зеркало из https://github.com/golang/tools.git
txtar: implement fs.FS
Implements a read-only fs.FS view of a txtar.Archive. It returns an error if the names in the archive are not valid file system names. The archive cannot be modified while the file system is in use. Fixes golang/go#44158 Change-Id: If1e77833545a5b5db28006322e7f214951bc52f6 Reviewed-on: https://go-review.googlesource.com/c/tools/+/598756 Reviewed-by: Ian Lance Taylor <iant@google.com> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
This commit is contained in:
Tim King
Родитель
2cb2f7d32f
Коммит
2fb3ebe9d9
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@ -0,0 +1,259 @@
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// Copyright 2024 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 txtar
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import (
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"errors"
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"fmt"
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"io"
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"io/fs"
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"path"
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"time"
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)
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// FS returns the file system form of an Archive.
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// It returns an error if any of the file names in the archive
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// are not valid file system names.
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// The archive must not be modified while the FS is in use.
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//
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// If the file system detects that it has been modified, calls to the
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// file system return an ErrModified error.
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func FS(a *Archive) (fs.FS, error) {
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// Create a filesystem with a root directory.
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root := &node{fileinfo: fileinfo{path: ".", mode: readOnlyDir}}
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fsys := &filesystem{a, map[string]*node{root.path: root}}
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if err := initFiles(fsys); err != nil {
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return nil, fmt.Errorf("cannot create fs.FS from txtar.Archive: %s", err)
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}
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return fsys, nil
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}
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const (
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readOnly fs.FileMode = 0o444 // read only mode
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readOnlyDir = readOnly | fs.ModeDir
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)
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// ErrModified indicates that file system returned by FS
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// noticed that the underlying archive has been modified
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// since the call to FS. Detection of modification is best effort,
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// to help diagnose misuse of the API, and is not guaranteed.
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var ErrModified error = errors.New("txtar.Archive has been modified during txtar.FS")
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// A filesystem is a simple in-memory file system for txtar archives,
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// represented as a map from valid path names to information about the
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// files or directories they represent.
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//
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// File system operations are read only. Modifications to the underlying
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// *Archive may race. To help prevent this, the filesystem tries
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// to detect modification during Open and return ErrModified if it
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// is able to detect a modification.
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type filesystem struct {
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ar *Archive
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nodes map[string]*node
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}
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// node is a file or directory in the tree of a filesystem.
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type node struct {
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fileinfo // fs.FileInfo and fs.DirEntry implementation
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idx int // index into ar.Files (for files)
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entries []fs.DirEntry // subdirectories and files (for directories)
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}
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var _ fs.FS = (*filesystem)(nil)
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var _ fs.DirEntry = (*node)(nil)
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// initFiles initializes fsys from fsys.ar.Files. Returns an error if there are any
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// invalid file names or collisions between file or directories.
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func initFiles(fsys *filesystem) error {
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for idx, file := range fsys.ar.Files {
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name := file.Name
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if !fs.ValidPath(name) {
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return fmt.Errorf("file %q is an invalid path", name)
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}
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n := &node{idx: idx, fileinfo: fileinfo{path: name, size: len(file.Data), mode: readOnly}}
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if err := insert(fsys, n); err != nil {
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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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// insert adds node n as an entry to its parent directory within the filesystem.
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func insert(fsys *filesystem, n *node) error {
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if m := fsys.nodes[n.path]; m != nil {
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return fmt.Errorf("duplicate path %q", n.path)
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}
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fsys.nodes[n.path] = n
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// fsys.nodes contains "." to prevent infinite loops.
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parent, err := directory(fsys, path.Dir(n.path))
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if err != nil {
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return err
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}
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parent.entries = append(parent.entries, n)
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return nil
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}
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// directory returns the directory node with the path dir and lazily-creates it
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// if it does not exist.
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func directory(fsys *filesystem, dir string) (*node, error) {
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if m := fsys.nodes[dir]; m != nil && m.IsDir() {
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return m, nil // pre-existing directory
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}
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n := &node{fileinfo: fileinfo{path: dir, mode: readOnlyDir}}
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if err := insert(fsys, n); err != nil {
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return nil, err
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}
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return n, nil
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}
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// dataOf returns the data associated with the file t.
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// May return ErrModified if fsys.ar has been modified.
