Use MultiMap for Stanza extension elements

smack-core/src/main/java/org/jivesoftware/smack/packet/Packet.java

@@ -18,17 +18,14 @@
 package org.jivesoftware.smack.packet;
 
 import org.jivesoftware.smack.packet.id.StanzaIdUtil;
+import org.jivesoftware.smack.util.MultiMap;
 import org.jivesoftware.smack.util.PacketUtil;
 import org.jivesoftware.smack.util.XmlStringBuilder;
 import org.jxmpp.util.XmppStringUtils;
 
-import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
-import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Locale;
-import java.util.Map;
 
 /**
  * Base class for XMPP Stanzas, which are called packets in Smack.
@@ -50,7 +47,7 @@ public abstract class Packet implements TopLevelStreamElement {
     protected static final String DEFAULT_LANGUAGE =
             java.util.Locale.getDefault().getLanguage().toLowerCase(Locale.US);
 
-    private final Map<String, PacketExtension> packetExtensions = new LinkedHashMap<String, PacketExtension>(12);
+    private final MultiMap<String, PacketExtension> packetExtensions = new MultiMap<>();
 
     private String packetID = null;
     private String to = null;
@@ -197,10 +194,7 @@ public abstract class Packet implements TopLevelStreamElement {
      */
     public List<PacketExtension> getExtensions() {
         synchronized (packetExtensions) {
-            if (packetExtensions.isEmpty()) {
+            return packetExtensions.values();
-                return Collections.emptyList();
-            }
-            return new ArrayList<PacketExtension>(packetExtensions.values());
         }
     }
 
@@ -240,7 +234,7 @@ public abstract class Packet implements TopLevelStreamElement {
         String key = XmppStringUtils.generateKey(elementName, namespace);
         PacketExtension packetExtension;
         synchronized (packetExtensions) {
-            packetExtension = packetExtensions.get(key);
+            packetExtension = packetExtensions.getFirst(key);
         }
         if (packetExtension == null) {
             return null;

smack-core/src/main/java/org/jivesoftware/smack/util/MultiMap.java

@@ -0,0 +1,234 @@
+/**
+ *
+ * Copyright © 2015 Florian Schmaus
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.jivesoftware.smack.util;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * A lightweight implementation of a MultiMap, that is a Map that is able to hold multiple values for every key.
+ * <p>
+ * This MultiMap uses a LinkedHashMap together with a LinkedHashSet in order to keep the order of its entries.
+ * </p>
+ *
+ * @param <K> the type of the keys the map uses.
+ * @param <V> the type of the values the map uses.
+ */
+public class MultiMap<K,V> {
+
+    /**
+     * The constant value '6'.
+     */
+    public static final int DEFAULT_MAP_SIZE = 6;
+
+    private static final int ENTRY_SET_SIZE = 3;
+
+    private final Map<K, Set<V>> map;
+
+    /**
+     * Constructs a new MultiMap with a initial capacity of {@link #DEFAULT_MAP_SIZE}.
+     */
+    public MultiMap() {
+        this(DEFAULT_MAP_SIZE);
+    }
+
+    /**
+     * Constructs a new MultiMap.
+     *
+     * @param size the initial capacity.
+     */
+    public MultiMap(int size) {
+        map = new LinkedHashMap<>(size);
+    }
+
+    public int size() {
+        int size = 0;
+        for (Set<V> set : map.values()) {
+            size += set.size();
+        }
+        return size;
+    }
+
+    public boolean isEmpty() {
+        return map.isEmpty();
+    }
+
+    public boolean containsKey(Object key) {
+        return map.containsKey(key);
+    }
+
+    public boolean containsValue(Object value) {
+        for (Set<V> set : map.values()) {
+            if (set.contains(value)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Get the first value for the given key, or <code>null</code> if there are no entries.
+     *
+     * @param key
+     * @return the first value or null.
+     */
+    public V getFirst(Object key) {
+        Set<V> res = getAll(key);
+        if (res.isEmpty()) {
+            return null;
+        } else {
+            return res.iterator().next();
+        }
+    }
+
+    /**
+     * Get all values for the given key. Returns the empty set if there are none.
+     * <p>
+     * Changes to the returned set will update the underlying MultiMap if the return set is not empty.
+     * </p>
+     *
+     * @param key
+     * @return all values for the given key.
+     */
+    public Set<V> getAll(Object key) {
+        Set<V> res = map.get(key);
+        if (res == null) {
+            res = Collections.emptySet();
+        }
+        return res;
+    }
+
+    public boolean put(K key, V value) {
+        boolean keyExisted;
+        Set<V> set = map.get(key);
+        if (set == null) {
+            set = new LinkedHashSet<>(ENTRY_SET_SIZE);
+            set.add(value);
+            map.put(key, set);
+            keyExisted = false;
+        } else {
+            set.add(value);
+            keyExisted = true;
+        }
+        return keyExisted;
+    }
+
+    /**
+     * Removes all mappings for the given key and returns the first value if there where mappings or <code>null</code> if not.
+     *
+     * @param key
+     * @return the first value of the given key or null.
+     */
+    public V remove(Object key) {
+        Set<V> res = map.remove(key);
+        if (res == null) {
+            return null;
+        }
+        assert(!res.isEmpty());
+        return res.iterator().next();
+    }
+
+    /**
+     * Remove the mapping of the given key to the value.
+     * <p>
+     * Returns <code>true</code> if the mapping was removed and <code>false</code> if the mapping did not exist.
+     * </p>
+     *
+     * @param key
+     * @param value
+     * @return true if the mapping was removed, false otherwise.
+     */
+    public boolean removeOne(Object key, V value) {
+        Set<V> set = map.get(key);
+        if (set == null) {
+            return false;
+        }
+        boolean res = set.remove(value);
+        if (set.isEmpty()) {
+            // Remove the key also if the value set is now empty
+            map.remove(key);
+        }
+        return res;
+    }
+
+    public void putAll(Map<? extends K, ? extends V> map) {
+        for (Map.Entry<? extends K, ? extends V> entry : map.entrySet()) {
+            put(entry.getKey(), entry.getValue());
+        }
+    }
+
+    public void clear() {
+        map.clear();
+    }
+
+    public Set<K> keySet() {
+        return map.keySet();
+    }
+
+    public List<V> values() {
+        List<V> values = new ArrayList<>(size());
+        for (Set<V> set : map.values()) {
+            values.addAll(set);
+        }
+        return values;
+    }
+
+    public Set<Map.Entry<K, V>> entrySet() {
+        Set<Map.Entry<K, V>> entrySet = new LinkedHashSet<>(size());
+        for (Map.Entry<K, Set<V>> entries : map.entrySet()) {
+            K key = entries.getKey();
+            for (V value : entries.getValue()) {
+                entrySet.add(new SimpleMapEntry<>(key, value));
+            }
+        }
+        return entrySet;
+    }
+
+    private static class SimpleMapEntry<K, V> implements Map.Entry<K, V> {
+
+        private final K key;
+        private V value;
+
+        private SimpleMapEntry(K key, V value) {
+            this.key = key;
+            this.value = value;
+        }
+
+        @Override
+        public K getKey() {
+            return key;
+        }
+
+        @Override
+        public V getValue() {
+            return value;
+        }
+
+        @Override
+        public V setValue(V value) {
+            V tmp = this.value;
+            this.value = value;
+            return tmp;
+        }
+    }
+
+}