// Package oserror defines errors values used in the os package.
//
// These types are defined here to permit the syscall package to reference them.
package oserror

import "errors"

var (
	ErrInvalid    = errors.New("invalid argument")
	ErrPermission = errors.New("permission denied")
	ErrExist      = errors.New("file already exists")
	ErrNotExist   = errors.New("file does not exist")

// chroot-style security mechanism, and Sub does not change that fact.
func Sub(fsys FS, dir string) (FS, error) {
	if !ValidPath(dir) {
		return nil, &PathError{Op: "sub", Path: dir, Err: ErrInvalid}
	}
	if dir == "." {
		return fsys, nil
	}
	if fsys, ok := fsys.(SubFS); ok {
		return fsys.Sub(dir)
	}
	return &subFS{fsys, dir}, nil
}

type subFS struct {
	fsys FS
	dir  string
}

	if !isClosed {
		t.Fatal("File ref count should be zero")
	}

	// Closing a file again should result in invalid argument.
	if err = rlk.Close(); err != os.ErrInvalid {
		t.Fatal(err)
	}

	_, err = newRLockedFile(nil)
	if err != os.ErrInvalid {
		t.Fatal("Unexpected error", err)
	}
}

// Tests lock and unlock semantics.
func TestLockAndUnlock(t *testing.T) {
	f, err := os.CreateTemp("", "lock")

// is already closed. This method is on File so that we can incorporate
// a nil test.
func (f *File) incref(op string) (err error) {
	if f == nil {
		return ErrInvalid
	}
	if !f.fdmu.Incref() {
		err = ErrClosed
		if op != "" {
			err = &PathError{Op: op, Path: f.name, Err: err}
		}
	}
	return err
}

// decref removes a reference to the file. If this is the last

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
}

func (z *Int) SetString(s string, base int) error {
	z.doinit()
	if base < 2 || base > 36 {
		return os.ErrInvalid
	}
	p := C.CString(s)
	defer C.free(unsafe.Pointer(p))
	if C.mpz_set_str(&z.i[0], p, C.int(base)) < 0 {
		return os.ErrInvalid
	}
	return nil
}

// String returns the decimal representation of z.
func (z *Int) String() string {
	if z == 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 {