From cfde002d29aac1f63b3faf8a67af991410e57146 Mon Sep 17 00:00:00 2001
From: Masaaki Goshima <goccy54@gmail.com>
Date: Fri, 24 Apr 2020 16:46:12 +0900
Subject: [PATCH] Add decoder of float

---
 decode.go       | 16 ++++++++++++++
 decode_float.go | 55 +++++++++++++++++++++++++++++++++++++++++++++++++
 decode_test.go  | 10 +++++++++
 3 files changed, 81 insertions(+)
 create mode 100644 decode_float.go

diff --git a/decode.go b/decode.go
index 280cdca..8966c67 100644
--- a/decode.go
+++ b/decode.go
@@ -150,6 +150,10 @@ func (d *Decoder) compile(typ reflect.Type) (decoder, error) {
 		return d.compileString()
 	case reflect.Bool:
 		return d.compileBool()
+	case reflect.Float32:
+		return d.compileFloat32()
+	case reflect.Float64:
+		return d.compileFloat64()
 	}
 	return nil, nil
 }
@@ -222,6 +226,18 @@ func (d *Decoder) compileUint64() (decoder, error) {
 	}), nil
 }
 
+func (d *Decoder) compileFloat32() (decoder, error) {
+	return newFloatDecoder(func(p uintptr, v float64) {
+		*(*float32)(unsafe.Pointer(p)) = float32(v)
+	}), nil
+}
+
+func (d *Decoder) compileFloat64() (decoder, error) {
+	return newFloatDecoder(func(p uintptr, v float64) {
+		*(*float64)(unsafe.Pointer(p)) = v
+	}), nil
+}
+
 func (d *Decoder) compileString() (decoder, error) {
 	return newStringDecoder(), nil
 }
diff --git a/decode_float.go b/decode_float.go
new file mode 100644
index 0000000..43eadd1
--- /dev/null
+++ b/decode_float.go
@@ -0,0 +1,55 @@
+package json
+
+import (
+	"errors"
+	"strconv"
+	"unsafe"
+)
+
+type floatDecoder struct {
+	op func(uintptr, float64)
+}
+
+func newFloatDecoder(op func(uintptr, float64)) *floatDecoder {
+	return &floatDecoder{op: op}
+}
+
+func (d *floatDecoder) decodeByte(ctx *context) ([]byte, error) {
+	buf := ctx.buf
+	cursor := ctx.cursor
+	buflen := ctx.buflen
+	for ; cursor < buflen; cursor++ {
+		switch buf[cursor] {
+		case ' ', '\n', '\t', '\r':
+			continue
+		case '-', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
+			start := cursor
+			cursor++
+			for ; cursor < buflen; cursor++ {
+				tk := int(buf[cursor])
+				if (int('0') <= tk && tk <= int('9')) || tk == '.' || tk == 'e' || tk == 'E' {
+					continue
+				}
+				break
+			}
+			num := ctx.buf[start:cursor]
+			ctx.cursor = cursor
+			return num, nil
+		}
+	}
+	return nil, errors.New("unexpected error number")
+}
+
+func (d *floatDecoder) decode(ctx *context, p uintptr) error {
+	bytes, err := d.decodeByte(ctx)
+	if err != nil {
+		return err
+	}
+	s := *(*string)(unsafe.Pointer(&bytes))
+	f64, err := strconv.ParseFloat(s, 64)
+	if err != nil {
+		return err
+	}
+	d.op(p, f64)
+	return nil
+}
diff --git a/decode_test.go b/decode_test.go
index 533664f..a391d37 100644
--- a/decode_test.go
+++ b/decode_test.go
@@ -74,6 +74,16 @@ func Test_Decoder(t *testing.T) {
 		assertErr(t, json.Unmarshal([]byte(`"hello"`), &v))
 		assertEq(t, "string", "hello", v)
 	})
+	t.Run("float32", func(t *testing.T) {
+		var v float32
+		assertErr(t, json.Unmarshal([]byte(`3.14`), &v))
+		assertEq(t, "float32", float32(3.14), v)
+	})
+	t.Run("float64", func(t *testing.T) {
+		var v float64
+		assertErr(t, json.Unmarshal([]byte(`3.14`), &v))
+		assertEq(t, "float64", float64(3.14), v)
+	})
 	t.Run("struct", func(t *testing.T) {
 		type T struct {
 			AA int    `json:"aa"`