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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package filepath implements utility routines for manipulating filename paths
// in a way compatible with the target operating system-defined file paths.
package walk
import (
"errors"
"os"
"sort"
"strings"
"sync"
)
// 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 = errors.New("skip this directory")
// WalkFunc is the type of the function called for each file or directory
// visited by Walk. The path argument contains the argument to Walk as a
// prefix; that is, if Walk is called with "dir", which is a directory
// containing the file "a", the walk function will be called with argument
// "dir/a". The info argument is the os.FileInfo for the named path.
//
// If there was a problem walking to the file or directory named by path, the
// incoming error will describe the problem and the function can decide how
// to handle that error (and Walk will not descend into that directory). If
// an error is returned, processing stops. The sole exception is that if path
// is a directory and the function returns the special value SkipDir, the
// contents of the directory are skipped and processing continues as usual on
// the next file.
type WalkFunc func(path string, info os.FileInfo, err error) error
var lstat = os.Lstat // for testing
var LstatP = &lstat
type VisitData struct {
path string
info os.FileInfo
}
type WalkState struct {
walkFn WalkFunc
v chan VisitData // files to be processed
active sync.WaitGroup // number of files to process
lock sync.RWMutex
firstError error // accessed using lock
}
func (ws *WalkState) terminated() bool {
ws.lock.RLock()
done := ws.firstError != nil
ws.lock.RUnlock()
return done
}
func (ws *WalkState) setTerminated(err error) {
ws.lock.Lock()
if ws.firstError == nil {
ws.firstError = err
}
ws.lock.Unlock()
return
}
func (ws *WalkState) visitChannel() {
for file := range ws.v {
ws.visitFile(file)
ws.active.Add(-1)
}
}
func (ws *WalkState) visitFile(file VisitData) {
if ws.terminated() {
return
}
err := ws.walkFn(file.path, file.info, nil)
if err != nil {
if !(file.info.IsDir() && err == SkipDir) {
ws.setTerminated(err)
}
return
}
if !file.info.IsDir() {
return
}
names, err := readDirNames(file.path)
if err != nil {
err = ws.walkFn(file.path, file.info, err)
if err != nil {
ws.setTerminated(err)
}
return
}
here := file.path
for _, name := range names {
file.path = Join(here, name)
file.info, err = lstat(file.path)
if err != nil {
err = ws.walkFn(file.path, file.info, err)
if err != nil && (!file.info.IsDir() || err != SkipDir) {
ws.setTerminated(err)
return
}
} else {
switch file.info.IsDir() {
case true:
ws.active.Add(1) // presume channel send will succeed
select {
case ws.v <- file:
// push directory info to queue for concurrent traversal
default:
// undo increment when send fails and handle now
ws.active.Add(-1)
ws.visitFile(file)
}
case false:
err = ws.walkFn(file.path, file.info, nil)
if err != nil {
ws.setTerminated(err)
return
}
}
}
}
}
// Walk walks the file tree rooted at root, calling walkFn for each file or
// directory in the tree, including root. All errors that arise visiting files
// and directories are filtered by walkFn. The files are walked in a random
// order. Walk does not follow symbolic links.
func Walk(root string, walkFn WalkFunc) error {
info, err := os.Lstat(root)
if err != nil {
return walkFn(root, nil, err)
}
ws := &WalkState{
walkFn: walkFn,
v: make(chan VisitData, 1024),
}
defer close(ws.v)
ws.active.Add(1)
ws.v <- VisitData{root, info}
walkers := 16
for i := 0; i < walkers; i++ {
go ws.visitChannel()
}
ws.active.Wait()
return ws.firstError
}
//
// THE REMAINDER IS UNCHANGED FROM THE ORGINAL GO LIBRARY ORIGINAL
//
// readDirNames reads the directory named by dirname and returns
// a sorted list of directory entries.
func readDirNames(dirname string) ([]string, error) {
f, err := os.Open(dirname)
if err != nil {
return nil, err
}
names, err := f.Readdirnames(-1)
f.Close()
if err != nil {
return nil, err
}
sort.Strings(names) // omit sort to save 1-2%
return names, nil
}
// A lazybuf is a lazily constructed path buffer.
// It supports append, reading previously appended bytes,
// and retrieving the final string. It does not allocate a buffer
// to hold the output until that output diverges from s.
type lazybuf struct {
path string
buf []byte
w int
volAndPath string
volLen int
}
func (b *lazybuf) index(i int) byte {
if b.buf != nil {
return b.buf[i]
}
return b.path[i]
}
func (b *lazybuf) append(c byte) {
if b.buf == nil {
if b.w < len(b.path) && b.path[b.w] == c {
b.w++
return
}
b.buf = make([]byte, len(b.path))
copy(b.buf, b.path[:b.w])
}
b.buf[b.w] = c
b.w++
}
func (b *lazybuf) string() string {
if b.buf == nil {
return b.volAndPath[:b.volLen+b.w]
}
return b.volAndPath[:b.volLen] + string(b.buf[:b.w])
}
const (
Separator = os.PathSeparator
ListSeparator = os.PathListSeparator
)
// Clean returns the shortest path name equivalent to path
// by purely lexical processing. It applies the following rules
// iteratively until no further processing can be done:
//
// 1. Replace multiple Separator elements with a single one.
// 2. Eliminate each . path name element (the current directory).
// 3. Eliminate each inner .. path name element (the parent directory)
// along with the non-.. element that precedes it.
// 4. Eliminate .. elements that begin a rooted path:
// that is, replace "/.." by "/" at the beginning of a path,
// assuming Separator is '/'.
//
// The returned path ends in a slash only if it represents a root directory,
// such as "/" on Unix or `C:\` on Windows.
