1 files changed, 82 insertions, 0 deletions
diff --git a/source/core/StarNetElementTop.hpp b/source/core/StarNetElementTop.hpp
new file mode 100644
index 0000000..fa85688
--- /dev/null
+++ b/source/core/StarNetElementTop.hpp
@@ -0,0 +1,82 @@
+#ifndef STAR_NET_ELEMENT_TOP_HPP
+#define STAR_NET_ELEMENT_TOP_HPP
+
+#include "StarNetElement.hpp"
+
+namespace Star {
+
+// Mixin for the NetElement that should be the top element for a network, wraps
+// any NetElement class and manages the NetElementVersion.
+template <typename BaseNetElement>
+class NetElementTop : public BaseNetElement {
+public:
+  NetElementTop();
+
+  // Returns the state update, combined with the version code that should be
+  // passed to the next call to writeState.  If 'fromVersion' is 0, then this
+  // is a full write for an initial read of a slave NetElementTop.
+  pair<ByteArray, uint64_t> writeNetState(uint64_t fromVersion = 0);
+  // Reads a state produced by a call to writeState, optionally with the
+  // interpolation delay time for the data contained in this state update.  If
+  // the state is a full update rather than a delta, the interoplation delay
+  // will be ignored.  Blank updates are not necessary to send to be read by
+  // readState, *unless* extrapolation is enabled.  If extrapolation is
+  // enabled, reading a blank update calls 'blankNetDelta' which is necessary
+  // to not improperly extrapolate past the end of incoming deltas.
+  void readNetState(ByteArray data, float interpolationTime = 0.0);
+
+private:
+  using BaseNetElement::initNetVersion;
+  using BaseNetElement::netStore;
+  using BaseNetElement::netLoad;
+  using BaseNetElement::writeNetDelta;
+  using BaseNetElement::readNetDelta;
+  using BaseNetElement::blankNetDelta;
+
+  NetElementVersion m_netVersion;
+};
+
+template <typename BaseNetElement>
+NetElementTop<BaseNetElement>::NetElementTop() {
+  BaseNetElement::initNetVersion(&m_netVersion);
+}
+
+template <typename BaseNetElement>
+pair<ByteArray, uint64_t> NetElementTop<BaseNetElement>::writeNetState(uint64_t fromVersion) {
+  if (fromVersion == 0) {
+    DataStreamBuffer ds;
+    ds.write<bool>(true);
+    BaseNetElement::netStore(ds);
+    m_netVersion.increment();
+    return {ds.takeData(), m_netVersion.current()};
+
+  } else {
+    DataStreamBuffer ds;
+    ds.write<bool>(false);
+    if (!BaseNetElement::writeNetDelta(ds, fromVersion)) {
+      return {ByteArray(), m_netVersion.current()};
+    } else {
+      m_netVersion.increment();
+      return {ds.takeData(), m_netVersion.current()};
+    }
+  }
+}
+
+template <typename BaseNetElement>
+void NetElementTop<BaseNetElement>::readNetState(ByteArray data, float interpolationTime) {
+  if (data.empty()) {
+    BaseNetElement::blankNetDelta(interpolationTime);
+
+  } else {
+    DataStreamBuffer ds(move(data));
+
+    if (ds.read<bool>())
+      BaseNetElement::netLoad(ds);
+    else
+      BaseNetElement::readNetDelta(ds, interpolationTime);
+  }
+}
+
+}
+
+#endif