Experimental fastnbt library

nbt/fastnbt/encode.go

@@ -0,0 +1,90 @@
+package fastnbt
+
+import (
+	"errors"
+	"io"
+
+	"github.com/Tnze/go-mc/nbt"
+)
+
+func (v *Value) TagType() byte { return v.tag }
+
+func (v *Value) MarshalNBT(w io.Writer) (err error) {
+	switch v.tag {
+	case nbt.TagEnd:
+
+	case nbt.TagByte, nbt.TagShort, nbt.TagInt, nbt.TagLong, nbt.TagFloat, nbt.TagDouble,
+		nbt.TagByteArray, nbt.TagString, nbt.TagIntArray, nbt.TagLongArray:
+		_, err = w.Write(v.data)
+
+	case nbt.TagList:
+		// Take a look at the first element's tag.
+		// If length == 0, use TagEnd
+		elemType := nbt.TagEnd
+		length := len(v.list)
+		if length > 0 {
+			elemType = v.list[0].tag
+		}
+
+		_, err = w.Write([]byte{elemType})
+		if err != nil {
+			return
+		}
+
+		err = writeInt32(w, int32(length))
+		if err != nil {
+			return
+		}
+
+		for _, val := range v.list {
+			err = val.MarshalNBT(w)
+			if err != nil {
+				return
+			}
+		}
+
+	case nbt.TagCompound:
+		for _, field := range v.comp.kvs {
+			err = writeTag(w, field.v.tag, field.tag)
+			if err != nil {
+				return
+			}
+
+			err = field.v.MarshalNBT(w)
+			if err != nil {
+				return
+			}
+		}
+
+		_, err = w.Write([]byte{nbt.TagEnd})
+		if err != nil {
+			return
+		}
+
+	default:
+		err = errors.New("internal: unknown tag")
+	}
+	return
+}
+
+func writeTag(w io.Writer, tagType byte, tagName string) error {
+	if _, err := w.Write([]byte{tagType}); err != nil {
+		return err
+	}
+	bName := []byte(tagName)
+	if err := writeInt16(w, int16(len(bName))); err != nil {
+		return err
+	}
+	_, err := w.Write(bName)
+	return err
+}
+
+func writeInt16(w io.Writer, n int16) error {
+	_, err := w.Write([]byte{byte(n >> 8), byte(n)})
+	return err
+}
+
+func writeInt32(w io.Writer, n int32) error {
+	_, err := w.Write([]byte{byte(n >> 24), byte(n >> 16), byte(n >> 8), byte(n)})
+	return err
+}