lib/fs: The interface and basicfs
GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3748
This commit is contained in:
Jakob Borg
Audrius Butkevicius
parent
3cde608eda
commit
fc1430aa92
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@ -0,0 +1,96 @@
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// Copyright (C) 2016 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 http://mozilla.org/MPL/2.0/.
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package fs
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import (
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"os"
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"time"
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)
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// The BasicFilesystem implements all aspects by delegating to package os.
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type BasicFilesystem struct {
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}
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func NewBasicFilesystem() *BasicFilesystem {
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return new(BasicFilesystem)
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}
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func (f *BasicFilesystem) Chmod(name string, mode FileMode) error {
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return os.Chmod(name, os.FileMode(mode))
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}
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func (f *BasicFilesystem) Chtimes(name string, atime time.Time, mtime time.Time) error {
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return os.Chtimes(name, atime, mtime)
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}
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func (f *BasicFilesystem) Mkdir(name string, perm FileMode) error {
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return os.Mkdir(name, os.FileMode(perm))
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}
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func (f *BasicFilesystem) Lstat(name string) (FileInfo, error) {
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fi, err := os.Lstat(name)
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if err != nil {
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return nil, err
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}
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return fsFileInfo{fi}, err
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}
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func (f *BasicFilesystem) Remove(name string) error {
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return os.Remove(name)
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}
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func (f *BasicFilesystem) Rename(oldpath, newpath string) error {
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return os.Rename(oldpath, newpath)
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}
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func (f *BasicFilesystem) Stat(name string) (FileInfo, error) {
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fi, err := os.Stat(name)
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if err != nil {
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return nil, err
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}
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return fsFileInfo{fi}, err
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}
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func (f *BasicFilesystem) DirNames(name string) ([]string, error) {
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fd, err := os.OpenFile(name, os.O_RDONLY, 0777)
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if err != nil {
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return nil, err
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}
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defer fd.Close()
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names, err := fd.Readdirnames(-1)
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if err != nil {
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return nil, err
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}
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return names, nil
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}
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func (f *BasicFilesystem) Open(name string) (File, error) {
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return os.Open(name)
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}
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func (f *BasicFilesystem) Create(name string) (File, error) {
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return os.Create(name)
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}
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// fsFileInfo implements the fs.FileInfo interface on top of an os.FileInfo.
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type fsFileInfo struct {
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os.FileInfo
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}
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func (e fsFileInfo) Mode() FileMode {
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return FileMode(e.FileInfo.Mode())
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}
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func (e fsFileInfo) IsRegular() bool {
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return e.FileInfo.Mode().IsRegular()
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}
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func (e fsFileInfo) IsSymlink() bool {
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return e.FileInfo.Mode()&os.ModeSymlink == os.ModeSymlink
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}
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// Copyright (C) 2016 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 http://mozilla.org/MPL/2.0/.
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// +build !windows
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package fs
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import "os"
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var symlinksSupported = true
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func DisableSymlinks() {
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symlinksSupported = false
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}
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func (BasicFilesystem) SymlinksSupported() bool {
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return symlinksSupported
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}
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func (BasicFilesystem) CreateSymlink(name, target string, _ LinkTargetType) error {
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return os.Symlink(target, name)
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}
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func (BasicFilesystem) ChangeSymlinkType(_ string, _ LinkTargetType) error {
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return nil
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}
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func (BasicFilesystem) ReadSymlink(path string) (string, LinkTargetType, error) {
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tt := LinkTargetUnknown
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if stat, err := os.Stat(path); err == nil {
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if stat.IsDir() {
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tt = LinkTargetDirectory
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} else {
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tt = LinkTargetFile
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}
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}
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path, err := os.Readlink(path)
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return path, tt, err
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}
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@ -0,0 +1,195 @@
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// Copyright (C) 2014 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 http://mozilla.org/MPL/2.0/.
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// +build windows
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package fs
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import (
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"os"
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"path/filepath"
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"github.com/syncthing/syncthing/lib/osutil"
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"syscall"
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"unicode/utf16"
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"unsafe"
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)
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const (
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win32FsctlGetReparsePoint = 0x900a8
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win32FileFlagOpenReparsePoint = 0x00200000
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win32SymbolicLinkFlagDirectory = 0x1
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)
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var (
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modkernel32 = syscall.NewLazyDLL("kernel32.dll")
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procDeviceIoControl = modkernel32.NewProc("DeviceIoControl")
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procCreateSymbolicLink = modkernel32.NewProc("CreateSymbolicLinkW")
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symlinksSupported = false
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)
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func init() {
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defer func() {
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if err := recover(); err != nil {
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// Ensure that the supported flag is disabled when we hit an
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// error, even though it should already be. Also, silently swallow
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// the error since it's fine for a system not to support symlinks.
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symlinksSupported = false
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}
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}()
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// Needs administrator privileges.
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// Let's check that everything works.
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// This could be done more officially:
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// http://stackoverflow.com/questions/2094663/determine-if-windows-process-has-privilege-to-create-symbolic-link
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// But I don't want to define 10 more structs just to look this up.
