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