support nil array

values.go

@@ -101,9 +101,13 @@ func readBulkString(prefix []byte, r io.Reader) (value, error) {
 		return nil, fmt.Errorf("unable to read bulkstring in redis protocol: bad prefix: %v", err)
 	}
 
-	if n == -1 {
+	switch {
+	case n == -1:
 		return nil, nil
+	case n < 0:
+		return nil, fmt.Errorf("redis protocol error: illegal bulk string of negative length %d", n)
 	}
+
 	n += 2
 	b := make([]byte, n)
 	n_read, err := r.Read(b)
@@ -135,6 +139,13 @@ func readArray(prefix []byte, r *bufio.Reader) (value, error) {
 		return nil, fmt.Errorf("unable to read array in redis protocol: bad prefix: %v", err)
 	}
 
+	switch {
+	case n == -1:
+		return nil, nil
+	case n < 0:
+		return nil, fmt.Errorf("redis protocol error: illegal array of negative length %d", n)
+	}
+
 	a := make(Array, n)
 	for i := int64(0); i < n; i++ {
 		v, err := readValue(r)

values_test.go

@@ -79,6 +79,7 @@ var valueTests = []valueTest{
 	{":9223372036854775807\r\n+extra\r\n", Integer(9223372036854775807)},   // int64 max
 	{":-9223372036854775808\r\n+extra\r\n", Integer(-9223372036854775808)}, // int64 min
 
+	{"*-1\r\n", nil},    // nil array
 	{"*0\r\n", Array{}}, // is this a thing?  I have no idea.
 	{"*1\r\n+hello\r\n", Array{String("hello")}},
 	{"*2\r\n+one\r\n+two", Array{String("one"), String("two")}},