From c1d2e38840c0596efd10e97ff5a9edaa20d5457e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C5=99emysl=20Eric=20Janouch?= <p@janouch.name>
Date: Wed, 14 Sep 2022 04:29:31 +0200
Subject: [PATCH] xP: generate our own JSON marshallers

For non-trivial types, which are expensive to serialize
with encoding/json's struct reflection.
---
 xC-gen-proto-go.awk | 67 +++++++++++++++++++++++++++++++++++++++++----
 xP/xP.go            |  6 ++--
 2 files changed, 65 insertions(+), 8 deletions(-)

diff --git a/xC-gen-proto-go.awk b/xC-gen-proto-go.awk
index 4220ccc..eb08477 100644
--- a/xC-gen-proto-go.awk
+++ b/xC-gen-proto-go.awk
@@ -206,13 +206,14 @@ function codegen_enum(name, cg,    gotype, fields) {
 	print "}"
 	print ""
 
+	CodegenIsMarshaler[name] = 1
 	fields = cg["marshal"]
 	sub(/,\n$/, ":", fields)
 	gsub(/\n/, "\n\t", fields)
 	print "func (v " gotype ") MarshalJSON() ([]byte, error) {"
 	print "\tswitch v {"
 	print indent("case " fields)
-	print "\t\treturn json.Marshal(v.String())"
+	print "\t\treturn []byte(`\"` + v.String() + `\"`), nil"
 	print "\t}"
 	print "\treturn json.Marshal(int(v))"
 	print "}"
@@ -252,7 +253,50 @@ function codegen_enum(name, cg,    gotype, fields) {
 		delete cg[i]
 }
 
+function codegen_struct_field_marshal(d, cg,    camel, f, marshal) {
+	camel = snaketocamel(d["name"])
+	f = "s." camel
+
+	# Complex types are json.Marshalers, there's no need to json.Marshal(&f).
+	if (!d["isarray"]) {
+		if (CodegenIsMarshaler[d["type"]])
+			marshal = f ".MarshalJSON()"
+		else
+			marshal = "json.Marshal(" f ")"
+
+		append(cg, "marshal",
+			"\tb = append(b, `,\"" decapitalize(camel) "\":`...)\n" \
+			"\tif j, err := " marshal "; err != nil {\n" \
+			"\t\treturn nil, err\n" \
+			"\t} else {\n" \
+			"\t\tb = append(b, j...)\n" \
+			"\t}\n")
+		return
+	}
+
+	if (CodegenIsMarshaler[d["type"]])
+		marshal = f "[i].MarshalJSON()"
+	else
+		marshal = "json.Marshal(" f "[i])"
+
+	append(cg, "marshal",
+		"\tb = append(b, `,\"" decapitalize(camel) "\":[`...)\n" \
+		"\tfor i := 0; i < len(" f "); i++ {\n" \
+		"\t\tif i > 0 {\n" \
+		"\t\t\tb = append(b, ',')\n" \
+		"\t\t}\n" \
+		"\t\tif j, err := " marshal "; err != nil {\n" \
+		"\t\t\treturn nil, err\n" \
+		"\t\t} else {\n" \
+		"\t\t\tb = append(b, j...)\n" \
+		"\t\t}\n" \
+		"\t}\n" \
+		"\tb = append(b, ']')\n")
+}
+
 function codegen_struct_field(d, cg,    camel, f, serialize, deserialize) {
+	codegen_struct_field_marshal(d, cg)
+
 	camel = snaketocamel(d["name"])
 	f = "s." camel
 	serialize = CodegenSerialize[d["type"]]
@@ -303,6 +347,8 @@ function codegen_struct_field(d, cg,    camel, f, serialize, deserialize) {
 }
 
 function codegen_struct_tag(d, cg,    camel, f) {
+	codegen_struct_field_marshal(d, cg)
+
 	camel = snaketocamel(d["name"])
 	f = "s." camel
 	append(cg, "fields", "\t" camel " " CodegenGoType[d["type"]] \
@@ -315,6 +361,16 @@ function codegen_struct(name, cg,    gotype) {
 	gotype = PrefixCamel name
 	print "type " gotype " struct {\n" cg["fields"] "}\n"
 
+	if (cg["marshal"]) {
+		CodegenIsMarshaler[name] = 1
+		print "func (s *" gotype ") MarshalJSON() ([]byte, error) {"
+		print "\tb := []byte{}"
+		print cg["marshal"] "\tb[0] = '{'"
+		print "\treturn append(b, '}'), nil"
+		print "}"
+		print ""
+	}
+
 	if (cg["serialize"]) {
 		print "func (s *" gotype ") AppendTo(data []byte) ([]byte, bool) {"
 		print "\tok := true"
@@ -362,15 +418,15 @@ function codegen_union_struct(name, casename, cg, scg,     structname, init) {
 		"\tcase " CodegenGoType[cg["tagtype"]] snaketocamel(casename) ":\n" \
 		"\t\ts := " init "\n" \
 		"\t\terr = json.Unmarshal(data, &s)\n" \
-		"\t\tu.Interface = s\n")
+		"\t\tu.Interface = &s\n")
 	append(cg, "serialize",
-		"\tcase " CodegenGoType[structname] ":\n" \
+		"\tcase *" CodegenGoType[structname] ":\n" \
 		indent(sprintf(CodegenSerialize[structname], "union")))
 	append(cg, "deserialize",
 		"\tcase " CodegenGoType[cg["tagtype"]] snaketocamel(casename) ":\n" \
 		"\t\ts := " init "\n" \
 		indent(sprintf(CodegenDeserialize[structname], "s")) \
-		"\t\tu.Interface = s\n")
+		"\t\tu.Interface = &s\n")
 }
 
 function codegen_union(name, cg,    gotype, tagfield, tagvar) {
@@ -381,8 +437,9 @@ function codegen_union(name, cg,    gotype, tagfield, tagvar) {
 	print ""
 
 	# This cannot be a pointer method, it wouldn't work recursively.
+	CodegenIsMarshaler[name] = 1
 	print "func (u " gotype ") MarshalJSON() ([]byte, error) {"
-	print "\treturn json.Marshal(u.Interface)"
+	print "\treturn u.Interface.(json.Marshaler).MarshalJSON()"
 	print "}"
 	print ""
 
diff --git a/xP/xP.go b/xP/xP.go
index dc5aa5e..2d6e096 100644
--- a/xP/xP.go
+++ b/xP/xP.go
@@ -50,7 +50,7 @@ func relayReadJSON(conn net.Conn) []byte {
 		return nil
 	}
 
-	j, err := json.Marshal(&m)
+	j, err := m.MarshalJSON()
 	if err != nil {
 		log.Println("Event marshalling failed: " + err.Error())
 		return nil
@@ -126,7 +126,7 @@ func clientWriteJSON(ctx context.Context, ws *websocket.Conn, j []byte) bool {
 }
 
 func clientWriteError(ctx context.Context, ws *websocket.Conn, err error) bool {
-	j, err := json.Marshal(&RelayEventMessage{
+	j, err := (&RelayEventMessage{
 		EventSeq: 0,
 		Data: RelayEventData{
 			Interface: RelayEventDataError{
@@ -135,7 +135,7 @@ func clientWriteError(ctx context.Context, ws *websocket.Conn, err error) bool {
 				Error:      err.Error(),
 			},
 		},
-	})
+	}).MarshalJSON()
 	if err != nil {
 		log.Println("Event marshalling failed: " + err.Error())
 		return false