79 lines
1.8 KiB
Go
79 lines
1.8 KiB
Go
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/*
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Copyright 2013 The Go Authors
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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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http://www.apache.org/licenses/LICENSE-2.0
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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
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import (
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"fmt"
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"io"
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"os"
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"sync"
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"golang.org/x/sys/windows"
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)
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func init() {
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lockFn = lockWindows
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}
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type winUnlocker struct {
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h windows.Handle
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abs string
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// err holds the error returned by Close.
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err error
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// once guards the close method call.
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once sync.Once
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}
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func (u *winUnlocker) Close() error {
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u.once.Do(u.close)
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return u.err
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}
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func (u *winUnlocker) close() {
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lockmu.Lock()
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defer lockmu.Unlock()
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delete(locked, u.abs)
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u.err = windows.CloseHandle(u.h)
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}
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func lockWindows(name string) (io.Closer, error) {
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fi, err := os.Stat(name)
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if err == nil && fi.Size() > 0 {
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return nil, fmt.Errorf("can't lock file %q: %s", name, "has non-zero size")
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}
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handle, err := winCreateEphemeral(name)
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if err != nil {
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return nil, fmt.Errorf("creation of lock %s failed: %v", name, err)
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}
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return &winUnlocker{h: handle, abs: name}, nil
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}
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func winCreateEphemeral(name string) (windows.Handle, error) {
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const (
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FILE_ATTRIBUTE_TEMPORARY = 0x100
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FILE_FLAG_DELETE_ON_CLOSE = 0x04000000
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)
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handle, err := windows.CreateFile(windows.StringToUTF16Ptr(name), 0, 0, nil, windows.OPEN_ALWAYS, FILE_ATTRIBUTE_TEMPORARY|FILE_FLAG_DELETE_ON_CLOSE, 0)
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if err != nil {
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return 0, err
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}
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return handle, nil
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}
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