From 2121b5e2274a2bd66eafc581828487f5586bcbc8 Mon Sep 17 00:00:00 2001
From: lichao115 <lichao12@jd.com>
Date: Sat, 1 Apr 2017 15:06:26 +0800
Subject: [PATCH] first init

---
 jsonfield.go      | 118 ++++++++++++++++++++++++++++++++++++++++++++++
 jsonfield_test.go |  25 ++++++++++
 2 files changed, 143 insertions(+)
 create mode 100644 jsonfield.go
 create mode 100644 jsonfield_test.go

diff --git a/jsonfield.go b/jsonfield.go
new file mode 100644
index 0000000..c6b3beb
--- /dev/null
+++ b/jsonfield.go
@@ -0,0 +1,118 @@
+package jsonfield
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"reflect"
+	"strconv"
+
+	fflib "github.com/pquerna/ffjson/fflib/v1"
+)
+
+func Marshal(v interface{}, fields ...string) ([]byte, error) {
+	if len(fields) == 0 {
+		return json.Marshal(v)
+	} else {
+		return MarshalFields(v, fields)
+	}
+}
+
+func MarshalFields(c interface{}, fields []string) ([]byte, error) {
+	buf := bytes.NewBuffer(nil)
+
+	_, v := Reflect(c)
+
+	buf.WriteString("{")
+	for i, field := range fields {
+		vv := v.FieldByName(field)
+		if vv.Kind() != reflect.Invalid {
+			buf.WriteString(`"` + field + `":`)
+
+			var err error
+			switch vv.Kind() {
+			case reflect.Bool:
+				zzz := strconv.AppendBool(nil, vv.Bool())
+				_, err = buf.Write(zzz)
+			case reflect.Int8, reflect.Int, reflect.Int16, reflect.Int32, reflect.Int64:
+				i := vv.Int()
+				fflib.FormatBits2(buf, uint64(i), 10, i < 0)
+			case reflect.Uint, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uint8:
+				i := vv.Uint()
+				fflib.FormatBits2(buf, uint64(i), 10, i < 0)
+			case reflect.Float32, reflect.Float64:
+				zzz := strconv.AppendFloat(nil, vv.Float(), 'g', -1, 64)
+				_, err = buf.Write(zzz)
+			case reflect.String:
+				_, err = buf.WriteString(vv.String())
+			case reflect.Slice, reflect.Map, reflect.Array:
+				if vv.IsNil() {
+					buf.WriteString("null")
+				} else {
+					_, err = buf.WriteString(fmt.Sprintf(`"%+v"`, vv.Interface()))
+				}
+			case reflect.Struct:
+				tt := reflect.TypeOf(vv.Interface())
+				if tt.Implements(marshalerType) {
+					m := vv.Interface().(json.Marshaler)
+					b, err := m.MarshalJSON()
+					if err != nil {
+						return nil, err
+					} else {
+						b, err := json.Marshal(vv.Interface())
+						if err != nil {
+							return nil, err
+						}
+						_, err = buf.Write(b)
+					}
+					_, err = buf.Write(b)
+				}
+			case reflect.Ptr:
+				tt := reflect.TypeOf(vv.Interface()).Elem()
+				if tt.Implements(marshalerType) {
+					m := vv.Interface().(json.Marshaler)
+					b, err := m.MarshalJSON()
+					if err != nil {
+						return nil, err
+					}
+					_, err = buf.Write(b)
+				} else {
+					b, err := json.Marshal(vv.Interface())
+					if err != nil {
+						return nil, err
+					}
+					_, err = buf.Write(b)
+				}
+			default:
+				_, err = buf.WriteString(vv.String())
+			}
+
+			if err != nil {
+				return nil, err
+			}
+		}
+
+		if i != len(fields)-1 {
+			buf.WriteString(",")
+		}
+	}
+
+	buf.WriteString("}")
+
+	return buf.Bytes(), nil
+}
+
+func Reflect(c interface{}) (reflect.Type, reflect.Value) {
+	t := reflect.TypeOf(c)
+	v := reflect.ValueOf(c)
+	if t.Kind() == reflect.Ptr {
+		t = t.Elem()
+		v = reflect.Indirect(v)
+	}
+
+	return t, v
+}
+
+var (
+	marshalerType = reflect.TypeOf(new(json.Marshaler)).Elem()
+)
diff --git a/jsonfield_test.go b/jsonfield_test.go
new file mode 100644
index 0000000..47eaaf5
--- /dev/null
+++ b/jsonfield_test.go
@@ -0,0 +1,25 @@
+package jsonfield
+
+import "testing"
+
+func TestJsonTest(t *testing.T) {
+	jj := new(A)
+	jj.A, jj.B = 111, 222
+
+	if byts, err := Marshal(jj); err != nil || string(byts) != `{"A":111,"B":222}` {
+		t.Error(string(byts), err)
+	}
+
+	if byts, err := Marshal(jj, "A"); err != nil || string(byts) != `{"A":111}` {
+		t.Error(string(byts), err)
+	}
+
+	if byts, err := Marshal(jj, "B"); err != nil || string(byts) != `{"B":222}` {
+		t.Error(string(byts), err)
+	}
+}
+
+type A struct {
+	A int
+	B int
+}