[New go generator] Implement declaring unions.

mojom/generators/go/templates/unions.go

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package templates
+
+import (
+        "text/template"
+)
+
+const unionTmplText = `
+{{- define "Union" -}}
+{{- $union := . }}
+{{ template "UnionInterfaceDecl" $union }}
+
+{{ template "UnknownUnionFieldDecl" $union }}
+{{ template "UnknownUnionFieldEncode" $union }}
+
+{{- range $field := $union.Field}}
+{{ template "UnionFieldDecl" $field }}
+
+{{ template "UnionFieldEncode" $field }}
+
+{{ template "UnionFieldDecode" $field }}
+{{- end}}
+
+{{ template "UnionDecode" $union }}
+
+{{- end -}}
+`
+
+const unionInterfaceDeclTmplText = `
+{{- define "UnionInterfaceDecl" -}}
+{{$union := . -}}
+type {{$union.Name}} interface {
+        Tag() uint32
+        Interface() interface{}
+        __Reflect(__SomeUnionReflect)
+        Encode(encoder *bindings.Encoder) error
+}
+
+type __{{$union.Name}}Reflect struct {
+{{- range $field := $union.Fields}}
+        {{$field.Name}} {{$field.Type}}
+{{- end}}
+}
+{{- end -}}
+`
+
+const unionFieldDeclTmplText = `
+{{- define "UnionFieldDecl" -}}
+{{$field := . -}}
+{{$unionName := $field.Union.Name -}}
+type {{$unionName}}{{$field.Name}} struct{ Value {{$field.Type}} }
+func (u *{{$unionName}}{{$field.Name}}) Tag() uint32 { return {{$field.Tag}} }
+func (u *{{$unionName}}{{$field.Name}}) Interface() interface{} { return u.Value }
+func (u *{{$unionName}}{{$field.Name}}) __Reflect(__{{$unionName}}Reflect) {}
+{{- end -}}
+`
+
+const unionFieldEncodeTmplText = `
+{{- define "UnionFieldEncode" -}}
+{{$field := . -}}
+{{$unionName := $field.Union.Name -}}
+func (u *{{$unionName}}{{$field.Name}}) Encode(encoder *bindings.Encoder) error {
+        encoder.WriteUnionHeader(u.Tag())
+        {{ template "FieldEncodingTmpl" $field.EncodingInfo }}
+        
+        encoder.FinishWritingUnionValue()
+        return nil
+}
+{{- end -}}
+`
+
+const unknownUnionFieldDeclTmplText = `
+{{- define "UnknownUnionFieldDecl" -}}
+{{$union := . -}}
+type {{$union.Name}}Unknown struct { tag uint32 }
+func (u *{{$union.Name}}Unknown) Tag() uint32 { return u.tag }
+func (u *{{$union.Name}}Unknown) Interface() interface{} { return nil }
+func (u *{{$union.Name}}Unknown) __Reflect(__{{$union.Name}}Reflect) {}
+{{- end -}}
+`
+
+const unknownUnionFieldEncodeTmplText = `
+{{- define "UnknownUnionFieldEncode" -}}
+{{$union := . -}}
+func (u *{{$union.Name}}Unknown) Encode(encoder *bindings.Encoder) error {
+        return fmt.Errorf("Trying to serialize an unknown {{$union.Name}}. There is no sane way to do that!");
+}
+{{- end -}}
+`
+
+const unionFieldDecodeTmplText = `
+{{- define "UnionFieldDecode" -}}
+{{$field := . -}}
+{{$unionName := $field.Union.Name -}}
+func (u *{{$unionName}}{{$field.Name}}) decodeInternal(decoder *bindings.Decoder) error {
+        {{ template "FieldDecodingTmpl" $field.EncodingInfo }}
+
+        return nil
+}
+{{- end -}}
+`
+
+const unionDecodeTmplText = `
+{{- define "UnionDecode" -}}
+{{$union := . -}}
+func Decode{{$union.Name}}(decoder *bindings.Decoder) ({{$union.Name}}, error) {
+        size, tag, err := decoder.ReadUnionHeader()
+        if err != nil {
+                return nil, err
+        }
+
+        if size == 0 {
+                decoder.SkipUnionValue()
+                return nil, nil
+        }
+
+        switch tag {
+{{- range $field := $union.Fields}}
+        case {{$field.Tag}}:
+                var value {{$union.Name}}{{$field.Name}}
+                if err := value.decodeInternal(decoder); err != nil {
+                        return nil, err
+                }
+                decoder.FinishReadingUnionValue()
+                return &value, nil
+{{- end -}}
+        }
+
+        decoder.SkipUnionValue()
+        return &{{$union.Name}}Unknown{tag: tag}, nil
+}
+{{- end -}}
+`
+
+func initUnionTemplates() {
+        template.Must(goFileTmpl.Parse(unionTmplText))
+        template.Must(goFileTmpl.Parse(unionInterfaceDeclTmplText))
+        template.Must(goFileTmpl.Parse(unionFieldDeclTmplText))
+        template.Must(goFileTmpl.Parse(unknownUnionFieldDeclTmplText))
+        template.Must(goFileTmpl.Parse(unknownUnionFieldEncodeTmplText))
+        template.Must(goFileTmpl.Parse(unionFieldEncodeTmplText))
+        template.Must(goFileTmpl.Parse(unionFieldDecodeTmplText))
+        template.Must(goFileTmpl.Parse(unionDecodeTmplText))
+}