Fix recursive type definition

encode.go

@@ -12,14 +12,20 @@ import (
 
 // An Encoder writes JSON values to an output stream.
 type Encoder struct {
-	w                 io.Writer
-	buf               []byte
-	pool              sync.Pool
-	enabledIndent     bool
-	enabledHTMLEscape bool
-	prefix            []byte
-	indentStr         []byte
-	indent            int
+	w                              io.Writer
+	buf                            []byte
+	pool                           sync.Pool
+	enabledIndent                  bool
+	enabledHTMLEscape              bool
+	prefix                         []byte
+	indentStr                      []byte
+	indent                         int
+	structTypeToCompiledCode       map[uintptr]*compiledCode
+	structTypeToCompiledIndentCode map[uintptr]*compiledCode
+}
+
+type compiledCode struct {
+	code *opcode
 }
 
 const (
@@ -58,8 +64,10 @@ func init() {
 	encPool = sync.Pool{
 		New: func() interface{} {
 			return &Encoder{
-				buf:  make([]byte, 0, bufSize),
-				pool: encPool,
+				buf:                            make([]byte, 0, bufSize),
+				pool:                           encPool,
+				structTypeToCompiledCode:       map[uintptr]*compiledCode{},
+				structTypeToCompiledIndentCode: map[uintptr]*compiledCode{},
 			}
 		},
 	}

encode_compile.go

@@ -747,6 +747,38 @@ func (e *Encoder) optimizeStructField(op opType, isOmitEmpty, withIndent bool) o
 }
 
 func (e *Encoder) compileStruct(typ *rtype, root, withIndent bool) (*opcode, error) {
+	typeptr := uintptr(unsafe.Pointer(typ))
+	if withIndent {
+		if compiled, exists := e.structTypeToCompiledCode[typeptr]; exists {
+			return (*opcode)(unsafe.Pointer(&recursiveCode{
+				opcodeHeader: &opcodeHeader{
+					op:     opStructFieldRecursive,
+					typ:    typ,
+					indent: e.indent,
+					next:   newEndOp(e.indent),
+				},
+				jmp: compiled,
+			})), nil
+		}
+	} else {
+		if compiled, exists := e.structTypeToCompiledIndentCode[typeptr]; exists {
+			return (*opcode)(unsafe.Pointer(&recursiveCode{
+				opcodeHeader: &opcodeHeader{
+					op:     opStructFieldRecursive,
+					typ:    typ,
+					indent: e.indent,
+					next:   newEndOp(e.indent),
+				},
+				jmp: compiled,
+			})), nil
+		}
+	}
+	compiled := &compiledCode{}
+	if withIndent {
+		e.structTypeToCompiledCode[typeptr] = compiled
+	} else {
+		e.structTypeToCompiledIndentCode[typeptr] = compiled
+	}
 	// header => code => structField => code => end
 	//                        ^          |
 	//                        |__________|
@@ -851,5 +883,7 @@ func (e *Encoder) compileStruct(typ *rtype, root, withIndent bool) (*opcode, err
 	head.end = structEndCode
 	code.next = structEndCode
 	structEndCode.next = newEndOp(e.indent)
-	return (*opcode)(unsafe.Pointer(head)), nil
+	ret := (*opcode)(unsafe.Pointer(head))
+	compiled.code = ret
+	return ret, nil
 }

encode_opcode.go

@@ -145,6 +145,8 @@ const (
 	opStructFieldPtrHeadString
 	opStructFieldPtrHeadBool
 
+	opStructFieldRecursive
+
 	opStructFieldPtrHeadIndent
 	opStructFieldPtrHeadIntIndent
 	opStructFieldPtrHeadInt8Indent
@@ -362,6 +364,8 @@ func (t opType) String() string {
 	case opMapEndIndent:
 		return "MAP_END_INDENT"
 
+	case opStructFieldRecursive:
+		return "STRUCT_FIELD_RECURSIVE"
 	case opStructFieldHead:
 		return "STRUCT_FIELD_HEAD"
 	case opStructFieldHeadInt:
@@ -831,6 +835,8 @@ func (c *opcode) copy(codeMap map[uintptr]*opcode) *opcode {
 		code = c.toMapKeyCode().copy(codeMap)
 	case opMapValue, opMapValueIndent:
 		code = c.toMapValueCode().copy(codeMap)
+	case opStructFieldRecursive:
+		code = c.toRecursiveCode().copy(codeMap)
 	case opStructFieldHead,
 		opStructFieldHeadInt,
 		opStructFieldHeadInt8,
@@ -1076,6 +1082,10 @@ func (c *opcode) toInterfaceCode() *interfaceCode {
 	return (*interfaceCode)(unsafe.Pointer(c))
 }
 
