84 lines
2.7 KiB
Go
84 lines
2.7 KiB
Go
// Copyright (C) 2014 Jakob Borg and Contributors (see the CONTRIBUTORS file).
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//
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// This program is free software: you can redistribute it and/or modify it
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// under the terms of the GNU General Public License as published by the Free
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// Software Foundation, either version 3 of the License, or (at your option)
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// any later version.
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//
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// This program is distributed in the hope that it will be useful, but WITHOUT
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// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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// more details.
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//
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// You should have received a copy of the GNU General Public License along
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// with this program. If not, see <http://www.gnu.org/licenses/>.
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// Package osutil implements utilities for native OS support.
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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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"runtime"
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"sync"
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)
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// Try to keep this entire operation atomic-like. We shouldn't be doing this
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// often enough that there is any contention on this lock.
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var renameLock sync.Mutex
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// Rename renames a file, while trying hard to succeed on various systems by
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// temporarily tweaking directory permissions and removing the destination
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// file when necessary. Will make sure to delete the from file if the
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// operation fails, so use only for situations like committing a temp file to
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// it's final location.
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func Rename(from, to string) error {
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renameLock.Lock()
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defer renameLock.Unlock()
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// Make sure the destination directory is writeable
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toDir := filepath.Dir(to)
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if info, err := os.Stat(toDir); err == nil {
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os.Chmod(toDir, 0777)
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defer os.Chmod(toDir, info.Mode())
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}
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// On Windows, make sure the destination file is writeable (or we can't delete it)
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if runtime.GOOS == "windows" {
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os.Chmod(to, 0666)
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err := os.Remove(to)
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if err != nil && !os.IsNotExist(err) {
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return err
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}
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}
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// Don't leave a dangling temp file in case of rename error
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defer os.Remove(from)
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return os.Rename(from, to)
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}
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// InWritableDir calls fn(path), while making sure that the directory
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// containing `path` is writable for the duration of the call.
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func InWritableDir(fn func(string) error, path string) error {
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dir := filepath.Dir(path)
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if info, err := os.Stat(dir); err == nil && info.IsDir() && info.Mode()&04 == 0 {
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// A non-writeable directory (for this user; we assume that's the
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// relevant part). Temporarily change the mode so we can delete the
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// file or directory inside it.
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err = os.Chmod(dir, 0755)
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if err == nil {
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defer func() {
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err = os.Chmod(dir, info.Mode())
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if err != nil {
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// We managed to change the permission bits like a
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// millisecond ago, so it'd be bizarre if we couldn't
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// change it back.
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panic(err)
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}
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}()
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}
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}
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return fn(path)
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}
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