// Fill in the response that should be sent to the kernel, or set noResponse if
// the op requires no response.
func (c *Connection) kernelResponse(
	m *buffer.OutMessage,
	fuseID uint64,
	op interface{},
	opErr error) (noResponse bool) {
	h := m.OutHeader()
	h.Unique = fuseID

	// Special case: handle the ops for which the kernel expects no response.
	// interruptOp .
	switch op.(type) {
	case *fuseops.ForgetInodeOp:
		noResponse = true
		return

	case *interruptOp:
		noResponse = true
		return
	}

	// If the user returned the error, fill in the error field of the outgoing
	// message header.
	if opErr != nil {
		m.OutHeader().Error = -int32(syscall.EIO)
		if errno, ok := opErr.(syscall.Errno); ok {
			m.OutHeader().Error = -int32(errno)
		}

		// Special case: for some types, convertInMessage grew the message in order
		// to obtain a destination buffer. Make sure that we shrink back to just
		// the header, because on OS X the kernel otherwise returns EINVAL when we
		// attempt to write an error response with a length that extends beyond the
		// header.
		m.ShrinkTo(buffer.OutMessageInitialSize)
	}

	// Otherwise, fill in the rest of the response.
	if opErr == nil {
		c.kernelResponseForOp(m, op)
	}

	h.Len = uint32(m.Len())
	return
}

// Like kernelResponse, but assumes the user replied with a nil error to the
// op.
func (c *Connection) kernelResponseForOp(
	m *buffer.OutMessage,
	op interface{}) {
	// Create the appropriate output message
	switch o := op.(type) {
	case *fuseops.LookUpInodeOp:
		size := fusekernel.EntryOutSize(c.protocol)
		out := (*fusekernel.EntryOut)(m.Grow(size))
		convertChildInodeEntry(&o.Entry, out)

	case *fuseops.GetInodeAttributesOp:
		size := fusekernel.AttrOutSize(c.protocol)
		out := (*fusekernel.AttrOut)(m.Grow(size))
		out.AttrValid, out.AttrValidNsec = convertExpirationTime(
			o.AttributesExpiration)
		convertAttributes(o.Inode, &o.Attributes, &out.Attr)

	case *fuseops.SetInodeAttributesOp:
		size := fusekernel.AttrOutSize(c.protocol)
		out := (*fusekernel.AttrOut)(m.Grow(size))
		out.AttrValid, out.AttrValidNsec = convertExpirationTime(
			o.AttributesExpiration)
		convertAttributes(o.Inode, &o.Attributes, &out.Attr)

	case *fuseops.MkDirOp:
		size := fusekernel.EntryOutSize(c.protocol)
		out := (*fusekernel.EntryOut)(m.Grow(size))
		convertChildInodeEntry(&o.Entry, out)

	case *fuseops.CreateFileOp:
		eSize := fusekernel.EntryOutSize(c.protocol)

		e := (*fusekernel.EntryOut)(m.Grow(eSize))
		convertChildInodeEntry(&o.Entry, e)

		oo := (*fusekernel.OpenOut)(m.Grow(unsafe.Sizeof(fusekernel.OpenOut{})))
		oo.Fh = uint64(o.Handle)

	case *fuseops.CreateSymlinkOp:
		size := fusekernel.EntryOutSize(c.protocol)
		out := (*fusekernel.EntryOut)(m.Grow(size))
		convertChildInodeEntry(&o.Entry, out)

	case *fuseops.RenameOp:
		// Empty response

	case *fuseops.RmDirOp:
		// Empty response

	case *fuseops.UnlinkOp:
		// Empty response

	case *fuseops.OpenDirOp:
		out := (*fusekernel.OpenOut)(m.Grow(unsafe.Sizeof(fusekernel.OpenOut{})))
		out.Fh = uint64(o.Handle)

	case *fuseops.ReadDirOp:
		// convertInMessage already set up the destination buffer to be at the end
		// of the out message. We need only shrink to the right size based on how
		// much the user read.
		m.ShrinkTo(buffer.OutMessageInitialSize + uintptr(o.BytesRead))

	case *fuseops.ReleaseDirHandleOp:
		// Empty response

	case *fuseops.OpenFileOp:
		out := (*fusekernel.OpenOut)(m.Grow(unsafe.Sizeof(fusekernel.OpenOut{})))
		out.Fh = uint64(o.Handle)

