52 lines
1.2 KiB
Go
52 lines
1.2 KiB
Go
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// Copyright 2012 The LevelDB-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 filelock
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import (
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"io"
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"os"
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"syscall"
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"unsafe"
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)
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// lockCloser hides all of an os.File's methods, except for Close.
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type lockCloser struct {
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f *os.File
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}
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func (l lockCloser) Close() error {
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return l.f.Close()
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}
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func Lock(name string) (io.Closer, error) {
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f, err := os.Create(name)
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if err != nil {
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return nil, err
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}
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// This type matches C's "struct flock" defined in /usr/include/sys/fcntl.h.
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// TODO: move this into the standard syscall package.
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k := struct {
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Start uint64 // sizeof(off_t): 8
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Len uint64 // sizeof(off_t): 8
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Pid uint32 // sizeof(pid_t): 4
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Type uint16 // sizeof(short): 2
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Whence uint16 // sizeof(short): 2
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}{
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Type: syscall.F_WRLCK,
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Whence: uint16(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: uint32(os.Getpid()),
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}
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_, _, errno := syscall.Syscall(syscall.SYS_FCNTL, f.Fd(), uintptr(syscall.F_SETLK), uintptr(unsafe.Pointer(&k)))
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if errno != 0 {
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f.Close()
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return nil, errno
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}
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return lockCloser{f}, nil
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}
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