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 ptypes
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/golang/protobuf/proto"
43	"github.com/golang/protobuf/ptypes/any"
44)
45
46const googleApis = "type.googleapis.com/"
47
48// AnyMessageName returns the name of the message contained in a google.protobuf.Any message.
49//
50// Note that regular type assertions should be done using the Is
51// function. AnyMessageName is provided for less common use cases like filtering a
52// sequence of Any messages based on a set of allowed message type names.
53func AnyMessageName(any *any.Any) (string, error) {
54	if any == nil {
55		return "", fmt.Errorf("message is nil")
56	}
57	slash := strings.LastIndex(any.TypeUrl, "/")
58	if slash < 0 {
59		return "", fmt.Errorf("message type url %q is invalid", any.TypeUrl)
60	}
61	return any.TypeUrl[slash+1:], nil
62}
63
64// MarshalAny takes the protocol buffer and encodes it into google.protobuf.Any.
65func MarshalAny(pb proto.Message) (*any.Any, error) {
66	value, err := proto.Marshal(pb)
67	if err != nil {
68		return nil, err
69	}
70	return &any.Any{TypeUrl: googleApis + proto.MessageName(pb), Value: value}, nil
71}
72
73// DynamicAny is a value that can be passed to UnmarshalAny to automatically
74// allocate a proto.Message for the type specified in a google.protobuf.Any
75// message. The allocated message is stored in the embedded proto.Message.
76//
77// Example:
78//
79//   var x ptypes.DynamicAny
80//   if err := ptypes.UnmarshalAny(a, &x); err != nil { ... }
81//   fmt.Printf("unmarshaled message: %v", x.Message)
82type DynamicAny struct {
83	proto.Message
84}
85
86// Empty returns a new proto.Message of the type specified in a
87// google.protobuf.Any message. It returns an error if corresponding message
88// type isn't linked in.
89func Empty(any *any.Any) (proto.Message, error) {
90	aname, err := AnyMessageName(any)
91	if err != nil {
92		return nil, err
93	}
94
95	t := proto.MessageType(aname)
96	if t == nil {
97		return nil, fmt.Errorf("any: message type %q isn't linked in", aname)
98	}
99	return reflect.New(t.Elem()).Interface().(proto.Message), nil
100}
101
102// UnmarshalAny parses the protocol buffer representation in a google.protobuf.Any
103// message and places the decoded result in pb. It returns an error if type of
104// contents of Any message does not match type of pb message.
105//
106// pb can be a proto.Message, or a *DynamicAny.
107func UnmarshalAny(any *any.Any, pb proto.Message) error {
108	if d, ok := pb.(*DynamicAny); ok {
109		if d.Message == nil {
110			var err error
111			d.Message, err = Empty(any)
112			if err != nil {
113				return err
114			}
115		}
116		return UnmarshalAny(any, d.Message)
117	}
118
119	aname, err := AnyMessageName(any)
120	if err != nil {
121		return err
122	}
123
124	mname := proto.MessageName(pb)
125	if aname != mname {
126		return fmt.Errorf("mismatched message type: got %q want %q", aname, mname)
127	}
128	return proto.Unmarshal(any.Value, pb)
129}
130
131// Is returns true if any value contains a given message type.
132func Is(any *any.Any, pb proto.Message) bool {
133	// The following is equivalent to AnyMessageName(any) == proto.MessageName(pb),
134	// but it avoids scanning TypeUrl for the slash.
135	if any == nil {
136		return false
137	}
138	name := proto.MessageName(pb)
139	prefix := len(any.TypeUrl) - len(name)
140	return prefix >= 1 && any.TypeUrl[prefix-1] == '/' && any.TypeUrl[prefix:] == name
141}
142