runtime.SetFinalizer(file, nil)
	return err
}

// seek sets the offset for the next Read or Write on file to offset, interpreted
// according to whence: 0 means relative to the origin of the file, 1 means
// relative to the current offset, and 2 means relative to the end.
// It returns the new offset and an error, if any.
func (f *File) seek(offset int64, whence int) (ret int64, err error) {

	if err != nil {
		t.Fatal(err)
	}
	_, err = r.Seek(0, 0)
	if err == nil {
		t.Fatal("Seek on pipe should fail")
	}
	if perr, ok := err.(*PathError); !ok || perr.Err != syscall.ESPIPE {
		t.Errorf("Seek returned error %v, want &PathError{Err: syscall.ESPIPE}", err)
	}
	_, err = w.Seek(0, 0)
	if err == nil {
		t.Fatal("Seek on pipe should fail")
	}

	cmdOffset := unsafe.Sizeof(exem.FileHeader)
	if is64bit := exem.Magic == macho.Magic64; is64bit {
		// mach_header_64 has one extra uint32.
		cmdOffset += unsafe.Sizeof(exem.Magic)
	}
	if _, err := outf.Seek(int64(cmdOffset), 0); err != nil {
		return err
	}

	// Read the load commands, looking for the LC_UUID cmd. If/when we
	// locate it, overwrite it with a new value produced by
	// uuidFromGoBuildId.

		file, err := os.OpenFile(filename, os.O_RDWR, 0)
		if err != nil {
			return nil, err
		}
		defer file.Close()

		_, err = file.Seek(0, io.SeekStart)
		if err != nil {
			return nil, err
		}
		_, err = file.WriteString(query)
		if err != nil {
			return nil, err
		}
		_, err = file.Seek(0, io.SeekStart)
		if err != nil {
			return nil, err
		}
		buf := make([]byte, bufSize)
		for {
			n, _ := file.Read(buf)

* `write(daten)`: Schreibt `daten` (`str` oder `bytes`) in die Datei.
* `read(anzahl)`: Liest `anzahl` (`int`) bytes/Zeichen aus der Datei.
* `seek(versatz)`: Geht zur Position `versatz` (`int`) in der Datei.
    * Z. B. würde `await myfile.seek(0)` zum Anfang der Datei gehen.
    * Das ist besonders dann nützlich, wenn Sie `await myfile.read()` einmal ausführen und dann diese Inhalte erneut auslesen müssen.

`UploadFile` 支持以下 `async` 方法，（使用内部 `SpooledTemporaryFile`）可调用相应的文件方法。

* `write(data)`：把 `data` （`str` 或 `bytes`）写入文件；
* `read(size)`：按指定数量的字节或字符（`size` (`int`)）读取文件内容；
* `seek(offset)`：移动至文件 `offset` （`int`）字节处的位置；
    * 例如，`await myfile.seek(0) ` 移动到文件开头；
    * 执行 `await myfile.read()` 后，需再次读取已读取内容时，这种方法特别好用；
* `close()`：关闭文件。

因为上述方法都是 `async` 方法，要搭配「await」使用。

例如，在 `async` *路径操作函数* 内，要用以下方式读取文件内容：

```Python

		fd, err := syscall.Dup(int(f.Fd()), -1)
		if err != nil {
			return nil, os.NewSyscallError("dup", err)
		}
		defer close(fd)

		dir := netdir + "/" + comp[n-2]
		ctl = os.NewFile(uintptr(fd), dir+"/"+file)
		ctl.Seek(0, io.SeekStart)
		var buf [16]byte
		n, err := ctl.Read(buf[:])
		if err != nil {
			return nil, err
		}
		name = string(buf[:n])
	default:
		if len(comp) < 4 {

		if fd < 0 {
			return
		}
		defer closefd(fd)
		n := len(buf)
		r := 0
		for {
			r = int(pread(fd, unsafe.Pointer(&buf[0]), int32(n), 0))
			if r < n {
				break
			}
			n = int(seek(fd, 0, 2)) + 1
			if len(buf) < n {
				buf = make([]byte, n)
			}
		}
		if r <= 0 {
			r = 0
		} else if buf[r-1] == 0 {
			r--
		}
		name[len(name)-1] = '='
		env := make([]byte, len(name)+r)

            try {
                if (decoder == null) {
                    RandomAccessFile randomAccess = new RandomAccessFile(inputFile, "r");
                    randomAccess.seek(offset);
                    decoder = new StringDeduplicatingKryoBackedDecoder(new RandomAccessFileInputStream(randomAccess));
                    resources = new CompositeStoppable().add(randomAccess, decoder);
                }

	} else {
		rlim.Cur = uint64(rl.Cur)
	}

	if rl.Max == rlimInf32 {
		rlim.Max = rlimInf64
	} else {
		rlim.Max = uint64(rl.Max)
	}
	return
}

func Seek(fd int, offset int64, whence int) (newoffset int64, err error) {
	newoffset, errno := seek(fd, offset, whence)
	if errno != 0 {
		return 0, errno
	}
	return newoffset, nil
}

//sys	futimesat(dirfd int, path string, times *[2]Timeval) (err error)