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 // Finally, any occurrences of slash are replaced by Separator.
77 // If the result of this process is an empty string, Clean
78 // returns the string ".".
80 // See also Rob Pike, ``Lexical File Names in Plan 9 or
81 // Getting Dot-Dot Right,''
82 // https://9p.io/sys/doc/lexnames.html
83 func Clean(path string) string {
85 volLen := volumeNameLen(path)
88 if volLen > 1 && originalPath[1] != ':' {
90 return FromSlash(originalPath)
92 return originalPath + "."
94 rooted := os.IsPathSeparator(path[0])
97 // reading from path; r is index of next byte to process.
98 // writing to buf; w is index of next byte to write.
99 // dotdot is index in buf where .. must stop, either because
100 // it is the leading slash or it is a leading ../../.. prefix.
102 out := lazybuf{path: path, volAndPath: originalPath, volLen: volLen}
105 out.append(Separator)
111 case os.IsPathSeparator(path[r]):
112 // empty path element
114 case path[r] == '.' && (r+1 == n || os.IsPathSeparator(path[r+1])):
117 case path[r] == '.' && path[r+1] == '.' && (r+2 == n || os.IsPathSeparator(path[r+2])):
118 // .. element: remove to last separator
124 for out.w > dotdot && !os.IsPathSeparator(out.index(out.w)) {
128 // cannot backtrack, but not rooted, so append .. element.
130 out.append(Separator)
137 // real path element.
138 // add slash if needed
139 if rooted && out.w != 1 || !rooted && out.w != 0 {
140 out.append(Separator)
143 for ; r < n && !os.IsPathSeparator(path[r]); r++ {
149 // Turn empty string into "."
154 return FromSlash(out.string())
157 // ToSlash returns the result of replacing each separator character
158 // in path with a slash ('/') character. Multiple separators are
159 // replaced by multiple slashes.
160 func ToSlash(path string) string {
161 if Separator == '/' {
164 return strings.Replace(path, string(Separator), "/", -1)
167 // FromSlash returns the result of replacing each slash ('/') character
168 // in path with a separator character. Multiple slashes are replaced
169 // by multiple separators.
170 func FromSlash(path string) string {
171 if Separator == '/' {
174 return strings.Replace(path, "/", string(Separator), -1)
177 // SplitList splits a list of paths joined by the OS-specific ListSeparator,
178 // usually found in PATH or GOPATH environment variables.
179 // Unlike strings.Split, SplitList returns an empty slice when passed an empty
181 func SplitList(path string) []string {
182 return splitList(path)
185 // Split splits path immediately following the final Separator,
186 // separating it into a directory and file name component.
187 // If there is no Separator in path, Split returns an empty dir
188 // and file set to path.
189 // The returned values have the property that path = dir+file.
190 func Split(path string) (dir, file string) {
191 vol := VolumeName(path)
193 for i >= len(vol) && !os.IsPathSeparator(path[i]) {
196 return path[:i+1], path[i+1:]
199 // Join joins any number of path elements into a single path, adding
200 // a Separator if necessary. Join calls Clean on the result; in particular,
201 // all empty strings are ignored.
202 // On Windows, the result is a UNC path if and only if the first path
203 // element is a UNC path.
204 func Join(elem ...string) string {
208 // Ext returns the file name extension used by path.
209 // The extension is the suffix beginning at the final dot
210 // in the final element of path; it is empty if there is
212 func Ext(path string) string {
213 for i := len(path) - 1; i >= 0 && !os.IsPathSeparator(path[i]); i-- {
221 // EvalSymlinks returns the path name after the evaluation of any symbolic
223 // If path is relative the result will be relative to the current directory,
224 // unless one of the components is an absolute symbolic link.
225 // EvalSymlinks calls Clean on the result.
226 func EvalSymlinks(path string) (string, error) {
227 return evalSymlinks(path)
230 // Abs returns an absolute representation of path.
231 // If the path is not absolute it will be joined with the current
232 // working directory to turn it into an absolute path. The absolute
233 // path name for a given file is not guaranteed to be unique.
234 // Abs calls Clean on the result.
235 func Abs(path string) (string, error) {
239 func unixAbs(path string) (string, error) {
241 return Clean(path), nil
243 wd, err := os.Getwd()
247 return Join(wd, path), nil
250 // Rel returns a relative path that is lexically equivalent to targpath when
251 // joined to basepath with an intervening separator. That is,
252 // Join(basepath, Rel(basepath, targpath)) is equivalent to targpath itself.
253 // On success, the returned path will always be relative to basepath,
254 // even if basepath and targpath share no elements.
255 // An error is returned if targpath can't be made relative to basepath or if
256 // knowing the current working directory would be necessary to compute it.
257 // Rel calls Clean on the result.
258 func Rel(basepath, targpath string) (string, error) {
259 baseVol := VolumeName(basepath)
260 targVol := VolumeName(targpath)
261 base := Clean(basepath)
262 targ := Clean(targpath)
263 if sameWord(targ, base) {
266 base = base[len(baseVol):]
267 targ = targ[len(targVol):]
271 // Can't use IsAbs - `\a` and `a` are both relative in Windows.
