//
// Errors returned from this package may be tested against these errors
// with [errors.Is].
var (
	// ErrInvalid indicates an invalid argument.
	// Methods on File will return this error when the receiver is nil.
	ErrInvalid = fs.ErrInvalid // "invalid argument"

	ErrPermission = fs.ErrPermission // "permission denied"
	ErrExist      = fs.ErrExist      // "file already exists"

// and a non-nil error.
//
// Most clients are better served by the more efficient ReadDir method.
func (f *File) Readdir(n int) ([]FileInfo, error) {
	if f == nil {
		return nil, ErrInvalid
	}
	_, _, infos, err := f.readdir(n, readdirFileInfo)
	if infos == nil {
		// Readdir has historically always returned a non-nil empty slice, never nil,
		// even on error (except misuse with nil receiver above).

		return 0, &fs.PathError{Op: "seek", Path: f.path, Err: fs.ErrInvalid}
	}
	f.offset = offset
	return offset, nil
}

func (f *openMapFile) ReadAt(b []byte, offset int64) (int, error) {
	if offset < 0 || offset > int64(len(f.f.Data)) {
		return 0, &fs.PathError{Op: "read", Path: f.path, Err: fs.ErrInvalid}
	}
	n := copy(b, f.f.Data[offset:])
	if n < len(b) {
		return n, io.EOF
	}

import (
	"syscall"
)

// Stat returns the [FileInfo] structure describing file.
// If there is an error, it will be of type [*PathError].
func (f *File) Stat() (FileInfo, error) {
	if f == nil {
		return nil, ErrInvalid
	}
	var fs fileStat
	err := f.pfd.Fstat(&fs.sys)
	if err != nil {
		return nil, f.wrapErr("stat", err)
	}
	fillFileStatFromSys(&fs, f.name)
	return &fs, nil
}

type failPermFS struct{}

func (f failPermFS) Open(name string) (fs.File, error) {
	if !fs.ValidPath(name) {
		return nil, &fs.PathError{Op: "open", Path: name, Err: fs.ErrInvalid}
	}
	return nil, &fs.PathError{Op: "open", Path: name, Err: fs.ErrPermission}
}

func TestTestFSWrappedErrors(t *testing.T) {
	err := TestFS(failPermFS{})
	if err == nil {
		t.Fatal("error expected")
	}

func (p *Process) kill() error {
	return p.signal(Kill)
}

func (p *Process) wait() (ps *ProcessState, err error) {
	var waitmsg syscall.Waitmsg

	switch p.pidStatus() {
	case statusReleased:
		return nil, ErrInvalid
	}

	err = syscall.WaitProcess(p.Pid, &waitmsg)
	if err != nil {
		return nil, NewSyscallError("wait", err)
	}

	p.pidDeactivate(statusDone)
	ps = &ProcessState{
		pid:    waitmsg.Pid,

// be canceled and return immediately with an [ErrClosed] error.
// Close will return an error if it has already been called.
func (f *File) Close() error {
	if f == nil {
		return ErrInvalid
	}
	return f.file.close()
}

// read reads up to len(b) bytes from the File.
// It returns the number of bytes read and an error, if any.
func (f *File) read(b []byte) (n int, err error) {

// and the Err field describing the problem.
//
// Open should reject attempts to open names that do not satisfy
// ValidPath(name), returning a *PathError with Err set to
// ErrInvalid or ErrNotExist.
func (ffs *fakeFsWithFakeFds) Open(name string) (fs.File, error) {
	f, err := ffs.ReadDirFS.Open(name)
	if err != nil {
		return nil, err
	}
	return wrapFile(f), nil
}

	"unsafe"
)

// Stat returns the [FileInfo] structure describing file.
// If there is an error, it will be of type [*PathError].
func (file *File) Stat() (FileInfo, error) {
	if file == nil {
		return nil, ErrInvalid
	}
	return statHandle(file.name, file.pfd.Sysfd)
}

// stat implements both Stat and Lstat of a file.
func stat(funcname, name string, followSurrogates bool) (FileInfo, error) {
	if len(name) == 0 {