map support

etf.go

@@ -43,6 +43,13 @@ type Ref struct {
 	Id       []uint32
 }
 
+type MapEntry struct {
+	Key   Term
+	Value Term
+}
+
+type Map []MapEntry
+
 type Function struct {
 	Arity     byte
 	Unique    [16]byte
@@ -90,6 +97,7 @@ const (
 	ettSmallInteger  = 'a'
 	ettSmallTuple    = 'h'
 	ettString        = 'k'
+	ettMap           = 't'
 )
 
 const (
@@ -129,6 +137,7 @@ var tagNames = map[byte]string{
 	ettSmallInteger:  "SMALL_INTEGER_EXT",
 	ettSmallTuple:    "SMALL_TUPLE_EXT",
 	ettString:        "STRING_EXT",
+	ettMap:           "MAP",
 }
 
 func (t Tuple) Element(i int) Term {

read.go

@@ -287,6 +287,23 @@ func (c *Context) Read(r io.Reader) (term Term, err error) {
 		}
 		term = tuple
 
+	case ettMap:
+		// $iKVKVKV…
+		var arity uint32
+		if arity, err = ruint32(r); err != nil {
+			break
+		}
+		mapVal := make(Map, arity)
+		for i := 0; i < cap(mapVal); i++ {
+			if mapVal[i].Key, err = c.Read(r); err != nil {
+				break
+			}
+			if mapVal[i].Value, err = c.Read(r); err != nil {
+				break
+			}
+		}
+		term = mapVal
+
 	case ettList:
 		// $lLLLL…$j
 		var n uint32

write.go

@@ -43,6 +43,8 @@ func (c *Context) Write(w io.Writer, term interface{}) (err error) {
 		err = c.writePid(w, v)
 	case Tuple:
 		err = c.writeTuple(w, v)
+	case Map:
+		err = c.writeMap(w, v)
 	case Ref:
 		err = c.writeRef(w, v)
 	default:
@@ -353,6 +355,32 @@ func (c *Context) writeTuple(w io.Writer, tuple Tuple) (err error) {
 	return
 }
 
+func (c *Context) writeMap(w io.Writer, theMap Map) (err error) {
+	n := len(theMap)
+	_, err = w.Write([]byte{
+		ettMap,
+		byte(n >> 24),
+		byte(n >> 16),
+		byte(n >> 8),
+		byte(n),
+	})
+
+	if err != nil {
+		return
+	}
+
+	for _, v := range theMap {
+		if err = c.Write(w, v.Key); err != nil {
+			return
+		}
+		if err = c.Write(w, v.Value); err != nil {
+			return
+		}
+	}
+
+	return
+}
+
 func reverse(b []byte) []byte {
 	size := len(b)
 	hsize := size >> 1