From 99a5b20e5e4a5b194036fff4127118fedac83f97 Mon Sep 17 00:00:00 2001
From: Masaaki Goshima <goccy54@gmail.com>
Date: Tue, 25 Aug 2020 17:18:37 +0900
Subject: [PATCH] Fix decoding of recursive type

---
 decode.go         | 8 ++++++--
 decode_compile.go | 9 ++++++++-
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/decode.go b/decode.go
index d092057..56b9c24 100644
--- a/decode.go
+++ b/decode.go
@@ -23,6 +23,7 @@ type decoder interface {
 type Decoder struct {
 	s                     *stream
 	disallowUnknownFields bool
+	structTypeToDecoder   map[uintptr]decoder
 }
 
 type decoderMap struct {
@@ -61,7 +62,9 @@ const (
 func NewDecoder(r io.Reader) *Decoder {
 	s := &stream{r: r}
 	s.read()
-	return &Decoder{s: s}
+	return &Decoder{
+		s: s,
+	}
 }
 
 // Buffered returns a reader of the data remaining in the Decoder's
@@ -90,7 +93,7 @@ func (d *Decoder) decode(src []byte, header *interfaceHeader) error {
 	}
 	dec := cachedDecoder.get(typeptr)
 	if dec == nil {
-
+		d.structTypeToDecoder = map[uintptr]decoder{}
 		compiledDec, err := d.compileHead(copiedType)
 		if err != nil {
 			return err
@@ -155,6 +158,7 @@ func (d *Decoder) Decode(v interface{}) error {
 
 	dec := cachedDecoder.get(typeptr)
 	if dec == nil {
+		d.structTypeToDecoder = map[uintptr]decoder{}
 		compiledDec, err := d.compileHead(typ)
 		if err != nil {
 			return err
diff --git a/decode_compile.go b/decode_compile.go
index bb6ab06..1ed11aa 100644
--- a/decode_compile.go
+++ b/decode_compile.go
@@ -204,6 +204,12 @@ func (d *Decoder) compileInterface(typ *rtype) (decoder, error) {
 func (d *Decoder) compileStruct(typ *rtype) (decoder, error) {
 	fieldNum := typ.NumField()
 	fieldMap := map[string]*structFieldSet{}
+	typeptr := uintptr(unsafe.Pointer(typ))
+	if dec, exists := d.structTypeToDecoder[typeptr]; exists {
+		return dec, nil
+	}
+	structDec := newStructDecoder(fieldMap)
+	d.structTypeToDecoder[typeptr] = structDec
 	for i := 0; i < fieldNum; i++ {
 		field := typ.Field(i)
 		if isIgnoredStructField(field) {
@@ -222,5 +228,6 @@ func (d *Decoder) compileStruct(typ *rtype) (decoder, error) {
 		fieldMap[tag.key] = fieldSet
 		fieldMap[strings.ToLower(tag.key)] = fieldSet
 	}
-	return newStructDecoder(fieldMap), nil
+	delete(d.structTypeToDecoder, typeptr)
+	return structDec, nil
 }