1// Go support for Protocol Buffers - Google's data interchange format
2//
3// Copyright 2016 The Go Authors.  All rights reserved.
4// https://github.com/golang/protobuf
5//
6// Redistribution and use in source and binary forms, with or without
7// modification, are permitted provided that the following conditions are
8// met:
9//
10//     * Redistributions of source code must retain the above copyright
11// notice, this list of conditions and the following disclaimer.
12//     * Redistributions in binary form must reproduce the above
13// copyright notice, this list of conditions and the following disclaimer
14// in the documentation and/or other materials provided with the
15// distribution.
16//     * Neither the name of Google Inc. nor the names of its
17// contributors may be used to endorse or promote products derived from
18// this software without specific prior written permission.
19//
20// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
23// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
24// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
25// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
26// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
30// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31
32package types
33
34// This file implements functions to marshal proto.Message to/from
35// google.protobuf.Any message.
36
37import (
38	"fmt"
39	"reflect"
40	"strings"
41
42	"github.com/gogo/protobuf/proto"
43)
44
45const googleApis = "type.googleapis.com/"
46
47// AnyMessageName returns the name of the message contained in a google.protobuf.Any message.
48//
49// Note that regular type assertions should be done using the Is
50// function. AnyMessageName is provided for less common use cases like filtering a
51// sequence of Any messages based on a set of allowed message type names.
52func AnyMessageName(any *Any) (string, error) {
53	if any == nil {
54		return "", fmt.Errorf("message is nil")
55	}
56	slash := strings.LastIndex(any.TypeUrl, "/")
57	if slash < 0 {
58		return "", fmt.Errorf("message type url %q is invalid", any.TypeUrl)
59	}
60	return any.TypeUrl[slash+1:], nil
61}
62
63// MarshalAny takes the protocol buffer and encodes it into google.protobuf.Any.
64func MarshalAny(pb proto.Message) (*Any, error) {
65	value, err := proto.Marshal(pb)
66	if err != nil {
67		return nil, err
68	}
69	return &Any{TypeUrl: googleApis + proto.MessageName(pb), Value: value}, nil
70}
71
72// DynamicAny is a value that can be passed to UnmarshalAny to automatically
73// allocate a proto.Message for the type specified in a google.protobuf.Any
74// message. The allocated message is stored in the embedded proto.Message.
75//
76// Example:
77//
78//   var x ptypes.DynamicAny
79//   if err := ptypes.UnmarshalAny(a, &x); err != nil { ... }
80//   fmt.Printf("unmarshaled message: %v", x.Message)
81type DynamicAny struct {
82	proto.Message
83}
84
85// Empty returns a new proto.Message of the type specified in a
86// google.protobuf.Any message. It returns an error if corresponding message
87// type isn't linked in.
88func EmptyAny(any *Any) (proto.Message, error) {
89	aname, err := AnyMessageName(any)
90	if err != nil {
91		return nil, err
92	}
93
94	t := proto.MessageType(aname)
95	if t == nil {
96		return nil, fmt.Errorf("any: message type %q isn't linked in", aname)
97	}
98	return reflect.New(t.Elem()).Interface().(proto.Message), nil
99}
100
101// UnmarshalAny parses the protocol buffer representation in a google.protobuf.Any
102// message and places the decoded result in pb. It returns an error if type of
103// contents of Any message does not match type of pb message.
104//
105// pb can be a proto.Message, or a *DynamicAny.
106func UnmarshalAny(any *Any, pb proto.Message) error {
107	if d, ok := pb.(*DynamicAny); ok {
108		if d.Message == nil {
109			var err error
110			d.Message, err = EmptyAny(any)
111			if err != nil {
112				return err
113			}
114		}
115		return UnmarshalAny(any, d.Message)
116	}
117
118	aname, err := AnyMessageName(any)
119	if err != nil {
120		return err
121	}
122
123	mname := proto.MessageName(pb)
124	if aname != mname {
125		return fmt.Errorf("mismatched message type: got %q want %q", aname, mname)
126	}
127	return proto.Unmarshal(any.Value, pb)
128}
129
130// Is returns true if any value contains a given message type.
131func Is(any *Any, pb proto.Message) bool {
132	// The following is equivalent to AnyMessageName(any) == proto.MessageName(pb),
133	// but it avoids scanning TypeUrl for the slash.
134	if any == nil {
135		return false
136	}
137	name := proto.MessageName(pb)
138	prefix := len(any.TypeUrl) - len(name)
139	return prefix >= 1 && any.TypeUrl[prefix-1] == '/' && any.TypeUrl[prefix:] == name
140}
141