		if o.KeepPageCache {
			out.OpenFlags |= uint32(fusekernel.OpenKeepCache)
		}

	case *fuseops.ReadFileOp:
		// convertInMessage already set up the destination buffer to be at the end
		// of the out message. We need only shrink to the right size based on how
		// much the user read.
		m.ShrinkTo(buffer.OutMessageInitialSize + uintptr(o.BytesRead))

	case *fuseops.WriteFileOp:
		out := (*fusekernel.WriteOut)(m.Grow(unsafe.Sizeof(fusekernel.WriteOut{})))
		out.Size = uint32(len(o.Data))

	case *fuseops.SyncFileOp:
		// Empty response

	case *fuseops.FlushFileOp:
		// Empty response

	case *fuseops.ReleaseFileHandleOp:
		// Empty response

	case *fuseops.ReadSymlinkOp:
		m.AppendString(o.Target)

	case *statFSOp:
		m.Grow(unsafe.Sizeof(fusekernel.StatfsOut{}))

//.........这里部分代码省略.........

// Convert a kernel message to an appropriate op. If the op is unknown, a
// special unexported type will be used.
//
// The caller is responsible for arranging for the message to be destroyed.
func convertInMessage(
	inMsg *buffer.InMessage,
	outMsg *buffer.OutMessage,
	protocol fusekernel.Protocol) (o interface{}, err error) {
	switch inMsg.Header().Opcode {
	case fusekernel.OpLookup:
		buf := inMsg.ConsumeBytes(inMsg.Len())
		n := len(buf)
		if n == 0 || buf[n-1] != '\x00' {
			err = errors.New("Corrupt OpLookup")
			return
		}

		o = &fuseops.LookUpInodeOp{
			Parent: fuseops.InodeID(inMsg.Header().Nodeid),
			Name:   string(buf[:n-1]),
		}

	case fusekernel.OpGetattr:
		o = &fuseops.GetInodeAttributesOp{
			Inode: fuseops.InodeID(inMsg.Header().Nodeid),
		}

	case fusekernel.OpSetattr:
		type input fusekernel.SetattrIn
		in := (*input)(inMsg.Consume(unsafe.Sizeof(input{})))
		if in == nil {
			err = errors.New("Corrupt OpSetattr")
			return
		}

		to := &fuseops.SetInodeAttributesOp{
			Inode: fuseops.InodeID(inMsg.Header().Nodeid),
		}
		o = to

		valid := fusekernel.SetattrValid(in.Valid)
		if valid&fusekernel.SetattrSize != 0 {
			to.Size = &in.Size
		}

		if valid&fusekernel.SetattrMode != 0 {
			mode := convertFileMode(in.Mode)
			to.Mode = &mode
		}

		if valid&fusekernel.SetattrAtime != 0 {
			t := time.Unix(int64(in.Atime), int64(in.AtimeNsec))
			to.Atime = &t
		}

		if valid&fusekernel.SetattrMtime != 0 {
			t := time.Unix(int64(in.Mtime), int64(in.MtimeNsec))
			to.Mtime = &t
		}

	case fusekernel.OpForget:
		type input fusekernel.ForgetIn
		in := (*input)(inMsg.Consume(unsafe.Sizeof(input{})))
		if in == nil {
			err = errors.New("Corrupt OpForget")
			return
		}

		o = &fuseops.ForgetInodeOp{
			Inode: fuseops.InodeID(inMsg.Header().Nodeid),
			N:     in.Nlookup,
		}

	case fusekernel.OpMkdir:
		in := (*fusekernel.MkdirIn)(inMsg.Consume(fusekernel.MkdirInSize(protocol)))
		if in == nil {
			err = errors.New("Corrupt OpMkdir")
			return
		}

		name := inMsg.ConsumeBytes(inMsg.Len())
		i := bytes.IndexByte(name, '\x00')
		if i < 0 {
			err = errors.New("Corrupt OpMkdir")
			return
		}
		name = name[:i]

		o = &fuseops.MkDirOp{
			Parent: fuseops.InodeID(inMsg.Header().Nodeid),
			Name:   string(name),

			// On Linux, vfs_mkdir calls through to the inode with at most
			// permissions and sticky bits set (cf. https://goo.gl/WxgQXk), and fuse
			// passes that on directly (cf. https://goo.gl/f31aMo). In other words,
			// the fact that this is a directory is implicit in the fact that the
			// opcode is mkdir. But we want the correct mode to go through, so ensure
			// that os.ModeDir is set.
			Mode: convertFileMode(in.Mode) | os.ModeDir,
		}
//.........这里部分代码省略.........

