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- // Copyright (C) 2014 The Syncthing Authors.
- //
- // This Source Code Form is subject to the terms of the Mozilla Public
- // License, v. 2.0. If a copy of the MPL was not distributed with this file,
- // You can obtain one at https://mozilla.org/MPL/2.0/.
- // Package osutil implements utilities for native OS support.
- package osutil
- import (
- "path/filepath"
- "strings"
- "github.com/syncthing/syncthing/lib/build"
- "github.com/syncthing/syncthing/lib/fs"
- "github.com/syncthing/syncthing/lib/sync"
- )
- // Try to keep this entire operation atomic-like. We shouldn't be doing this
- // often enough that there is any contention on this lock.
- var renameLock = sync.NewMutex()
- // RenameOrCopy renames a file, leaving source file intact in case of failure.
- // Tries hard to succeed on various systems by temporarily tweaking directory
- // permissions and removing the destination file when necessary.
- func RenameOrCopy(method fs.CopyRangeMethod, src, dst fs.Filesystem, from, to string) error {
- renameLock.Lock()
- defer renameLock.Unlock()
- return withPreparedTarget(dst, from, to, func() error {
- // Optimisation 1
- if src.Type() == dst.Type() && src.URI() == dst.URI() {
- return src.Rename(from, to)
- }
- // "Optimisation" 2
- // Try to find a common prefix between the two filesystems, use that as the base for the new one
- // and try a rename.
- if src.Type() == dst.Type() {
- commonPrefix := fs.CommonPrefix(src.URI(), dst.URI())
- if len(commonPrefix) > 0 {
- commonFs := fs.NewFilesystem(src.Type(), commonPrefix)
- err := commonFs.Rename(
- filepath.Join(strings.TrimPrefix(src.URI(), commonPrefix), from),
- filepath.Join(strings.TrimPrefix(dst.URI(), commonPrefix), to),
- )
- if err == nil {
- return nil
- }
- }
- }
- // Everything is sad, do a copy and delete.
- if _, err := dst.Stat(to); !fs.IsNotExist(err) {
- err := dst.Remove(to)
- if err != nil {
- return err
- }
- }
- err := copyFileContents(method, src, dst, from, to)
- if err != nil {
- _ = dst.Remove(to)
- return err
- }
- return withPreparedTarget(src, from, from, func() error {
- return src.Remove(from)
- })
- })
- }
- // Copy copies the file content from source to destination.
- // Tries hard to succeed on various systems by temporarily tweaking directory
- // permissions and removing the destination file when necessary.
- func Copy(method fs.CopyRangeMethod, src, dst fs.Filesystem, from, to string) (err error) {
- return withPreparedTarget(dst, from, to, func() error {
- return copyFileContents(method, src, dst, from, to)
- })
- }
- // Tries hard to succeed on various systems by temporarily tweaking directory
- // permissions and removing the destination file when necessary.
- func withPreparedTarget(filesystem fs.Filesystem, from, to string, f func() error) error {
- // Make sure the destination directory is writeable
- toDir := filepath.Dir(to)
- if info, err := filesystem.Stat(toDir); err == nil && info.IsDir() && info.Mode()&0200 == 0 {
- filesystem.Chmod(toDir, 0755)
- defer filesystem.Chmod(toDir, info.Mode())
- }
- // On Windows, make sure the destination file is writeable (or we can't delete it)
- if build.IsWindows {
- filesystem.Chmod(to, 0666)
- if !strings.EqualFold(from, to) {
- err := filesystem.Remove(to)
- if err != nil && !fs.IsNotExist(err) {
- return err
- }
- }
- }
- return f()
- }
- // copyFileContents copies the contents of the file named src to the file named
- // by dst. The file will be created if it does not already exist. If the
- // destination file exists, all its contents will be replaced by the contents
- // of the source file.
- func copyFileContents(method fs.CopyRangeMethod, srcFs, dstFs fs.Filesystem, src, dst string) (err error) {
- in, err := srcFs.Open(src)
- if err != nil {
- return
- }
- defer in.Close()
- out, err := dstFs.Create(dst)
- if err != nil {
- return
- }
- defer func() {
- cerr := out.Close()
- if err == nil {
- err = cerr
- }
- }()
- inFi, err := in.Stat()
- if err != nil {
- return
- }
- err = fs.CopyRange(method, in, out, 0, 0, inFi.Size())
- return
- }
- func IsDeleted(ffs fs.Filesystem, name string) bool {
- if _, err := ffs.Lstat(name); err != nil {
- if fs.IsNotExist(err) || fs.IsErrCaseConflict(err) {
- return true
- }
- }
- switch TraversesSymlink(ffs, filepath.Dir(name)).(type) {
- case *NotADirectoryError, *TraversesSymlinkError:
- return true
- }
- return false
- }
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