Golang conversion.EnforcePtr函数代码示例

// SetList sets the given list object's Items member have the elements given in
// objects.
// Returns an error if list is not a List type (does not have an Items member),
// or if any of the objects are not of the right type.
// TODO: move me to pkg/api/meta
func SetList(list Object, objects []Object) error {
	itemsPtr, err := GetItemsPtr(list)
	if err != nil {
		return err
	}
	items, err := conversion.EnforcePtr(itemsPtr)
	if err != nil {
		return err
	}
	if items.Type() == objectSliceType {
		items.Set(reflect.ValueOf(objects))
		return nil
	}
	slice := reflect.MakeSlice(items.Type(), len(objects), len(objects))
	for i := range objects {
		dest := slice.Index(i)
		src, err := conversion.EnforcePtr(objects[i])
		if err != nil {
			return err
		}
		if src.Type().AssignableTo(dest.Type()) {
			dest.Set(src)
		} else if src.Type().ConvertibleTo(dest.Type()) {
			dest.Set(src.Convert(dest.Type()))
		} else {
			return fmt.Errorf("item[%d]: Type mismatch: Expected %v, got %v", i, dest.Type(), src.Type())
		}
	}
	items.Set(slice)
	return nil
}

// ListFromMemory implements list operation (the same signature as List method)
// but it serves the contents from memory.
// Current we cannot use ListFromMemory() instead of List(), because it only
// guarantees eventual consistency (e.g. it's possible for Get called right after
// Create to return not-exist, before the change is propagate).
// TODO: We may consider changing to use ListFromMemory in the future, but this
// requires wider discussion as an "api semantic change".
func (c *Cacher) ListFromMemory(key string, listObj runtime.Object) error {
	// Do NOT allow Watch to start when the underlying structures are not propagated.
	c.usable.RLock()
	defer c.usable.RUnlock()

	listPtr, err := runtime.GetItemsPtr(listObj)
	if err != nil {
		return err
	}
	listVal, err := conversion.EnforcePtr(listPtr)
	if err != nil || listVal.Kind() != reflect.Slice {
		return fmt.Errorf("need a pointer to slice, got %v", listVal.Kind())
	}
	filter := filterFunction(key, c.keyFunc, Everything)

	objs, resourceVersion := c.watchCache.ListWithVersion()
	for _, obj := range objs {
		object, ok := obj.(runtime.Object)
		if !ok {
			return fmt.Errorf("non runtime.Object returned from storage: %v", obj)
		}
		if filter(object) {
			listVal.Set(reflect.Append(listVal, reflect.ValueOf(object).Elem()))
		}
	}
	if c.versioner != nil {
		if err := c.versioner.UpdateList(listObj, resourceVersion); err != nil {
			return err
		}
	}
	return nil
}

func (h *etcdHelper) extractObj(response *etcd.Response, inErr error, objPtr runtime.Object, ignoreNotFound, prevNode bool) (body string, node *etcd.Node, err error) {
	if response != nil {
		if prevNode {
			node = response.PrevNode
		} else {
			node = response.Node
		}
	}
	if inErr != nil || node == nil || len(node.Value) == 0 {
		if ignoreNotFound {
			v, err := conversion.EnforcePtr(objPtr)
			if err != nil {
				return "", nil, err
			}
			v.Set(reflect.Zero(v.Type()))
			return "", nil, nil
		} else if inErr != nil {
			return "", nil, inErr
		}
		return "", nil, fmt.Errorf("unable to locate a value on the response: %#v", response)
	}
	body = node.Value
	err = h.codec.DecodeInto([]byte(body), objPtr)
	if h.versioner != nil {
		_ = h.versioner.UpdateObject(objPtr, node.Expiration, node.ModifiedIndex)
		// being unable to set the version does not prevent the object from being extracted
	}
	return body, node, err
}

