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Diffstat (limited to '')
| -rw-r--r-- | src/path/filepath/path.go | 659 |
1 files changed, 659 insertions, 0 deletions
diff --git a/src/path/filepath/path.go b/src/path/filepath/path.go new file mode 100644 index 0000000..485ef4e --- /dev/null +++ b/src/path/filepath/path.go @@ -0,0 +1,659 @@ +// 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. +// +// The filepath package uses either forward slashes or backslashes, +// depending on the operating system. To process paths such as URLs +// that always use forward slashes regardless of the operating +// system, see the path package. +package filepath + +import ( + "errors" + "io/fs" + "os" + "sort" + "strings" +) + +// 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) prepend(prefix ...byte) { + b.buf = append(prefix, b.buf...) + b.w += len(prefix) +} + +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. +// +// Finally, any occurrences of slash are replaced by Separator. +// +// 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,” +// https://9p.io/sys/doc/lexnames.html +func Clean(path string) string { + originalPath := path + volLen := volumeNameLen(path) + path = path[volLen:] + if path == "" { + if volLen > 1 && os.IsPathSeparator(originalPath[0]) && os.IsPathSeparator(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('.') + } + + postClean(&out) // avoid creating absolute paths on Windows + return FromSlash(out.string()) +} + +// IsLocal reports whether path, using lexical analysis only, has all of these properties: +// +// - is within the subtree rooted at the directory in which path is evaluated +// - is not an absolute path +// - is not empty +// - on Windows, is not a reserved name such as "NUL" +// +// If IsLocal(path) returns true, then +// Join(base, path) will always produce a path contained within base and +// Clean(path) will always produce an unrooted path with no ".." path elements. +// +// IsLocal is a purely lexical operation. +// In particular, it does not account for the effect of any symbolic links +// that may exist in the filesystem. +func IsLocal(path string) bool { + return isLocal(path) +} + +func unixIsLocal(path string) bool { + if IsAbs(path) || path == "" { + return false + } + hasDots := false + for p := path; p != ""; { + var part string + part, p, _ = strings.Cut(p, "/") + if part == "." || part == ".." { + hasDots = true + break + } + } + if hasDots { + path = Clean(path) + } + if path == ".." || strings.HasPrefix(path, "../") { + return false + } + return true +} + +// 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.ReplaceAll(path, string(Separator), "/") +} + +// 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.ReplaceAll(path, "/", string(Separator)) +} + +// SplitList splits a list of paths joined by the OS-specific ListSeparator, +// usually found in PATH or GOPATH environment variables. +// Unlike strings.Split, SplitList returns an empty slice when passed an empty +// string. +func SplitList(path string) []string { + return splitList(path) +} + +// Split splits path immediately following the final Separator, +// separating it into a directory and file name component. +// If there is no Separator in path, Split returns an empty dir +// and file set to path. +// The returned values have the property that path = dir+file. +func Split(path string) (dir, file string) { + vol := VolumeName(path) + i := len(path) - 1 + for i >= len(vol) && !os.IsPathSeparator(path[i]) { + i-- + } + return path[:i+1], path[i+1:] +} + +// Join joins any number of path elements into a single path, +// separating them with an OS specific Separator. Empty elements +// are ignored. The result is Cleaned. However, if the argument +// list is empty or all its elements are empty, Join returns +// an empty string. +// On Windows, the result will only be a UNC path if the first +// non-empty element is a UNC path. +func Join(elem ...string) string { + return join(elem) +} + +// Ext returns the file name extension used by path. +// The extension is the suffix beginning at the final dot +// in the final element of path; it is empty if there is +// no dot. +func Ext(path string) string { + for i := len(path) - 1; i >= 0 && !os.IsPathSeparator(path[i]); i-- { + if path[i] == '.' { + return path[i:] + } + } + return "" +} + +// 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. +// EvalSymlinks calls Clean on the result. +func EvalSymlinks(path string) (string, error) { + return evalSymlinks(path) +} + +// Abs returns an absolute representation of path. +// If the path is not absolute it will be joined with the current +// working directory to turn it into an absolute path. The absolute +// path name for a given file is not guaranteed to be unique. +// Abs calls Clean on the result. +func Abs(path string) (string, error) { + return abs(path) +} + +func unixAbs(path