Golang Type.Kind方法代碼示例

func labelType(t reflect.Type) bool {
	switch t.Kind() {
	case reflect.Interface, reflect.Struct:
		return true
	}
	return false
}

// lessFunc returns a function that implements the "<" operator
// for the given type, or nil if the type doesn't support "<" .
func lessFunc(t reflect.Type) func(v1, v2 interface{}) bool {
	switch t.Kind() {
	case reflect.String:
		return func(v1, v2 interface{}) bool { return v1.(string) < v2.(string) }
	case reflect.Int:
		return func(v1, v2 interface{}) bool { return v1.(int) < v2.(int) }
	case reflect.Int8:
		return func(v1, v2 interface{}) bool { return v1.(int8) < v2.(int8) }
	case reflect.Int16:
		return func(v1, v2 interface{}) bool { return v1.(int16) < v2.(int16) }
	case reflect.Int32:
		return func(v1, v2 interface{}) bool { return v1.(int32) < v2.(int32) }
	case reflect.Int64:
		return func(v1, v2 interface{}) bool { return v1.(int64) < v2.(int64) }
	case reflect.Uint:
		return func(v1, v2 interface{}) bool { return v1.(uint) < v2.(uint) }
	case reflect.Uint8:
		return func(v1, v2 interface{}) bool { return v1.(uint8) < v2.(uint8) }
	case reflect.Uint16:
		return func(v1, v2 interface{}) bool { return v1.(uint16) < v2.(uint16) }
	case reflect.Uint32:
		return func(v1, v2 interface{}) bool { return v1.(uint32) < v2.(uint32) }
	case reflect.Uint64:
		return func(v1, v2 interface{}) bool { return v1.(uint64) < v2.(uint64) }
	case reflect.Float32:
		return func(v1, v2 interface{}) bool { return v1.(float32) < v2.(float32) }
	case reflect.Float64:
		return func(v1, v2 interface{}) bool { return v1.(float64) < v2.(float64) }
	default:
		return nil
	}
}

// Copy matching Lua table entries to a struct, given the struct type
// and the index on the Lua stack.
func CopyTableToStruct(L *lua.State, t reflect.Type, idx int) interface{} {
	was_ptr := t.Kind() == reflect.Ptr
	if was_ptr {
		t = t.Elem()
	}
	s := reflect.New(t) // T -> *T
	ref := s.Elem()
	L.PushNil()
	if idx < 0 {
		idx--
	}
	for L.Next(idx) != 0 {
		key := L.ToString(-2)
		f := ref.FieldByName(strings.Title(key))
		if f.IsValid() {
			val := luaToGoValue(L, f.Type(), -1)
			f.Set(val)
		}
		L.Pop(1)
	}
	if was_ptr {
		return s.Interface()
	}
	return s.Elem().Interface()
}

func getComparator(dt reflect.Type) (funcPointer interface{}) {
	switch dt.Kind() {
	case reflect.Int:
		funcPointer = func(a, b int) int64 { return int64(a - b) }
	case reflect.Int8:
		funcPointer = func(a, b int8) int64 { return int64(a - b) }
	case reflect.Int16:
		funcPointer = func(a, b int16) int64 { return int64(a - b) }
	case reflect.Int32:
		funcPointer = func(a, b int32) int64 { return int64(a - b) }
	case reflect.Uint:
		funcPointer = func(a, b uint) int64 { return int64(a - b) }
	case reflect.Uint8:
		funcPointer = func(a, b uint8) int64 { return int64(a - b) }
	case reflect.Uint16:
		funcPointer = func(a, b uint16) int64 { return int64(a - b) }
	case reflect.Uint32:
		funcPointer = func(a, b uint32) int64 { return int64(a - b) }
	case reflect.Uint64:
		funcPointer = func(a, b uint64) int64 { return int64(a - b) }
	case reflect.Int64:
		funcPointer = func(a, b int64) int64 { return a - b }
	case reflect.Float32:
		funcPointer = DefaultFloat32Comparator
	case reflect.Float64:
		funcPointer = DefaultFloat64Comparator
	case reflect.String:
		funcPointer = DefaultStringComparator
	default:
		log.Panicf("No default comparator for %s:%s", dt.String(), dt.Kind().String())
	}
	return
}

