From f36e24c8aeb2019ad052ea52c319333f6f690426 Mon Sep 17 00:00:00 2001
From: Masaaki Goshima <goccy54@gmail.com>
Date: Sat, 25 Apr 2020 22:48:16 +0900
Subject: [PATCH] Add decoder for map type

---
 decode.go      | 14 ++++++++
 decode_map.go  | 90 ++++++++++++++++++++++++++++++++++++++++++++++++++
 decode_test.go |  8 +++++
 3 files changed, 112 insertions(+)
 create mode 100644 decode_map.go

diff --git a/decode.go b/decode.go
index 2b18a56..3459da5 100644
--- a/decode.go
+++ b/decode.go
@@ -154,6 +154,8 @@ func (d *Decoder) compile(typ *rtype) (decoder, error) {
 		return d.compileSlice(typ)
 	case reflect.Array:
 		return d.compileArray(typ)
+	case reflect.Map:
+		return d.compileMap(typ)
 	case reflect.Int:
 		return d.compileInt()
 	case reflect.Int8:
@@ -292,6 +294,18 @@ func (d *Decoder) compileArray(typ *rtype) (decoder, error) {
 	return newArrayDecoder(decoder, elem, typ.Len()), nil
 }
 
+func (d *Decoder) compileMap(typ *rtype) (decoder, error) {
+	keyDec, err := d.compile(typ.Key())
+	if err != nil {
+		return nil, err
+	}
+	valueDec, err := d.compile(typ.Elem())
+	if err != nil {
+		return nil, err
+	}
+	return newMapDecoder(typ, keyDec, valueDec), nil
+}
+
 func (d *Decoder) getTag(field reflect.StructField) string {
 	return field.Tag.Get("json")
 }
diff --git a/decode_map.go b/decode_map.go
new file mode 100644
index 0000000..a4a1d72
--- /dev/null
+++ b/decode_map.go
@@ -0,0 +1,90 @@
+package json
+
+import (
+	"errors"
+	"fmt"
+	"unsafe"
+)
+
+type mapDecoder struct {
+	mapType      *rtype
+	keyDecoder   decoder
+	valueDecoder decoder
+}
+
+func newMapDecoder(mapType *rtype, keyDec decoder, valueDec decoder) *mapDecoder {
+	return &mapDecoder{
+		mapType:      mapType,
+		keyDecoder:   keyDec,
+		valueDecoder: valueDec,
+	}
+}
+
+//go:linkname makemap reflect.makemap
+func makemap(*rtype, int) unsafe.Pointer
+
+//go:linkname mapassign reflect.mapassign
+//go:noescape
+func mapassign(t *rtype, m unsafe.Pointer, key, val unsafe.Pointer)
+
+func (d *mapDecoder) setKey(ctx *context, key interface{}) error {
+	header := (*interfaceHeader)(unsafe.Pointer(&key))
+	if err := d.keyDecoder.decode(ctx, uintptr(header.ptr)); err != nil {
+		return err
+	}
+	//fmt.Println("key = ", *(*string)(header.ptr))
+	//fmt.Println("Key = ", key.(*string))
+	//fmt.Println("key = ", *(*string)(unsafe.Pointer(key)))
+	return nil
+}
+
+func (d *mapDecoder) setValue(ctx *context, key interface{}) error {
+	header := (*interfaceHeader)(unsafe.Pointer(&key))
+	return d.valueDecoder.decode(ctx, uintptr(header.ptr))
+}
+
+func (d *mapDecoder) decode(ctx *context, p uintptr) error {
+	ctx.skipWhiteSpace()
+	buf := ctx.buf
+	buflen := ctx.buflen
+	cursor := ctx.cursor
+	if buflen < 2 {
+		return errors.New("unexpected error {}")
+	}
+	if buf[cursor] != '{' {
+		return errors.New("unexpected error {")
+	}
+	cursor++
+	mapValue := makemap(d.mapType, 0)
+	fmt.Println("mapValue = ", mapValue)
+	for ; cursor < buflen; cursor++ {
+		ctx.cursor = cursor
+		var key interface{}
+		if err := d.setKey(ctx, &key); err != nil {
+			return err
+		}
+		cursor = ctx.skipWhiteSpace()
+		if buf[cursor] != ':' {
+			return errors.New("unexpected error invalid delimiter for object")
+		}
+		cursor++
+		if cursor >= buflen {
+			return errors.New("unexpected error missing value")
+		}
+		ctx.cursor = cursor
+		var value interface{}
+		if err := d.setValue(ctx, &value); err != nil {
+			return err
+		}
+		mapassign(d.mapType, mapValue, unsafe.Pointer(&key), unsafe.Pointer(&value))
+		cursor = ctx.skipWhiteSpace()
+		if buf[cursor] == '}' {
+			*(*unsafe.Pointer)(unsafe.Pointer(p)) = mapValue
+			return nil
+		}
+		if buf[cursor] != ',' {
+			return errors.New("unexpected error ,")
+		}
+	}
+	return nil
+}
diff --git a/decode_test.go b/decode_test.go
index 9cac903..e72e0b9 100644
--- a/decode_test.go
+++ b/decode_test.go
@@ -95,6 +95,14 @@ func Test_Decoder(t *testing.T) {
 		assertErr(t, json.Unmarshal([]byte(` [ 1 , 2 , 3 , 4 ] `), &v))
 		assertEq(t, "array", fmt.Sprint([4]int{1, 2, 3, 4}), fmt.Sprint(v))
 	})
+	t.Run("map", func(t *testing.T) {
+		var v map[string]int
+		assertErr(t, json.Unmarshal([]byte(` { "a": 1, "b": 2, "c": 3, "d": 4 } `), &v))
+		assertEq(t, "map.a", v["a"], 1)
+		assertEq(t, "map.b", v["b"], 2)
+		assertEq(t, "map.c", v["c"], 3)
+		assertEq(t, "map.d", v["d"], 4)
+	})
 	t.Run("struct", func(t *testing.T) {
 		type T struct {
 			AA int    `json:"aa"`