protobuf-go/internal/impl/legacy_file.go
Joe Tsai d888139e7b internal/filedesc, internal/filetype: initial commit
The internal/fileinit package is split apart into two packages:
* internal/filedesc constructs descriptors from the raw proto.
It is very similar to the previous internal/fileinit package.
* internal/filetype wraps descriptors with Go type information

Overview:
* The internal/fileinit package will be deleted in a future CL.
It is kept around since the v1 repo currently depends on it.
* The internal/prototype package is deleted. All former usages of it
are now using internal/filedesc instead. Most significantly,
the reflect/protodesc package was almost entirely re-written.
* The internal/impl package drops support for messages that do not
have a Descriptor method (pre-2016). This removes a significant amount
of technical debt.
filedesc.Builder to parse raw descriptors.
* The internal/encoding/defval package now handles enum values by name.

Change-Id: I3957bcc8588a70470fd6c7de1122216b80615ab7
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/182360
Reviewed-by: Damien Neil <dneil@google.com>
2019-06-20 02:06:11 +00:00

74 lines
2.2 KiB
Go

// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package impl
import (
"bytes"
"compress/gzip"
"io/ioutil"
"sync"
"google.golang.org/protobuf/internal/filedesc"
"google.golang.org/protobuf/reflect/protoreflect"
"google.golang.org/protobuf/reflect/protoregistry"
)
// Every enum and message type generated by protoc-gen-go since commit 2fc053c5
// on February 25th, 2016 has had a method to get the raw descriptor.
// Types that were not generated by protoc-gen-go or were generated prior
// to that version are not supported.
//
// The []byte returned is the encoded form of a FileDescriptorProto message
// compressed using GZIP. The []int is the path from the top-level file
// to the specific message or enum declaration.
type (
enumV1 interface {
EnumDescriptor() ([]byte, []int)
}
messageV1 interface {
Descriptor() ([]byte, []int)
}
)
var legacyFileDescCache sync.Map // map[*byte]protoreflect.FileDescriptor
// legacyLoadFileDesc unmarshals b as a compressed FileDescriptorProto message.
//
// This assumes that b is immutable and that b does not refer to part of a
// concatenated series of GZIP files (which would require shenanigans that
// rely on the concatenation properties of both protobufs and GZIP).
// File descriptors generated by protoc-gen-go do not rely on that property.
func legacyLoadFileDesc(b []byte) protoreflect.FileDescriptor {
// Fast-path: check whether we already have a cached file descriptor.
if fd, ok := legacyFileDescCache.Load(&b[0]); ok {
return fd.(protoreflect.FileDescriptor)
}
// Slow-path: decompress and unmarshal the file descriptor proto.
zr, err := gzip.NewReader(bytes.NewReader(b))
if err != nil {
panic(err)
}
b2, err := ioutil.ReadAll(zr)
if err != nil {
panic(err)
}
fd := filedesc.DescBuilder{
RawDescriptor: b2,
FileRegistry: resolverOnly{protoregistry.GlobalFiles}, // do not register back to global registry
}.Build().File
if fd, ok := legacyFileDescCache.LoadOrStore(&b[0], fd); ok {
return fd.(protoreflect.FileDescriptor)
}
return fd
}
type resolverOnly struct {
*protoregistry.Files
}
func (resolverOnly) Register(...protoreflect.FileDescriptor) error { return nil }