// Implements storage.Interface.
func (h *etcdHelper) Create(key string, obj, out runtime.Object, ttl uint64) error {
	key = h.prefixEtcdKey(key)
	data, err := h.codec.Encode(obj)
	if err != nil {
		return err
	}
	if h.versioner != nil {
		if version, err := h.versioner.ObjectResourceVersion(obj); err == nil && version != 0 {
			return errors.New("resourceVersion may not be set on objects to be created")
		}
	}

	startTime := time.Now()
	response, err := h.client.Create(key, string(data), ttl)
	metrics.RecordEtcdRequestLatency("create", getTypeName(obj), startTime)
	if err != nil {
		return err
	}
	if out != nil {
		if _, err := conversion.EnforcePtr(out); err != nil {
			panic("unable to convert output object to pointer")
		}
		_, _, err = h.extractObj(response, err, out, false, false)
	}
	return err
}

// ExtractList returns obj's Items element as an array of runtime.Objects.
// Returns an error if obj is not a List type (does not have an Items member).
// TODO: move me to pkg/api/meta
func ExtractList(obj Object) ([]Object, error) {
	itemsPtr, err := GetItemsPtr(obj)
	if err != nil {
		return nil, err
	}
	items, err := conversion.EnforcePtr(itemsPtr)
	if err != nil {
		return nil, err
	}
	list := make([]Object, items.Len())
	for i := range list {
		raw := items.Index(i)
		switch item := raw.Interface().(type) {
		case Object:
			list[i] = item
		case RawExtension:
			list[i] = &Unknown{
				RawJSON: item.RawJSON,
			}
		default:
			var found bool
			if list[i], found = raw.Addr().Interface().(Object); !found {
				return nil, fmt.Errorf("%v: item[%v]: Expected object, got %#v(%s)", obj, i, raw.Interface(), raw.Kind())
			}
		}
	}
	return list, nil
}

// ExtractList returns obj's Items element as an array of runtime.Objects.
// Returns an error if obj is not a List type (does not have an Items member).
// TODO: move me to pkg/api/meta
func ExtractList(obj Object) ([]Object, error) {
	itemsPtr, err := GetItemsPtr(obj)
	if err != nil {
		return nil, err
	}
	items, err := conversion.EnforcePtr(itemsPtr)
	if err != nil {
		return nil, err
	}
	list := make([]Object, items.Len())
	for i := range list {
		raw := items.Index(i)
		var found bool
		switch raw.Kind() {
		case reflect.Interface, reflect.Ptr:
			list[i], found = raw.Interface().(Object)
		default:
			list[i], found = raw.Addr().Interface().(Object)
		}
		if !found {
			return nil, fmt.Errorf("item[%v]: Expected object, got %#v(%s)", i, raw.Interface(), raw.Kind())
		}
	}
	return list, nil
}

// ListMetaFor returns a pointer to a provided object's ListMeta,
// or an error if the object does not have that pointer.
// TODO: allow runtime.Unknown to extract this object
func ListMetaFor(obj runtime.Object) (*ListMeta, error) {
	v, err := conversion.EnforcePtr(obj)
	if err != nil {
		return nil, err
	}
	var meta *ListMeta
	err = runtime.FieldPtr(v, "ListMeta", &meta)
	return meta, err
}

// Implements storage.Interface.
func (h *etcdHelper) Delete(key string, out runtime.Object) error {
	key = h.prefixEtcdKey(key)
	if _, err := conversion.EnforcePtr(out); err != nil {
		panic("unable to convert output object to pointer")
	}

	startTime := time.Now()
	response, err := h.client.Delete(key, false)
	metrics.RecordEtcdRequestLatency("delete", getTypeName(out), startTime)
	if !IsEtcdNotFound(err) {
		// if the object that existed prior to the delete is returned by etcd, update out.
		if err != nil || response.PrevNode != nil {
			_, _, err = h.extractObj(response, err, out, false, true)
		}
	}
	return err
}

func listToItems(listObj runtime.Object) ([]runtime.Object, error) {
	v, err := conversion.EnforcePtr(listObj)
	if err != nil {
		return nil, fmt.Errorf("unexpected error: %v", err)
	}
	items := v.FieldByName("Items")
	if !items.IsValid() {
		return nil, fmt.Errorf("unexpected Items field in %v", listObj)
	}
	if items.Type().Kind() != reflect.Slice {
		return nil, fmt.Errorf("unexpected Items field type: %v", items.Type().Kind())
	}
	result := make([]runtime.Object, items.Len())
	for i := 0; i < items.Len(); i++ {
		result[i] = items.Index(i).Addr().Interface().(runtime.Object)
	}
	return result, nil
}

