| // Copyright 2020 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 fs |
| |
| import ( |
| "errors" |
| |
| "golang.org/x/website/internal/backport/path" |
| ) |
| |
| // SkipDir is used as a return value from WalkDirFuncs 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") |
| |
| // WalkDirFunc is the type of the function called by WalkDir to visit |
| // each file or directory. |
| // |
| // The path argument contains the argument to WalkDir as a prefix. |
| // That is, if WalkDir 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 d argument is the fs.DirEntry for the named path. |
| // |
| // The error result returned by the function controls how WalkDir |
| // continues. If the function returns the special value SkipDir, WalkDir |
| // skips the current directory (path if d.IsDir() is true, otherwise |
| // path's parent directory). Otherwise, if the function returns a non-nil |
| // error, WalkDir stops entirely and returns that error. |
| // |
| // The err argument reports an error related to path, signaling that |
| // WalkDir will not walk into that directory. The function can decide how |
| // to handle that error; as described earlier, returning the error will |
| // cause WalkDir to stop walking the entire tree. |
| // |
| // WalkDir calls the function with a non-nil err argument in two cases. |
| // |
| // First, if the initial fs.Stat on the root directory fails, WalkDir |
| // calls the function with path set to root, d set to nil, and err set to |
| // the error from fs.Stat. |
| // |
| // Second, if a directory's ReadDir method fails, WalkDir calls the |
| // function with path set to the directory's path, d set to an |
| // fs.DirEntry describing the directory, and err set to the error from |
| // ReadDir. In this second case, the function is called twice with the |
| // path of the directory: the first call is before the directory read is |
| // attempted and has err set to nil, giving the function a chance to |
| // return SkipDir and avoid the ReadDir entirely. The second call is |
| // after a failed ReadDir and reports the error from ReadDir. |
| // (If ReadDir succeeds, there is no second call.) |
| // |
| // The differences between WalkDirFunc compared to filepath.WalkFunc are: |
| // |
| // - The second argument has type fs.DirEntry instead of fs.FileInfo. |
| // - The function is called before reading a directory, to allow SkipDir |
| // to bypass the directory read entirely. |
| // - If a directory read fails, the function is called a second time |
| // for that directory to report the error. |
| // |
| type WalkDirFunc func(path string, d DirEntry, err error) error |
| |
| // walkDir recursively descends path, calling walkDirFn. |
| func walkDir(fsys FS, name string, d DirEntry, walkDirFn WalkDirFunc) error { |
| if err := walkDirFn(name, d, nil); err != nil || !d.IsDir() { |
| if err == SkipDir && d.IsDir() { |
| // Successfully skipped directory. |
| err = nil |
| } |
| return err |
| } |
| |
| dirs, err := ReadDir(fsys, name) |
| if err != nil { |
| // Second call, to report ReadDir error. |
| err = walkDirFn(name, d, err) |
| if err != nil { |
| return err |
| } |
| } |
| |
| for _, d1 := range dirs { |
| name1 := path.Join(name, d1.Name()) |
| if err := walkDir(fsys, name1, d1, walkDirFn); err != nil { |
| if err == SkipDir { |
| break |
| } |
| 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 found in directories, |
| // but if root itself is a symbolic link, its target will be walked. |
| func WalkDir(fsys FS, root string, fn WalkDirFunc) error { |
| info, err := Stat(fsys, root) |
| if err != nil { |
| err = fn(root, nil, err) |
| } else { |
| err = walkDir(fsys, root, &statDirEntry{info}, fn) |
| } |
| if err == SkipDir { |
| return nil |
| } |
| return err |
| } |
| |
| type statDirEntry struct { |
| info FileInfo |
| } |
| |
| func (d *statDirEntry) Name() string { return d.info.Name() } |
| func (d *statDirEntry) IsDir() bool { return d.info.IsDir() } |
| func (d *statDirEntry) Type() FileMode { return d.info.Mode() & ModeType } |
| func (d *statDirEntry) Info() (FileInfo, error) { return d.info, nil } |