string) (string, error) { + if IsAbs(path) { + return Clean(path), nil + } + wd, err := os.Getwd() + if err != nil { + return "", err + } + return Join(wd, path), nil +} + +// 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. +// Rel calls Clean on the result. +func Rel(basepath, targpath string) (string, error) { + baseVol := VolumeName(basepath) + targVol := VolumeName(targpath) + base := Clean(basepath) + targ := Clean(targpath) + if sameWord(targ, base) { + return ".", nil + } + base = base[len(baseVol):] + targ = targ[len(targVol):] + if base == "." { + base = "" + } else if base == "" && volumeNameLen(baseVol) > 2 /* isUNC */ { + // Treat any targetpath matching `\\host\share` basepath as absolute path. + base = string(Separator) + } + + // 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 || !sameWord(baseVol, targVol) { + return "", errors.New("Rel: can't make " + targpath + " relative to " + basepath) + } + // 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 !sameWord(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 " + targpath + " relative to " + basepath) + } + 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 +} + +// 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 error = fs.SkipDir + +// SkipAll is used as a return value from WalkFuncs to indicate that +// all remaining files and directories are to be skipped. It is not returned +// as an error by any function. +var SkipAll error = fs.SkipAll + +// WalkFunc is the type of the function called by Walk to visit each +// file or directory. +// +// The path argument contains the argument to Walk as a prefix. +// That is, if Walk is called with root argument "dir" and finds a file +// named "a" in that directory, the walk function will be called with +// argument "dir/a". +// +// The directory and file are joined with Join, which may clean the +// directory name: if Walk is called with the root argument "x/../dir" +// and finds a file named "a" in that directory, the walk function will +// be called with argument "dir/a", not "x/../dir/a". +// +// The info argument is the fs.FileInfo for the named path. +// +// The error result returned by the function controls how Walk continues. +// If the function returns the special value SkipDir, Walk skips the +// current directory (path if info.IsDir() is true, otherwise path's +// parent directory). If the function returns the special value SkipAll, +// Walk skips all remaining files and directories. Otherwise, if the function +// returns a non-nil error, Walk stops entirely and returns that error. +// +// The err argument reports an error related to path, signaling that Walk +// will not walk into that directory. The function can decide how to +// handle that error; as described earlier, returning the error will +// cause Walk to stop walking the entire tree. +// +// Walk calls the function with a non-nil err argument in two cases. +// +// First, if an os.Lstat on the root directory or any directory or file +// in the tree fails, Walk calls the function with path set to that +// directory or file's path, info set to nil, and err set to the error +// from os.Lstat. +// +// Second, if a directory's Readdirnames method fails, Walk calls the +// function with path set to the directory's path, info, set to an +// fs.FileInfo describing the directory, and err set to the error from +// Readdirnames. +type WalkFunc func(path string, info fs.FileInfo, err error) error + +var lstat = os.Lstat // for testing + +// walkDir recursively descends path, calling walkDirFn. +func walkDir(path string, d fs.DirEntry, walkDirFn fs.WalkDirFunc) error { + if err := walkDirFn(path, d, nil); err != nil || !d.IsDir() { + if err == SkipDir && d.IsDir() { + // Successfully skipped directory. + err = nil + } + return err + } + + dirs, err := readDir(path) + if err != nil { + // Second call, to report ReadDir error. + err = walkDirFn(path, d, err) + if err != nil { + if err == SkipDir && d.IsDir() { + err = nil + } + return err + } + } + + for _, d1 := range dirs { + path1 := Join(path, d1.Name()) + if err := walkDir(path1, d1, walkDirFn); err != nil { + if err == SkipDir { + break + } + return err + } + } + return nil +} + +// walk recursively descends path, calling walkFn. +func walk(path string, info fs.FileInfo, walkFn WalkFunc) error { + if !info.IsDir() { + return walkFn(path, info, nil) + } + + names, err := readDirNames(path) + err1 := walkFn(path, info, err) + // If err != nil, walk can't walk into this directory. + // err1 != nil means walkFn want walk to skip this directory or stop walking. + // Therefore, if one of err and err1 isn't nil, walk will return. + if err != nil || err1 != nil { + // The caller's behavior is controlled by the return value, which is decided + // by walkFn. walkFn may ignore err and return nil. + // If walkFn returns SkipDir or SkipAll, it will be handled by the