Add test for packet read io error (#94)

serve.go

@@ -28,7 +28,7 @@ func readPacket(r io.Reader) (packetType, byte, []byte, error) {
 	var remainingLength int
 	for shift := uint(0); ; shift += 7 {
 		remainingLength |= (int(buf[1]) & 0x7F) << shift
-		if !(buf[1]&0x80 != 0) {
+		if buf[1]&0x80 == 0 {
 			break
 		}
 		if _, err := io.ReadFull(r, buf[1:]); err != nil {

serve_test.go

@@ -15,7 +15,9 @@
 package mqtt
 
 import (
+	"bytes"
 	"context"
+	"io"
 	"net"
 	"testing"
 	"time"
@@ -116,3 +118,24 @@ func TestServeParseError(t *testing.T) {
 		})
 	}
 }
+
+func TestReadPacketError(t *testing.T) {
+	pkt := []byte{0x10, 0x80, 0x01}
+	pkt = append(pkt, make([]byte, 128)...)
+
+	// Ensure full packet doesn't error
+	_, _, _, err := readPacket(bytes.NewReader(pkt))
+	if err != nil {
+		t.Fatalf("Unexpected error: '%v'", err)
+	}
+
+	for i := 1; i < len(pkt)-1; i++ {
+		_, _, _, err := readPacket(bytes.NewReader(pkt[:i]))
+		if err != io.ErrUnexpectedEOF && err != io.EOF {
+			t.Fatalf(
+				"Expected error for %d: '%v' or %v'', got: '%v'",
+				i, io.ErrUnexpectedEOF, io.EOF, err,
+			)
+		}
+	}
+}