mirror of
https://github.com/protocolbuffers/protobuf-go.git
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b936504483
When concurrent requests to wrap a type occurs, it is possible that two different descriptors are created for the same Go type. Add sufficient synchronization to ensure that one descriptor is ever returned for one Go type. Change-Id: Idbbca4c1877a70317b39900ae83bfc3085d4a9c5 Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/168398 Reviewed-by: Herbie Ong <herbie@google.com>
79 lines
2.4 KiB
Go
79 lines
2.4 KiB
Go
// Copyright 2018 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package legacy
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import (
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"bytes"
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"compress/gzip"
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"io/ioutil"
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"sync"
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"github.com/golang/protobuf/v2/proto"
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pref "github.com/golang/protobuf/v2/reflect/protoreflect"
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descriptorpb "github.com/golang/protobuf/v2/types/descriptor"
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)
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// Every enum and message type generated by protoc-gen-go since commit 2fc053c5
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// on February 25th, 2016 has had a method to get the raw descriptor.
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// Types that were not generated by protoc-gen-go or were generated prior
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// to that version are not supported.
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//
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// The []byte returned is the encoded form of a FileDescriptorProto message
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// compressed using GZIP. The []int is the path from the top-level file
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// to the specific message or enum declaration.
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type (
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enumV1 interface {
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EnumDescriptor() ([]byte, []int)
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}
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messageV1 interface {
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Descriptor() ([]byte, []int)
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}
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)
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var fileDescCache sync.Map // map[*byte]*descriptorpb.FileDescriptorProto
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// loadFileDesc unmarshals b as a compressed FileDescriptorProto message.
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//
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// This assumes that b is immutable and that b does not refer to part of a
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// concatenated series of GZIP files (which would require shenanigans that
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// rely on the concatenation properties of both protobufs and GZIP).
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// File descriptors generated by protoc-gen-go do not rely on that property.
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func loadFileDesc(b []byte) *descriptorpb.FileDescriptorProto {
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// Fast-path: check whether we already have a cached file descriptor.
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if fd, ok := fileDescCache.Load(&b[0]); ok {
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return fd.(*descriptorpb.FileDescriptorProto)
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}
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// Slow-path: decompress and unmarshal the file descriptor proto.
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fd := new(descriptorpb.FileDescriptorProto)
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zr, err := gzip.NewReader(bytes.NewReader(b))
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if err != nil {
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panic(err)
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}
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b, err = ioutil.ReadAll(zr)
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if err != nil {
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panic(err)
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}
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err = proto.UnmarshalOptions{DiscardUnknown: true}.Unmarshal(b, fd)
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if err != nil {
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panic(err)
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}
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if fd, ok := fileDescCache.LoadOrStore(&b[0], fd); ok {
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return fd.(*descriptorpb.FileDescriptorProto)
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}
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return fd
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}
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// parentFileDescriptor returns the parent protoreflect.FileDescriptor for the
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// provide descriptor. It returns nil if there is no parent.
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func parentFileDescriptor(d pref.Descriptor) pref.FileDescriptor {
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for ok := true; ok; d, ok = d.Parent() {
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if fd, _ := d.(pref.FileDescriptor); fd != nil {
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return fd
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}
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}
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return nil
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}
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