codec: change field switch code

The code for decoding struct fields is now a switch with contiguous
constants.

Although the Go compiler doesn't yet generate jump tables, it
hopefully will someday (golang/go#5496), and these switches will get
faster.

Also, fix registration of benchmark types.

internal/benchmarks/data/ast.go

@@ -21,60 +21,60 @@ import (
 var ASTData = gobBenchmarkData("ast", func() interface{} { return new(map[string]*ast.File) })
 
 var astTypes = []interface{}{
-	ast.ArrayType{},
-	ast.AssignStmt{},
-	ast.BadDecl{},
-	ast.BadExpr{},
-	ast.BadStmt{},
-	ast.BasicLit{},
-	ast.BinaryExpr{},
-	ast.BlockStmt{},
-	ast.BranchStmt{},
-	ast.CallExpr{},
-	ast.CaseClause{},
-	ast.ChanType{},
-	ast.CommClause{},
-	ast.CommentGroup{},
-	ast.Comment{},
-	ast.CompositeLit{},
-	ast.DeclStmt{},
-	ast.DeferStmt{},
-	ast.Ellipsis{},
-	ast.EmptyStmt{},
-	ast.ExprStmt{},
-	ast.FieldList{},
-	ast.Field{},
-	ast.ForStmt{},
-	ast.FuncDecl{},
-	ast.FuncLit{},
-	ast.FuncType{},
-	ast.GenDecl{},
-	ast.GoStmt{},
-	ast.Ident{},
-	ast.IfStmt{},
-	ast.ImportSpec{},
-	ast.IncDecStmt{},
-	ast.IndexExpr{},
-	ast.InterfaceType{},
-	ast.KeyValueExpr{},
-	ast.LabeledStmt{},
-	ast.MapType{},
-	ast.ParenExpr{},
-	ast.RangeStmt{},
-	ast.ReturnStmt{},
-	ast.Scope{},
-	ast.SelectStmt{},
-	ast.SelectorExpr{},
-	ast.SendStmt{},
-	ast.SliceExpr{},
-	ast.StarExpr{},
-	ast.StructType{},
-	ast.SwitchStmt{},
-	ast.TypeAssertExpr{},
-	ast.TypeSpec{},
-	ast.TypeSwitchStmt{},
-	ast.UnaryExpr{},
-	ast.ValueSpec{},
+	&ast.ArrayType{},
+	&ast.AssignStmt{},
+	&ast.BadDecl{},
+	&ast.BadExpr{},
+	&ast.BadStmt{},
+	&ast.BasicLit{},
+	&ast.BinaryExpr{},
+	&ast.BlockStmt{},
+	&ast.BranchStmt{},
+	&ast.CallExpr{},
+	&ast.CaseClause{},
+	&ast.ChanType{},
+	&ast.CommClause{},
+	&ast.CommentGroup{},
+	&ast.Comment{},
+	&ast.CompositeLit{},
+	&ast.DeclStmt{},
+	&ast.DeferStmt{},
+	&ast.Ellipsis{},
+	&ast.EmptyStmt{},
+	&ast.ExprStmt{},
+	&ast.FieldList{},
+	&ast.Field{},
+	&ast.ForStmt{},
+	&ast.FuncDecl{},
+	&ast.FuncLit{},
+	&ast.FuncType{},
+	&ast.GenDecl{},
+	&ast.GoStmt{},
+	&ast.Ident{},
+	&ast.IfStmt{},
+	&ast.ImportSpec{},
+	&ast.IncDecStmt{},
+	&ast.IndexExpr{},
+	&ast.InterfaceType{},
+	&ast.KeyValueExpr{},
+	&ast.LabeledStmt{},
+	&ast.MapType{},
+	&ast.ParenExpr{},
+	&ast.RangeStmt{},
+	&ast.ReturnStmt{},
+	&ast.Scope{},
+	&ast.SelectStmt{},
+	&ast.SelectorExpr{},
+	&ast.SendStmt{},
+	&ast.SliceExpr{},
+	&ast.StarExpr{},
+	&ast.StructType{},
+	&ast.SwitchStmt{},
+	&ast.TypeAssertExpr{},
+	&ast.TypeSpec{},
+	&ast.TypeSwitchStmt{},
+	&ast.UnaryExpr{},
+	&ast.ValueSpec{},
 }
 
 func init() {

internal/benchmarks/data/data.go

@@ -68,7 +68,7 @@ func Generate(words []string) error {
 		switch w {
 		case "code":
 			err = codec.GenerateFile("types.gen.go", thisPkgPath, nil,
-				LicenseData{}, submittedData{}, []*StockData(nil), []Score(nil))
+				&LicenseData{}, submittedData{}, []*StockData(nil), []Score(nil))
 			if err == nil {
 				err = codec.GenerateFile("ast_types.gen.go", thisPkgPath, nil,
 					append(astTypes, map[string]*ast.File{})...)

struct.tmpl

@@ -67,18 +67,21 @@ func (c *«$typeName») Decode(d *codecapi.Decoder) interface{} {
 
 func (c *«$typeName») decode(d *codecapi.Decoder, x *«$goName») {
 	d.StartStruct()
-	for {
+	loop: for {
 		n := d.NextStructField(c.fieldMap)
-		if n == -1 { break }
 		switch n {
 		«range $i, $f := .Fields -»
 			«- if $f.Type -»
-				case «$i»:
-		        «decodeStmt $f.Type (print "x." $f.Name)»
+			   case «$i»:
+				«decodeStmt $f.Type (print "x." $f.Name)»
 			«end -»
 		«end -»
-		default:
+		case -1:
+			break loop
+		case -2:
 			d.UnknownField("«$goName»", n)
+		default:
+			codecapi.Failf("bad struct field value: %d", n)
 		}
 	}
 }