272 baseSlashed := len(base) > 0 && base[0] == Separator
273 targSlashed := len(targ) > 0 && targ[0] == Separator
274 if baseSlashed != targSlashed || !sameWord(baseVol, targVol) {
275 return "", errors.New("Rel: can't make " + targpath + " relative to " + basepath)
277 // Position base[b0:bi] and targ[t0:ti] at the first differing elements.
280 var b0, bi, t0, ti int
282 for bi < bl && base[bi] != Separator {
285 for ti < tl && targ[ti] != Separator {
288 if !sameWord(targ[t0:ti], base[b0:bi]) {
300 if base[b0:bi] == ".." {
301 return "", errors.New("Rel: can't make " + targpath + " relative to " + basepath)
304 // Base elements left. Must go up before going down.
305 seps := strings.Count(base[b0:bl], string(Separator))
310 buf := make([]byte, size)
312 for i := 0; i < seps; i++ {
314 copy(buf[n+1:], "..")
319 copy(buf[n+1:], targ[t0:])
321 return string(buf), nil
323 return targ[t0:], nil
326 // SkipDir is used as a return value from WalkFuncs to indicate that
327 // the directory named in the call is to be skipped. It is not returned
328 // as an error by any function.
329 var SkipDir = errors.New("skip this directory")
331 // WalkFunc is the type of the function called for each file or directory
332 // visited by Walk. The path argument contains the argument to Walk as a
333 // prefix; that is, if Walk is called with "dir", which is a directory
334 // containing the file "a", the walk function will be called with argument
335 // "dir/a". The info argument is the os.FileInfo for the named path.
337 // If there was a problem walking to the file or directory named by path, the
338 // incoming error will describe the problem and the function can decide how
339 // to handle that error (and Walk will not descend into that directory). If
340 // an error is returned, processing stops. The sole exception is when the function
341 // returns the special value SkipDir. If the function returns SkipDir when invoked
342 // on a directory, Walk skips the directory's contents entirely.
343 // If the function returns SkipDir when invoked on a non-directory file,
344 // Walk skips the remaining files in the containing directory.
345 type WalkFunc func(path string, info os.FileInfo, err error) error
347 var lstat = os.Lstat // for testing
349 // walk recursively descends path, calling w.
350 func walk(path string, info os.FileInfo, walkFn WalkFunc) error {
351 err := walkFn(path, info, nil)
353 if info.IsDir() && err == SkipDir {
363 names, err := readDirNames(path)
365 return walkFn(path, info, err)
368 for _, name := range names {
369 filename := Join(path, name)
370 fileInfo, err := lstat(filename)
372 if err := walkFn(filename, fileInfo, err); err != nil && err != SkipDir {
376 err = walk(filename, fileInfo, walkFn)
378 if !fileInfo.IsDir() || err != SkipDir {
387 // Walk walks the file tree rooted at root, calling walkFn for each file or
388 // directory in the tree, including root. All errors that arise visiting files
389 // and directories are filtered by walkFn. The files are walked in lexical
390 // order, which makes the output deterministic but means that for very
391 // large directories Walk can be inefficient.
392 // Walk does not follow symbolic links.
393 func Walk(root string, walkFn WalkFunc) error {
394 info, err := os.Lstat(root)
396 err = walkFn(root, nil, err)
398 err = walk(root, info, walkFn)
406 // readDirNames reads the directory named by dirname and returns
407 // a sorted list of directory entries.
408 func readDirNames(dirname string) ([]string, error) {
409 f, err := os.Open(dirname)
413 names, err := f.Readdirnames(-1)
422 // Base returns the last element of path.
423 // Trailing path separators are removed before extracting the last element.
424 // If the path is empty, Base returns ".".
425 // If the path consists entirely of separators, Base returns a single separator.
426 func Base(path string) string {
430 // Strip trailing slashes.
431 for len(path) > 0 && os.IsPathSeparator(path[len(path)-1]) {
432 path = path[0 : len(path)-1]
434 // Throw away volume name
435 path = path[len(VolumeName(path)):]
436 // Find the last element
438 for i >= 0 && !os.IsPathSeparator(path[i]) {
444 // If empty now, it had only slashes.
446 return string(Separator)
451 // Dir returns all but the last element of path, typically the path's directory.
452 // After dropping the final element, Dir calls Clean on the path and trailing
453 // slashes are removed.
454 // If the path is empty, Dir returns ".".
455 // If the path consists entirely of separators, Dir returns a single separator.
456 // The returned path does not end in a separator unless it is the root directory.
457 func Dir(path string) string {
458 vol := VolumeName(path)
460 for i >= len(vol) && !os.IsPathSeparator(path[i]) {
463 dir := Clean(path[len(vol) : i+1])
467 // VolumeName returns leading volume name.
468 // Given "C:\foo\bar" it returns "C:" on Windows.
469 // Given "\\host\share\foo" it returns "\\host\share".
470 // On other platforms it returns "".
471 func VolumeName(path string) string {
472 return path[:volumeNameLen(path)]