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func dataOf(fsys *filesystem, n *node) ([]byte, error) {
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if n.idx >= len(fsys.ar.Files) {
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return nil, ErrModified
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}
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f := fsys.ar.Files[n.idx]
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if f.Name != n.path || len(f.Data) != n.size {
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return nil, ErrModified
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}
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return f.Data, nil
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}
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func (fsys *filesystem) Open(name string) (fs.File, error) {
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if !fs.ValidPath(name) {
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return nil, &fs.PathError{Op: "open", Path: name, Err: fs.ErrInvalid}
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}
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n := fsys.nodes[name]
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switch {
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case n == nil:
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return nil, &fs.PathError{Op: "open", Path: name, Err: fs.ErrNotExist}
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case n.IsDir():
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return &openDir{fileinfo: n.fileinfo, entries: n.entries}, nil
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default:
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data, err := dataOf(fsys, n)
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if err != nil {
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return nil, err
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}
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return &openFile{fileinfo: n.fileinfo, data: data}, nil
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}
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}
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func (fsys *filesystem) ReadFile(name string) ([]byte, error) {
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file, err := fsys.Open(name)
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if err != nil {
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return nil, err
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}
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if file, ok := file.(*openFile); ok {
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// TODO: use slices.Clone once x/tools has 1.21 available.
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cp := make([]byte, file.size)
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copy(cp, file.data)
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return cp, err
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}
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return nil, &fs.PathError{Op: "read", Path: name, Err: fs.ErrInvalid}
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}
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// A fileinfo implements fs.FileInfo and fs.DirEntry for a given archive file.
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type fileinfo struct {
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path string // unique path to the file or directory within a filesystem
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size int
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mode fs.FileMode
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}
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var _ fs.FileInfo = (*fileinfo)(nil)
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var _ fs.DirEntry = (*fileinfo)(nil)
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func (i *fileinfo) Name() string { return path.Base(i.path) }
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func (i *fileinfo) Size() int64 { return int64(i.size) }
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func (i *fileinfo) Mode() fs.FileMode { return i.mode }
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func (i *fileinfo) Type() fs.FileMode { return i.mode.Type() }
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func (i *fileinfo) ModTime() time.Time { return time.Time{} }
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func (i *fileinfo) IsDir() bool { return i.mode&fs.ModeDir != 0 }
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func (i *fileinfo) Sys() any { return nil }
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func (i *fileinfo) Info() (fs.FileInfo, error) { return i, nil }
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// An openFile is a regular (non-directory) fs.File open for reading.
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type openFile struct {
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fileinfo
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data []byte
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offset int64
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}
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var _ fs.File = (*openFile)(nil)
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func (f *openFile) Stat() (fs.FileInfo, error) { return &f.fileinfo, nil }
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func (f *openFile) Close() error { return nil }
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func (f *openFile) Read(b []byte) (int, error) {
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if f.offset >= int64(len(f.data)) {
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return 0, io.EOF
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}
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if f.offset < 0 {
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return 0, &fs.PathError{Op: "read", Path: f.path, Err: fs.ErrInvalid}
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}
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n := copy(b, f.data[f.offset:])
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f.offset += int64(n)
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return n, nil
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}
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func (f *openFile) Seek(offset int64, whence int) (int64, error) {
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switch whence {
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case 0:
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// offset += 0
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case 1:
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offset += f.offset
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case 2:
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offset += int64(len(f.data))
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}
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if offset < 0 || offset > int64(len(f.data)) {
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return 0, &fs.PathError{Op: "seek", Path: f.path, Err: fs.ErrInvalid}
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}
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f.offset = offset
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return offset, nil
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}
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func (f *openFile) ReadAt(b []byte, offset int64) (int, error) {
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if offset < 0 || offset > int64(len(f.data)) {
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return 0, &fs.PathError{Op: "read", Path: f.path, Err: fs.ErrInvalid}
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}
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n := copy(b, f.data[offset:])
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if n < len(b) {
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return n, io.EOF
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}
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return n, nil
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}
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// A openDir is a directory fs.File (so also an fs.ReadDirFile) open for reading.