// Like kernelResponse, but assumes the user replied with a nil error to the
// op.
func (c *Connection) kernelResponseForOp(
	m *buffer.OutMessage,
	op interface{}) {
	// Create the appropriate output message
	switch o := op.(type) {
	case *fuseops.LookUpInodeOp:
		size := fusekernel.EntryOutSize(c.protocol)
		out := (*fusekernel.EntryOut)(m.Grow(size))
		convertChildInodeEntry(&o.Entry, out)

	case *fuseops.GetInodeAttributesOp:
		size := fusekernel.AttrOutSize(c.protocol)
		out := (*fusekernel.AttrOut)(m.Grow(size))
		out.AttrValid, out.AttrValidNsec = convertExpirationTime(
			o.AttributesExpiration)
		convertAttributes(o.Inode, &o.Attributes, &out.Attr)

	case *fuseops.SetInodeAttributesOp:
		size := fusekernel.AttrOutSize(c.protocol)
		out := (*fusekernel.AttrOut)(m.Grow(size))
		out.AttrValid, out.AttrValidNsec = convertExpirationTime(
			o.AttributesExpiration)
		convertAttributes(o.Inode, &o.Attributes, &out.Attr)

	case *fuseops.MkDirOp:
		size := fusekernel.EntryOutSize(c.protocol)
		out := (*fusekernel.EntryOut)(m.Grow(size))
		convertChildInodeEntry(&o.Entry, out)

	case *fuseops.CreateFileOp:
		eSize := fusekernel.EntryOutSize(c.protocol)

		e := (*fusekernel.EntryOut)(m.Grow(eSize))
		convertChildInodeEntry(&o.Entry, e)

		oo := (*fusekernel.OpenOut)(m.Grow(unsafe.Sizeof(fusekernel.OpenOut{})))
		oo.Fh = uint64(o.Handle)

	case *fuseops.CreateSymlinkOp:
		size := fusekernel.EntryOutSize(c.protocol)
		out := (*fusekernel.EntryOut)(m.Grow(size))
		convertChildInodeEntry(&o.Entry, out)

	case *fuseops.RenameOp:
		// Empty response

	case *fuseops.RmDirOp:
		// Empty response

	case *fuseops.UnlinkOp:
		// Empty response

	case *fuseops.OpenDirOp:
		out := (*fusekernel.OpenOut)(m.Grow(unsafe.Sizeof(fusekernel.OpenOut{})))
		out.Fh = uint64(o.Handle)

	case *fuseops.ReadDirOp:
		// convertInMessage already set up the destination buffer to be at the end
		// of the out message. We need only shrink to the right size based on how
		// much the user read.
		m.ShrinkTo(buffer.OutMessageInitialSize + uintptr(o.BytesRead))

	case *fuseops.ReleaseDirHandleOp:
		// Empty response

	case *fuseops.OpenFileOp:
		out := (*fusekernel.OpenOut)(m.Grow(unsafe.Sizeof(fusekernel.OpenOut{})))
		out.Fh = uint64(o.Handle)

		if o.KeepPageCache {
			out.OpenFlags |= uint32(fusekernel.OpenKeepCache)
		}

	case *fuseops.ReadFileOp:
		// convertInMessage already set up the destination buffer to be at the end
		// of the out message. We need only shrink to the right size based on how
		// much the user read.
		m.ShrinkTo(buffer.OutMessageInitialSize + uintptr(o.BytesRead))

	case *fuseops.WriteFileOp:
		out := (*fusekernel.WriteOut)(m.Grow(unsafe.Sizeof(fusekernel.WriteOut{})))
		out.Size = uint32(len(o.Data))

	case *fuseops.SyncFileOp:
		// Empty response

	case *fuseops.FlushFileOp:
		// Empty response

	case *fuseops.ReleaseFileHandleOp:
		// Empty response

	case *fuseops.ReadSymlinkOp:
		m.AppendString(o.Target)

	case *fuseops.StatFSOp:
		out := (*fusekernel.StatfsOut)(m.Grow(unsafe.Sizeof(fusekernel.StatfsOut{})))
		out.St.Blocks = o.Blocks
//.........这里部分代码省略.........