// Accessor takes an arbitrary object pointer and returns meta.Interface.
// obj must be a pointer to an API type. An error is returned if the minimum
// required fields are missing. Fields that are not required return the default
// value and are a no-op if set.
// TODO: add a fast path for *TypeMeta and *ObjectMeta for internal objects
func Accessor(obj interface{}) (Interface, error) {
	v, err := conversion.EnforcePtr(obj)
	if err != nil {
		return nil, err
	}
	t := v.Type()
	if v.Kind() != reflect.Struct {
		return nil, fmt.Errorf("expected struct, but got %v: %v (%#v)", v.Kind(), t, v.Interface())
	}

	typeMeta := v.FieldByName("TypeMeta")
	if !typeMeta.IsValid() {
		return nil, fmt.Errorf("struct %v lacks embedded TypeMeta type", t)
	}

	a := &genericAccessor{}
	if err := extractFromTypeMeta(typeMeta, a); err != nil {
		return nil, fmt.Errorf("unable to find type fields on %#v: %v", typeMeta, err)
	}

	objectMeta := v.FieldByName("ObjectMeta")
	if objectMeta.IsValid() {
		// look for the ObjectMeta fields
		if err := extractFromObjectMeta(objectMeta, a); err != nil {
			return nil, fmt.Errorf("unable to find object fields on %#v: %v", objectMeta, err)
		}
	} else {
		listMeta := v.FieldByName("ListMeta")
		if listMeta.IsValid() {
			// look for the ListMeta fields
			if err := extractFromListMeta(listMeta, a); err != nil {
				return nil, fmt.Errorf("unable to find list fields on %#v: %v", listMeta, err)
			}
		} else {
			// look for the older TypeMeta with all metadata
			if err := extractFromObjectMeta(typeMeta, a); err != nil {
				return nil, fmt.Errorf("unable to find object fields on %#v: %v", typeMeta, err)
			}
		}
	}

	return a, nil
}

// Implements storage.Interface.
func (h *etcdHelper) Set(ctx context.Context, key string, obj, out runtime.Object, ttl uint64) error {
	if ctx == nil {
		glog.Errorf("Context is nil")
	}
	var response *etcd.Response
	data, err := h.codec.Encode(obj)
	if err != nil {
		return err
	}
	key = h.prefixEtcdKey(key)

	create := true
	if h.versioner != nil {
		if version, err := h.versioner.ObjectResourceVersion(obj); err == nil && version != 0 {
			create = false
			startTime := time.Now()
			response, err = h.client.CompareAndSwap(key, string(data), ttl, "", version)
			metrics.RecordEtcdRequestLatency("compareAndSwap", getTypeName(obj), startTime)
			if err != nil {
				return err
			}
		}
	}
	if create {
		// Create will fail if a key already exists.
		startTime := time.Now()
		response, err = h.client.Create(key, string(data), ttl)
		metrics.RecordEtcdRequestLatency("create", getTypeName(obj), startTime)
	}

	if err != nil {
		return err
	}
	if out != nil {
		if _, err := conversion.EnforcePtr(out); err != nil {
			panic("unable to convert output object to pointer")
		}
		_, _, err = h.extractObj(response, err, out, false, false)
	}

