infer compress type before decode NBT fail

nbt/nbt.go

@@ -26,7 +26,7 @@ const (
 
 type Decoder struct {
 	r interface {
-		io.ByteReader
+		io.ByteScanner
 		io.Reader
 	}
 }
@@ -34,7 +34,7 @@ type Decoder struct {
 func NewDecoder(r io.Reader) *Decoder {
 	d := new(Decoder)
 	if br, ok := r.(interface {
-		io.ByteReader
+		io.ByteScanner
 		io.Reader
 	}); ok {
 		d.r = br

nbt/read.go

@@ -18,6 +18,17 @@ func (d *Decoder) Decode(v interface{}) error {
 	if val.Kind() != reflect.Ptr {
 		return errors.New("non-pointer passed to Unmarshal")
 	}
+
+	// check the head
+	compress, err := d.checkCompressed()
+	if err != nil {
+		return fmt.Errorf("check compressed fail: %v", err)
+	}
+	if compress != "" {
+		return fmt.Errorf("data may compressed with %s", compress)
+	}
+
+	//start read NBT
 	tagType, tagName, err := d.readTag()
 	if err != nil {
 		return err
@@ -25,6 +36,29 @@ func (d *Decoder) Decode(v interface{}) error {
 	return d.unmarshal(val.Elem(), tagType, tagName)
 }
 
+// check the first byte and return if it use compress
+func (d *Decoder) checkCompressed() (compress string, err error) {
+	var head byte
+	head, err = d.r.ReadByte()
+	if err != nil {
+		return
+	}
+
+	if head <= 12 { //NBT
+		compress = ""
+	} else if head == 0x1f { //gzip
+		compress = "gzip"
+	} else if head == 0x78 { //zlib
+		compress = "zlib"
+	} else {
+		compress = "unknown"
+	}
+
+	err = d.r.UnreadByte()
+
+	return
+}
+
 // ErrEND error will be returned when reading a NBT with only Tag_End
 var ErrEND = errors.New("unexpected TAG_End")
 

save/level.go

@@ -0,0 +1,4 @@
+package save
+
+type Level struct {
+}

save/playerdata.go

@@ -0,0 +1,16 @@
+package save
+
+import (
+	"github.com/Tnze/go-mc/nbt"
+	"io"
+)
+
+type PlayerData struct {
+	Pos    [3]float64
+	Motion [3]float64
+}
+
+func ReadPlayerData(r io.Reader) (data PlayerData, err error) {
+	err = nbt.NewDecoder(r).Decode(&data)
+	return
+}

save/playerdata_test.go

@@ -0,0 +1,33 @@
+package save
+
+import (
+	"compress/gzip"
+	"os"
+	"testing"
+)
+
+func TestPlayerData(t *testing.T) {
+	f, err := os.Open("testdata/playerdata/58f6356e-b30c-4811-8bfc-d72a9ee99e73.dat")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	r, err := gzip.NewReader(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	data, err := ReadPlayerData(r)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	want := PlayerData{
+		Pos:    [3]float64{-41.5, 65, -89.5},
+		Motion: [3]float64{0, -0.0784000015258789, 0},
+	}
+
+	if data != want {
+		t.Errorf("player data parse error: get %v, want %v", data, want)
+	}
+}

save/save.go

@@ -0,0 +1 @@
+package save

save/testdata/advancements/58f6356e-b30c-4811-8bfc-d72a9ee99e73.json

@@ -0,0 +1,9 @@
+{
+  "minecraft:adventure/adventuring_time": {
+    "criteria": {
+      "minecraft:plains": "2019-07-31 15:56:59 +0800"
+    },
+    "done": false
+  },
+  "DataVersion": 1976
+}

save/testdata/stats/58f6356e-b30c-4811-8bfc-d72a9ee99e73.json

@@ -0,0 +1 @@
+{"stats":{"minecraft:custom":{"minecraft:time_since_rest":6,"minecraft:play_one_minute":6,"minecraft:leave_game":1,"minecraft:time_since_death":6}},"DataVersion":1976}