examples: add library usage examples

refs: #4793

Change-Id: I660ed74bca55debd885b4cdefb230225ccdfe4ca
diff --git a/examples/producer.cpp b/examples/producer.cpp
new file mode 100644
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--- /dev/null
+++ b/examples/producer.cpp
@@ -0,0 +1,117 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/*
+ * Copyright (c) 2014-2019,  The University of Memphis
+ *
+ * This file is part of PSync.
+ * See AUTHORS.md for complete list of PSync authors and contributors.
+ *
+ * PSync is free software: you can redistribute it and/or modify it under the terms
+ * of the GNU General Public License as published by the Free Software Foundation,
+ * either version 3 of the License, or (at your option) any later version.
+ *
+ * PSync is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+ * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+ * PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * PSync, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ **/
+
+#include <PSync/partial-producer.hpp>
+
+#include <ndn-cxx/util/logger.hpp>
+#include <ndn-cxx/util/random.hpp>
+
+#include <iostream>
+
+NDN_LOG_INIT(examples.PartialSyncProducerApp);
+
+class PSyncPartialProducer
+{
+public:
+  /**
+   * @brief Initialize producer and schedule updates
+   *
+   * IBF size is set to 40 in m_producer as the expected number of update to IBF in a sync cycle
+   */
+  PSyncPartialProducer(const ndn::Name& syncPrefix, const std::string& userPrefix,
+                       int nDataStreams, int maxNumPublish)
+    : m_scheduler(m_face.getIoService())
+    , m_producer(40, m_face, syncPrefix, userPrefix + "-0")
+    , m_nDataStreams(nDataStreams)
+    , m_maxNumPublish(maxNumPublish)
+    , m_rng(ndn::random::getRandomNumberEngine())
+    , m_rangeUniformRandom(0, 60000)
+  {
+    // Add user prefixes and schedule updates for them
+    for (int i = 0; i < m_nDataStreams; i++) {
+      ndn::Name updateName(userPrefix + "-" + ndn::to_string(i));
+
+      // Add the user prefix to the producer
+      // Note that this does not add the already added userPrefix-0 in the constructor
+      m_producer.addUserNode(updateName);
+
+      // Each user prefix is updated at random interval between 0 and 60 second
+      m_scheduler.scheduleEvent(ndn::time::milliseconds(m_rangeUniformRandom(m_rng)),
+                                [this, updateName] {
+                                  doUpdate(updateName);
+                                });
+    }
+  }
+
+  void
+  run()
+  {
+    m_face.processEvents();
+  }
+
+private:
+  void
+  doUpdate(const ndn::Name& updateName)
+  {
+    // Publish an update to this user prefix
+    m_producer.publishName(updateName);
+
+    uint64_t seqNo =  m_producer.getSeqNo(updateName).value();
+    NDN_LOG_INFO("Publish: " << updateName << "/" << seqNo);
+
+    if (seqNo < m_maxNumPublish) {
+      // Schedule the next update for this user prefix b/w 0 and 60 seconds
+      m_scheduler.scheduleEvent(ndn::time::milliseconds(m_rangeUniformRandom(m_rng)),
+                                [this, updateName] {
+                                  doUpdate(updateName);
+                                });
+    }
+  }
+
+private:
+  ndn::Face m_face;
+  ndn::util::Scheduler m_scheduler;
+
+  psync::PartialProducer m_producer;
+
+  int m_nDataStreams;
+  uint64_t m_maxNumPublish;
+
+  ndn::random::RandomNumberEngine& m_rng;
+  std::uniform_int_distribution<int> m_rangeUniformRandom;
+};
+
+int
+main(int argc, char* argv[])
+{
+  if (argc != 5) {
+    std::cout << "usage: " << argv[0] << " <sync-prefix> <user-prefix> "
+              << "<number-of-user-prefixes> <max-number-of-updates-per-user-prefix>"
+              << std::endl;
+    return 1;
+  }
+
+  try {
+    PSyncPartialProducer producer(argv[1], argv[2], std::stoi(argv[3]), std::stoi(argv[4]));
+    producer.run();
+  }
+  catch (const std::exception& e) {
+    NDN_LOG_ERROR(e.what());
+  }
+}
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