94 lines
3.3 KiB
Go
94 lines
3.3 KiB
Go
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// Go support for Protocol Buffers - Google's data interchange format
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//
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// Copyright 2016 The Go Authors. All rights reserved.
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// https://github.com/golang/protobuf
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following disclaimer
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// in the documentation and/or other materials provided with the
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// distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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// Package descriptor provides functions for obtaining protocol buffer
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// descriptors for generated Go types.
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//
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// These functions cannot go in package proto because they depend on the
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// generated protobuf descriptor messages, which themselves depend on proto.
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package descriptor
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import (
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"bytes"
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"compress/gzip"
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"fmt"
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"io/ioutil"
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"github.com/golang/protobuf/proto"
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protobuf "google.golang.org/genproto/protobuf"
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)
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// extractFile extracts a FileDescriptorProto from a gzip'd buffer.
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func extractFile(gz []byte) (*protobuf.FileDescriptorProto, error) {
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r, err := gzip.NewReader(bytes.NewReader(gz))
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if err != nil {
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return nil, fmt.Errorf("failed to open gzip reader: %v", err)
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}
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defer r.Close()
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b, err := ioutil.ReadAll(r)
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if err != nil {
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return nil, fmt.Errorf("failed to uncompress descriptor: %v", err)
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}
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fd := new(protobuf.FileDescriptorProto)
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if err := proto.Unmarshal(b, fd); err != nil {
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return nil, fmt.Errorf("malformed FileDescriptorProto: %v", err)
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}
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return fd, nil
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}
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// Message is a proto.Message with a method to return its descriptor.
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//
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// Message types generated by the protocol compiler always satisfy
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// the Message interface.
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type Message interface {
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proto.Message
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Descriptor() ([]byte, []int)
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}
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// ForMessage returns a FileDescriptorProto and a DescriptorProto from within it
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// describing the given message.
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func ForMessage(msg Message) (fd *protobuf.FileDescriptorProto, md *protobuf.DescriptorProto) {
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gz, path := msg.Descriptor()
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fd, err := extractFile(gz)
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if err != nil {
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panic(fmt.Sprintf("invalid FileDescriptorProto for %T: %v", msg, err))
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}
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md = fd.MessageType[path[0]]
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for _, i := range path[1:] {
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md = md.NestedType[i]
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}
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return fd, md
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}
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