msgpack: sort code constants and use typed code

Author: zchee

msgpack/msgpack.go

@@ -11,9 +11,15 @@ const (
 	fixStringCodeMin = 0xa0
 	fixStringCodeMax = 0xbf
 	nilCode          = 0xc0
-	unusedCode       = 0xc1
+	unusedCode       = 0xc1 // never used
 	falseCode        = 0xc2
 	trueCode         = 0xc3
+	binary8Code      = 0xc4
+	binary16Code     = 0xc5
+	binary32Code     = 0xc6
+	ext8Code         = 0xc7
+	ext16Code        = 0xc8
+	ext32Code        = 0xc9
 	float32Code      = 0xca
 	float64Code      = 0xcb
 	uint8Code        = 0xcc
@@ -24,24 +30,18 @@ const (
 	int16Code        = 0xd1
 	int32Code        = 0xd2
 	int64Code        = 0xd3
+	fixext1Code      = 0xd4
+	fixext2Code      = 0xd5
+	fixext4Code      = 0xd6
+	fixext8Code      = 0xd7
+	fixext16Code     = 0xd8
 	string8Code      = 0xd9
 	string16Code     = 0xda
 	string32Code     = 0xdb
-	binary8Code      = 0xc4
-	binary16Code     = 0xc5
-	binary32Code     = 0xc6
 	array16Code      = 0xdc
 	array32Code      = 0xdd
 	map16Code        = 0xde
 	map32Code        = 0xdf
-	fixext1Code      = 0xd4
-	fixext2Code      = 0xd5
-	fixext4Code      = 0xd6
-	fixext8Code      = 0xd7
-	fixext16Code     = 0xd8
-	ext8Code         = 0xc7
-	ext16Code        = 0xc8
-	ext32Code        = 0xc9
 	negFixIntCodeMin = 0xe0
 	negFixIntCodeMax = 0xff
 )

msgpack/unpack.go

@@ -252,15 +252,15 @@ var formats = [256]*struct {
 	},
 	fixMapCodeMin: {
 		t: MapLen,
-		n: func(d *Decoder, code byte) (uint64, error) { return uint64(code) - fixMapCodeMin, nil },
+		n: func(d *Decoder, code byte) (uint64, error) { return uint64(code) - uint64(fixMapCodeMin), nil },
 	},
 	fixArrayCodeMin: {
 		t: ArrayLen,
-		n: func(d *Decoder, code byte) (uint64, error) { return uint64(code) - fixArrayCodeMin, nil },
+		n: func(d *Decoder, code byte) (uint64, error) { return uint64(code) - uint64(fixArrayCodeMin), nil },
 	},
 	fixStringCodeMin: {
 		t:    String,
-		n:    func(d *Decoder, code byte) (uint64, error) { return uint64(code) - fixStringCodeMin, nil },
+		n:    func(d *Decoder, code byte) (uint64, error) { return uint64(code) - uint64(fixStringCodeMin), nil },
 		more: true,
 	},
 	negFixIntCodeMin: {