+func (c *opcode) toRecursiveCode() *recursiveCode {
+	return (*recursiveCode)(unsafe.Pointer(c))
+}
+
 type sliceHeaderCode struct {
 	*opcodeHeader
 	elem *sliceElemCode
@@ -1301,27 +1311,6 @@ func (c *mapKeyCode) set(len int, iter unsafe.Pointer) {
 	c.iter = iter
 }
 
-type interfaceCode struct {
-	*opcodeHeader
-	root bool
-}
-
-func (c *interfaceCode) copy(codeMap map[uintptr]*opcode) *opcode {
-	if c == nil {
-		return nil
-	}
-	addr := uintptr(unsafe.Pointer(c))
-	if code, exists := codeMap[addr]; exists {
-		return code
-	}
-	iface := &interfaceCode{}
-	code := (*opcode)(unsafe.Pointer(iface))
-	codeMap[addr] = code
-
-	iface.opcodeHeader = c.opcodeHeader.copy(codeMap)
-	return code
-}
-
 type mapValueCode struct {
 	*opcodeHeader
 	iter unsafe.Pointer
@@ -1382,3 +1371,48 @@ func newMapValueCode(indent int) *mapValueCode {
 		},
 	}
 }
+
+type interfaceCode struct {
+	*opcodeHeader
+	root bool
+}
+
+func (c *interfaceCode) copy(codeMap map[uintptr]*opcode) *opcode {
+	if c == nil {
+		return nil
+	}
+	addr := uintptr(unsafe.Pointer(c))
+	if code, exists := codeMap[addr]; exists {
+		return code
+	}
+	iface := &interfaceCode{}
+	code := (*opcode)(unsafe.Pointer(iface))
+	codeMap[addr] = code
+
+	iface.opcodeHeader = c.opcodeHeader.copy(codeMap)
+	return code
+}
+
+type recursiveCode struct {
+	*opcodeHeader
+	jmp *compiledCode
+}
+
+func (c *recursiveCode) copy(codeMap map[uintptr]*opcode) *opcode {
+	if c == nil {
+		return nil
+	}
+	addr := uintptr(unsafe.Pointer(c))
+	if code, exists := codeMap[addr]; exists {
+		return code
+	}
+	recur := &recursiveCode{}
+	code := (*opcode)(unsafe.Pointer(recur))
+	codeMap[addr] = code
+
+	recur.opcodeHeader = c.opcodeHeader.copy(codeMap)
+	recur.jmp = &compiledCode{
+		code: c.jmp.code.copy(codeMap),
+	}
+	return code
+}

encode_test.go

@@ -9,6 +9,15 @@ import (
 	"github.com/goccy/go-json"
 )
 
+type recursiveT struct {
+	A *recursiveT `json:"a,omitempty"`
+	B *recursiveU `json:"b,omitempty"`
+	C string      `json:"c,omitempty"`
+}
+type recursiveU struct {
+	T *recursiveT `json:"t,omitempty"`
+}
+
 func Test_Marshal(t *testing.T) {
 	t.Run("int", func(t *testing.T) {
 		bytes, err := json.Marshal(-10)
@@ -103,6 +112,19 @@ func Test_Marshal(t *testing.T) {
 			assertErr(t, err)
 			assertEq(t, "struct", `{"a":null}`, string(bytes))
 		})
+		t.Run("recursive", func(t *testing.T) {
+			bytes, err := json.Marshal(recursiveT{
+				A: &recursiveT{
+					B: &recursiveU{
+						T: &recursiveT{
+							C: "hello",
+						},
+					},
+				},
+			})
+			assertErr(t, err)
+			assertEq(t, "recursive", `{"a":{"b":{"t":{"c":"hello"}}}}`, string(bytes))
+		})
 		t.Run("omitempty", func(t *testing.T) {
 			type T struct {
 				A int                    `json:",omitempty"`

encode_vm.go

@@ -458,6 +458,14 @@ func (e *Encoder) run(code *opcode) error {
 			c.next.ptr = uintptr(value)
 			mapiternext(c.iter)
 			code = c.next
+		case opStructFieldRecursive:
+			recursive := code.toRecursiveCode()
+			c := copyOpcode(recursive.jmp.code)
+			c.ptr = recursive.ptr
+			if err := e.run(c); err != nil {
+				return err
+			}
+			code = recursive.next
 		case opStructFieldPtrHead:
 			if code.ptr != 0 {
 				code.ptr = e.ptrToPtr(code.ptr)