ErrNotExist   = fs.ErrNotExist   // "file does not exist"
	ErrClosed     = fs.ErrClosed     // "file already closed"

	ErrNoDeadline       = errNoDeadline()       // "file type does not support deadline"
	ErrDeadlineExceeded = errDeadlineExceeded() // "i/o timeout"
)

func errNoDeadline() error { return poll.ErrNoDeadline }

// errDeadlineExceeded returns the value for os.ErrDeadlineExceeded.

// ErrFileClosing is returned when a file descriptor is used after it
// has been closed.
var ErrFileClosing = errors.New("use of closed file")

// ErrNoDeadline is returned when a request is made to set a deadline
// on a file type that does not use the poller.
var ErrNoDeadline = errors.New("file type does not support deadline")

// Return the appropriate closing error based on isFile.
func errClosing(isFile bool) error {
	if isFile {

	if err := f.SetDeadline(deadline); err != os.ErrNoDeadline {
		t.Errorf("SetDeadline on file returned %v, wanted %v", err, os.ErrNoDeadline)
	}
	if err := f.SetReadDeadline(deadline); err != os.ErrNoDeadline {
		t.Errorf("SetReadDeadline on file returned %v, wanted %v", err, os.ErrNoDeadline)
	}
	if err := f.SetWriteDeadline(deadline); err != os.ErrNoDeadline {

	if err := f.checkValid("SetDeadline"); err != nil {
		return err
	}
	return poll.ErrNoDeadline
}

// setReadDeadline sets the read deadline.
func (f *File) setReadDeadline(time.Time) error {
	if err := f.checkValid("SetReadDeadline"); err != nil {
		return err
	}
	return poll.ErrNoDeadline
}

// setWriteDeadline sets the write deadline.
func (f *File) setWriteDeadline(time.Time) error {

		if d == 0 {
			d = -1 // don't confuse deadline right now with no deadline
		}
	}
	if err := fd.incref(); err != nil {
		return err
	}
	defer fd.decref()
	if fd.pd.runtimeCtx == 0 {
		return ErrNoDeadline
	}
	runtime_pollSetDeadline(fd.pd.runtimeCtx, d, mode)
	return nil
}

// IsPollDescriptor reports whether fd is the descriptor being used by the poller.
// This is only used for testing.
//

pkg os, method (*File) SetReadDeadline(time.Time) error
pkg os, method (*File) SetWriteDeadline(time.Time) error
pkg os, method (*PathError) Timeout() bool
pkg os, method (*SyscallError) Timeout() bool
pkg os, var ErrNoDeadline error
pkg strings, method (*Builder) Grow(int)
pkg strings, method (*Builder) Len() int
pkg strings, method (*Builder) Reset()
pkg strings, method (*Builder) String() string

// It is equivalent to calling both SetReadDeadline and SetWriteDeadline.
//
// Only some kinds of files support setting a deadline. Calls to SetDeadline
// for files that do not support deadlines will return ErrNoDeadline.
// On most systems ordinary files do not support deadlines, but pipes do.
//
// A deadline is an absolute time after which I/O operations fail with an

		{"DirEntry", Type, 16},
		{"DirFS", Func, 16},
		{"Environ", Func, 0},
		{"ErrClosed", Var, 8},
		{"ErrDeadlineExceeded", Var, 15},
		{"ErrExist", Var, 0},
		{"ErrInvalid", Var, 0},
		{"ErrNoDeadline", Var, 10},
		{"ErrNotExist", Var, 0},
		{"ErrPermission", Var, 0},
		{"ErrProcessDone", Var, 16},
		{"Executable", Func, 8},
		{"Exit", Func, 0},
		{"Expand", Func, 0},
		{"ExpandEnv", Func, 0},