate
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// a nil test.
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func (f *File) incref(op string) (err error) {
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if f == nil {
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return ErrInvalid
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}
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if !f.fdmu.Incref() {
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err = ErrClosed
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if op != "" {
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err = &PathError{Op: op, Path: f.name, Err: err}
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}
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}
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return err
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}
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// decref removes a reference to the file. If this is the last
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// remaining reference, and the file has been marked to be closed,
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// then actually close it.
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func (file *file) decref() error {
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if file.fdmu.Decref() {
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return file.destroy()
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}
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return nil
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}
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// readLock adds a reference to the file and locks it for reading.
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// It returns an error if the file is already closed.
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func (file *file) readLock() error {
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if !file.fdmu.ReadLock() {
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return ErrClosed
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}
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return nil
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}
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// readUnlock removes a reference from the file and unlocks it for reading.
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// It also closes the file if it marked as closed and there is no remaining
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// reference.
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func (file *file) readUnlock() {
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if file.fdmu.ReadUnlock() {
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file.destroy()
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}
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}
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// writeLock adds a reference to the file and locks it for writing.
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// It returns an error if the file is already closed.
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func (file *file) writeLock() error {
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if !file.fdmu.WriteLock() {
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return ErrClosed
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}
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return nil
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}
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// writeUnlock removes a reference from the file and unlocks it for writing.
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// It also closes the file if it is marked as closed and there is no remaining
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// reference.
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func (file *file) writeUnlock() {
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if file.fdmu.WriteUnlock() {
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file.destroy()
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}
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}
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