From 3f90e88a94115844ead9a0b4e44fdefa8e312ed2 Mon Sep 17 00:00:00 2001
From: Masaaki Goshima <goccy54@gmail.com>
Date: Thu, 11 Feb 2021 00:45:38 +0900
Subject: [PATCH] Refactor Unmarshal/UnmarshalNoEscape

---
 decode.go | 89 +++++++++++++++++++++++++++++--------------------------
 json.go   | 10 ++-----
 2 files changed, 49 insertions(+), 50 deletions(-)

diff --git a/decode.go b/decode.go
index 6abb85f..86cacbb 100644
--- a/decode.go
+++ b/decode.go
@@ -20,8 +20,7 @@ type decoder interface {
 }
 
 type Decoder struct {
-	s                   *stream
-	structTypeToDecoder map[uintptr]decoder
+	s *stream
 }
 
 var (
@@ -33,6 +32,51 @@ const (
 	nul = '\000'
 )
 
+func unmarshal(data []byte, v interface{}) error {
+	src := make([]byte, len(data)+1) // append nul byte to the end
+	copy(src, data)
+
+	header := (*interfaceHeader)(unsafe.Pointer(&v))
+	header.typ.escape()
+	return decode(src, header)
+}
+
+func unmarshalNoEscape(data []byte, v interface{}) error {
+	src := make([]byte, len(data)+1) // append nul byte to the end
+	copy(src, data)
+
+	header := (*interfaceHeader)(unsafe.Pointer(&v))
+	return decode(src, header)
+}
+
+func decode(src []byte, header *interfaceHeader) error {
+	typ := header.typ
+	typeptr := uintptr(unsafe.Pointer(typ))
+
+	// noescape trick for header.typ ( *reflect.rtype )
+	copiedType := *(**rtype)(unsafe.Pointer(&typeptr))
+	ptr := uintptr(header.ptr)
+
+	if err := validateType(copiedType, ptr); err != nil {
+		return err
+	}
+	dec, err := decodeCompileToGetDecoder(typeptr, typ)
+	if err != nil {
+		return err
+	}
+	if _, err := dec.decode(src, 0, header.ptr); err != nil {
+		return err
+	}
+	return nil
+}
+
+func validateType(typ *rtype, p uintptr) error {
+	if typ.Kind() != reflect.Ptr || p == 0 {
+		return &InvalidUnmarshalError{Type: rtype2type(typ)}
+	}
+	return nil
+}
+
 // NewDecoder returns a new decoder that reads from r.
 //
 // The decoder introduces its own buffering and may
@@ -50,45 +94,6 @@ func (d *Decoder) Buffered() io.Reader {
 	return d.s.buffered()
 }
 
-func (d *Decoder) validateType(typ *rtype, p uintptr) error {
-	if typ.Kind() != reflect.Ptr || p == 0 {
-		return &InvalidUnmarshalError{Type: rtype2type(typ)}
-	}
-	return nil
-}
-
-func (d *Decoder) decode(src []byte, header *interfaceHeader) error {
-	typ := header.typ
-	typeptr := uintptr(unsafe.Pointer(typ))
-
-	// noescape trick for header.typ ( reflect.*rtype )
-	copiedType := *(**rtype)(unsafe.Pointer(&typeptr))
-	ptr := uintptr(header.ptr)
-
-	if err := d.validateType(copiedType, ptr); err != nil {
-		return err
-	}
-	dec, err := decodeCompileToGetDecoder(typeptr, typ)
-	if err != nil {
-		return err
-	}
-	if _, err := dec.decode(src, 0, header.ptr); err != nil {
-		return err
-	}
-	return nil
-}
-
-func (d *Decoder) decodeForUnmarshal(src []byte, v interface{}) error {
-	header := (*interfaceHeader)(unsafe.Pointer(&v))
-	header.typ.escape()
-	return d.decode(src, header)
-}
-
-func (d *Decoder) decodeForUnmarshalNoEscape(src []byte, v interface{}) error {
-	header := (*interfaceHeader)(unsafe.Pointer(&v))
-	return d.decode(src, header)
-}
-
 func (d *Decoder) prepareForDecode() error {
 	s := d.s
 	for {
@@ -123,7 +128,7 @@ func (d *Decoder) Decode(v interface{}) error {
 	// noescape trick for header.typ ( reflect.*rtype )
 	copiedType := *(**rtype)(unsafe.Pointer(&typeptr))
 
-	if err := d.validateType(copiedType, ptr); err != nil {
+	if err := validateType(copiedType, ptr); err != nil {
 		return err
 	}
 
diff --git a/json.go b/json.go
index ee21941..b3f7ae6 100644
--- a/json.go
+++ b/json.go
@@ -262,17 +262,11 @@ func MarshalIndentWithOption(v interface{}, prefix, indent string, optFuncs ...E
 // character U+FFFD.
 //
 func Unmarshal(data []byte, v interface{}) error {
-	src := make([]byte, len(data)+1) // append nul byte to end
-	copy(src, data)
-	var dec Decoder
-	return dec.decodeForUnmarshal(src, v)
+	return unmarshal(data, v)
 }
 
 func UnmarshalNoEscape(data []byte, v interface{}) error {
-	src := make([]byte, len(data)+1) // append nul byte to end
-	copy(src, data)
-	var dec Decoder
-	return dec.decodeForUnmarshalNoEscape(src, v)
+	return unmarshalNoEscape(data, v)
 }
 
 // A Token holds a value of one of these types: