1 // Copyright 2009 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
5 // Package filepath implements utility routines for manipulating filename paths
6 // in a way compatible with the target operating system-defined file paths.
16 // A lazybuf is a lazily constructed path buffer.
17 // It supports append, reading previously appended bytes,
18 // and retrieving the final string. It does not allocate a buffer
19 // to hold the output until that output diverges from s.
28 func (b *lazybuf) index(i int) byte {
35 func (b *lazybuf) append(c byte) {
37 if b.w < len(b.path) && b.path[b.w] == c {
41 b.buf = make([]byte, len(b.path))
42 copy(b.buf, b.path[:b.w])
48 func (b *lazybuf) string() string {
50 return b.volAndPath[:b.volLen+b.w]
52 return b.volAndPath[:b.volLen] + string(b.buf[:b.w])
56 Separator = os.PathSeparator
57 ListSeparator = os.PathListSeparator
60 // Clean returns the shortest path name equivalent to path
61 // by purely lexical processing. It applies the following rules
62 // iteratively until no further processing can be done:
64 // 1. Replace multiple Separator elements with a single one.
65 // 2. Eliminate each . path name element (the current directory).
66 // 3. Eliminate each inner .. path name element (the parent directory)
67 // along with the non-.. element that precedes it.
68 // 4. Eliminate .. elements that begin a rooted path:
69 // that is, replace "/.." by "/" at the beginning of a path,
70 // assuming Separator is '/'.
72 // The returned path ends in a slash only if it represents a root directory,
73 // such as "/" on Unix or `C:\` on Windows.
75 // If the result of this process is an empty string, Clean
76 // returns the string ".".
78 // See also Rob Pike, ``Lexical File Names in Plan 9 or
79 // Getting Dot-Dot Right,''
80 // http://plan9.bell-labs.com/sys/doc/lexnames.html
81 func Clean(path string) string {
83 volLen := volumeNameLen(path)
86 if volLen > 1 && originalPath[1] != ':' {
88 return FromSlash(originalPath)
90 return originalPath + "."
92 rooted := os.IsPathSeparator(path[0])
95 // reading from path; r is index of next byte to process.
96 // writing to buf; w is index of next byte to write.
97 // dotdot is index in buf where .. must stop, either because
98 // it is the leading slash or it is a leading ../../.. prefix.
100 out := lazybuf{path: path, volAndPath: originalPath, volLen: volLen}
103 out.append(Separator)
109 case os.IsPathSeparator(path[r]):
110 // empty path element
112 case path[r] == '.' && (r+1 == n || os.IsPathSeparator(path[r+1])):
115 case path[r] == '.' && path[r+1] == '.' && (r+2 == n || os.IsPathSeparator(path[r+2])):
116 // .. element: remove to last separator
122 for out.w > dotdot && !os.IsPathSeparator(out.index(out.w)) {
126 // cannot backtrack, but not rooted, so append .. element.
128 out.append(Separator)
135 // real path element.
136 // add slash if needed
137 if rooted && out.w != 1 || !rooted && out.w != 0 {
138 out.append(Separator)
141 for ; r < n && !os.IsPathSeparator(path[r]); r++ {
147 // Turn empty string into "."
152 return FromSlash(out.string())
155 // ToSlash returns the result of replacing each separator character
156 // in path with a slash ('/') character. Multiple separators are
157 // replaced by multiple slashes.
158 func ToSlash(path string) string {
159 if Separator == '/' {
162 return strings.Replace(path, string(Separator), "/", -1)
165 // FromSlash returns the result of replacing each slash ('/') character
166 // in path with a separator character. Multiple slashes are replaced
167 // by multiple separators.
168 func FromSlash(path string) string {
169 if Separator == '/' {
172 return strings.Replace(path, "/", string(Separator), -1)
175 // SplitList splits a list of paths joined by the OS-specific ListSeparator,
176 // usually found in PATH or GOPATH environment variables.
177 // Unlike strings.Split, SplitList returns an empty slice when passed an empty string.
178 func SplitList(path string) []string {
179 return splitList(path)
182 // Split splits path immediately following the final Separator,
183 // separating it into a directory and file name component.
184 // If there is no Separator in path, Split returns an empty dir
185 // and file set to path.
186 // The returned values have the property that path = dir+file.
187 func Split(path string) (dir, file string) {
188 vol := VolumeName(path)
190 for i >= len(vol) && !os.IsPathSeparator(path[i]) {
193 return path[:i+1], path[i+1:]
196 // Join joins any number of path elements into a single path, adding
197 // a Separator if necessary. The result is Cleaned, in particular
198 // all empty strings are ignored.
199 // On Windows, the result is a UNC path if and only if the first path
200 // element is a UNC path.
201 func Join(elem ...string) string {
205 // Ext returns the file name extension used by path.
206 // The extension is the suffix beginning at the final dot
207 // in the final element of path; it is empty if there is
209 func Ext(path string) string {
210 for i := len(path) - 1; i >= 0 && !os.IsPathSeparator(path[i]); i-- {
218 // EvalSymlinks returns the path name after the evaluation of any symbolic
220 // If path is relative the result will be relative to the current directory,
221 // unless one of the components is an absolute symbolic link.
222 func EvalSymlinks(path string) (string, error) {
223 return evalSymlinks(path)
226 // Abs returns an absolute representation of path.
227 // If the path is not absolute it will be joined with the current
228 // working directory to turn it into an absolute path. The absolute
229 // path name for a given file is not guaranteed to be unique.
