68 строки
1.8 KiB
Go
68 строки
1.8 KiB
Go
// Copyright 2018 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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//go:build !plan9
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// +build !plan9
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//nolint
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package lockedfile
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import (
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"io/fs"
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"os"
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"github.com/Azure/azure-container-networking/internal/lockedfile/internal/filelock"
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)
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func openFile(name string, flag int, perm fs.FileMode) (*os.File, error) {
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// On BSD systems, we could add the O_SHLOCK or O_EXLOCK flag to the OpenFile
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// call instead of locking separately, but we have to support separate locking
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// calls for Linux and Windows anyway, so it's simpler to use that approach
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// consistently.
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f, err := os.OpenFile(name, flag&^os.O_TRUNC, perm)
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if err != nil {
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return nil, err
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}
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switch flag & (os.O_RDONLY | os.O_WRONLY | os.O_RDWR) {
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case os.O_WRONLY, os.O_RDWR:
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err = filelock.Lock(f)
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default:
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err = filelock.RLock(f)
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}
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if err != nil {
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f.Close()
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return nil, err
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}
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if flag&os.O_TRUNC == os.O_TRUNC {
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if err := f.Truncate(0); err != nil {
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// The documentation for os.O_TRUNC says “if possible, truncate file when
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// opened”, but doesn't define “possible” (golang.org/issue/28699).
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// We'll treat regular files (and symlinks to regular files) as “possible”
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// and ignore errors for the rest.
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if fi, statErr := f.Stat(); statErr != nil || fi.Mode().IsRegular() {
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filelock.Unlock(f)
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f.Close()
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return nil, err
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}
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}
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}
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return f, nil
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}
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func closeFile(f *os.File) error {
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// Since locking syscalls operate on file descriptors, we must unlock the file
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// while the descriptor is still valid — that is, before the file is closed —
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// and avoid unlocking files that are already closed.
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err := filelock.Unlock(f)
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if closeErr := f.Close(); err == nil {
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err = closeErr
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}
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return err
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}
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