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128 lines
4.5 KiB
Go
128 lines
4.5 KiB
Go
// Copyright 2020 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package fs
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import (
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"errors"
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"path"
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)
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// SkipDir is used as a return value from WalkDirFuncs to indicate that
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// the directory named in the call is to be skipped. It is not returned
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// as an error by any function.
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var SkipDir = errors.New("skip this directory")
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// WalkDirFunc is the type of the function called by WalkDir to visit
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// each file or directory.
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//
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// The path argument contains the argument to WalkDir as a prefix.
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// That is, if WalkDir is called with root argument "dir" and finds a file
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// named "a" in that directory, the walk function will be called with
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// argument "dir/a".
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//
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// The d argument is the fs.DirEntry for the named path.
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//
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// The error result returned by the function controls how WalkDir
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// continues. If the function returns the special value SkipDir, WalkDir
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// skips the current directory (path if d.IsDir() is true, otherwise
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// path's parent directory). Otherwise, if the function returns a non-nil
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// error, WalkDir stops entirely and returns that error.
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//
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// The err argument reports an error related to path, signaling that
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// WalkDir will not walk into that directory. The function can decide how
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// to handle that error; as described earlier, returning the error will
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// cause WalkDir to stop walking the entire tree.
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//
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// WalkDir calls the function with a non-nil err argument in two cases.
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//
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// First, if the initial fs.Stat on the root directory fails, WalkDir
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// calls the function with path set to root, d set to nil, and err set to
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// the error from fs.Stat.
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//
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// Second, if a directory's ReadDir method fails, WalkDir calls the
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// function with path set to the directory's path, d set to an
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// fs.DirEntry describing the directory, and err set to the error from
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// ReadDir. In this second case, the function is called twice with the
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// path of the directory: the first call is before the directory read is
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// attempted and has err set to nil, giving the function a chance to
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// return SkipDir and avoid the ReadDir entirely. The second call is
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// after a failed ReadDir and reports the error from ReadDir.
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// (If ReadDir succeeds, there is no second call.)
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//
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// The differences between WalkDirFunc compared to filepath.WalkFunc are:
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//
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// - The second argument has type fs.DirEntry instead of fs.FileInfo.
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// - The function is called before reading a directory, to allow SkipDir
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// to bypass the directory read entirely.
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// - If a directory read fails, the function is called a second time
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// for that directory to report the error.
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//
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type WalkDirFunc func(path string, d DirEntry, err error) error
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// walkDir recursively descends path, calling walkDirFn.
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func walkDir(fsys FS, name string, d DirEntry, walkDirFn WalkDirFunc) error {
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if err := walkDirFn(name, d, nil); err != nil || !d.IsDir() {
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if err == SkipDir && d.IsDir() {
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// Successfully skipped directory.
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err = nil
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}
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return err
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}
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dirs, err := ReadDir(fsys, name)
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if err != nil {
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// Second call, to report ReadDir error.
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err = walkDirFn(name, d, err)
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if err != nil {
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return err
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}
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}
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for _, d1 := range dirs {
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name1 := path.Join(name, d1.Name())
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if err := walkDir(fsys, name1, d1, walkDirFn); err != nil {
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if err == SkipDir {
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break
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}
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return err
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}
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}
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return nil
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}
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// WalkDir walks the file tree rooted at root, calling fn for each file or
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// directory in the tree, including root.
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//
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// All errors that arise visiting files and directories are filtered by fn:
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// see the fs.WalkDirFunc documentation for details.
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//
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// The files are walked in lexical order, which makes the output deterministic
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// but requires WalkDir to read an entire directory into memory before proceeding
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// to walk that directory.
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//
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// WalkDir does not follow symbolic links found in directories,
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// but if root itself is a symbolic link, its target will be walked.
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func WalkDir(fsys FS, root string, fn WalkDirFunc) error {
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info, err := Stat(fsys, root)
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if err != nil {
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err = fn(root, nil, err)
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} else {
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err = walkDir(fsys, root, &statDirEntry{info}, fn)
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}
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if err == SkipDir {
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return nil
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}
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return err
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}
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type statDirEntry struct {
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info FileInfo
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}
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func (d *statDirEntry) Name() string { return d.info.Name() }
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func (d *statDirEntry) IsDir() bool { return d.info.IsDir() }
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func (d *statDirEntry) Type() FileMode { return d.info.Mode().Type() }
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func (d *statDirEntry) Info() (FileInfo, error) { return d.info, nil }
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