added ability to export array as raw data

bitarray.go

@@ -265,3 +265,28 @@ func (bits *BitArray) ToArray() []int {
 
 	return ints
 }
+
+func (bits *BitArray) ToByteArray() []byte {
+	return bits.bytes
+}
+
+// New create a new BitArray with length(bits).
+func FromByteArray(length int, data []byte) (*BitArray, error) {
+	if data == nil {
+		return nil, errors.New("data can't be nil")
+	}
+	lenpad := nwords(length) * _BytesPW
+	if len(data) != lenpad {
+		return nil, errors.New("length and size of data don't match")
+	}
+	return &BitArray{
+		lenpad: lenpad,
+		length: length,
+		bytes:  data,
+	}, nil
+}
+
+func BitLenToByteLen(length int) int {
+	lenpad := nwords(length) * _BytesPW
+	return lenpad
+}

bitarray_test.go

@@ -226,3 +226,27 @@ func TestLeq(t *testing.T) {
 
 	_testLtOrEq(t, true)
 }
+
+func TestFromByteArray(t *testing.T) {
+	fmt.Println("Test: FromByteArray")
+
+	_, e := FromByteArray(0, nil)
+	if e == nil {
+		t.Error("allowed nil data")
+	}
+
+	bits := New(64)
+	data := bits.ToByteArray()
+
+	recreatedData, e := FromByteArray(64, data)
+
+	if e != nil || recreatedData == nil {
+		t.Error("failed to re-cteate byte array", e)
+	}
+
+	recreatedData, e = FromByteArray(88, data)
+
+	if e == nil || recreatedData != nil {
+		t.Error("failed to check for correct length", e)
+	}
+}