230 func Abs(path string) (string, error) {
234 func unixAbs(path string) (string, error) {
236 return Clean(path), nil
238 wd, err := os.Getwd()
242 return Join(wd, path), nil
245 // Rel returns a relative path that is lexically equivalent to targpath when
246 // joined to basepath with an intervening separator. That is,
247 // Join(basepath, Rel(basepath, targpath)) is equivalent to targpath itself.
248 // On success, the returned path will always be relative to basepath,
249 // even if basepath and targpath share no elements.
250 // An error is returned if targpath can't be made relative to basepath or if
251 // knowing the current working directory would be necessary to compute it.
252 func Rel(basepath, targpath string) (string, error) {
253 baseVol := VolumeName(basepath)
254 targVol := VolumeName(targpath)
255 base := Clean(basepath)
256 targ := Clean(targpath)
260 base = base[len(baseVol):]
261 targ = targ[len(targVol):]
265 // Can't use IsAbs - `\a` and `a` are both relative in Windows.
266 baseSlashed := len(base) > 0 && base[0] == Separator
267 targSlashed := len(targ) > 0 && targ[0] == Separator
268 if baseSlashed != targSlashed || baseVol != targVol {
269 return "", errors.New("Rel: can't make " + targ + " relative to " + base)
271 // Position base[b0:bi] and targ[t0:ti] at the first differing elements.
274 var b0, bi, t0, ti int
276 for bi < bl && base[bi] != Separator {
279 for ti < tl && targ[ti] != Separator {
282 if targ[t0:ti] != base[b0:bi] {
294 if base[b0:bi] == ".." {
295 return "", errors.New("Rel: can't make " + targ + " relative to " + base)
298 // Base elements left. Must go up before going down.
299 seps := strings.Count(base[b0:bl], string(Separator))
304 buf := make([]byte, size)
306 for i := 0; i < seps; i++ {
308 copy(buf[n+1:], "..")
313 copy(buf[n+1:], targ[t0:])
315 return string(buf), nil
317 return targ[t0:], nil
320 // SkipDir is used as a return value from WalkFuncs to indicate that
321 // the directory named in the call is to be skipped. It is not returned
322 // as an error by any function.
323 var SkipDir = errors.New("skip this directory")
325 // WalkFunc is the type of the function called for each file or directory
326 // visited by Walk. The path argument contains the argument to Walk as a
327 // prefix; that is, if Walk is called with "dir", which is a directory
328 // containing the file "a", the walk function will be called with argument
329 // "dir/a". The info argument is the os.FileInfo for the named path.
331 // If there was a problem walking to the file or directory named by path, the
332 // incoming error will describe the problem and the function can decide how
333 // to handle that error (and Walk will not descend into that directory). If
334 // an error is returned, processing stops. The sole exception is that if path
335 // is a directory and the function returns the special value SkipDir, the
336 // contents of the directory are skipped and processing continues as usual on
338 type WalkFunc func(path string, info os.FileInfo, err error) error
340 var lstat = os.Lstat // for testing
342 // walk recursively descends path, calling w.
343 func walk(path string, info os.FileInfo, walkFn WalkFunc) error {
344 err := walkFn(path, info, nil)
346 if info.IsDir() && err == SkipDir {
356 names, err := readDirNames(path)
358 return walkFn(path, info, err)
361 for _, name := range names {
362 filename := Join(path, name)
363 fileInfo, err := lstat(filename)
365 if err := walkFn(filename, fileInfo, err); err != nil && err != SkipDir {
369 err = walk(filename, fileInfo, walkFn)
371 if !fileInfo.IsDir() || err != SkipDir {
380 // Walk walks the file tree rooted at root, calling walkFn for each file or
381 // directory in the tree, including root. All errors that arise visiting files
382 // and directories are filtered by walkFn. The files are walked in lexical
383 // order, which makes the output deterministic but means that for very
384 // large directories Walk can be inefficient.
385 // Walk does not follow symbolic links.
386 func Walk(root string, walkFn WalkFunc) error {
387 info, err := os.Lstat(root)
389 return walkFn(root, nil, err)
391 return walk(root, info, walkFn)
394 // readDirNames reads the directory named by dirname and returns
395 // a sorted list of directory entries.
396 func readDirNames(dirname string) ([]string, error) {
397 f, err := os.Open(dirname)
401 names, err := f.Readdirnames(-1)
410 // Base returns the last element of path.
411 // Trailing path separators are removed before extracting the last element.
412 // If the path is empty, Base returns ".".
413 // If the path consists entirely of separators, Base returns a single separator.
414 func Base(path string) string {
418 // Strip trailing slashes.
419 for len(path) > 0 && os.IsPathSeparator(path[len(path)-1]) {
420 path = path[0 : len(path)-1]
422 // Throw away volume name
423 path = path[len(VolumeName(path)):]
424 // Find the last element
426 for i >= 0 && !os.IsPathSeparator(path[i]) {
432 // If empty now, it had only slashes.
434 return string(Separator)
439 // Dir returns all but the last element of path, typically the path's directory.
440 // After dropping the final element, the path is Cleaned and trailing
441 // slashes are removed.
442 // If the path is empty, Dir returns ".".
443 // If the path consists entirely of separators, Dir returns a single separator.
444 // The returned path does not end in a separator unless it is the root directory.
445 func Dir(path string) string {
446 vol := VolumeName(path)
448 for i >= len(vol) && !os.IsPathSeparator(path[i]) {
451 dir := Clean(path[len(vol) : i+1])
455 // VolumeName returns leading volume name.
456 // Given "C:\foo\bar" it returns "C:" on Windows.
457 // Given "\\host\share\foo" it returns "\\host\share".
458 // On other platforms it returns "".
459 func VolumeName(path string) string {
460 return path[:volumeNameLen(path)]