// canBeNil reports whether an untyped nil can be assigned to the type. See reflect.Zero.
//
// Copied from Go stdlib src/text/template/exec.go.
func canBeNil(typ reflect.Type) bool {
	switch typ.Kind() {
	case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Ptr, reflect.Slice:
		return true
	}
	return false
}

func getSetter(outt reflect.Type, out reflect.Value) Setter {
	setterMutex.RLock()
	style := setterStyle[outt]
	setterMutex.RUnlock()
	if style == setterNone {
		return nil
	}
	if style == setterUnknown {
		setterMutex.Lock()
		defer setterMutex.Unlock()
		if outt.Implements(setterIface) {
			setterStyle[outt] = setterType
		} else if reflect.PtrTo(outt).Implements(setterIface) {
			setterStyle[outt] = setterAddr
		} else {
			setterStyle[outt] = setterNone
			return nil
		}
		style = setterStyle[outt]
	}
	if style == setterAddr {
		if !out.CanAddr() {
			return nil
		}
		out = out.Addr()
	} else if outt.Kind() == reflect.Ptr && out.IsNil() {
		out.Set(reflect.New(outt.Elem()))
	}
	return out.Interface().(Setter)
}

// sizeof returns the size >= 0 of variables for the given type or -1 if the type is not acceptable.
func sizeof(t reflect.Type) int {
	switch t.Kind() {
	case reflect.Array:
		if s := sizeof(t.Elem()); s >= 0 {
			return s * t.Len()
		}

	case reflect.Struct:
		sum := 0
		for i, n := 0, t.NumField(); i < n; i++ {
			s := sizeof(t.Field(i).Type)
			if s < 0 {
				return -1
			}
			sum += s
		}
		return sum

	case reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
		reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
		reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128, reflect.Ptr:
		return int(t.Size())
	}

	return -1
}

func defaultType(t reflect.Type) TypeDesc {
	switch t.Kind() {
	case reflect.Bool:
		return BooleanType
	case reflect.String:
		return UTF8Type
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		return LongType
	case reflect.Float32:
		return FloatType
	case reflect.Float64:
		return DoubleType
	case reflect.Array:
		if t.Name() == "UUID" && t.Size() == 16 {
			return UUIDType
		}
		return UnknownType
	case reflect.Struct:
		if t.Name() == "Time" && t.PkgPath() == "time" {
			return DateType
		}
		return UnknownType
	case reflect.Slice:
		if et := t.Elem(); et.Kind() == reflect.Uint8 {
			return BytesType
		}
		return UnknownType
	}
	return UnknownType
}

// Recursively check composite literals, where a child composite lit's type depends the
// parent's type For example, the expression [][]int{{1,2},{3,4}} contains two
// slice lits, {1,2} and {3,4}, but their types are inferenced from the parent [][]int{}.
func checkCompositeLitR(lit *ast.CompositeLit, t reflect.Type, env Env) (*CompositeLit, []error) {
	alit := &CompositeLit{CompositeLit: lit}

	// We won't generate any errors here if the given type does not match lit.Type.
	// The caller will need to detect the type incompatibility.
	if lit.Type != nil {
		var errs []error
		lit.Type, t, _, errs = checkType(lit.Type, env)
		if errs != nil {
			return alit, errs
		}
	} else if t == nil {
		return alit, []error{ErrMissingCompositeLitType{alit}}
	}

	alit.knownType = knownType{t}
	if alit.CompositeLit.Elts != nil {
		alit.Elts = make([]Expr, len(alit.CompositeLit.Elts))
	}

	switch t.Kind() {
	case reflect.Map:
		return checkCompositeLitMap(alit, t, env)
	case reflect.Array, reflect.Slice:
		return checkCompositeLitArrayOrSlice(alit, t, env)
	case reflect.Struct:
		return checkCompositeLitStruct(alit, t, env)
	default:
		panic("eval: unimplemented composite lit " + t.Kind().String())
	}
}

// Convert a string into the specified type. Return the type's zero value
// if we receive an empty string
func convert(t reflect.Type, value string) (reflect.Value, error) {
	if value == "" {
		return reflect.ValueOf(nil), nil
	}

	var d time.Duration

	switch t {
	case reflect.TypeOf(d):
		result, err := time.ParseDuration(value)
		return reflect.ValueOf(result), err
	default:
	}

	switch t.Kind() {
	case reflect.String:
		return reflect.ValueOf(value), nil
	case reflect.Int:
		return parseInt(value)
	case reflect.Bool:
		return parseBool(value)
	}

	return reflect.ValueOf(nil), conversionError(value, `unsupported `+t.Kind().String())
}

func unflattenValue(v reflect.Value, t reflect.Type) reflect.Value {
	// When t is an Interface, we can't do much, since we don't know the
	// original (unflattened) type of the value placed in v, so we just nop it.
	if t.Kind() == reflect.Interface {
		return v
	}
	// v can be invalid, if it holds the nil value for pointer type
	if !v.IsValid() {
		return v
	}
	// Make sure v is indeed flat
	if v.Kind() == reflect.Ptr {
		panic("unflattening non-flat value")
	}
	// Add a *, one at a time
	for t.Kind() == reflect.Ptr {
		if v.CanAddr() {
			v = v.Addr()
		} else {
			pw := reflect.New(v.Type())
			pw.Elem().Set(v)
			v = pw
		}
		t = t.Elem()
	}
	return v
}

