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memfs.go
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memfs.go
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package memfs
import (
"bytes"
"errors"
"fmt"
"io/fs"
"os"
syspath "path"
"strings"
"sync"
"time"
)
// FS is an in-memory filesystem that implements
// io/fs.FS
type FS struct {
dir *dir
}
// New creates a new in-memory FileSystem.
func New() *FS {
return &FS{
dir: &dir{
children: make(map[string]childI),
},
}
}
// MkdirAll creates a directory named path,
// along with any necessary parents, and returns nil,
// or else returns an error.
// The permission bits perm (before umask) are used for all
// directories that MkdirAll creates.
// If path is already a directory, MkdirAll does nothing
// and returns nil.
func (rootFS *FS) MkdirAll(path string, perm os.FileMode) error {
if !fs.ValidPath(path) {
return fmt.Errorf("invalid path: %s: %w", path, fs.ErrInvalid)
}
if path == "." {
// root dir always exists
return nil
}
parts := strings.Split(path, "/")
next := rootFS.dir
for _, part := range parts {
cur := next
cur.mu.Lock()
child := cur.children[part]
if child == nil {
newDir := &dir{
name: part,
perm: perm,
children: make(map[string]childI),
}
cur.children[part] = newDir
next = newDir
} else {
childDir, ok := child.(*dir)
if !ok {
return fmt.Errorf("not a directory: %s: %w", part, fs.ErrInvalid)
}
next = childDir
}
cur.mu.Unlock()
}
return nil
}
func (rootFS *FS) getDir(path string) (*dir, error) {
if path == "" {
return rootFS.dir, nil
}
parts := strings.Split(path, "/")
cur := rootFS.dir
for _, part := range parts {
err := func() error {
cur.mu.Lock()
defer cur.mu.Unlock()
child := cur.children[part]
if child == nil {
return fmt.Errorf("not a directory: %s: %w", part, fs.ErrNotExist)
} else {
childDir, ok := child.(*dir)
if !ok {
return fmt.Errorf("no such file or directory: %s: %w", part, fs.ErrNotExist)
}
cur = childDir
}
return nil
}()
if err != nil {
return nil, err
}
}
return cur, nil
}
func (rootFS *FS) get(path string) (childI, error) {
if path == "" {
return rootFS.dir, nil
}
parts := strings.Split(path, "/")
var (
cur = rootFS.dir
chld childI
err error
)
for i, part := range parts {
chld, err = func() (childI, error) {
cur.mu.Lock()
defer cur.mu.Unlock()
child := cur.children[part]
if child == nil {
return nil, fmt.Errorf("not a directory: %s: %w", part, fs.ErrNotExist)
} else {
_, isFile := child.(*File)
if isFile {
if i == len(parts)-1 {
return child, nil
} else {
return nil, fmt.Errorf("no such file or directory: %s: %w", part, fs.ErrNotExist)
}
}
childDir, ok := child.(*dir)
if !ok {
return nil, errors.New("not a directory")
}
cur = childDir
}
return child, nil
}()
if err != nil {
return nil, err
}
}
return chld, nil
}
func (rootFS *FS) create(path string) (*File, error) {
if !fs.ValidPath(path) {
return nil, fmt.Errorf("invalid path: %s: %w", path, fs.ErrInvalid)
}
if path == "." {
// root dir
path = ""
}
dirPart, filePart := syspath.Split(path)
dirPart = strings.TrimSuffix(dirPart, "/")
dir, err := rootFS.getDir(dirPart)
if err != nil {
return nil, err
}
dir.mu.Lock()
defer dir.mu.Unlock()
existing := dir.children[filePart]
if existing != nil {
_, ok := existing.(*File)
if !ok {
return nil, fmt.Errorf("path is a directory: %s: %w", path, fs.ErrExist)
}
}
newFile := &File{
name: filePart,
perm: 0666,
content: &bytes.Buffer{},
}
dir.children[filePart] = newFile
return newFile, nil
}
// WriteFile writes data to a file named by filename.
