Merge pull request #96 from verytable/feature/provide-decoded-array-index

add Index() method to Decoder

Author: francoispqt

README.md

@@ -286,6 +286,20 @@ func (c ChannelArray) UnmarshalJSONArray(dec *gojay.Decoder) error {
 }
 ```
 
+Example of implementation with an array:
+```go
+type testArray [3]string
+// implement UnmarshalerJSONArray
+func (a *testArray) UnmarshalJSONArray(dec *Decoder) error {
+	var str string
+	if err := dec.String(&str); err != nil {
+		return err
+	}
+	a[dec.Index()] = str
+	return nil
+}
+```
+
 ### Other types
 To decode other types (string, int, int32, int64, uint32, uint64, float, booleans), you don't need to implement any interface. 
 

decode.go

@@ -235,15 +235,16 @@ type UnmarshalerJSONArray interface {
 
 // A Decoder reads and decodes JSON values from an input stream.
 type Decoder struct {
-	r        io.Reader
-	data     []byte
-	err      error
-	isPooled byte
-	called   byte
-	child    byte
-	cursor   int
-	length   int
-	keysDone int
+	r          io.Reader
+	data       []byte
+	err        error
+	isPooled   byte
+	called     byte
+	child      byte
+	cursor     int
+	length     int
+	keysDone   int
+	arrayIndex int
 }
 
 // Decode reads the next JSON-encoded value from the decoder's input (io.Reader) and stores it in the value pointed to by v.

decode_array.go

@@ -16,6 +16,12 @@ func (dec *Decoder) DecodeArray(v UnmarshalerJSONArray) error {
 	return err
 }
 func (dec *Decoder) decodeArray(arr UnmarshalerJSONArray) (int, error) {
+	// remember last array index in case of nested arrays
+	lastArrayIndex := dec.arrayIndex
+	dec.arrayIndex = 0
+	defer func() {
+		dec.arrayIndex = lastArrayIndex
+	}()
 	for ; dec.cursor < dec.length || dec.read(); dec.cursor++ {
 		switch dec.data[dec.cursor] {
 		case ' ', '\n', '\t', '\r', ',':
@@ -34,6 +40,7 @@ func (dec *Decoder) decodeArray(arr UnmarshalerJSONArray) (int, error) {
 				if err != nil {
 					return 0, err
 				}
+				dec.arrayIndex++
 			}
 			return 0, dec.raiseInvalidJSONErr(dec.cursor)
 		case 'n':
@@ -60,6 +67,12 @@ func (dec *Decoder) decodeArray(arr UnmarshalerJSONArray) (int, error) {
 	return 0, dec.raiseInvalidJSONErr(dec.cursor)
 }
 func (dec *Decoder) decodeArrayNull(v interface{}) (int, error) {
+	// remember last array index in case of nested arrays
+	lastArrayIndex := dec.arrayIndex
+	dec.arrayIndex = 0
+	defer func() {
+		dec.arrayIndex = lastArrayIndex
+	}()
 	vv := reflect.ValueOf(v)
 	vvt := vv.Type()
 	if vvt.Kind() != reflect.Ptr || vvt.Elem().Kind() != reflect.Ptr {
@@ -96,6 +109,7 @@ func (dec *Decoder) decodeArrayNull(v interface{}) (int, error) {
 				if err != nil {
 					return 0, err
 				}
+				dec.arrayIndex++
 			}
 			return 0, dec.raiseInvalidJSONErr(dec.cursor)
 		case 'n':
@@ -226,3 +240,8 @@ func (dec *Decoder) ArrayNull(v interface{}) error {
 	dec.called |= 1
 	return nil
 }
+
+// Index returns the index of an array being decoded.
+func (dec *Decoder) Index() int {
+	return dec.arrayIndex
+}

decode_array_test.go

@@ -627,3 +627,74 @@ func TestDecoderArrayFunc(t *testing.T) {
 	var f DecodeArrayFunc
 	assert.True(t, f.IsNil())
 }
+
+type testArrayStrings [3]string
+
+func (a *testArrayStrings) UnmarshalJSONArray(dec *Decoder) error {
+	var str string
+	if err := dec.String(&str); err != nil {
+		return err
+	}
+	a[dec.Index()] = str
+	return nil
+}
+
+func TestArrayStrings(t *testing.T) {
+	data := []byte(`["a", "b", "c"]`)
+	arr := testArrayStrings{}
+	err := Unmarshal(data, &arr)
+	assert.Nil(t, err, "err must be nil")
+	assert.Equal(t, "a", arr[0], "arr[0] must be equal to 'a'")
+	assert.Equal(t, "b", arr[1], "arr[1] must be equal to 'b'")
+	assert.Equal(t, "c", arr[2], "arr[2] must be equal to 'c'")
+}
+
+type testSliceArraysStrings struct {
+	arrays []testArrayStrings
+	t      *testing.T
+}
+
+func (s *testSliceArraysStrings) UnmarshalJSONArray(dec *Decoder) error {
+	var a testArrayStrings
+	assert.Equal(s.t, len(s.arrays), dec.Index(), "decoded array index must be equal to current slice len")
+	if err := dec.AddArray(&a); err != nil {
+		return err
+	}
+	assert.Equal(s.t, len(s.arrays), dec.Index(), "decoded array index must be equal to current slice len")
+	s.arrays = append(s.arrays, a)
+	return nil
+}
+
+func TestIndex(t *testing.T) {
+	testCases := []struct {
+		name           string
+		json           string
+		expectedResult []testArrayStrings
+	}{
+		{
+			name:           "basic-test",
+			json:           `[["a","b","c"],["1","2","3"],["x","y","z"]]`,
+			expectedResult: []testArrayStrings{{"a", "b", "c"}, {"1", "2", "3"}, {"x", "y", "z"}},
+		},
+		{
+			name:           "basic-test-null",
+			json:           `[["a","b","c"],null,["x","y","z"]]`,
+			expectedResult: []testArrayStrings{{"a", "b", "c"}, {"", "", ""}, {"x", "y", "z"}},
+		},
+	}
+
+	for _, testCase := range testCases {
+		t.Run(testCase.name, func(t *testing.T) {
+			s := make([]testArrayStrings, 0)
+			dec := BorrowDecoder(strings.NewReader(testCase.json))
+			defer dec.Release()
+			a := testSliceArraysStrings{arrays: s, t: t}
+			err := dec.Decode(&a)
+			assert.Nil(t, err, "err should be nil")
+			assert.Zero(t, dec.Index(), "Index() must return zero after decoding")
+			for k, v := range testCase.expectedResult {
+				assert.Equal(t, v, a.arrays[k], "value at given index should be the same as expected results")
+			}
+		})
+	}
+}