mirror of https://github.com/k3s-io/k3s
105 lines
3.7 KiB
Go
105 lines
3.7 KiB
Go
/*
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Copyright 2014 Google Inc. All rights reserved.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package conversion
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import (
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"encoding/json"
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"fmt"
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)
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// EncodeToVersion turns the given api object into an appropriate JSON string.
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// Obj may be a pointer to a struct, or a struct. If a struct, a copy
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// will be made, therefore it's recommended to pass a pointer to a
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// struct. The type must have been registered.
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//
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// Memory/wire format differences:
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// * Having to keep track of the Kind and Version fields makes tests
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// very annoying, so the rule is that they are set only in wire format
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// (json), not when in native (memory) format. This is possible because
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// both pieces of information are implicit in the go typed object.
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// * An exception: note that, if there are embedded API objects of known
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// type, for example, PodList{... Items []Pod ...}, these embedded
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// objects must be of the same version of the object they are embedded
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// within, and their Version and Kind must both be empty.
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// * Note that the exception does not apply to a generic APIObject type
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// which recursively does Encode()/Decode(), and is capable of
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// expressing any API object.
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// * Only versioned objects should be encoded. This means that, if you pass
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// a native object, Encode will convert it to a versioned object. For
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// example, an api.Pod will get converted to a v1beta1.Pod. However, if
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// you pass in an object that's already versioned (v1beta1.Pod), Encode
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// will not modify it.
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//
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// The purpose of the above complex conversion behavior is to allow us to
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// change the memory format yet not break compatibility with any stored
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// objects, whether they be in our storage layer (e.g., etcd), or in user's
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// config files.
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//
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func (s *Scheme) EncodeToVersion(obj interface{}, destVersion string) (data []byte, err error) {
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obj = maybeCopy(obj)
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v, _ := EnforcePtr(obj) // maybeCopy guarantees a pointer
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if _, registered := s.typeToVersion[v.Type()]; !registered {
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return nil, fmt.Errorf("type %v is not registered and it will be impossible to Decode it, therefore Encode will refuse to encode it.", v.Type())
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}
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objVersion, objKind, err := s.ObjectVersionAndKind(obj)
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if err != nil {
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return nil, err
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}
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// Perform a conversion if necessary.
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if objVersion != destVersion {
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objOut, err := s.NewObject(destVersion, objKind)
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if err != nil {
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return nil, err
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}
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flags, meta := s.generateConvertMeta(objVersion, destVersion, obj)
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err = s.converter.Convert(obj, objOut, flags, meta)
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if err != nil {
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return nil, err
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}
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obj = objOut
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}
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// ensure the output object name comes from the destination type
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_, objKind, err = s.ObjectVersionAndKind(obj)
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if err != nil {
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return nil, err
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}
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// Version and Kind should be set on the wire.
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err = s.SetVersionAndKind(destVersion, objKind, obj)
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if err != nil {
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return nil, err
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}
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// To add metadata, do some simple surgery on the JSON.
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data, err = json.Marshal(obj)
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if err != nil {
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return nil, err
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}
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// Version and Kind should be blank in memory. Reset them, since it's
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// possible that we modified a user object and not a copy above.
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err = s.SetVersionAndKind("", "", obj)
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if err != nil {
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return nil, err
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}
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return data, nil
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}
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