1// Go support for Protocol Buffers - Google's data interchange format
2//
3// Copyright 2010 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 proto
33
34/*
35 * Support for message sets.
36 */
37
38import (
39	"errors"
40)
41
42// errNoMessageTypeID occurs when a protocol buffer does not have a message type ID.
43// A message type ID is required for storing a protocol buffer in a message set.
44var errNoMessageTypeID = errors.New("proto does not have a message type ID")
45
46// The first two types (_MessageSet_Item and messageSet)
47// model what the protocol compiler produces for the following protocol message:
48//   message MessageSet {
49//     repeated group Item = 1 {
50//       required int32 type_id = 2;
51//       required string message = 3;
52//     };
53//   }
54// That is the MessageSet wire format. We can't use a proto to generate these
55// because that would introduce a circular dependency between it and this package.
56
57type _MessageSet_Item struct {
58	TypeId  *int32 `protobuf:"varint,2,req,name=type_id"`
59	Message []byte `protobuf:"bytes,3,req,name=message"`
60}
61
62type messageSet struct {
63	Item             []*_MessageSet_Item `protobuf:"group,1,rep"`
64	XXX_unrecognized []byte
65	// TODO: caching?
66}
67
68// Make sure messageSet is a Message.
69var _ Message = (*messageSet)(nil)
70
71// messageTypeIder is an interface satisfied by a protocol buffer type
72// that may be stored in a MessageSet.
73type messageTypeIder interface {
74	MessageTypeId() int32
75}
76
77func (ms *messageSet) find(pb Message) *_MessageSet_Item {
78	mti, ok := pb.(messageTypeIder)
79	if !ok {
80		return nil
81	}
82	id := mti.MessageTypeId()
83	for _, item := range ms.Item {
84		if *item.TypeId == id {
85			return item
86		}
87	}
88	return nil
89}
90
91func (ms *messageSet) Has(pb Message) bool {
92	return ms.find(pb) != nil
93}
94
95func (ms *messageSet) Unmarshal(pb Message) error {
96	if item := ms.find(pb); item != nil {
97		return Unmarshal(item.Message, pb)
98	}
99	if _, ok := pb.(messageTypeIder); !ok {
100		return errNoMessageTypeID
101	}
102	return nil // TODO: return error instead?
103}
104
105func (ms *messageSet) Marshal(pb Message) error {
106	msg, err := Marshal(pb)
107	if err != nil {
108		return err
109	}
110	if item := ms.find(pb); item != nil {
111		// reuse existing item
112		item.Message = msg
113		return nil
114	}
115
116	mti, ok := pb.(messageTypeIder)
117	if !ok {
118		return errNoMessageTypeID
119	}
120
121	mtid := mti.MessageTypeId()
122	ms.Item = append(ms.Item, &_MessageSet_Item{
123		TypeId:  &mtid,
124		Message: msg,
125	})
126	return nil
127}
128
129func (ms *messageSet) Reset()         { *ms = messageSet{} }
130func (ms *messageSet) String() string { return CompactTextString(ms) }
131func (*messageSet) ProtoMessage()     {}
132
133// Support for the message_set_wire_format message option.
134
135func skipVarint(buf []byte) []byte {
136	i := 0
137	for ; buf[i]&0x80 != 0; i++ {
138	}
139	return buf[i+1:]
140}
141
142// unmarshalMessageSet decodes the extension map encoded in buf in the message set wire format.
143// It is called by Unmarshal methods on protocol buffer messages with the message_set_wire_format option.
144func unmarshalMessageSet(buf []byte, exts interface{}) error {
145	var m map[int32]Extension
146	switch exts := exts.(type) {
147	case *XXX_InternalExtensions:
148		m = exts.extensionsWrite()
149	case map[int32]Extension:
150		m = exts
151	default:
152		return errors.New("proto: not an extension map")
153	}
154
155	ms := new(messageSet)
156	if err := Unmarshal(buf, ms); err != nil {
157		return err
158	}
159	for _, item := range ms.Item {
160		id := *item.TypeId
161		msg := item.Message
162
163		// Restore wire type and field number varint, plus length varint.
164		// Be careful to preserve duplicate items.
165		b := EncodeVarint(uint64(id)<<3 | WireBytes)
166		if ext, ok := m[id]; ok {
167			// Existing data; rip off the tag and length varint
168			// so we join the new data correctly.
169			// We can assume that ext.enc is set because we are unmarshaling.
170			o := ext.enc[len(b):]   // skip wire type and field number
171			_, n := DecodeVarint(o) // calculate length of length varint
172			o = o[n:]               // skip length varint
173			msg = append(o, msg...) // join old data and new data
174		}
175		b = append(b, EncodeVarint(uint64(len(msg)))...)
176		b = append(b, msg...)
177
178		m[id] = Extension{enc: b}
179	}
180	return nil
181}
182