// If the file does not exist, WriteFile creates it with permissions perm
// (before umask); otherwise WriteFile truncates it before writing, without changing permissions.
func (rootFS *FS) WriteFile(path string, data []byte, perm os.FileMode) error {
if !fs.ValidPath(path) {
return fmt.Errorf("invalid path: %s: %w", path, fs.ErrInvalid)
}
if path == "." {
// root dir
path = ""
}
f, err := rootFS.create(path)
if err != nil {
return err
}
f.content = bytes.NewBuffer(data)
f.perm = perm
return nil
}
// Open opens the named file.
func (rootFS *FS) Open(name string) (fs.File, error) {
if !fs.ValidPath(name) {
return nil, &fs.PathError{
Op: "open",
Path: name,
Err: fs.ErrInvalid,
}
}
if name == "." {
// root dir
name = ""
}
child, err := rootFS.get(name)
if err != nil {
return nil, err
}
switch cc := child.(type) {
case *File:
handle := &File{
name: cc.name,
perm: cc.perm,
content: bytes.NewBuffer(cc.content.Bytes()),
}
return handle, nil
case *dir:
handle := &fhDir{
dir: cc,
}
return handle, nil
}
return nil, fmt.Errorf("unexpected file type in fs: %s: %w", name, fs.ErrInvalid)
}
type dir struct {
mu sync.Mutex
name string
perm os.FileMode
modTime time.Time
children map[string]childI
}
type fhDir struct {
dir *dir
idx int
}
func (d *fhDir) Stat() (fs.FileInfo, error) {
fi := fileInfo{
name: d.dir.name,
size: 4096,
modTime: d.dir.modTime,
mode: d.dir.perm | fs.ModeDir,
}
return &fi, nil
}
func (d *fhDir) Read(b []byte) (int, error) {
return 0, errors.New("is a directory")
}
func (d *fhDir) Close() error {
return nil
}
func (d *fhDir) ReadDir(n int) ([]fs.DirEntry, error) {
d.dir.mu.Lock()
defer d.dir.mu.Unlock()
names := make([]string, 0, len(d.dir.children))
for name := range d.dir.children {
names = append(names, name)
}
if n <= 0 {
n = len(names)
}
out := make([]fs.DirEntry, 0, n)
for i := d.idx; i < n && i < len(names); i++ {
name := names[i]
child := d.dir.children[name]
f, isFile := child.(*File)
if isFile {
stat, _ := f.Stat()
out = append(out, &dirEntry{
info: stat,
})
} else {
d := child.(*dir)
fi := fileInfo{
name: d.name,
size: 4096,
modTime: d.modTime,
mode: d.perm | fs.ModeDir,
}
out = append(out, &dirEntry{
info: &fi,
})
}
d.idx = i
}
return out, nil
}
type File struct {
name string
perm os.FileMode
content *bytes.Buffer
modTime time.Time
closed bool
}
func (f *File) Stat() (fs.FileInfo, error) {
if f.closed {
return nil, fs.ErrClosed
}
fi := fileInfo{
name: f.name,
size: int64(f.content.Len()),
modTime: f.modTime,
mode: f.perm,
}
return &fi, nil
}
func (f *File) Read(b []byte) (int, error) {
if f.closed {
return 0, fs.ErrClosed
}
return f.content.Read(b)
}
func (f *File) Close() error {
if f.closed {
return fs.ErrClosed
}
f.closed = true
return nil
}
type childI interface {
}
type fileInfo struct {
name string
size int64
modTime time.Time
mode fs.FileMode
}
// base name of the file
func (fi *fileInfo) Name() string {
return fi.name
}
// length in bytes for regular files; system-dependent for others
func (fi *fileInfo) Size() int64 {
return fi.size
}
// file mode bits
func (fi *fileInfo) Mode() fs.FileMode {
return fi.mode
}
// modification time
func (fi *fileInfo) ModTime() time.Time {
return fi.modTime
}
// abbreviation for Mode().IsDir()
func (fi *fileInfo) IsDir() bool {
return fi.mode&fs.ModeDir > 0
}
// underlying data source (can return nil)
func (fi *fileInfo) Sys() interface{} {
return nil
}
type dirEntry struct {
info fs.FileInfo
}
func (de *dirEntry) Name() string {
return de.info.Name()
}
func (de *dirEntry) IsDir() bool {
return de.info.IsDir()
}
func (de *dirEntry) Type() fs.FileMode {
return de.info.Mode()
}
func (de *dirEntry) Info() (fs.FileInfo, error) {
return de.info, nil
}