From 8d59667de469e31fd9b68994d2e06b5d34bd58aa Mon Sep 17 00:00:00 2001
From: Silvio Giebl <silvio.giebl@dc-square.de>
Date: Fri, 6 Jul 2018 10:38:24 +0200
Subject: [PATCH] Improved incoming TopicAliasMapping #175

---
 .../org/mqttbee/mqtt/MqttClientConnectionData.java    | 11 +++++++----
 .../mqtt/codec/decoder/mqtt5/Mqtt5PublishDecoder.java |  9 +++++----
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/src/main/java/org/mqttbee/mqtt/MqttClientConnectionData.java b/src/main/java/org/mqttbee/mqtt/MqttClientConnectionData.java
index 6ef05ae80..bbca8260f 100644
--- a/src/main/java/org/mqttbee/mqtt/MqttClientConnectionData.java
+++ b/src/main/java/org/mqttbee/mqtt/MqttClientConnectionData.java
@@ -26,6 +26,7 @@
 import org.mqttbee.api.mqtt.mqtt5.auth.Mqtt5EnhancedAuthProvider;
 import org.mqttbee.mqtt.datatypes.MqttTopicImpl;
 import org.mqttbee.mqtt.datatypes.MqttVariableByteInteger;
+import org.mqttbee.util.collections.IntMap;
 
 import java.util.Optional;
 
@@ -37,7 +38,8 @@ public class MqttClientConnectionData implements Mqtt5ClientConnectionData, Mqtt
     private int keepAlive;
     private long sessionExpiryInterval;
     private final int receiveMaximum;
-    private final MqttTopicImpl[] topicAliasMapping;
+    private final int topicAliasMaximum;
+    private final IntMap<MqttTopicImpl> topicAliasMapping;
     private final int maximumPacketSize;
     private final int subscriptionIdentifierMaximum;
     private final Mqtt5EnhancedAuthProvider enhancedAuthProvider;
@@ -56,7 +58,8 @@ public MqttClientConnectionData(
         this.keepAlive = keepAlive;
         this.sessionExpiryInterval = sessionExpiryInterval;
         this.receiveMaximum = receiveMaximum;
-        this.topicAliasMapping = (topicAliasMaximum == 0) ? null : new MqttTopicImpl[topicAliasMaximum];
+        this.topicAliasMaximum = topicAliasMaximum;
+        this.topicAliasMapping = (topicAliasMaximum == 0) ? null : IntMap.range(1, topicAliasMaximum);
         this.maximumPacketSize = maximumPacketSize;
         this.subscriptionIdentifierMaximum =
                 MqttVariableByteInteger.FOUR_BYTES_MAX_VALUE; // TODO CONNECT + CONNACK user properties
@@ -92,11 +95,11 @@ public int getReceiveMaximum() {
 
     @Override
     public int getTopicAliasMaximum() {
-        return (topicAliasMapping == null) ? 0 : topicAliasMapping.length;
+        return topicAliasMaximum;
     }
 
     @Nullable
-    public MqttTopicImpl[] getTopicAliasMapping() {
+    public IntMap<MqttTopicImpl> getTopicAliasMapping() {
         return topicAliasMapping;
     }
 
diff --git a/src/main/java/org/mqttbee/mqtt/codec/decoder/mqtt5/Mqtt5PublishDecoder.java b/src/main/java/org/mqttbee/mqtt/codec/decoder/mqtt5/Mqtt5PublishDecoder.java
index 23e32a1d2..93af4e556 100644
--- a/src/main/java/org/mqttbee/mqtt/codec/decoder/mqtt5/Mqtt5PublishDecoder.java
+++ b/src/main/java/org/mqttbee/mqtt/codec/decoder/mqtt5/Mqtt5PublishDecoder.java
@@ -36,6 +36,7 @@
 import org.mqttbee.mqtt.message.publish.MqttStatefulPublish;
 import org.mqttbee.mqtt.netty.ChannelAttributes;
 import org.mqttbee.util.ByteBufferUtil;
+import org.mqttbee.util.collections.IntMap;
 
 import javax.inject.Inject;
 import javax.inject.Singleton;
@@ -183,20 +184,20 @@ public MqttStatefulPublish decode(
 
         boolean isNewTopicAlias = false;
         if (topicAlias != DEFAULT_NO_TOPIC_ALIAS) {
-            final MqttTopicImpl[] topicAliasMapping = clientConnectionData.getTopicAliasMapping();
-            if ((topicAliasMapping == null) || (topicAlias > topicAliasMapping.length)) {
+            final IntMap<MqttTopicImpl> topicAliasMapping = clientConnectionData.getTopicAliasMapping();
+            if ((topicAliasMapping == null) || (topicAlias > clientConnectionData.getTopicAliasMaximum())) {
                 throw new MqttDecoderException(
                         Mqtt5DisconnectReasonCode.TOPIC_ALIAS_INVALID,
                         "topic alias must not exceed topic alias maximum");
             }
             if (topic == null) {
-                topic = topicAliasMapping[topicAlias - 1];
+                topic = topicAliasMapping.get(topicAlias);
                 if (topic == null) {
                     throw new MqttDecoderException(
                             Mqtt5DisconnectReasonCode.TOPIC_ALIAS_INVALID, "topic alias has no mapping");
                 }
             } else {
-                topicAliasMapping[topicAlias - 1] = topic;
+                topicAliasMapping.put(topicAlias, topic);
                 isNewTopicAlias = true;
             }
         } else if (topic == null) {