parse input containing NaN and Infinity values

JSON standard does not allow NaN or Infinity, but some applications
produce output that contains such values. One example of such
application would be TensorFlow Serving[1]. An example of JSON parser
that accepts NaN and Infinity is the one that comes with Python[2]. This
commit introduces a new configuration parameter AllowNaN, that enables
jsoniter to unmarshal input containing NaN and Infinity.

1. https://www.tensorflow.org/tfx/serving/api_rest#json_conformance
2. https://docs.python.org/3/library/json.html#infinite-and-nan-number-values

config.go

@@ -25,6 +25,8 @@ type Config struct {
 	ValidateJsonRawMessage        bool
 	ObjectFieldMustBeSimpleString bool
 	CaseSensitive                 bool
+	// AllowNaN parses input that contains non-standard NaN and Infinity values
+	AllowNaN bool
 }
 
 // API the public interface of this package.
@@ -49,6 +51,7 @@ type API interface {
 // ConfigDefault the default API
 var ConfigDefault = Config{
 	EscapeHTML: true,
+	AllowNaN:   true,
 }.Froze()
 
 // ConfigCompatibleWithStandardLibrary tries to be 100% compatible with standard library behavior

iter.go

@@ -59,6 +59,8 @@ func init() {
 	valueTypes['7'] = NumberValue
 	valueTypes['8'] = NumberValue
 	valueTypes['9'] = NumberValue
+	valueTypes['N'] = NumberValue
+	valueTypes['I'] = NumberValue
 	valueTypes['t'] = BoolValue
 	valueTypes['f'] = BoolValue
 	valueTypes['n'] = NilValue

iter_float.go

@@ -156,6 +156,46 @@ non_decimal_loop:
 	return iter.readFloat32SlowPath()
 }
 
+var nanBytes = []byte("NaN")
+
+func (iter *Iterator) readNaN() (ret string) {
+	for _, b := range nanBytes {
+		if iter.readByte() != b {
+			iter.ReportError("readNaN", "expect NaN")
+			return
+		}
+	}
+	if !iter.cfg.configBeforeFrozen.AllowNaN {
+		iter.ReportError("readInfinity", "invalid number, AllowNaN is not set")
+		return
+	}
+	return "NaN"
+}
+
+var infinityBytes = []byte("Infinity")
+
+func (iter *Iterator) readInfinity() (ret string) {
+	var negative bool
+	if iter.buf[iter.head] == '-' {
+		negative = true
+		iter.head++
+	}
+	for _, b := range infinityBytes {
+		if iter.readByte() != b {
+			iter.ReportError("readInfinity", "expect Infinity")
+			return
+		}
+	}
+	if !iter.cfg.configBeforeFrozen.AllowNaN {
+		iter.ReportError("readInfinity", "invalid number, AllowNaN is not set")
+		return
+	}
+	if negative {
+		return "-Infinity"
+	}
+	return "Infinity"
+}
+
 func (iter *Iterator) readNumberAsString() (ret string) {
 	strBuf := [16]byte{}
 	str := strBuf[0:0]
@@ -167,10 +207,19 @@ load_loop:
 			case '+', '-', '.', 'e', 'E', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
 				str = append(str, c)
 				continue
-			default:
-				iter.head = i
-				break load_loop
+			case 'N':
+				if len(str) == 0 {
+					return iter.readNaN()
+				}
+			case 'I':
+				if len(str) == 0 {
+					return iter.readInfinity()
+				} else if len(str) == 1 && str[0] == '-' {
+					return iter.readInfinity()
+				}
 			}
+			iter.head = i
+			break load_loop
 		}
 		if !iter.loadMore() {
 			break

value_tests/float_test.go

@@ -6,10 +6,43 @@ import (
 	"fmt"
 	"github.com/json-iterator/go"
 	"github.com/stretchr/testify/require"
+	"math"
 	"strconv"
 	"testing"
 )
 
+func Test_NaN_Inf(t *testing.T) {
+	cases := []struct {
+		json  string
+		check func(float64) bool
+	}{
+		{
+			json:  "NaN",
+			check: math.IsNaN,
+		},
+		{
+			json:  "-Infinity",
+			check: func(f float64) bool { return math.IsInf(f, -1) },
+		},
+		{
+			json:  "Infinity",
+			check: func(f float64) bool { return math.IsInf(f, 1) },
+		},
+	}
+
+	for _, tc := range cases {
+		iter := jsoniter.ParseString(jsoniter.ConfigDefault, tc.json+",")
+		if res := iter.ReadFloat64(); !tc.check(res) || iter.Error != nil {
+			t.Errorf("couldn't parse %s, got %f (%v)", tc.json, res, iter.Error)
+		}
+		iterStd := jsoniter.ParseString(jsoniter.ConfigCompatibleWithStandardLibrary, tc.json+",")
+		res := iterStd.Read()
+		if iterStd.Error == nil {
+			t.Errorf("standard compatible parser should have returned an error for %s, got %v", tc.json, res)
+		}
+	}
+}
+
 func Test_read_float(t *testing.T) {
 	inputs := []string{
 		`1.1`, `1000`, `9223372036854775807`, `12.3`, `-12.3`, `720368.54775807`, `720368.547758075`,