// prepareMethod returns a methodType for the provided method or nil
// in case if the method was unsuitable.
func prepareMethod(method reflect.Method) *methodType {
	mtype := method.Type
	mname := method.Name
	var replyType, argType, contextType reflect.Type

	stream := false
	// Method must be exported.
	if method.PkgPath != "" {
		return nil
	}

	switch mtype.NumIn() {
	case 3:
		// normal method
		argType = mtype.In(1)
		replyType = mtype.In(2)
		contextType = nil
	case 4:
		// method that takes a context
		argType = mtype.In(2)
		replyType = mtype.In(3)
		contextType = mtype.In(1)
	default:
		log.Println("method", mname, "of", mtype, "has wrong number of ins:", mtype.NumIn())
		return nil
	}

	// First arg need not be a pointer.
	if !isExportedOrBuiltinType(argType) {
		log.Println(mname, "argument type not exported:", argType)
		return nil
	}

	// the second argument will tell us if it's a streaming call
	// or a regular call
	if replyType == typeOfStream {
		// this is a streaming call
		stream = true
	} else if replyType.Kind() != reflect.Ptr {
		log.Println("method", mname, "reply type not a pointer:", replyType)
		return nil
	}

	// Reply type must be exported.
	if !isExportedOrBuiltinType(replyType) {
		log.Println("method", mname, "reply type not exported:", replyType)
		return nil
	}
	// Method needs one out.
	if mtype.NumOut() != 1 {
		log.Println("method", mname, "has wrong number of outs:", mtype.NumOut())
		return nil
	}
	// The return type of the method must be error.
	if returnType := mtype.Out(0); returnType != typeOfError {
		log.Println("method", mname, "returns", returnType.String(), "not error")
		return nil
	}
	return &methodType{method: method, ArgType: argType, ReplyType: replyType, ContextType: contextType, stream: stream}
}

// AddExt registers an encode and decode function for a reflect.Type.
// Note that the type must be a named type, and specifically not
// a pointer or Interface. An error is returned if that is not honored.
//
// To Deregister an ext, call AddExt with 0 tag, nil encfn and nil decfn.
func (o *extHandle) AddExt(
	rt reflect.Type,
	tag byte,
	encfn func(reflect.Value) ([]byte, error),
	decfn func(reflect.Value, []byte) error,
) (err error) {
	// o is a pointer, because we may need to initialize it
	if rt.PkgPath() == "" || rt.Kind() == reflect.Interface {
		err = fmt.Errorf("codec.Handle.AddExt: Takes named type, especially not a pointer or interface: %T",
			reflect.Zero(rt).Interface())
		return
	}

	// o cannot be nil, since it is always embedded in a Handle.
	// if nil, let it panic.
	// if o == nil {
	// 	err = errors.New("codec.Handle.AddExt: extHandle cannot be a nil pointer.")
	// 	return
	// }

	rtid := reflect.ValueOf(rt).Pointer()
	for _, v := range *o {
		if v.rtid == rtid {
			v.tag, v.encFn, v.decFn = tag, encfn, decfn
			return
		}
	}

	*o = append(*o, &extTypeTagFn{rtid, rt, tag, encfn, decfn})
	return
}

func sizeof(t reflect.Type) (int, error) {
	switch t.Kind() {
	case reflect.Array:
		n, err := sizeof(t.Elem())
		if err != nil {
			return 0, err
		}
		return t.Len() * n, nil

	case reflect.Struct:
		sum := 0
		for i, n := 0, t.NumField(); i < n; i++ {
			s, err := sizeof(t.Field(i).Type)
			if err != nil {
				return 0, err
			}
			sum += s
		}
		return sum, nil

	case reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
		reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
		reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128:
		return int(t.Size()), nil
	}
	return 0, errors.New("invalid type " + t.String())
}

// alignment returns the alignment of values of type t.
func alignment(t reflect.Type) int {
	switch t {
	case variantType:
		return 1
	case objectPathType:
		return 4
	case signatureType:
		return 1
	case interfacesType:
		return 4
	}
	switch t.Kind() {
	case reflect.Uint8:
		return 1
	case reflect.Uint16, reflect.Int16:
		return 2
	case reflect.Uint32, reflect.Int32, reflect.String, reflect.Array, reflect.Slice, reflect.Map:
		return 4
	case reflect.Uint64, reflect.Int64, reflect.Float64, reflect.Struct:
		return 8
	case reflect.Ptr:
		return alignment(t.Elem())
	}
	return 1
}