description.go

Documentation: github.com/gogo/protobuf/plugin/description

     1  // Protocol Buffers for Go with Gadgets
     2  //
     3  // Copyright (c) 2013, The GoGo Authors. All rights reserved.
     4  // http://github.com/gogo/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  //
    17  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
    18  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
    19  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
    20  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
    21  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    22  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    23  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
    24  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    25  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    26  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
    27  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
    28  
    29  /*
    30  The description (experimental) plugin generates a Description method for each message.
    31  The Description method returns a populated google_protobuf.FileDescriptorSet struct.
    32  This contains the description of the files used to generate this message.
    33  
    34  It is enabled by the following extensions:
    35  
    36    - description
    37    - description_all
    38  
    39  The description plugin also generates a test given it is enabled using one of the following extensions:
    40  
    41    - testgen
    42    - testgen_all
    43  
    44  Let us look at:
    45  
    46    github.com/gogo/protobuf/test/example/example.proto
    47  
    48  Btw all the output can be seen at:
    49  
    50    github.com/gogo/protobuf/test/example/*
    51  
    52  The following message:
    53  
    54    message B {
    55  	option (gogoproto.description) = true;
    56  	optional A A = 1 [(gogoproto.nullable) = false, (gogoproto.embed) = true];
    57  	repeated bytes G = 2 [(gogoproto.customtype) = "github.com/gogo/protobuf/test/custom.Uint128", (gogoproto.nullable) = false];
    58    }
    59  
    60  given to the description plugin, will generate the following code:
    61  
    62    func (this *B) Description() (desc *google_protobuf.FileDescriptorSet) {
    63  	return ExampleDescription()
    64    }
    65  
    66  and the following test code:
    67  
    68    func TestDescription(t *testing9.T) {
    69  	ExampleDescription()
    70    }
    71  
    72  The hope is to use this struct in some way instead of reflect.
    73  This package is subject to change, since a use has not been figured out yet.
    74  
    75  */
    76  package description
    77  
    78  import (
    79  	"bytes"
    80  	"compress/gzip"
    81  	"fmt"
    82  	"github.com/gogo/protobuf/gogoproto"
    83  	"github.com/gogo/protobuf/proto"
    84  	descriptor "github.com/gogo/protobuf/protoc-gen-gogo/descriptor"
    85  	"github.com/gogo/protobuf/protoc-gen-gogo/generator"
    86  )
    87  
    88  type plugin struct {
    89  	*generator.Generator
    90  	generator.PluginImports
    91  }
    92  
    93  func NewPlugin() *plugin {
    94  	return &plugin{}
    95  }
    96  
    97  func (p *plugin) Name() string {
    98  	return "description"
    99  }
   100  
   101  func (p *plugin) Init(g *generator.Generator) {
   102  	p.Generator = g
   103  }
   104  
   105  func (p *plugin) Generate(file *generator.FileDescriptor) {
   106  	used := false
   107  	localName := generator.FileName(file)
   108  
   109  	p.PluginImports = generator.NewPluginImports(p.Generator)
   110  	descriptorPkg := p.NewImport("github.com/gogo/protobuf/protoc-gen-gogo/descriptor")
   111  	protoPkg := p.NewImport("github.com/gogo/protobuf/proto")
   112  	gzipPkg := p.NewImport("compress/gzip")
   113  	bytesPkg := p.NewImport("bytes")
   114  	ioutilPkg := p.NewImport("io/ioutil")
   115  
   116  	for _, message := range file.Messages() {
   117  		if !gogoproto.HasDescription(file.FileDescriptorProto, message.DescriptorProto) {
   118  			continue
   119  		}
   120  		if message.DescriptorProto.GetOptions().GetMapEntry() {
   121  			continue
   122  		}
   123  		used = true
   124  		ccTypeName := generator.CamelCaseSlice(message.TypeName())
   125  		p.P(`func (this *`, ccTypeName, `) Description() (desc *`, descriptorPkg.Use(), `.FileDescriptorSet) {`)
   126  		p.In()
   127  		p.P(`return `, localName, `Description()`)
   128  		p.Out()
   129  		p.P(`}`)
   130  	}
   131  
   132  	if used {
   133  
   134  		p.P(`func `, localName, `Description() (desc *`, descriptorPkg.Use(), `.FileDescriptorSet) {`)
   135  		p.In()
   136  		//Don't generate SourceCodeInfo, since it will create too much code.
   137  
   138  		ss := make([]*descriptor.SourceCodeInfo, 0)
   139  		for _, f := range p.Generator.AllFiles().GetFile() {
   140  			ss = append(ss, f.SourceCodeInfo)
   141  			f.SourceCodeInfo = nil
   142  		}
   143  		b, err := proto.Marshal(p.Generator.AllFiles())
   144  		if err != nil {
   145  			panic(err)
   146  		}
   147  		for i, f := range p.Generator.AllFiles().GetFile() {
   148  			f.SourceCodeInfo = ss[i]
   149  		}
   150  		p.P(`d := &`, descriptorPkg.Use(), `.FileDescriptorSet{}`)
   151  		var buf bytes.Buffer
   152  		w, _ := gzip.NewWriterLevel(&buf, gzip.BestCompression)
   153  		w.Write(b)
   154  		w.Close()
   155  		b = buf.Bytes()
   156  		p.P("var gzipped = []byte{")
   157  		p.In()
   158  		p.P("// ", len(b), " bytes of a gzipped FileDescriptorSet")
   159  		for len(b) > 0 {
   160  			n := 16
   161  			if n > len(b) {
   162  				n = len(b)
   163  			}
   164  
   165  			s := ""
   166  			for _, c := range b[:n] {
   167  				s += fmt.Sprintf("0x%02x,", c)
   168  			}
   169  			p.P(s)
   170  
   171  			b = b[n:]
   172  		}
   173  		p.Out()
   174  		p.P("}")
   175  		p.P(`r := `, bytesPkg.Use(), `.NewReader(gzipped)`)
   176  		p.P(`gzipr, err := `, gzipPkg.Use(), `.NewReader(r)`)
   177  		p.P(`if err != nil {`)
   178  		p.In()
   179  		p.P(`panic(err)`)
   180  		p.Out()
   181  		p.P(`}`)
   182  		p.P(`ungzipped, err := `, ioutilPkg.Use(), `.ReadAll(gzipr)`)
   183  		p.P(`if err != nil {`)
   184  		p.In()
   185  		p.P(`panic(err)`)
   186  		p.Out()
   187  		p.P(`}`)
   188  		p.P(`if err := `, protoPkg.Use(), `.Unmarshal(ungzipped, d); err != nil {`)
   189  		p.In()
   190  		p.P(`panic(err)`)
   191  		p.Out()
   192  		p.P(`}`)
   193  		p.P(`return d`)
   194  		p.Out()
   195  		p.P(`}`)
   196  	}
   197  }
   198  
   199  func init() {
   200  	generator.RegisterPlugin(NewPlugin())
   201  }
   202
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