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
32// Package descriptor provides functions for obtaining protocol buffer
33// descriptors for generated Go types.
34//
35// These functions cannot go in package proto because they depend on the
36// generated protobuf descriptor messages, which themselves depend on proto.
37package descriptor
38
39import (
40	"bytes"
41	"compress/gzip"
42	"fmt"
43	"io/ioutil"
44
45	"github.com/gogo/protobuf/proto"
46)
47
48// extractFile extracts a FileDescriptorProto from a gzip'd buffer.
49func extractFile(gz []byte) (*FileDescriptorProto, error) {
50	r, err := gzip.NewReader(bytes.NewReader(gz))
51	if err != nil {
52		return nil, fmt.Errorf("failed to open gzip reader: %v", err)
53	}
54	defer r.Close()
55
56	b, err := ioutil.ReadAll(r)
57	if err != nil {
58		return nil, fmt.Errorf("failed to uncompress descriptor: %v", err)
59	}
60
61	fd := new(FileDescriptorProto)
62	if err := proto.Unmarshal(b, fd); err != nil {
63		return nil, fmt.Errorf("malformed FileDescriptorProto: %v", err)
64	}
65
66	return fd, nil
67}
68
69// Message is a proto.Message with a method to return its descriptor.
70//
71// Message types generated by the protocol compiler always satisfy
72// the Message interface.
73type Message interface {
74	proto.Message
75	Descriptor() ([]byte, []int)
76}
77
78// ForMessage returns a FileDescriptorProto and a DescriptorProto from within it
79// describing the given message.
80func ForMessage(msg Message) (fd *FileDescriptorProto, md *DescriptorProto) {
81	gz, path := msg.Descriptor()
82	fd, err := extractFile(gz)
83	if err != nil {
84		panic(fmt.Sprintf("invalid FileDescriptorProto for %T: %v", msg, err))
85	}
86
87	md = fd.MessageType[path[0]]
88	for _, i := range path[1:] {
89		md = md.NestedType[i]
90	}
91	return fd, md
92}
93
94// Is this field a scalar numeric type?
95func (field *FieldDescriptorProto) IsScalar() bool {
96	if field.Type == nil {
97		return false
98	}
99	switch *field.Type {
100	case FieldDescriptorProto_TYPE_DOUBLE,
101		FieldDescriptorProto_TYPE_FLOAT,
102		FieldDescriptorProto_TYPE_INT64,
103		FieldDescriptorProto_TYPE_UINT64,
104		FieldDescriptorProto_TYPE_INT32,
105		FieldDescriptorProto_TYPE_FIXED64,
106		FieldDescriptorProto_TYPE_FIXED32,
107		FieldDescriptorProto_TYPE_BOOL,
108		FieldDescriptorProto_TYPE_UINT32,
109		FieldDescriptorProto_TYPE_ENUM,
110		FieldDescriptorProto_TYPE_SFIXED32,
111		FieldDescriptorProto_TYPE_SFIXED64,
112		FieldDescriptorProto_TYPE_SINT32,
113		FieldDescriptorProto_TYPE_SINT64:
114		return true
115	default:
116		return false
117	}
118}
119