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+// Go support for Protocol Buffers - Google's data interchange format
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+//
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+// Copyright 2010 Google Inc. All rights reserved.
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+// http://code.google.com/p/goprotobuf/
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+//
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+// Redistribution and use in source and binary forms, with or without
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+// modification, are permitted provided that the following conditions are
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+// met:
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+//
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+// * Redistributions of source code must retain the above copyright
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+// notice, this list of conditions and the following disclaimer.
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+// * Redistributions in binary form must reproduce the above
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+// copyright notice, this list of conditions and the following disclaimer
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+// in the documentation and/or other materials provided with the
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+// distribution.
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+// * Neither the name of Google Inc. nor the names of its
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+// contributors may be used to endorse or promote products derived from
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+// this software without specific prior written permission.
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+//
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+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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+
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+package proto
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+
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+/*
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+ * Support for message sets.
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+ */
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+
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+import (
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+ "bytes"
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+ "os"
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+)
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+
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+// ErrNoMessageTypeId occurs when a protocol buffer does not have a message type ID.
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+// A message type ID is required for storing a protocol buffer in a message set.
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+var ErrNoMessageTypeId = os.NewError("proto does not have a message type ID")
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+
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+// The first two types (_MessageSet_Item and MessageSet)
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+// model what the protocol compiler produces for the following protocol message:
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+// message MessageSet {
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+// repeated group Item = 1 {
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+// required int32 type_id = 2;
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+// required string message = 3;
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+// };
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+// }
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+// That is the MessageSet wire format. We can't use a proto to generate these
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+// because that would introduce a circular dependency between it and this package.
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+//
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+// When a proto1 proto has a field that looks like:
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+// optional message<MessageSet> info = 3;
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+// the protocol compiler produces a field in the generated struct that looks like:
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+// Info *_proto_.MessageSet "PB(bytes,3,opt,name=info)"
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+// The package is automatically inserted so there is no need for that proto file to
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+// import this package.
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+
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+type _MessageSet_Item struct {
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+ TypeId *int32 "PB(varint,2,req,name=type_id)"
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+ Message []byte "PB(bytes,3,req,name=message)"
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+}
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+
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+type MessageSet struct {
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+ Item []*_MessageSet_Item "PB(group,1,rep)"
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+ XXX_unrecognized *bytes.Buffer
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+ // TODO: caching?
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+}
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+
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+// messageTypeIder is an interface satisfied by a protocol buffer type
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+// that may be stored in a MessageSet.
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+type messageTypeIder interface {
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+ MessageTypeId() int32
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+}
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+
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+func (ms *MessageSet) find(pb interface{}) *_MessageSet_Item {
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+ mti, ok := pb.(messageTypeIder)
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+ if !ok {
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+ return nil
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+ }
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+ id := mti.MessageTypeId()
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+ for _, item := range ms.Item {
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+ if *item.TypeId == id {
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+ return item
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+ }
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+ }
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+ return nil
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+}
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+
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+func (ms *MessageSet) Has(pb interface{}) bool {
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+ if ms.find(pb) != nil {
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+ return true
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+ }
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+ return false
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+}
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+
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+func (ms *MessageSet) Unmarshal(pb interface{}) os.Error {
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+ if item := ms.find(pb); item != nil {
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+ return Unmarshal(item.Message, pb)
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+ }
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+ if _, ok := pb.(messageTypeIder); !ok {
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+ return ErrNoMessageTypeId
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+ }
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+ return nil // TODO: return error instead?
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+}
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+
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+func (ms *MessageSet) Marshal(pb interface{}) os.Error {
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+ msg, err := Marshal(pb)
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+ if err != nil {
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+ return err
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+ }
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+ if item := ms.find(pb); item != nil {
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+ // reuse existing item
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+ item.Message = msg
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+ return nil
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+ }
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+
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+ mti, ok := pb.(messageTypeIder)
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+ if !ok {
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+ return ErrWrongType // TODO: custom error?
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+ }
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+
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+ mtid := mti.MessageTypeId()
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+ ms.Item = append(ms.Item, &_MessageSet_Item{
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+ TypeId: &mtid,
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+ Message: msg,
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+ })
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+ return nil
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+}
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+
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+// Support for the message_set_wire_format message option.
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+
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+func skipVarint(buf []byte) []byte {
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+ i := 0
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+ for ; buf[i]&0x80 != 0; i++ {
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+ }
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+ return buf[i+1:]
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+}
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+
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+// MarshalMessageSet encodes the extension map represented by m in the message set wire format.
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+// It is called by generated Marshal methods on protocol buffer messages with the message_set_wire_format option.
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+func MarshalMessageSet(m map[int32][]byte) ([]byte, os.Error) {
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+ ms := &MessageSet{Item: make([]*_MessageSet_Item, len(m))}
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+ i := 0
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+ for k, v := range m {
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+ // Remove the wire type and field number varint, as well as the length varint.
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+ v = skipVarint(skipVarint(v))
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+
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+ ms.Item[i] = &_MessageSet_Item{
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+ TypeId: Int32(k),
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+ Message: v,
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+ }
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+ i++
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+ }
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+ return Marshal(ms)
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+}
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+
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+// UnmarshalMessageSet decodes the extension map encoded in buf in the message set wire format.
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+// It is called by generated Unmarshal methods on protocol buffer messages with the message_set_wire_format option.
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+func UnmarshalMessageSet(buf []byte, m map[int32][]byte) os.Error {
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+ ms := new(MessageSet)
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+ if err := Unmarshal(buf, ms); err != nil {
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+ return err
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+ }
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+ for _, item := range ms.Item {
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+ // restore wire type and field number varint, plus length varint.
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+ b := EncodeVarint(uint64(*item.TypeId)<<3 | WireBytes)
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+ b = append(b, EncodeVarint(uint64(len(item.Message)))...)
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+ b = append(b, item.Message...)
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+
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+ m[*item.TypeId] = b
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+ }
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+ return nil
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+}
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David Symonds