//
// If the result of this process is an empty string, Clean
// returns the string ".".
//
// See also Rob Pike, ``Lexical File Names in Plan 9 or
// Getting Dot-Dot Right,''
// http://plan9.bell-labs.com/sys/doc/lexnames.html
func Clean(path string) string {
originalPath := path
volLen := volumeNameLen(path)
path = path[volLen:]
if path == "" {
if volLen > 1 && originalPath[1] != ':' {
// should be UNC
return FromSlash(originalPath)
}
return originalPath + "."
}
rooted := os.IsPathSeparator(path[0])
// Invariants:
// reading from path; r is index of next byte to process.
// writing to buf; w is index of next byte to write.
// dotdot is index in buf where .. must stop, either because
// it is the leading slash or it is a leading ../../.. prefix.
n := len(path)
out := lazybuf{path: path, volAndPath: originalPath, volLen: volLen}
r, dotdot := 0, 0
if rooted {
out.append(Separator)
r, dotdot = 1, 1
}
for r < n {
switch {
case os.IsPathSeparator(path[r]):
// empty path element
r++
case path[r] == '.' && (r+1 == n || os.IsPathSeparator(path[r+1])):
// . element
r++
case path[r] == '.' && path[r+1] == '.' && (r+2 == n || os.IsPathSeparator(path[r+2])):
// .. element: remove to last separator
r += 2
switch {
case out.w > dotdot:
// can backtrack
out.w--
for out.w > dotdot && !os.IsPathSeparator(out.index(out.w)) {
out.w--
}
case !rooted:
// cannot backtrack, but not rooted, so append .. element.
if out.w > 0 {
out.append(Separator)
}
out.append('.')
out.append('.')
dotdot = out.w
}
default:
// real path element.
// add slash if needed
if rooted && out.w != 1 || !rooted && out.w != 0 {
out.append(Separator)
}
// copy element
for ; r < n && !os.IsPathSeparator(path[r]); r++ {
out.append(path[r])
}
}
}
// Turn empty string into "."
if out.w == 0 {
out.append('.')
}
return FromSlash(out.string())
}
// ToSlash returns the result of replacing each separator character
// in path with a slash ('/') character. Multiple separators are
// replaced by multiple slashes.
func ToSlash(path string) string {
if Separator == '/' {
return path
}
return strings.Replace(path, string(Separator), "/", -1)
}
// FromSlash returns the result of replacing each slash ('/') character
// in path with a separator character. Multiple slashes are replaced
// by multiple separators.
func FromSlash(path string) string {
if Separator == '/' {
return path
}
return strings.Replace(path, "/", string(Separator), -1)
}
// Join joins any number of path elements into a single path, adding
// a Separator if necessary. The result is Cleaned, in particular
// all empty strings are ignored.
func Join(elem ...string) string {
for i, e := range elem {
if e != "" {
return Clean(strings.Join(elem[i:], string(Separator)))
}
}
return ""
}
// Rel returns a relative path that is lexically equivalent to targpath when
// joined to basepath with an intervening separator. That is,
// Join(basepath, Rel(basepath, targpath)) is equivalent to targpath itself.
// On success, the returned path will always be relative to basepath,
// even if basepath and targpath share no elements.
// An error is returned if targpath can't be made relative to basepath or if
// knowing the current working directory would be necessary to compute it.
func Rel(basepath, targpath string) (string, error) {
baseVol := VolumeName(basepath)
targVol := VolumeName(targpath)
base := Clean(basepath)
targ := Clean(targpath)
if targ == base {
return ".", nil
}
base = base[len(baseVol):]
targ = targ[len(targVol):]
if base == "." {
base = ""
}
// Can't use IsAbs - `\a` and `a` are both relative in Windows.
baseSlashed := len(base) > 0 && base[0] == Separator
targSlashed := len(targ) > 0 && targ[0] == Separator
if baseSlashed != targSlashed || baseVol != targVol {
return "", errors.New("Rel: can't make " + targ + " relative to " + base)
}
// Position base[b0:bi] and targ[t0:ti] at the first differing elements.
bl := len(base)
tl := len(targ)
var b0, bi, t0, ti int
for {
for bi < bl && base[bi] != Separator {
bi++
}
for ti < tl && targ[ti] != Separator {
ti++
}
if targ[t0:ti] != base[b0:bi] {
break
}
if bi < bl {
bi++
}
if ti < tl {
ti++
}
b0 = bi
t0 = ti
}
if base[b0:bi] == ".." {
return "", errors.New("Rel: can't make " + targ + " relative to " + base)
}
if b0 != bl {
// Base elements left. Must go up before going down.
seps := strings.Count(base[b0:bl], string(Separator))
size := 2 + seps*3
if tl != t0 {
size += 1 + tl - t0
}
buf := make([]byte, size)
n := copy(buf, "..")
for i := 0; i < seps; i++ {
buf[n] = Separator
copy(buf[n+1:], "..")
n += 3
}
if t0 != tl {
buf[n] = Separator
copy(buf[n+1:], targ[t0:])
}
return string(buf), nil
}
return targ[t0:], nil
}
// VolumeName returns leading volume name.
// Given "C:\foo\bar" it returns "C:" under windows.
// Given "\\host\share\foo" it returns "\\host\share".
// On other platforms it returns "".
func VolumeName(path string) (v string) {
return path[:volumeNameLen(path)]
}
// EvalSymlinks returns the path name after the evaluation of any symbolic
// links.
// If path is relative the result will be relative to the current directory,
// unless one of the components is an absolute symbolic link.
func EvalSymlinks(path string) (string, error) {
return evalSymlinks(path)
}
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