Add (partial) support for IoT XEPs

That is XEP-0323, -0324, -0325, and -0347.

SMACK-727.

smack-im/src/main/java/org/jivesoftware/smack/roster/Roster.java

@@ -1074,13 +1074,7 @@ public final class Roster extends Manager {
         if (entry == null) {
             return false;
         }
-        switch (entry.getType()) {
-        case from:
-        case both:
-            return true;
-        default:
-            return false;
-        }
+        return entry.canSeeMyPresence();
     }
 
     /**

smack-im/src/main/java/org/jivesoftware/smack/roster/RosterEntry.java

@@ -176,6 +176,39 @@ public final class RosterEntry extends Manager {
         return item.isSubscriptionPending();
     }
 
+    /**
+     * Check if the contact is subscribed to "my" presence. This allows the contact to see the presence information.
+     *
+     * @return true if the contact has a presence subscription.
+     * @since 4.2
+     */
+    public boolean canSeeMyPresence() {
+        switch (getType()) {
+        case from:
+        case both:
+            return true;
+        default:
+            return false;
+        }
+    }
+
+    /**
+     * Check if we are subscribed to the contact's presence. If <code>true</code> then the contact has allowed us to
+     * receive presence information.
+     *
+     * @return true if we are subscribed to the contact's presence.
+     * @since 4.2
+     */
+    public boolean canSeeHisPresence() {
+        switch (getType()) {
+        case to:
+        case both:
+            return true;
+        default:
+            return false;
+        }
+    }
+
     public String toString() {
         StringBuilder buf = new StringBuilder();
         if (getName() != null) {

smack-im/src/main/java/org/jivesoftware/smack/roster/RosterUtil.java

@@ -0,0 +1,83 @@
+/**
+ *
+ * Copyright 2016 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.roster;
+
+import java.util.Collection;
+import java.util.Date;
+import java.util.concurrent.TimeoutException;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+
+import org.jxmpp.jid.BareJid;
+import org.jxmpp.jid.Jid;
+
+public class RosterUtil {
+
+    public static void waitUntilOtherEntityIsSubscribed(Roster roster, BareJid otherEntity, long timeoutMillis)
+                    throws InterruptedException, TimeoutException {
+        Date deadline = new Date(System.currentTimeMillis() + timeoutMillis);
+        waitUntilOtherEntityIsSubscribed(roster, otherEntity, deadline);
+    }
+
+    public static void waitUntilOtherEntityIsSubscribed(Roster roster, final BareJid otherEntity, Date deadline)
+                    throws InterruptedException, TimeoutException {
+        final Lock lock = new ReentrantLock();
+        final Condition maybeSubscribed = lock.newCondition();
+        RosterListener rosterListener = new AbstractRosterListener() {
+            private void signal() {
+                lock.lock();
+                try {
+                    // No need to use signalAll() here.
+                    maybeSubscribed.signal();
+                }
+                finally {
+                    lock.unlock();
+                }
+            }
+
+            @Override
+            public void entriesAdded(Collection<Jid> addresses) {
+                signal();
+            }
+
+            @Override
+            public void entriesUpdated(Collection<Jid> addresses) {
+                signal();
+            }
+        };
+
+        roster.addRosterListener(rosterListener);
+
+        boolean stillWaiting = true;
+        // Using the example code pattern from Condition.awaitUntil(Date) javadoc.
+        lock.lock();
+        try {
+            while (!roster.isSubscribedToMyPresence(otherEntity)) {
+                if (!stillWaiting) {
+                    throw new TimeoutException();
+                }
+                stillWaiting = maybeSubscribed.awaitUntil(deadline);
+            }
+        }
+        finally {
+            lock.unlock();
+            // Make sure the listener is removed, so we don't leak it.
+            roster.removeRosterListener(rosterListener);
+        }
+    }
+}