From bb169a5cf6b654f216f33ef50f953546425d604f Mon Sep 17 00:00:00 2001
From: Masaaki Goshima <goccy54@gmail.com>
Date: Fri, 8 May 2020 20:25:49 +0900
Subject: [PATCH] Support UnmarshalText for decoding

---
 decode.go                |  4 ++--
 decode_test.go           | 21 +++++++++++++++++++++
 decode_unmarshal_text.go | 32 ++++++++++++++++++++++++++++++++
 3 files changed, 55 insertions(+), 2 deletions(-)
 create mode 100644 decode_unmarshal_text.go

diff --git a/decode.go b/decode.go
index 143294a..923cdce 100644
--- a/decode.go
+++ b/decode.go
@@ -152,7 +152,7 @@ func (d *Decoder) compileHead(typ *rtype) (decoder, error) {
 	if typ.Implements(unmarshalJSONType) {
 		return newUnmarshalJSONDecoder(typ), nil
 	} else if typ.Implements(unmarshalTextType) {
-
+		return newUnmarshalTextDecoder(typ), nil
 	}
 	return d.compile(typ.Elem())
 }
@@ -161,7 +161,7 @@ func (d *Decoder) compile(typ *rtype) (decoder, error) {
 	if typ.Implements(unmarshalJSONType) {
 		return newUnmarshalJSONDecoder(typ), nil
 	} else if typ.Implements(unmarshalTextType) {
-
+		return newUnmarshalTextDecoder(typ), nil
 	}
 	switch typ.Kind() {
 	case reflect.Ptr:
diff --git a/decode_test.go b/decode_test.go
index cd9011d..ca975bb 100644
--- a/decode_test.go
+++ b/decode_test.go
@@ -197,3 +197,24 @@ func Test_UnmarshalJSON(t *testing.T) {
 		assertEq(t, "unmarshal", v.v, 10)
 	})
 }
+
+type unmarshalText struct {
+	v int
+}
+
+func (u *unmarshalText) UnmarshalText(b []byte) error {
+	var v int
+	if err := json.Unmarshal(b, &v); err != nil {
+		return err
+	}
+	u.v = v
+	return nil
+}
+
+func Test_UnmarshalText(t *testing.T) {
+	t.Run("*struct", func(t *testing.T) {
+		var v unmarshalText
+		assertErr(t, json.Unmarshal([]byte(`11`), &v))
+		assertEq(t, "unmarshal", v.v, 11)
+	})
+}
diff --git a/decode_unmarshal_text.go b/decode_unmarshal_text.go
new file mode 100644
index 0000000..b74dda8
--- /dev/null
+++ b/decode_unmarshal_text.go
@@ -0,0 +1,32 @@
+package json
+
+import (
+	"encoding"
+	"unsafe"
+)
+
+type unmarshalTextDecoder struct {
+	typ *rtype
+}
+
+func newUnmarshalTextDecoder(typ *rtype) *unmarshalTextDecoder {
+	return &unmarshalTextDecoder{typ: typ}
+}
+
+func (d *unmarshalTextDecoder) decode(buf []byte, cursor int, p uintptr) (int, error) {
+	cursor = skipWhiteSpace(buf, cursor)
+	start := cursor
+	end, err := skipValue(buf, cursor)
+	if err != nil {
+		return 0, err
+	}
+	src := buf[start:end]
+	v := *(*interface{})(unsafe.Pointer(&interfaceHeader{
+		typ: d.typ,
+		ptr: unsafe.Pointer(p),
+	}))
+	if err := v.(encoding.TextUnmarshaler).UnmarshalText(src); err != nil {
+		return 0, err
+	}
+	return end, nil
+}