Fix bugs with pk.Ary. Add tests and examples.

net/packet/util.go

@@ -1,19 +1,31 @@
 package packet
 
 import (
+	"errors"
 	"io"
 	"reflect"
 )
 
+// Ary is used to send or receive the packet field like "Array of X"
+// which has a count must be known from the context.
+//
+// Typically, you must decode an integer representing the length. Then
+// receive the corresponding amount of data according to the length.
+// In this case, the field Len should be a pointer of integer type so
+// the value can be updating when Packet.Scan() method is decoding the
+// previous field.
+// In some special cases, you might want to read an "Array of X" with a fix length.
+// So it's allowed to directly set an integer type Len, but not a pointer.
+//
+// Note that Ary DO NOT read or write the Len. You are controlling it manually.
 type Ary struct {
-	Len Field       // Pointer of VarInt, VarLong, Int or Long
+	Len interface{} // Value or Pointer of any integer type, only needed in ReadFrom
 	Ary interface{} // Slice of FieldEncoder, FieldDecoder or both (Field)
 }
 
 func (a Ary) WriteTo(r io.Writer) (n int64, err error) {
-	length := int(reflect.ValueOf(a.Len).Int())
 	array := reflect.ValueOf(a.Ary)
-	for i := 0; i < length; i++ {
+	for i := 0; i < array.Len(); i++ {
 		elem := array.Index(i)
 		nn, err := elem.Interface().(FieldEncoder).WriteTo(r)
 		n += nn
@@ -24,8 +36,24 @@ func (a Ary) WriteTo(r io.Writer) (n int64, err error) {
 	return n, nil
 }
 
+func (a Ary) length() int {
+	v := reflect.ValueOf(a.Len)
+	for {
+		switch v.Kind() {
+		case reflect.Ptr:
+			v = v.Elem()
+		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+			return int(v.Int())
+		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+			return int(v.Uint())
+		default:
+			panic(errors.New("unsupported Len value: " + v.Type().String()))
+		}
+	}
+}
+
 func (a Ary) ReadFrom(r io.Reader) (n int64, err error) {
-	length := int(reflect.ValueOf(a.Len).Elem().Int())
+	length := a.length()
 	array := reflect.ValueOf(a.Ary).Elem()
 	if array.Cap() < length {
 		array.Set(reflect.MakeSlice(array.Type(), length, length))
@@ -42,19 +70,32 @@ func (a Ary) ReadFrom(r io.Reader) (n int64, err error) {
 }
 
 type Opt struct {
-	Has   *Boolean
+	Has   interface{} // Boolean, *Boolean or func() bool
 	Field interface{} // FieldEncoder, FieldDecoder or both (Field)
 }
 
+func (o Opt) has() bool {
+	switch o.Has.(type) {
+	case Boolean:
+		return bool(o.Has.(Boolean))
+	case *Boolean:
+		return bool(*o.Has.(*Boolean))
+	case func() bool:
+		return o.Has.(func() bool)()
+	default:
+		panic(errors.New("unsupported Has value"))
+	}
+}
+
 func (o Opt) WriteTo(w io.Writer) (int64, error) {
-	if *o.Has {
+	if o.has() {
 		return o.Field.(FieldEncoder).WriteTo(w)
 	}
 	return 0, nil
 }
 
 func (o Opt) ReadFrom(r io.Reader) (int64, error) {
-	if *o.Has {
+	if o.has() {
 		return o.Field.(FieldDecoder).ReadFrom(r)
 	}
 	return 0, nil

net/packet/util_test.go

@@ -0,0 +1,72 @@
+package packet_test
+
+import (
+	"bytes"
+	"testing"
+
+	pk "github.com/Tnze/go-mc/net/packet"
+)
+
+func ExampleAry_WriteTo() {
+	data := []pk.Int{0, 1, 2, 3, 4, 5, 6}
+	// Len is completely ignored by WriteTo method.
+	// The length is inferred from the length of Ary.
+	pk.Marshal(
+		0x00,
+		// It's important to remember that
+		// typically the responsibility of
+		// sending the length field
+		// is on you.
+		pk.VarInt(len(data)),
+		pk.Ary{
+			Len: len(data), // this line can be removed
+			Ary: data,
+		},
+	)
+}
+
+func ExampleAry_ReadFrom() {
+	var length pk.VarInt
+	var data []pk.String
+
+	var p pk.Packet // = conn.ReadPacket()
+	if err := p.Scan(
+
+		&length, // decode length first
+		pk.Ary{ // then decode Ary according to length
+			Len: &length,
+			Ary: &data,
+		},
+	); err != nil {
+		panic(err)
+	}
+}
+
+func TestAry_WriteTo(t *testing.T) {
+	var buf bytes.Buffer
+	want := []byte{
+		0x00, 0x00, 0x00, 0x01,
+		0x00, 0x00, 0x00, 0x02,
+		0x00, 0x00, 0x00, 0x03,
+	}
+	int3, long3, varint3, varlong3 := pk.Int(3), pk.Long(3), pk.VarInt(3), pk.VarLong(3)
+	for _, item := range [...]pk.Ary{
+		{Len: int3, Ary: []pk.Int{1, 2, 3}},
+		{Len: long3, Ary: []pk.Int{1, 2, 3}},
+		{Len: varint3, Ary: []pk.Int{1, 2, 3}},
+		{Len: varlong3, Ary: []pk.Int{1, 2, 3}},
+		{Len: &int3, Ary: []pk.Int{1, 2, 3}},
+		{Len: &long3, Ary: []pk.Int{1, 2, 3}},
+		{Len: &varint3, Ary: []pk.Int{1, 2, 3}},
+		{Len: &varlong3, Ary: []pk.Int{1, 2, 3}},
+	} {
+		_, err := item.WriteTo(&buf)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if !bytes.Equal(buf.Bytes(), want) {
+			t.Fatalf("Ary encoding error: got %#v, want %#v", buf.Bytes(), want)
+		}
+		buf.Reset()
+	}
+}

save/chunk_test.go

@@ -86,14 +86,19 @@ func ExampleColumn_send() {
 			_, err := pk.Tuple{
 				pk.Short(0),          // Block count
 				pk.UnsignedByte(bpb), // Bits Per Block
-				pk.Opt{
+				hasPalette, pk.Opt{
 					Has: &hasPalette,
-					Field: pk.Ary{
+					Field: pk.Tuple{
+						paletteLength, pk.Ary{
 							Len: &paletteLength,
 							Ary: nil, // TODO: We need translate v.Palette (with type of []Block) to state ID
 						},
+					},
 				}, // Palette
-				pk.Ary{Len: &dataArrayLength, Ary: dataArray}, // Data Array
+				dataArrayLength, pk.Ary{
+					Len: &dataArrayLength,
+					Ary: dataArray,
+				}, // Data Array
 			}.WriteTo(&buf)
 			if err != nil {
 				panic(err)
@@ -110,12 +115,12 @@ func ExampleColumn_send() {
 		pk.Boolean(true),           // Full chunk
 		PrimaryBitMask,             // PrimaryBitMask
 		pk.NBT(c.Level.Heightmaps), // Heightmaps
-		pk.Ary{
-			Len: &bal,           // Biomes array length
+		bal, pk.Ary{
+			Len: bal,            // Biomes array length
 			Ary: c.Level.Biomes, // Biomes
 		},
-		pk.Ary{
-			Len: &size,                     // Size
+		size, pk.Ary{
+			Len: size,                      // Size
 			Ary: pk.ByteArray(buf.Bytes()), // Data
 		},
 		pk.VarInt(0), // Block entities array length