Experimental fastnbt library

nbt/fastnbt/decode.go

@@ -0,0 +1,198 @@
+package fastnbt
+
+import (
+	"errors"
+	"fmt"
+	"io"
+
+	"github.com/Tnze/go-mc/nbt"
+)
+
+//func (v *Value) Parse(data []byte) {
+//	// TODO
+//}
+
+func (v *Value) UnmarshalNBT(tagType byte, r nbt.DecoderReader) error {
+	v.tag = tagType
+	var buf [8]byte
+	switch tagType {
+	case nbt.TagEnd:
+	case nbt.TagByte:
+		n, err := r.ReadByte()
+		if err != nil {
+			return err
+		}
+		v.data = append(v.data[:0], n)
+
+	case nbt.TagShort:
+		if _, err := r.Read(buf[:2]); err != nil {
+			return err
+		}
+		v.data = append(v.data[:0], buf[:2]...)
+
+	case nbt.TagInt, nbt.TagFloat:
+		if _, err := r.Read(buf[:4]); err != nil {
+			return err
+		}
+		v.data = append(v.data[:0], buf[:4]...)
+
+	case nbt.TagLong, nbt.TagDouble:
+		if _, err := r.Read(buf[:]); err != nil {
+			return err
+		}
+		v.data = append(v.data[:0], buf[:]...)
+
+	case nbt.TagByteArray:
+		n, err := readInt32(r)
+		if err != nil {
+			return err
+		}
+
+		v.data = append(v.data[:0], make([]byte, 4+n)...)
+		v.data[0], v.data[1], v.data[2], v.data[3] = byte(n>>24), byte(n>>16), byte(n>>8), byte(n)
+
+		_, err = io.ReadFull(r, v.data[4:])
+		if err != nil {
+			return err
+		}
+
+	case nbt.TagString:
+		n, err := readInt16(r)
+		if err != nil {
+			return err
+		}
+
+		v.data = append(v.data[:0], make([]byte, 2+n)...)
+		v.data[0], v.data[1] = byte(n>>8), byte(n)
+
+		_, err = io.ReadFull(r, v.data[2:])
+		if err != nil {
+			return err
+		}
+
+	case nbt.TagList:
+		t, err := r.ReadByte()
+		if err != nil {
+			return err
+		}
+
+		length, err := readInt32(r)
+		if err != nil {
+			return err
+		}
+
+		v.list = v.list[:0]
+
+		for i := int32(0); i < length; i++ {
+			field := new(Value)
+			err = field.UnmarshalNBT(t, r)
+			if err != nil {
+				return err
+			}
+
+			v.list = append(v.list, field)
+		}
+
+	case nbt.TagCompound:
+		for {
+			t, name, err := readTag(r)
+			if err != nil {
+				return err
+			}
+
+			if t == nbt.TagEnd {
+				break
+			}
+
+			field := new(Value)
+			err = field.UnmarshalNBT(t, r)
+			if err != nil {
+				return decodeErr{name, err}
+			}
+
+			v.comp.kvs = append(v.comp.kvs, kv{tag: name, v: field})
+		}
+	case nbt.TagIntArray:
+		n, err := readInt32(r)
+		if err != nil {
+			return err
+		}
+
+		v.data = append(v.data[:0], make([]byte, 4+n*4)...)
+		v.data[0], v.data[1], v.data[2], v.data[3] = byte(n>>24), byte(n>>16), byte(n>>8), byte(n)
+
+		_, err = io.ReadFull(r, v.data[4:])
+		if err != nil {
+			return err
+		}
+
+	case nbt.TagLongArray:
+		n, err := readInt32(r)
+		if err != nil {
+			return err
+		}
+
+		v.data = append(v.data[:0], make([]byte, 4+n*8)...)
+		v.data[0], v.data[1], v.data[2], v.data[3] = byte(n>>24), byte(n>>16), byte(n>>8), byte(n)
+
+		_, err = io.ReadFull(r, v.data[4:])
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func readTag(r nbt.DecoderReader) (tagType byte, tagName string, err error) {
+	tagType, err = r.ReadByte()
+	if err != nil {
+		return
+	}
+
+	switch tagType {
+	// case 0x1f, 0x78:
+	case nbt.TagEnd:
+	default: // Read Tag
+		tagName, err = readString(r)
+	}
+	return
+}
+
+func readInt16(r nbt.DecoderReader) (int16, error) {
+	var data [2]byte
+	_, err := io.ReadFull(r, data[:])
+	return int16(data[0])<<8 | int16(data[1]), err
+}
+
+func readInt32(r nbt.DecoderReader) (int32, error) {
+	var data [4]byte
+	_, err := io.ReadFull(r, data[:])
+	return int32(data[0])<<24 | int32(data[1])<<16 |
+		int32(data[2])<<8 | int32(data[3]), err
+}
+
+func readString(r nbt.DecoderReader) (string, error) {
+	length, err := readInt16(r)
+	if err != nil {
+		return "", err
+	} else if length < 0 {
+		return "", errors.New("string length less than 0")
+	}
+
+	var str string
+	if length > 0 {
+		buf := make([]byte, length)
+		_, err = io.ReadFull(r, buf)
+		str = string(buf)
+	}
+	return str, err
+}
+
+type decodeErr struct {
+	decoding string
+	err      error
+}
+
+func (d decodeErr) Error() string {
+	return fmt.Sprintf("fail to decode tag %q: %v", d.decoding, d.err)
+}