1// Go support for Protocol Buffers - Google's data interchange format 2// 3// Copyright 2016 The Go Authors. All rights reserved. 4// https://github.com/golang/protobuf 5// 6// Redistribution and use in source and binary forms, with or without 7// modification, are permitted provided that the following conditions are 8// met: 9// 10// * Redistributions of source code must retain the above copyright 11// notice, this list of conditions and the following disclaimer. 12// * Redistributions in binary form must reproduce the above 13// copyright notice, this list of conditions and the following disclaimer 14// in the documentation and/or other materials provided with the 15// distribution. 16// * Neither the name of Google Inc. nor the names of its 17// contributors may be used to endorse or promote products derived from 18// this software without specific prior written permission. 19// 20// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 23// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 24// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 25// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 26// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 27// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 28// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 29// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 30// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 31 32// Package descriptor provides functions for obtaining protocol buffer 33// descriptors for generated Go types. 34// 35// These functions cannot go in package proto because they depend on the 36// generated protobuf descriptor messages, which themselves depend on proto. 37package descriptor 38 39import ( 40 "bytes" 41 "compress/gzip" 42 "fmt" 43 "io/ioutil" 44 45 "github.com/golang/protobuf/proto" 46 protobuf "github.com/golang/protobuf/protoc-gen-go/descriptor" 47) 48 49// extractFile extracts a FileDescriptorProto from a gzip'd buffer. 50func extractFile(gz []byte) (*protobuf.FileDescriptorProto, error) { 51 r, err := gzip.NewReader(bytes.NewReader(gz)) 52 if err != nil { 53 return nil, fmt.Errorf("failed to open gzip reader: %v", err) 54 } 55 defer r.Close() 56 57 b, err := ioutil.ReadAll(r) 58 if err != nil { 59 return nil, fmt.Errorf("failed to uncompress descriptor: %v", err) 60 } 61 62 fd := new(protobuf.FileDescriptorProto) 63 if err := proto.Unmarshal(b, fd); err != nil { 64 return nil, fmt.Errorf("malformed FileDescriptorProto: %v", err) 65 } 66 67 return fd, nil 68} 69 70// Message is a proto.Message with a method to return its descriptor. 71// 72// Message types generated by the protocol compiler always satisfy 73// the Message interface. 74type Message interface { 75 proto.Message 76 Descriptor() ([]byte, []int) 77} 78 79// ForMessage returns a FileDescriptorProto and a DescriptorProto from within it 80// describing the given message. 81func ForMessage(msg Message) (fd *protobuf.FileDescriptorProto, md *protobuf.DescriptorProto) { 82 gz, path := msg.Descriptor() 83 fd, err := extractFile(gz) 84 if err != nil { 85 panic(fmt.Sprintf("invalid FileDescriptorProto for %T: %v", msg, err)) 86 } 87 88 md = fd.MessageType[path[0]] 89 for _, i := range path[1:] { 90 md = md.NestedType[i] 91 } 92 return fd, md 93} 94