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type openDir struct {
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fileinfo
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entries []fs.DirEntry
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offset int
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}
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var _ fs.ReadDirFile = (*openDir)(nil)
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func (d *openDir) Stat() (fs.FileInfo, error) { return &d.fileinfo, nil }
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func (d *openDir) Close() error { return nil }
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func (d *openDir) Read(b []byte) (int, error) {
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return 0, &fs.PathError{Op: "read", Path: d.path, Err: fs.ErrInvalid}
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}
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func (d *openDir) ReadDir(count int) ([]fs.DirEntry, error) {
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n := len(d.entries) - d.offset
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if n == 0 && count > 0 {
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return nil, io.EOF
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}
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if count > 0 && n > count {
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n = count
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}
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list := make([]fs.DirEntry, n)
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copy(list, d.entries[d.offset:d.offset+n])
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d.offset += n
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return list, nil
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}
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@ -0,0 +1,183 @@
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// Copyright 2024 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 txtar_test
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import (
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"io/fs"
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"strings"
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"testing"
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"testing/fstest"
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"golang.org/x/tools/txtar"
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)
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func TestFS(t *testing.T) {
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var fstestcases = []struct {
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name, input, files string
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}{
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{
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name: "empty",
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input: ``,
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files: "",
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},
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{
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name: "one",
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input: `
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-- one.txt --
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one
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`,
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files: "one.txt",
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},
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{
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name: "two",
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input: `
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-- one.txt --
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one
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-- two.txt --
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two
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`,
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files: "one.txt two.txt",
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},
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{
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name: "subdirectories",
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input: `
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-- one.txt --
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one
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-- 2/two.txt --
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two
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-- 2/3/three.txt --
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three
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-- 4/four.txt --
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four
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`,
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files: "one.txt 2/two.txt 2/3/three.txt 4/four.txt",
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},
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}
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for _, tc := range fstestcases {
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t.Run(tc.name, func(t *testing.T) {
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a := txtar.Parse([]byte(tc.input))
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fsys, err := txtar.FS(a)
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if err != nil {
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t.Fatal(err)
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}
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files := strings.Fields(tc.files)
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if err := fstest.TestFS(fsys, files...); err != nil {
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t.Fatal(err)
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}
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for _, f := range a.Files {
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b, err := fs.ReadFile(fsys, f.Name)
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if err != nil {
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t.Errorf("ReadFile(%q) failed with error: %v", f.Name, err)
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}
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if got, want := string(b), string(f.Data); got != want {
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t.Errorf("ReadFile(%q) = %q; want %q", f.Name, got, want)
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}
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}
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})
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}
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}
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func TestInvalid(t *testing.T) {
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invalidtestcases := []struct {
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name, want string
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input string
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}{
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{"unclean file names", "invalid path", `
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-- 1/../one.txt --
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one
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-- 2/sub/../two.txt --
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two
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`},
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{"duplicate name", `cannot create fs.FS from txtar.Archive: duplicate path "1/2/one.txt"`, `
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-- 1/2/one.txt --
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one
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-- 1/2/one.txt --
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two
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`},
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{"file conflicts with directory", `duplicate path "1/2"`, `
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-- 1/2 --
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one
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-- 1/2/one.txt --
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two
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`},
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}
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for _, tc := range invalidtestcases {
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t.Run(tc.name, func(t *testing.T) {
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a := txtar.Parse([]byte(tc.input))
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_, err := txtar.FS(a)
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if err == nil {
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t.Fatal("txtar.FS(...) succeeded; expected an error")
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}
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if got := err.Error(); !strings.Contains(got, tc.want) || tc.want == "" {
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t.Errorf("txtar.FS(...) got error %q; want %q", got, tc.want)
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}
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})
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}
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}
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func TestModified(t *testing.T) {
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const input = `
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-- one.txt --
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one
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`
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for _, mod := range []func(a *txtar.Archive){
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func(a *txtar.Archive) { a.Files[0].Data = []byte("other") },
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func(a *txtar.Archive) { a.Files[0].Name = "other" },
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func(a *txtar.Archive) { a.Files = nil },
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} {
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a := txtar.Parse([]byte(input))
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if n := len(a.Files); n != 1 {
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t.Fatalf("txtar.Parse(%q) got %d files; expected 1", input, n)
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}
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fsys, err := txtar.FS(a)
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if err != nil {
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t.Fatal(err)
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}
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// Confirm we can open "one.txt".
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_, err = fsys.Open("one.txt")
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if err != nil {
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t.Fatal(err)
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}
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// Modify a to get ErrModified when opening "one.txt".
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mod(a)
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_, err = fsys.Open("one.txt")
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if err != txtar.ErrModified {
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t.Errorf("Open(%q) got error %s; want ErrModified", "one.txt", err)
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}
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}
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}
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func TestReadFile(t *testing.T) {
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const input = `
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-- 1/one.txt --
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one
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`
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a := txtar.Parse([]byte(input))
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fsys, err := txtar.FS(a)
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if err != nil {
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t.Fatal(err)
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}
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readfs := fsys.(fs.ReadFileFS)
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_, err = readfs.ReadFile("1")
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if err == nil {
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t.Errorf("ReadFile(%q) succeeded; expected an error when reading a directory", "1")
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}
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content, err := readfs.ReadFile("1/one.txt")
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if err != nil {
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t.Fatal(err)
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}
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want := "one\n"
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if got := string(content); want != got {
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t.Errorf("ReadFile(%q) = %q; want %q", "1/one.txt", got, want)
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}
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}
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