	return err
}

// decodeNodeList walks the tree of each node in the list and decodes into the specified object
func (h *etcdHelper) decodeNodeList(nodes []*etcd.Node, filter storage.FilterFunc, slicePtr interface{}) error {
	trace := util.NewTrace("decodeNodeList " + getTypeName(slicePtr))
	defer trace.LogIfLong(500 * time.Millisecond)
	v, err := conversion.EnforcePtr(slicePtr)
	if err != nil || v.Kind() != reflect.Slice {
		// This should not happen at runtime.
		panic("need ptr to slice")
	}
	for _, node := range nodes {
		if node.Dir {
			trace.Step("Decoding dir " + node.Key + " START")
			if err := h.decodeNodeList(node.Nodes, filter, slicePtr); err != nil {
				return err
			}
			trace.Step("Decoding dir " + node.Key + " END")
			continue
		}
		if obj, found := h.getFromCache(node.ModifiedIndex, filter); found {
			// obj != nil iff it matches the filter function.
			if obj != nil {
				v.Set(reflect.Append(v, reflect.ValueOf(obj).Elem()))
			}
		} else {
			obj := reflect.New(v.Type().Elem())
			if err := h.codec.DecodeInto([]byte(node.Value), obj.Interface().(runtime.Object)); err != nil {
				return err
			}
			if h.versioner != nil {
				// being unable to set the version does not prevent the object from being extracted
				_ = h.versioner.UpdateObject(obj.Interface().(runtime.Object), node.Expiration, node.ModifiedIndex)
			}
			if filter(obj.Interface().(runtime.Object)) {
				v.Set(reflect.Append(v, obj.Elem()))
			}
			if node.ModifiedIndex != 0 {
				h.addToCache(node.ModifiedIndex, obj.Interface().(runtime.Object))
			}
		}
	}
	trace.Step(fmt.Sprintf("Decoded %v nodes", len(nodes)))
	return nil
}

// TypeAccessor returns an interface that allows retrieving and modifying the APIVersion
// and Kind of an in-memory internal object.
// TODO: this interface is used to test code that does not have ObjectMeta or ListMeta
// in round tripping (objects which can use apiVersion/kind, but do not fit the Kube
// api conventions).
func TypeAccessor(obj interface{}) (TypeInterface, error) {
	v, err := conversion.EnforcePtr(obj)
	if err != nil {
		return nil, err
	}
	t := v.Type()
	if v.Kind() != reflect.Struct {
		return nil, fmt.Errorf("expected struct, but got %v: %v (%#v)", v.Kind(), t, v.Interface())
	}

	typeMeta := v.FieldByName("TypeMeta")
	if !typeMeta.IsValid() {
		return nil, fmt.Errorf("struct %v lacks embedded TypeMeta type", t)
	}
	a := &genericAccessor{}
	if err := extractFromTypeMeta(typeMeta, a); err != nil {
		return nil, fmt.Errorf("unable to find type fields on %#v: %v", typeMeta, err)
	}
	return a, nil
}

// fieldPtr puts the address of fieldName, which must be a member of v,
// into dest, which must be an address of a variable to which this field's
// address can be assigned.
func FieldPtr(v reflect.Value, fieldName string, dest interface{}) error {
	field := v.FieldByName(fieldName)
	if !field.IsValid() {
		return fmt.Errorf("couldn't find %v field in %#v", fieldName, v.Interface())
	}
	v, err := conversion.EnforcePtr(dest)
	if err != nil {
		return err
	}
	field = field.Addr()
	if field.Type().AssignableTo(v.Type()) {
		v.Set(field)
		return nil
	}
	if field.Type().ConvertibleTo(v.Type()) {
		v.Set(field.Convert(v.Type()))
		return nil
	}
	return fmt.Errorf("couldn't assign/convert %v to %v", field.Type(), v.Type())
}

// GetItemsPtr returns a pointer to the list object's Items member.
// If 'list' doesn't have an Items member, it's not really a list type
// and an error will be returned.
// This function will either return a pointer to a slice, or an error, but not both.
func GetItemsPtr(list Object) (interface{}, error) {
	v, err := conversion.EnforcePtr(list)
	if err != nil {
		return nil, err
	}
	items := v.FieldByName("Items")
	if !items.IsValid() {
		return nil, fmt.Errorf("no Items field in %#v", list)
	}
	switch items.Kind() {
	case reflect.Interface, reflect.Ptr:
		target := reflect.TypeOf(items.Interface()).Elem()
		if target.Kind() != reflect.Slice {
			return nil, fmt.Errorf("items: Expected slice, got %s", target.Kind())
		}
		return items.Interface(), nil
	case reflect.Slice:
		return items.Addr().Interface(), nil
	default:
		return nil, fmt.Errorf("items: Expected slice, got %s", items.Kind())
	}
}