64 lines
1.6 KiB
Go
64 lines
1.6 KiB
Go
// Copyright (C) 2015 The Syncthing Authors.
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this file,
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// You can obtain one at https://mozilla.org/MPL/2.0/.
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package osutil
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import (
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"os"
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"path/filepath"
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"strconv"
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"sync"
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"time"
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"github.com/syncthing/syncthing/lib/fs"
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)
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var rand uint32
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var randmu sync.Mutex
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func reseed() uint32 {
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return uint32(time.Now().UnixNano() + int64(os.Getpid()))
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}
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func nextSuffix() string {
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randmu.Lock()
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r := rand
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if r == 0 {
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r = reseed()
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}
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r = r*1664525 + 1013904223 // constants from Numerical Recipes
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rand = r
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randmu.Unlock()
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return strconv.Itoa(int(1e9 + r%1e9))[1:]
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}
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// TempFile creates a new temporary file in the directory dir
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// with a name beginning with prefix, opens the file for reading
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// and writing, and returns the resulting *os.File.
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// If dir is the empty string, TempFile uses the default directory
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// for temporary files (see os.TempDir).
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// Multiple programs calling TempFile simultaneously
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// will not choose the same file. The caller can use f.Name()
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// to find the pathname of the file. It is the caller's responsibility
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// to remove the file when no longer needed.
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func TempFile(filesystem fs.Filesystem, dir, prefix string) (f fs.File, err error) {
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nconflict := 0
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for i := 0; i < 10000; i++ {
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name := filepath.Join(dir, prefix+nextSuffix())
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f, err = filesystem.OpenFile(name, fs.OptReadWrite|fs.OptCreate|fs.OptExclusive, 0600)
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if fs.IsExist(err) {
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if nconflict++; nconflict > 10 {
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randmu.Lock()
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rand = reseed()
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randmu.Unlock()
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}
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continue
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}
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break
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}
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return
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}
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