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base := os.TempDir()
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path := filepath.Join(base, "symlinktest")
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defer os.Remove(path)
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err := DefaultFilesystem.CreateSymlink(path, base, LinkTargetDirectory)
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if err != nil {
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return
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}
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stat, err := osutil.Lstat(path)
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if err != nil || stat.Mode()&os.ModeSymlink == 0 {
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return
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}
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target, tt, err := DefaultFilesystem.ReadSymlink(path)
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if err != nil || osutil.NativeFilename(target) != base || tt != LinkTargetDirectory {
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return
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}
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symlinksSupported = true
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}
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func DisableSymlinks() {
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symlinksSupported = false
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}
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func (BasicFilesystem) SymlinksSupported() bool {
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return symlinksSupported
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}
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func (BasicFilesystem) ReadSymlink(path string) (string, LinkTargetType, error) {
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ptr, err := syscall.UTF16PtrFromString(path)
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if err != nil {
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return "", LinkTargetUnknown, err
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}
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handle, err := syscall.CreateFile(ptr, 0, syscall.FILE_SHARE_READ|syscall.FILE_SHARE_WRITE|syscall.FILE_SHARE_DELETE, nil, syscall.OPEN_EXISTING, syscall.FILE_FLAG_BACKUP_SEMANTICS|win32FileFlagOpenReparsePoint, 0)
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if err != nil || handle == syscall.InvalidHandle {
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return "", LinkTargetUnknown, err
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}
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defer syscall.Close(handle)
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var ret uint16
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var data reparseData
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r1, _, err := syscall.Syscall9(procDeviceIoControl.Addr(), 8, uintptr(handle), win32FsctlGetReparsePoint, 0, 0, uintptr(unsafe.Pointer(&data)), unsafe.Sizeof(data), uintptr(unsafe.Pointer(&ret)), 0, 0)
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if r1 == 0 {
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return "", LinkTargetUnknown, err
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}
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tt := LinkTargetUnknown
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if attr, err := syscall.GetFileAttributes(ptr); err == nil {
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if attr&syscall.FILE_ATTRIBUTE_DIRECTORY != 0 {
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tt = LinkTargetDirectory
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} else {
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tt = LinkTargetFile
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}
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}
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return osutil.NormalizedFilename(data.printName()), tt, nil
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}
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func (BasicFilesystem) CreateSymlink(path, target string, tt LinkTargetType) error {
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srcp, err := syscall.UTF16PtrFromString(path)
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if err != nil {
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return err
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}
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trgp, err := syscall.UTF16PtrFromString(osutil.NativeFilename(target))
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if err != nil {
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return err
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}
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// Sadly for Windows we need to specify the type of the symlink,
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// whether it's a directory symlink or a file symlink.
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// If the flags doesn't reveal the target type, try to evaluate it
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// ourselves, and worst case default to the symlink pointing to a file.
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mode := 0
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if tt == LinkTargetUnknown {
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path := target
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if !filepath.IsAbs(target) {
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path = filepath.Join(filepath.Dir(path), target)
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}
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stat, err := os.Stat(path)
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if err == nil && stat.IsDir() {
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mode = win32SymbolicLinkFlagDirectory
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}
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} else if tt == LinkTargetDirectory {
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mode = win32SymbolicLinkFlagDirectory
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}
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r0, _, err := syscall.Syscall(procCreateSymbolicLink.Addr(), 3, uintptr(unsafe.Pointer(srcp)), uintptr(unsafe.Pointer(trgp)), uintptr(mode))
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if r0 == 1 {
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return nil
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}
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return err
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}
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func (fs BasicFilesystem) ChangeSymlinkType(path string, tt LinkTargetType) error {
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target, existingTargetType, err := fs.ReadSymlink(path)
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if err != nil {
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return err
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}
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// If it's the same type, nothing to do.
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if tt == existingTargetType {
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return nil
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}
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// If the actual type is unknown, but the new type is file, nothing to do
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if existingTargetType == LinkTargetUnknown && tt != LinkTargetDirectory {
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return nil
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}
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return osutil.InWritableDir(func(path string) error {
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// It should be a symlink as well hence no need to change permissions on
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// the file.
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os.Remove(path)
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return fs.CreateSymlink(path, target, tt)
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}, path)
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}
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type reparseData struct {
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reparseTag uint32
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reparseDataLength uint16
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reserved uint16
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substitueNameOffset uint16
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substitueNameLength uint16
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printNameOffset uint16
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printNameLength uint16
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flags uint32
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// substituteName - 264 widechars max = 528 bytes
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// printName - 260 widechars max = 520 bytes
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// = 1048 bytes total
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buffer [1048 / 2]uint16
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}
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func (r *reparseData) printName() string {
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// offset and length are in bytes but we're indexing a []uint16
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offset := r.printNameOffset / 2
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length := r.printNameLength / 2
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return string(utf16.Decode(r.buffer[offset : offset+length]))
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}
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func (r *reparseData) substituteName() string {
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// offset and length are in bytes but we're indexing a []uint16
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offset := r.substitueNameOffset / 2
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length := r.substitueNameLength / 2
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return string(utf16.Decode(r.buffer[offset : offset+length]))
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}
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@ -0,0 +1,81 @@
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// Copyright 2009 The 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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// This part copied directly from golang.org/src/path/filepath/path.go (Go
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// 1.6) and lightly modified to be methods on BasicFilesystem.
