[New go generator] Implement declaring unions.

mojom/generators/go/templates/structs.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 structTmplText = `
+{{- define "Struct" -}}
+{{$struct := . -}}
+{{ template "StructDecl" $struct }}
+
+{{ template "StructEncodingTmpl" $struct }}
+
+{{ template "StructVersions" $struct }}
+
+{{ template "StructDecodingTmpl" $struct }}
+{{- end -}}
+`
+
+const structDeclTmplText = `
+{{- define "StructDecl" -}}
+{{$struct := . -}}
+type {{$struct.Name}} struct {
+{{- range $field := $struct.Fields}}
+        {{$field.Name}} {{$field.Type}}
+{{- end}}
+}
+{{- end -}}
+`
+
+const structEncodingTmplText = `
+{{- define "StructEncodingTmpl" -}}
+{{ $struct := . }}
+func (s *{{$struct.Name}}) Encode(encoder *bindings.Encoder) error {
+        encoder.StartStruct({{$struct.CurVersionSize}}, {{$struct.CurVersionNumber}})
+        {{- range $field := $struct.Fields}}
+                {{ template "FieldEncodingTmpl" $field.EncodingInfo }}
+        {{- end}}
+
+        if err := encoder.Finish(); err != nil {
+                return err
+        }
+        return nil
+}
+{{- end -}}
+`
+
+const structVersions = `
+{{- define "StructVersions" -}}
+{{- $struct := . -}}
+var {{$struct.PrivateName}}_Versions []bindings.DataHeader = []bindings.DataHeader{
+        {{- range $version := $struct.Versions}}
+        bindings.DataHeader{ {{$version.NumBytes}}, {{$version.Version}} },
+        {{- end}}
+}
+{{- end -}}
+`
+
+const structDecodingTmplText = `
+{{- define "StructDecodingTmpl" -}}
+{{- $struct := . -}}
+func (s *{{$struct.Name}}) Decode(decoder *bindings.Decoder) error {
+        header, err := decoder.StartStruct()
+        if err != nil {
+                return err
+        }
+
+        index := sort.Search(len({{$struct.PrivateName}}_Versions), func(i int) bool {
+                return {{$struct.PrivateName}}_Versions[i].ElementsOrVersion >= header.ElementsOrVersion
+        })
+        if index < len({{$struct.PrivateName}}_Versions) {
+                if {{$struct.PrivateName}}_Versions[index].ElementsOrVersion > header.ElementsOrVersion {
+                        index--
+                }
+                expectedSize := {{$struct.PrivateName}}_Versions[index].Size
+                if expectedSize != header.Size {
+                        return &bindings.ValidationError{bindings.UnexpectedStructHeader,
+                                fmt.Sprintf("invalid struct header size: should be %d, but was %d", expectedSize, header.Size),
+                        }
+                }
+        }
+
+        {{- range $field := $struct.Fields}}
+        if header.ElementsOrVersion >= {{$field.MinVersion}} {
+                {{ template "FieldDecodingTmpl" $field.EncodingInfo }}
+        }
+        {{- end}}
+}
+{{- end -}}
+`
+
+func initStructTemplates() {
+        template.Must(goFileTmpl.Parse(structEncodingTmplText))
+        template.Must(goFileTmpl.Parse(structDeclTmplText))
+        template.Must(goFileTmpl.Parse(structVersions))
+        template.Must(goFileTmpl.Parse(structDecodingTmplText))
+}