syncthing/lib/fs/filesystem.go

335 lines
8.5 KiB
Go

// Copyright (C) 2016 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 fs
import (
"context"
"errors"
"io"
"os"
"path/filepath"
"strings"
"time"
)
type filesystemWrapperType int32
const (
filesystemWrapperTypeNone filesystemWrapperType = iota
filesystemWrapperTypeMtime
filesystemWrapperTypeCase
filesystemWrapperTypeError
filesystemWrapperTypeWalk
filesystemWrapperTypeLog
)
// The Filesystem interface abstracts access to the file system.
type Filesystem interface {
Chmod(name string, mode FileMode) error
Lchown(name string, uid, gid int) error
Chtimes(name string, atime time.Time, mtime time.Time) error
Create(name string) (File, error)
CreateSymlink(target, name string) error
DirNames(name string) ([]string, error)
Lstat(name string) (FileInfo, error)
Mkdir(name string, perm FileMode) error
MkdirAll(name string, perm FileMode) error
Open(name string) (File, error)
OpenFile(name string, flags int, mode FileMode) (File, error)
ReadSymlink(name string) (string, error)
Remove(name string) error
RemoveAll(name string) error
Rename(oldname, newname string) error
Stat(name string) (FileInfo, error)
SymlinksSupported() bool
Walk(name string, walkFn WalkFunc) error
// If setup fails, returns non-nil error, and if afterwards a fatal (!)
// error occurs, sends that error on the channel. Afterwards this watch
// can be considered stopped.
Watch(path string, ignore Matcher, ctx context.Context, ignorePerms bool) (<-chan Event, <-chan error, error)
Hide(name string) error
Unhide(name string) error
Glob(pattern string) ([]string, error)
Roots() ([]string, error)
Usage(name string) (Usage, error)
Type() FilesystemType
URI() string
Options() []Option
SameFile(fi1, fi2 FileInfo) bool
// Used for unwrapping things
underlying() (Filesystem, bool)
wrapperType() filesystemWrapperType
}
// The File interface abstracts access to a regular file, being a somewhat
// smaller interface than os.File
type File interface {
io.Closer
io.Reader
io.ReaderAt
io.Seeker
io.Writer
io.WriterAt
Name() string
Truncate(size int64) error
Stat() (FileInfo, error)
Sync() error
}
// The FileInfo interface is almost the same as os.FileInfo, but with the
// Sys method removed (as we don't want to expose whatever is underlying)
// and with a couple of convenience methods added.
type FileInfo interface {
// Standard things present in os.FileInfo
Name() string
Mode() FileMode
Size() int64
ModTime() time.Time
IsDir() bool
// Extensions
IsRegular() bool
IsSymlink() bool
Owner() int
Group() int
}
// FileMode is similar to os.FileMode
type FileMode uint32
func (fm FileMode) String() string {
return os.FileMode(fm).String()
}
// Usage represents filesystem space usage
type Usage struct {
Free uint64
Total uint64
}
type Matcher interface {
ShouldIgnore(name string) bool
SkipIgnoredDirs() bool
}
type MatchResult interface {
IsIgnored() bool
}
type Event struct {
Name string
Type EventType
}
type EventType int
const (
NonRemove EventType = 1 + iota
Remove
Mixed // Should probably not be necessary to be used in filesystem interface implementation
)
// Merge returns Mixed, except if evType and other are the same and not Mixed.
func (evType EventType) Merge(other EventType) EventType {
return evType | other
}
func (evType EventType) String() string {
switch {
case evType == NonRemove:
return "non-remove"
case evType == Remove:
return "remove"
case evType == Mixed:
return "mixed"
default:
panic("bug: Unknown event type")
}
}
var ErrWatchNotSupported = errors.New("watching is not supported")
// Equivalents from os package.
const ModePerm = FileMode(os.ModePerm)
const ModeSetgid = FileMode(os.ModeSetgid)
const ModeSetuid = FileMode(os.ModeSetuid)
const ModeSticky = FileMode(os.ModeSticky)
const ModeSymlink = FileMode(os.ModeSymlink)
const ModeType = FileMode(os.ModeType)
const PathSeparator = os.PathSeparator
const OptAppend = os.O_APPEND
const OptCreate = os.O_CREATE
const OptExclusive = os.O_EXCL
const OptReadOnly = os.O_RDONLY
const OptReadWrite = os.O_RDWR
const OptSync = os.O_SYNC
const OptTruncate = os.O_TRUNC
const OptWriteOnly = os.O_WRONLY
// SkipDir is used as a return value from WalkFuncs to indicate that
// the directory named in the call is to be skipped. It is not returned
// as an error by any function.
