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