1 // Copyright 2018 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 impl
6 7 import (
8 "bytes"
9 "compress/gzip"
10 "io"
11 "sync"
12 13 "google.golang.org/protobuf/internal/filedesc"
14 "google.golang.org/protobuf/reflect/protoreflect"
15 "google.golang.org/protobuf/reflect/protoregistry"
16 )
17 18 // Every enum and message type generated by protoc-gen-go since commit 2fc053c5
19 // on February 25th, 2016 has had a method to get the raw descriptor.
20 // Types that were not generated by protoc-gen-go or were generated prior
21 // to that version are not supported.
22 //
23 // The []byte returned is the encoded form of a FileDescriptorProto message
24 // compressed using GZIP. The []int is the path from the top-level file
25 // to the specific message or enum declaration.
26 type (
27 enumV1 interface {
28 EnumDescriptor() ([]byte, []int)
29 }
30 messageV1 interface {
31 Descriptor() ([]byte, []int)
32 }
33 )
34 35 var legacyFileDescCache sync.Map // map[*byte]protoreflect.FileDescriptor
36 37 // legacyLoadFileDesc unmarshals b as a compressed FileDescriptorProto message.
38 //
39 // This assumes that b is immutable and that b does not refer to part of a
40 // concatenated series of GZIP files (which would require shenanigans that
41 // rely on the concatenation properties of both protobufs and GZIP).
42 // File descriptors generated by protoc-gen-go do not rely on that property.
43 func legacyLoadFileDesc(b []byte) protoreflect.FileDescriptor {
44 // Fast-path: check whether we already have a cached file descriptor.
45 if fd, ok := legacyFileDescCache.Load(&b[0]); ok {
46 return fd.(protoreflect.FileDescriptor)
47 }
48 49 // Slow-path: decompress and unmarshal the file descriptor proto.
50 zr, err := gzip.NewReader(bytes.NewReader(b))
51 if err != nil {
52 panic(err)
53 }
54 b2, err := io.ReadAll(zr)
55 if err != nil {
56 panic(err)
57 }
58 59 fd := filedesc.Builder{
60 RawDescriptor: b2,
61 FileRegistry: resolverOnly{protoregistry.GlobalFiles}, // do not register back to global registry
62 }.Build().File
63 if fd, ok := legacyFileDescCache.LoadOrStore(&b[0], fd); ok {
64 return fd.(protoreflect.FileDescriptor)
65 }
66 return fd
67 }
68 69 type resolverOnly struct {
70 reg *protoregistry.Files
71 }
72 73 func (r resolverOnly) FindFileByPath(path string) (protoreflect.FileDescriptor, error) {
74 return r.reg.FindFileByPath(path)
75 }
76 func (r resolverOnly) FindDescriptorByName(name protoreflect.FullName) (protoreflect.Descriptor, error) {
77 return r.reg.FindDescriptorByName(name)
78 }
79 func (resolverOnly) RegisterFile(protoreflect.FileDescriptor) error {
80 return nil
81 }
82