added preliminary shared memory physics client/server

fix a bug in CommonMultiBodyBase: don't use data if it hasn't been allocated

examples/SharedMemory/PhysicsClient.cpp

@@ -0,0 +1,80 @@
+
+#include "PhysicsClient.h"
+
+#include "../CommonInterfaces/CommonMultiBodyBase.h"
+#include "PosixSharedMemory.h"
+
+class PhysicsClient : public CommonMultiBodyBase
+{
+	SharedMemoryInterface* m_sharedMemory;
+	SharedMemoryExampleData*   m_testBlock1;
+    
+public:
+    
+	PhysicsClient(GUIHelperInterface* helper);
+	virtual ~PhysicsClient();
+    
+	virtual void	initPhysics();
+    
+	virtual void	stepSimulation(float deltaTime);
+    
+	virtual void resetCamera()
+	{
+		float dist = 1;
+		float pitch = 50;
+		float yaw = 35;
+		float targetPos[3]={-3,2.8,-2.5};
+		m_guiHelper->resetCamera(dist,pitch,yaw,targetPos[0],targetPos[1],targetPos[2]);
+	}
+    
+};
+
+PhysicsClient::PhysicsClient(GUIHelperInterface* helper)
+:CommonMultiBodyBase(helper),
+m_testBlock1(0)
+{
+	b3Printf("Started PhysicsClient");
+	m_sharedMemory = new PosixSharedMemory();
+}
+
+PhysicsClient::~PhysicsClient()
+{
+    b3Printf("~PhysicsClient");
+    m_sharedMemory->releaseSharedMemory(SHARED_MEMORY_KEY, SHARED_MEMORY_SIZE);
+	delete m_sharedMemory;
+}
+
+void	PhysicsClient::initPhysics()
+{
+    m_testBlock1 = (SharedMemoryExampleData*)m_sharedMemory->allocateSharedMemory(SHARED_MEMORY_KEY, SHARED_MEMORY_SIZE);
+    if (m_testBlock1)
+    {
+        btAssert(m_testBlock1->m_magicId == SHARED_MEMORY_MAGIC_NUMBER);
+    }
+    
+}
+
+void	PhysicsClient::stepSimulation(float deltaTime)
+{
+    
+    static int once = true;
+    
+    if (m_testBlock1)
+    {
+        if (once)
+        {
+            once=false;
+        
+            b3Printf("Client created CMD_LOAD_URDF");
+            m_testBlock1->m_clientCommands[0] =CMD_LOAD_URDF;
+            m_testBlock1->m_numClientCommands++;
+        }
+    }
+
+}
+
+
+class CommonExampleInterface*    PhysicsClientCreateFunc(struct CommonExampleOptions& options)
+{
+    return new PhysicsClient(options.m_guiHelper);
+}