syncthing/vendor/github.com/gogo/protobuf/plugin/union/union.go

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// Protocol Buffers for Go with Gadgets
//
// Copyright (c) 2013, The GoGo Authors. All rights reserved.
// http://github.com/gogo/protobuf
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
/*
The onlyone plugin generates code for the onlyone extension.
All fields must be nullable and only one of the fields may be set, like a union.
Two methods are generated
GetValue() interface{}
and
SetValue(v interface{}) (set bool)
These provide easier interaction with a onlyone.
The onlyone extension is not called union as this causes compile errors in the C++ generated code.
There can only be one ;)
It is enabled by the following extensions:
- onlyone
- onlyone_all
The onlyone plugin also generates a test given it is enabled using one of the following extensions:
- testgen
- testgen_all
Lets look at:
github.com/gogo/protobuf/test/example/example.proto
Btw all the output can be seen at:
github.com/gogo/protobuf/test/example/*
The following message:
message U {
option (gogoproto.onlyone) = true;
optional A A = 1;
optional B B = 2;
}
given to the onlyone plugin, will generate code which looks a lot like this:
func (this *U) GetValue() interface{} {
if this.A != nil {
return this.A
}
if this.B != nil {
return this.B
}
return nil
}
func (this *U) SetValue(value interface{}) bool {
switch vt := value.(type) {
case *A:
this.A = vt
case *B:
this.B = vt
default:
return false
}
return true
}
and the following test code:
func TestUUnion(t *testing.T) {
popr := math_rand.New(math_rand.NewSource(time.Now().UnixNano()))
p := NewPopulatedU(popr)
v := p.GetValue()
msg := &U{}
if !msg.SetValue(v) {
t.Fatalf("Union: Could not set Value")
}
if !p.Equal(msg) {
t.Fatalf("%#v !Union Equal %#v", msg, p)
}
}
*/
package union
import (
"github.com/gogo/protobuf/gogoproto"
"github.com/gogo/protobuf/protoc-gen-gogo/generator"
)
type union struct {
*generator.Generator
generator.PluginImports
}
func NewUnion() *union {
return &union{}
}
func (p *union) Name() string {
return "union"
}
func (p *union) Init(g *generator.Generator) {
p.Generator = g
}
func (p *union) Generate(file *generator.FileDescriptor) {
p.PluginImports = generator.NewPluginImports(p.Generator)
for _, message := range file.Messages() {
if !gogoproto.IsUnion(file.FileDescriptorProto, message.DescriptorProto) {
continue
}
if message.DescriptorProto.HasExtension() {
panic("onlyone does not currently support extensions")
}
if message.DescriptorProto.GetOptions().GetMapEntry() {
continue
}
ccTypeName := generator.CamelCaseSlice(message.TypeName())
p.P(`func (this *`, ccTypeName, `) GetValue() interface{} {`)
p.In()
for _, field := range message.Field {
fieldname := p.GetFieldName(message, field)
if fieldname == "Value" {
panic("cannot have a onlyone message " + ccTypeName + " with a field named Value")
}
p.P(`if this.`, fieldname, ` != nil {`)
p.In()
p.P(`return this.`, fieldname)
p.Out()
p.P(`}`)
}
p.P(`return nil`)
p.Out()
p.P(`}`)
p.P(``)
p.P(`func (this *`, ccTypeName, `) SetValue(value interface{}) bool {`)
p.In()
p.P(`switch vt := value.(type) {`)
p.In()
for _, field := range message.Field {
fieldname := p.GetFieldName(message, field)
goTyp, _ := p.GoType(message, field)
p.P(`case `, goTyp, `:`)
p.In()
p.P(`this.`, fieldname, ` = vt`)
p.Out()
}
p.P(`default:`)
p.In()
for _, field := range message.Field {
fieldname := p.GetFieldName(message, field)
if field.IsMessage() {
goTyp, _ := p.GoType(message, field)
obj := p.ObjectNamed(field.GetTypeName()).(*generator.Descriptor)
if gogoproto.IsUnion(obj.File(), obj.DescriptorProto) {
p.P(`this.`, fieldname, ` = new(`, generator.GoTypeToName(goTyp), `)`)
p.P(`if set := this.`, fieldname, `.SetValue(value); set {`)
p.In()
p.P(`return true`)
p.Out()
p.P(`}`)
p.P(`this.`, fieldname, ` = nil`)
}
}
}
p.P(`return false`)
p.Out()
p.P(`}`)
p.P(`return true`)
p.Out()
p.P(`}`)
}
}
func init() {
generator.RegisterPlugin(NewUnion())
}