var SkipDir = filepath.SkipDir
// IsExist is the equivalent of os.IsExist
var IsExist = os.IsExist
// IsExist is the equivalent of os.ErrExist
var ErrExist = os.ErrExist
// IsNotExist is the equivalent of os.IsNotExist
var IsNotExist = os.IsNotExist
// ErrNotExist is the equivalent of os.ErrNotExist
var ErrNotExist = os.ErrNotExist
// IsPermission is the equivalent of os.IsPermission
var IsPermission = os.IsPermission
// IsPathSeparator is the equivalent of os.IsPathSeparator
var IsPathSeparator = os.IsPathSeparator
// Option modifies a filesystem at creation. An option might be specific
// to a filesystem-type.
//
// String is used to detect options with the same effect, i.e. must be different
// for options with different effects. Meaning if an option has parameters, a
// representation of those must be part of the returned string.
type Option interface {
String() string
apply(Filesystem) Filesystem
}
func NewFilesystem(fsType FilesystemType, uri string, opts ...Option) Filesystem {
var caseOpt Option
var mtimeOpt Option
i := 0
for _, opt := range opts {
if caseOpt != nil && mtimeOpt != nil {
break
}
switch opt.(type) {
case *OptionDetectCaseConflicts:
caseOpt = opt
case *optionMtime:
mtimeOpt = opt
default:
opts[i] = opt
i++
}
}
opts = opts[:i]
var fs Filesystem
switch fsType {
case FilesystemTypeBasic:
fs = newBasicFilesystem(uri, opts...)
case FilesystemTypeFake:
fs = newFakeFilesystem(uri, opts...)
default:
l.Debugln("Unknown filesystem", fsType, uri)
fs = &errorFilesystem{
fsType: fsType,
uri: uri,
err: errors.New("filesystem with type " + fsType.String() + " does not exist."),
}
}
// Case handling is the innermost, as any filesystem calls by wrappers should be case-resolved
if caseOpt != nil {
fs = caseOpt.apply(fs)
}
// mtime handling should happen inside walking, as filesystem calls while
// walking should be mtime-resolved too
if mtimeOpt != nil {
fs = mtimeOpt.apply(fs)
}
if l.ShouldDebug("walkfs") {
return NewWalkFilesystem(&logFilesystem{fs})
}
if l.ShouldDebug("fs") {
return &logFilesystem{NewWalkFilesystem(fs)}
}
return NewWalkFilesystem(fs)
}
// IsInternal returns true if the file, as a path relative to the folder
// root, represents an internal file that should always be ignored. The file
// path must be clean (i.e., in canonical shortest form).
func IsInternal(file string) bool {
// fs cannot import config, so we hard code .stfolder here (config.DefaultMarkerName)
internals := []string{".stfolder", ".stignore", ".stversions"}
for _, internal := range internals {
if file == internal {
return true
}
if IsParent(file, internal) {
return true
}
}
return false
}
var (
errPathInvalid = errors.New("path is invalid")
errPathTraversingUpwards = errors.New("relative path traversing upwards (starting with ..)")
)
// Canonicalize checks that the file path is valid and returns it in the "canonical" form:
// - /foo/bar -> foo/bar
// - / -> "."
func Canonicalize(file string) (string, error) {
const pathSep = string(PathSeparator)
if strings.HasPrefix(file, pathSep+pathSep) {
// The relative path may pretend to be an absolute path within
// the root, but the double path separator on Windows implies
// something else and is out of spec.
return "", errPathInvalid
}
// The relative path should be clean from internal dotdots and similar
// funkyness.
file = filepath.Clean(file)
// It is not acceptable to attempt to traverse upwards.
if file == ".." {
return "", errPathTraversingUpwards
}
if strings.HasPrefix(file, ".."+pathSep) {
return "", errPathTraversingUpwards
}
if strings.HasPrefix(file, pathSep) {
if file == pathSep {
return ".", nil
}
return file[1:], nil
}
return file, nil
}
// unwrapFilesystem removes "wrapping" filesystems to expose the filesystem of the requested wrapperType, if it exists.
func unwrapFilesystem(fs Filesystem, wrapperType filesystemWrapperType) (Filesystem, bool) {
var ok bool
for {
if fs.wrapperType() == wrapperType {
return fs, true
}
fs, ok = fs.underlying()
if !ok {
return nil, false
}
}
}