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
5package impl
6
7import (
8	"bytes"
9	"compress/gzip"
10	"io/ioutil"
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.
26type (
27	enumV1 interface {
28		EnumDescriptor() ([]byte, []int)
29	}
30	messageV1 interface {
31		Descriptor() ([]byte, []int)
32	}
33)
34
35var 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.
43func 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 := ioutil.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
69type resolverOnly struct {
70	reg *protoregistry.Files
71}
72
73func (r resolverOnly) FindFileByPath(path string) (protoreflect.FileDescriptor, error) {
74	return r.reg.FindFileByPath(path)
75}
76func (r resolverOnly) FindDescriptorByName(name protoreflect.FullName) (protoreflect.Descriptor, error) {
77	return r.reg.FindDescriptorByName(name)
78}
79func (resolverOnly) RegisterFile(protoreflect.FileDescriptor) error {
80	return nil
81}
82