Unmarshalling float with lots of digits can cause >= 2 allocations per number

benchmarks/float_test.go

@@ -0,0 +1,28 @@
+package test
+
+import (
+ "testing"
+
+ jsoniter "github.com/json-iterator/go"
+)
+
+func BenchmarkFloatUnmarshal(b *testing.B) {
+ type floaty struct {
+ A float32
+ B float64
+ }
+
+ data, err := jsoniter.Marshal(floaty{A: 1.111111111111111, B: 1.11111111111111})
+ if err != nil {
+ b.Fatal(err)
+ }
+
+ b.ResetTimer()
+ b.ReportAllocs()
+ var out floaty
+ for i := 0; i < b.N; i++ {
+ if err := jsoniter.Unmarshal(data, &out); err != nil {
+ b.Fatal(err)
+ }
+ }
+}

benchmarks/stream_test.go

@@ -10,7 +10,8 @@ import (
 
 func Benchmark_stream_encode_big_object(b *testing.B) {
  var buf bytes.Buffer
- var stream = jsoniter.NewStream(jsoniter.ConfigDefault, &buf, 100)
+ stream := jsoniter.NewStream(jsoniter.ConfigDefault, &buf, 100)
+ b.ReportAllocs()
  for i := 0; i < b.N; i++ {
  buf.Reset()
  stream.Reset(&buf)
@@ -22,13 +23,13 @@ func Benchmark_stream_encode_big_object(b *testing.B) {
 }
 
 func TestEncodeObject(t *testing.T) {
- var stream = jsoniter.NewStream(jsoniter.ConfigDefault, nil, 100)
+ stream := jsoniter.NewStream(jsoniter.ConfigDefault, nil, 100)
  encodeObject(stream)
  if stream.Error != nil {
  t.Errorf("error encoding a test object: %+v", stream.Error)
  return
  }
- var m = make(map[string]interface{})
+ m := make(map[string]interface{})
  if err := jsoniter.Unmarshal(stream.Buffer(), &m); err != nil {
  t.Errorf("error unmarshaling a test object: %+v", err)
  return

iter.go

@@ -26,8 +26,10 @@ const (
  ObjectValue
 )
 
-var hexDigits []byte
-var valueTypes []ValueType
+var (
+ hexDigits []byte
+ valueTypes []ValueType
+)
 
 func init() {
  hexDigits = make([]byte, 256)
@@ -78,6 +80,7 @@ type Iterator struct {
  captureStartedAt int
  captured []byte
  Error error
+ scratch []byte
  Attachment interface{} // open for customized decoder
 }
 

iter_float.go

@@ -11,9 +11,11 @@ import (
 
 var floatDigits []int8
 
-const invalidCharForNumber = int8(-1)
-const endOfNumber = int8(-2)
-const dotInNumber = int8(-3)
+const (
+ invalidCharForNumber = int8(-1)
+ endOfNumber = int8(-2)
+ dotInNumber = int8(-3)
+)
 
 func init() {
  floatDigits = make([]int8, 256)
@@ -66,7 +68,7 @@ func (iter *Iterator) ReadBigInt() (ret *big.Int) {
  return ret
 }
 
-//ReadFloat32 read float32
+// ReadFloat32 read float32
 func (iter *Iterator) ReadFloat32() (ret float32) {
  c := iter.nextToken()
  if c == '-' {
@@ -185,11 +187,39 @@ load_loop:
  return *(*string)(unsafe.Pointer(&str))
 }
 
+func (iter *Iterator) appendNumber(buf []byte) []byte {
+load_loop:
+ for {
+ for i := iter.head; i < iter.tail; i++ {
+ c := iter.buf[i]
+ switch c {
+ case '+', '-', '.', 'e', 'E', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
+ buf = append(buf, c)
+ continue
+ default:
+ iter.head = i
+ break load_loop
+ }
+ }
+ if !iter.loadMore() {
+ break
+ }
+ }
+ if iter.Error != nil && iter.Error != io.EOF {
+ return buf
+ }
+ if len(buf) == 0 {
+ iter.ReportError("readNumberAsString", "invalid number")
+ }
+ return buf
+}
+
 func (iter *Iterator) readFloat32SlowPath() (ret float32) {
- str := iter.readNumberAsString()
+ iter.scratch = iter.appendNumber(iter.scratch[:0])
  if iter.Error != nil && iter.Error != io.EOF {
  return
  }
+ str := *(*string)(unsafe.Pointer(&iter.scratch))
  errMsg := validateFloat(str)
  if errMsg != "" {
  iter.ReportError("readFloat32SlowPath", errMsg)
@@ -297,10 +327,11 @@ non_decimal_loop:
 }
 
 func (iter *Iterator) readFloat64SlowPath() (ret float64) {
- str := iter.readNumberAsString()
+ iter.scratch = iter.appendNumber(iter.scratch[:0])
  if iter.Error != nil && iter.Error != io.EOF {
  return
  }
+ str := *(*string)(unsafe.Pointer(&iter.scratch))
  errMsg := validateFloat(str)
  if errMsg != "" {
  iter.ReportError("readFloat64SlowPath", errMsg)