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59 lines
1.4 KiB
Go
59 lines
1.4 KiB
Go
// +build linux darwin freebsd openbsd netbsd dragonfly solaris
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// +build !appengine
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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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"golang.org/x/sys/unix"
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)
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func init() {
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lockFn = lockFcntl
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}
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func lockFcntl(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: has non-zero size", name)
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}
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f, err := os.Create(name)
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if err != nil {
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return nil, fmt.Errorf("Lock Create of %s failed: %v", name, err)
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}
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err = unix.FcntlFlock(f.Fd(), unix.F_SETLK, &unix.Flock_t{
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Type: unix.F_WRLCK,
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Whence: int16(os.SEEK_SET),
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Start: 0,
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Len: 0, // 0 means to lock the entire file.
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Pid: 0, // only used by F_GETLK
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})
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if err != nil {
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f.Close()
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return nil, fmt.Errorf("Lock FcntlFlock of %s failed: %v", name, err)
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}
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return &unlocker{f: f, abs: name}, nil
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}
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