added a json parser with the ability to specify a field whitelist

xjson/LICENSE

@@ -0,0 +1,21 @@
+The MIT License (MIT)
+Copyright (c) 2016 Markus Ast
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+'Software'), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

xjson/xjson.go

@@ -0,0 +1,96 @@
+package xjson
+
+import (
+	"encoding/json"
+	"io"
+	"reflect"
+	"strings"
+)
+
+func Unmarshal(data []byte, v interface{}, whitelist ...string) error {
+	tmp := map[string]json.RawMessage{}
+
+	err := json.Unmarshal(data, &tmp)
+
+	if err != nil {
+		switch err {
+		case io.EOF:
+			return nil
+		default:
+			return err
+		}
+	}
+
+	fields := extract(v)
+
+	for _, name := range whitelist {
+		field, ok := fields[name]
+		if !ok {
+			continue
+		}
+
+		raw, ok := tmp[name]
+		if !ok {
+			continue
+		}
+
+		val := reflect.New(field.Type())
+		if err := json.Unmarshal(raw, val.Interface()); err != nil {
+			return err
+		}
+		field.Set(val.Elem())
+	}
+
+	return nil
+}
+
+func extract(dst interface{}) map[string]reflect.Value {
+	t := reflect.TypeOf(dst)
+	v := reflect.ValueOf(dst)
+
+	if t.Kind() == reflect.Ptr {
+		t = t.Elem()
+		v = v.Elem()
+	}
+
+	fields := map[string]reflect.Value{}
+	for i := 0; i < t.NumField(); i++ {
+		f := t.Field(i)
+		tags := strings.Split(f.Tag.Get("json"), ",")
+		name := ""
+		if len(tags) > 0 {
+			name = tags[0]
+		}
+		if name == "-" {
+			continue
+		}
+		if name == "" {
+			name = f.Name
+		}
+
+		fv := v.Field(i)
+
+		if f.Anonymous { // embedded struct
+			ft := f.Type
+			if ft.Kind() == reflect.Ptr {
+				ft = ft.Elem()
+				fv = fv.Elem()
+			}
+
+			if !fv.IsValid() { // eg. is nil
+				// init embedded struct
+				fv = reflect.New(ft)
+				v.Field(i).Set(fv)
+				fv = fv.Elem()
+			}
+
+			for k, v := range extract(fv.Addr().Interface()) {
+				fields[k] = v
+			}
+		}
+
+		fields[name] = fv
+	}
+
+	return fields
+}

xjson/xjson_test.go

@@ -0,0 +1,45 @@
+package xjson_test
+
+import (
+	"testing"
+
+	"github.com/unchainio/pkg/xjson"
+	"v/github.com/docker/[email protected]/pkg/testutil/assert"
+)
+
+type T struct {
+	A string
+	B string
+}
+
+type TestCase struct {
+	Data      []byte
+	Whitelist []string
+	Expected  *T
+}
+
+func TestUnmarshal(t *testing.T) {
+	cases := []TestCase{
+		{
+			Data:      []byte("{\"A\": \"a\", \"B\":\"b\"}"),
+			Whitelist: []string{"A"},
+			Expected:  &T{A: "a"},
+		},
+		{
+			Data:      []byte("{\"A\": \"a\", \"B\":\"b\"}"),
+			Whitelist: []string{"B"},
+			Expected:  &T{B: "b"},
+		},
+		{
+			Data:      []byte("{\"A\": \"a\", \"B\":\"b\"}"),
+			Whitelist: []string{"A", "B"},
+			Expected:  &T{A: "a", B: "b"},
+		},
+	}
+
+	for _, tc := range cases {
+		v := new(T)
+		xjson.Unmarshal(tc.Data, v, tc.Whitelist...)
+		assert.DeepEqual(t, v, tc.Expected)
+	}
+}