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// In our Walk() all paths given to a WalkFunc() are relative to the
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// filesystem root.
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package fs
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import "path/filepath"
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// WalkFunc is the type of the function called for each file or directory
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// visited by Walk. The path argument contains the argument to Walk as a
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// prefix; that is, if Walk is called with "dir", which is a directory
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// containing the file "a", the walk function will be called with argument
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// "dir/a". The info argument is the FileInfo for the named path.
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//
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// If there was a problem walking to the file or directory named by path, the
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// incoming error will describe the problem and the function can decide how
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// to handle that error (and Walk will not descend into that directory). If
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// an error is returned, processing stops. The sole exception is when the function
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// returns the special value SkipDir. If the function returns SkipDir when invoked
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// on a directory, Walk skips the directory's contents entirely.
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// If the function returns SkipDir when invoked on a non-directory file,
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// Walk skips the remaining files in the containing directory.
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type WalkFunc func(path string, info FileInfo, err error) error
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// walk recursively descends path, calling walkFn.
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func (f *BasicFilesystem) walk(path string, info FileInfo, walkFn WalkFunc) error {
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err := walkFn(path, info, nil)
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if err != nil {
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if info.IsDir() && err == SkipDir {
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return nil
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}
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return err
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}
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if !info.IsDir() {
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return nil
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}
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names, err := f.DirNames(path)
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if err != nil {
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return walkFn(path, info, err)
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}
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for _, name := range names {
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filename := filepath.Join(path, name)
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fileInfo, err := f.Lstat(filename)
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if err != nil {
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if err := walkFn(filename, fileInfo, err); err != nil && err != SkipDir {
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return err
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}
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} else {
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err = f.walk(filename, fileInfo, walkFn)
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if err != nil {
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if !fileInfo.IsDir() || err != SkipDir {
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return err
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}
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}
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}
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}
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return nil
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}
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// Walk walks the file tree rooted at root, calling walkFn for each file or
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// directory in the tree, including root. All errors that arise visiting files
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// and directories are filtered by walkFn. The files are walked in lexical
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// order, which makes the output deterministic but means that for very
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// large directories Walk can be inefficient.
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// Walk does not follow symbolic links.
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func (f *BasicFilesystem) Walk(root string, walkFn WalkFunc) error {
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info, err := f.Lstat(root)
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if err != nil {
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return walkFn(root, nil, err)
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}
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return f.walk(root, info, walkFn)
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}
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@ -0,0 +1,77 @@
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// Copyright (C) 2016 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 http://mozilla.org/MPL/2.0/.
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package fs
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import (
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"errors"
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"io"
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"time"
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)
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type LinkTargetType int
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const (
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LinkTargetFile LinkTargetType = iota
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LinkTargetDirectory
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LinkTargetUnknown
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)
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// The Filesystem interface abstracts access to the file system.
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type Filesystem interface {
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ChangeSymlinkType(name string, tt LinkTargetType) error
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Chmod(name string, mode FileMode) error
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Chtimes(name string, atime time.Time, mtime time.Time) error
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Create(name string) (File, error)
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CreateSymlink(name, target string, tt LinkTargetType) error
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DirNames(name string) ([]string, error)
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Lstat(name string) (FileInfo, error)
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Mkdir(name string, perm FileMode) error
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Open(name string) (File, error)
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ReadSymlink(name string) (string, LinkTargetType, error)
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Remove(name string) error
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Rename(oldname, newname string) error
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Stat(name string) (FileInfo, error)
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SymlinksSupported() bool
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Walk(root string, walkFn WalkFunc) error
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}
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// The File interface abstracts access to a regular file, being a somewhat
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// smaller interface than os.File
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type File interface {
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io.Reader
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io.WriterAt
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io.Closer
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Truncate(size int64) error
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}
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// The FileInfo interface is almost the same as os.FileInfo, but with the
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// Sys method removed (as we don't want to expose whatever is underlying)
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// and with a couple of convenience methods added.
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type FileInfo interface {
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// Standard things present in os.FileInfo
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Name() string
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Mode() FileMode
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Size() int64
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ModTime() time.Time
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IsDir() bool
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// Extensions
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IsRegular() bool
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IsSymlink() bool
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}
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// FileMode is similar to os.FileMode
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type FileMode uint32
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// DefaultFilesystem is the fallback to use when nothing explicitly has
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// been passed.
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var DefaultFilesystem Filesystem = new(BasicFilesystem)
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// SkipDir is used as a return value from WalkFuncs to indicate that
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// the directory named in the call is to be skipped. It is not returned
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// as an error by any function.
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var errSkipDir = errors.New("skip this directory")
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var SkipDir = errSkipDir // silences the lint warning...
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