Update README and add contrib dir

contrib/tsn/model/clock.cc

@@ -0,0 +1,98 @@
+#include "clock.h"
+
+#include "ns3/log.h"
+#include "ns3/simulator.h"
+
+namespace ns3
+{
+
+NS_LOG_COMPONENT_DEFINE("Clock");
+
+NS_OBJECT_ENSURE_REGISTERED(Clock);
+
+TypeId
+Clock::GetTypeId()
+{
+    static TypeId tid =
+        TypeId("ns3::Clock")
+            .SetParent<Object>()
+            .SetGroupName("tsn")
+            .AddConstructor<Clock>()
+            .AddAttribute("Granularity",
+                          "Clock granularity in ns",
+                          TimeValue(Time(NanoSeconds(1))),
+                          MakeTimeAccessor(&Clock::m_granularity),
+                          MakeTimeChecker());
+    return tid;
+}
+
+
+Clock::Clock()
+{
+    NS_LOG_FUNCTION(this);
+}
+
+Clock::~Clock()
+{
+    NS_LOG_FUNCTION(this);
+}
+
+Time
+Clock::GetLocalTime()
+{
+  NS_LOG_FUNCTION(this);
+  return GetUncorrectedLocalTime() + m_correctionOffset;
+}
+
+Time
+Clock::GetUncorrectedLocalTime()
+{
+  NS_LOG_FUNCTION(this);
+  return Simulator::Now();
+}
+
+Time
+Clock::GetTimeAt(Time t)
+{
+  NS_LOG_FUNCTION(this);
+  return t;
+}
+
+Time
+Clock::GetDuration(Time d)
+{
+  NS_LOG_FUNCTION(this);
+  return d;
+}
+
+void
+Clock::UpdateTime(){
+  NS_LOG_FUNCTION(this);
+}
+
+void
+Clock::SetOffsetTime(Time offset)
+{
+  NS_LOG_FUNCTION(this);
+  m_correctionOffset = offset;
+  TriggerCorrectionCallback();
+}
+
+void
+Clock::AddClockCorrectionCallback(Callback<void> cb)
+{
+  NS_LOG_FUNCTION(this);
+  m_callbacks.insert(m_callbacks.end(), cb);
+}
+
+void
+Clock::TriggerCorrectionCallback()
+{
+  NS_LOG_FUNCTION(this);
+  for(int i = 0; i < (int)m_callbacks.size(); i++)
+  {
+    m_callbacks[i]();
+  }
+}
+
+}