1// Copyright 2019 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// Package filedesc provides functionality for constructing descriptors.
6//
7// The types in this package implement interfaces in the protoreflect package
8// related to protobuf descripriptors.
9package filedesc
10
11import (
12	"google.golang.org/protobuf/encoding/protowire"
13	"google.golang.org/protobuf/internal/genid"
14	"google.golang.org/protobuf/reflect/protoreflect"
15	pref "google.golang.org/protobuf/reflect/protoreflect"
16	preg "google.golang.org/protobuf/reflect/protoregistry"
17)
18
19// Builder construct a protoreflect.FileDescriptor from the raw descriptor.
20type Builder struct {
21	// GoPackagePath is the Go package path that is invoking this builder.
22	GoPackagePath string
23
24	// RawDescriptor is the wire-encoded bytes of FileDescriptorProto
25	// and must be populated.
26	RawDescriptor []byte
27
28	// NumEnums is the total number of enums declared in the file.
29	NumEnums int32
30	// NumMessages is the total number of messages declared in the file.
31	// It includes the implicit message declarations for map entries.
32	NumMessages int32
33	// NumExtensions is the total number of extensions declared in the file.
34	NumExtensions int32
35	// NumServices is the total number of services declared in the file.
36	NumServices int32
37
38	// TypeResolver resolves extension field types for descriptor options.
39	// If nil, it uses protoregistry.GlobalTypes.
40	TypeResolver interface {
41		preg.ExtensionTypeResolver
42	}
43
44	// FileRegistry is use to lookup file, enum, and message dependencies.
45	// Once constructed, the file descriptor is registered here.
46	// If nil, it uses protoregistry.GlobalFiles.
47	FileRegistry interface {
48		FindFileByPath(string) (protoreflect.FileDescriptor, error)
49		FindDescriptorByName(pref.FullName) (pref.Descriptor, error)
50		RegisterFile(pref.FileDescriptor) error
51	}
52}
53
54// resolverByIndex is an interface Builder.FileRegistry may implement.
55// If so, it permits looking up an enum or message dependency based on the
56// sub-list and element index into filetype.Builder.DependencyIndexes.
57type resolverByIndex interface {
58	FindEnumByIndex(int32, int32, []Enum, []Message) pref.EnumDescriptor
59	FindMessageByIndex(int32, int32, []Enum, []Message) pref.MessageDescriptor
60}
61
62// Indexes of each sub-list in filetype.Builder.DependencyIndexes.
63const (
64	listFieldDeps int32 = iota
65	listExtTargets
66	listExtDeps
67	listMethInDeps
68	listMethOutDeps
69)
70
71// Out is the output of the Builder.
72type Out struct {
73	File pref.FileDescriptor
74
75	// Enums is all enum descriptors in "flattened ordering".
76	Enums []Enum
77	// Messages is all message descriptors in "flattened ordering".
78	// It includes the implicit message declarations for map entries.
79	Messages []Message
80	// Extensions is all extension descriptors in "flattened ordering".
81	Extensions []Extension
82	// Service is all service descriptors in "flattened ordering".
83	Services []Service
84}
85
86// Build constructs a FileDescriptor given the parameters set in Builder.
87// It assumes that the inputs are well-formed and panics if any inconsistencies
88// are encountered.
89//
90// If NumEnums+NumMessages+NumExtensions+NumServices is zero,
91// then Build automatically derives them from the raw descriptor.
92func (db Builder) Build() (out Out) {
93	// Populate the counts if uninitialized.
94	if db.NumEnums+db.NumMessages+db.NumExtensions+db.NumServices == 0 {
95		db.unmarshalCounts(db.RawDescriptor, true)
96	}
97
98	// Initialize resolvers and registries if unpopulated.
99	if db.TypeResolver == nil {
100		db.TypeResolver = preg.GlobalTypes
101	}
102	if db.FileRegistry == nil {
103		db.FileRegistry = preg.GlobalFiles
104	}
105
106	fd := newRawFile(db)
107	out.File = fd
108	out.Enums = fd.allEnums
109	out.Messages = fd.allMessages
110	out.Extensions = fd.allExtensions
111	out.Services = fd.allServices
112
113	if err := db.FileRegistry.RegisterFile(fd); err != nil {
114		panic(err)
115	}
116	return out
117}
118
119// unmarshalCounts counts the number of enum, message, extension, and service
120// declarations in the raw message, which is either a FileDescriptorProto
121// or a MessageDescriptorProto depending on whether isFile is set.
122func (db *Builder) unmarshalCounts(b []byte, isFile bool) {
123	for len(b) > 0 {
124		num, typ, n := protowire.ConsumeTag(b)
125		b = b[n:]
126		switch typ {
127		case protowire.BytesType:
128			v, m := protowire.ConsumeBytes(b)
129			b = b[m:]
130			if isFile {
131				switch num {
132				case genid.FileDescriptorProto_EnumType_field_number:
133					db.NumEnums++
134				case genid.FileDescriptorProto_MessageType_field_number:
135					db.unmarshalCounts(v, false)
136					db.NumMessages++
137				case genid.FileDescriptorProto_Extension_field_number:
138					db.NumExtensions++
139				case genid.FileDescriptorProto_Service_field_number:
140					db.NumServices++
141				}
142			} else {
143				switch num {
144				case genid.DescriptorProto_EnumType_field_number:
145					db.NumEnums++
146				case genid.DescriptorProto_NestedType_field_number:
147					db.unmarshalCounts(v, false)
148					db.NumMessages++
149				case genid.DescriptorProto_Extension_field_number:
150					db.NumExtensions++
151				}
152			}
153		default:
154			m := protowire.ConsumeFieldValue(num, typ, b)
155			b = b[m:]
156		}
157	}
158}
159