caller. + // So walk should return whatever walkFn returns. + return err1 + } + + for _, name := range names { + filename := Join(path, name) + fileInfo, err := lstat(filename) + if err != nil { + if err := walkFn(filename, fileInfo, err); err != nil && err != SkipDir { + return err + } + } else { + err = walk(filename, fileInfo, walkFn) + if err != nil { + if !fileInfo.IsDir() || err != SkipDir { + return err + } + } + } + } + return nil +} + +// WalkDir walks the file tree rooted at root, calling fn for each file or +// directory in the tree, including root. +// +// All errors that arise visiting files and directories are filtered by fn: +// see the fs.WalkDirFunc documentation for details. +// +// The files are walked in lexical order, which makes the output deterministic +// but requires WalkDir to read an entire directory into memory before proceeding +// to walk that directory. +// +// WalkDir does not follow symbolic links. +// +// WalkDir calls fn with paths that use the separator character appropriate +// for the operating system. This is unlike [io/fs.WalkDir], which always +// uses slash separated paths. +func WalkDir(root string, fn fs.WalkDirFunc) error { + info, err := os.Lstat(root) + if err != nil { + err = fn(root, nil, err) + } else { + err = walkDir(root, &statDirEntry{info}, fn) + } + if err == SkipDir || err == SkipAll { + return nil + } + return err +} + +type statDirEntry struct { + info fs.FileInfo +} + +func (d *statDirEntry) Name() string { return d.info.Name() } +func (d *statDirEntry) IsDir() bool { return d.info.IsDir() } +func (d *statDirEntry) Type() fs.FileMode { return d.info.Mode().Type() } +func (d *statDirEntry) Info() (fs.FileInfo, error) { return d.info, nil } + +// Walk walks the file tree rooted at root, calling fn for each file or +// directory in the tree, including root. +// +// All errors that arise visiting files and directories are filtered by fn: +// see the WalkFunc documentation for details. +// +// The files are walked in lexical order, which makes the output deterministic +// but requires Walk to read an entire directory into memory before proceeding +// to walk that directory. +// +// Walk does not follow symbolic links. +// +// Walk is less efficient than WalkDir, introduced in Go 1.16, +// which avoids calling os.Lstat on every visited file or directory. +func Walk(root string, fn WalkFunc) error { + info, err := os.Lstat(root) + if err != nil { + err = fn(root, nil, err) + } else { + err = walk(root, info, fn) + } + if err == SkipDir || err == SkipAll { + return nil + } + return err +} + +// readDir reads the directory named by dirname and returns +// a sorted list of directory entries. +func readDir(dirname string) ([]fs.DirEntry, error) { + f, err := os.Open(dirname) + if err != nil { + return nil, err + } + dirs, err := f.ReadDir(-1) + f.Close() + if err != nil { + return nil, err + } + sort.Slice(dirs, func(i, j int) bool { return dirs[i].Name() < dirs[j].Name() }) + return dirs, nil +} + +// readDirNames reads the directory named by dirname and returns +// a sorted list of directory entry names. +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) + return names, nil +} + +// Base returns the last element of path. +// Trailing path separators are removed before extracting the last element. +// If the path is empty, Base returns ".". +// If the path consists entirely of separators, Base returns a single separator. +func Base(path string) string { + if path == "" { + return "." + } + // Strip trailing slashes. + for len(path) > 0 && os.IsPathSeparator(path[len(path)-1]) { + path = path[0 : len(path)-1] + } + // Throw away volume name + path = path[len(VolumeName(path)):] + // Find the last element + i := len(path) - 1 + for i >= 0 && !os.IsPathSeparator(path[i]) { + i-- + } + if i >= 0 { + path = path[i+1:] + } + // If empty now, it had only slashes. + if path == "" { + return string(Separator) + } + return path +} + +// Dir returns all but the last element of path, typically the path's directory. +// After dropping the final element, Dir calls Clean on the path and trailing +// slashes are removed. +// If the path is empty, Dir returns ".". +// If the path consists entirely of separators, Dir returns a single separator. +// The returned path does not end in a separator unless it is the root directory. +func Dir(path string) string { + vol := VolumeName(path) + i := len(path) - 1 + for i >= len(vol) && !os.IsPathSeparator(path[i]) { + i-- + } + dir := Clean(path[len(vol) : i+1]) + if dir == "." && len(vol) > 2 { + // must be UNC + return vol + } + return vol + dir +} + +// VolumeName returns leading volume name. +// Given "C:\foo\bar" it returns "C:" on Windows. +// Given "\\host\share\foo" it returns "\\host\share". +// On other platforms it returns "". +func VolumeName(path string) string { + return FromSlash(path[:volumeNameLen(path)]) +} |