//.x C:/Code/MultiTreeDemo/ForumEntryTestRead.cpp
{
	//Create a list of files to read
	string base_data_dir = "C:/Code/MultiTreeDemo/";
	vector<string> files;
	files.push_back(base_data_dir + "ForestTest.root");
	files.push_back(base_data_dir + "FriendForestTest_main.root");	
		
	bool delete_ptr_after_use = false;//Set this to true to delete the tree and friend tree pointers after use
	bool verbose_output = true;//Set this to true to get more output
	int report_frequency = 1000;//Reduces the amount of output by doiong a full report for the last Tree in a group of 1000
	cout<<"Number of file to read : "<<files.size()<<endl;
	for(int f_idx =0;f_idx<files.size();f_idx++)		
	try
	{
		string file_name = files[f_idx];//retrieve the next filename
		cout<<f_idx<<":";
		cout<<"  Reading file "<<file_name<<endl;
		TFile * file = new TFile(file_name.c_str(),"UPDATE");//open file for read	
		TKey * pKey = 0;											//placeholder key address				
		int tree_idx=0;
		TIter NextKey(file->GetListOfKeys());					//	key iterator
		vector<double> rd_data;	//This vector will be used to retrieve the data		
		double * rd_data_root;//This will be used to read the data
		//file.Dump();
		int k =0;
		while ((pKey = static_cast<TKey *>(NextKey())))					//	loop over the object keys in the file
		{
			if (!strcmp("TTree", pKey->GetClassName()))							//	an object of type TTree is found
			{
				k++;
				bool reporting_period_reached = (k%report_frequency == 0);
				if(reporting_period_reached) cout<<"Name:"<< pKey->GetName()<<",Title: "<<pKey->GetTitle()<<",NBytes : "<< pKey->GetNbytes()<<",ObjLen:"<<pKey->GetObjlen()<<endl;
							
				TTree * t = static_cast<TTree *>(pKey->ReadObj());				//	return the address of that tree											
				TTree * friend_tree = static_cast<TTree *>(t->GetFriend(t->GetName()));						
				int n_total_branches = t->GetListOfBranches()->GetEntries();//Calculate total number of branches
				if(friend_tree) n_total_branches += friend_tree->GetListOfBranches()->GetEntries();
				
				if(rd_data.size() != n_total_branches)//resize read buffer if required
				{
					rd_data.resize(n_total_branches);
					rd_data_root = &(rd_data[0]);
				}
				
				TIter NextBranchKey(t->GetListOfBranches());//	branch iterator
				int branch_idx=0;
				vector<string> branch_names;
				while ((b = static_cast<TBranch *>(NextBranchKey())))// loop over every branch and 1. retrieve its name	2. set the buffer address to which data will be read
				{					
					b->SetAddress(branch_idx + rd_data_root);
					branch_names.push_back(b->GetName());
					branch_idx++;
				}		
				if(friend_tree)// do the same loop as above but for friend branches
				{	
					TIter NextFriendBranchKey(friend_tree->GetListOfBranches());						
					while ((f_b = static_cast<TBranch *>(NextFriendBranchKey())))				
					{					
						f_b->SetAddress(branch_idx + rd_data_root);
						branch_names.push_back(f_b->GetName());
						branch_idx++;
					}		
				}
				int bytes = t->GetEntry(0);//read the data
				
				
				if(reporting_period_reached) cout<<" name:"<<t->GetName()<<", bytes:"<<bytes;
						
				//attempting to reclaim some buffer space
				if(friend_tree)
				{								
					int f_bytes = friend_tree->GetEntry(0);//read friend data
					if(reporting_period_reached)cout<<", f_bytes:"<<f_bytes;
					friend_tree->DropBranchFromCache("*",true);//drop all reset buffers and backets
					friend_tree->DropBuffers(bytes);
					friend_tree->DropBaskets();				
					friend_tree->Reset();
				}
				t->DropBranchFromCache("*",true);//drop all reset buffers and backets
				t->DropBuffers(bytes);
				t->DropBaskets();
				t->Reset();	
			
				if(reporting_period_reached)
				{
					if(verbose_output)//print the data values out
					{	cout<<", data :"<<endl;
						for(int rd_data_idx=0;rd_data_idx<rd_data.size();rd_data_idx++)
						{
							cout<<"    "<<branch_names[rd_data_idx]<<" = "<<rd_data[rd_data_idx]<<" "<<endl;
						}
					}	
					cout<<endl;
				}
				
				if(delete_ptr_after_use)//delete pointers to tree  and friend tree
				{
					if(friend_tree)
					{
						if(reporting_period_reached && verbose_output)cout<<"Delete friend ptr"<<endl;
						TFile * friend_file  = friend_tree->GetCurrentFile();
						delete friend_file->Remove(friend_tree);
					}
					if(t)
					{						
						if(reporting_period_reached && verbose_output)cout<<"Delete t ptr"<<endl;				
						delete file->Remove(t);
					}
				}
			}
		}
		if(file)//delete file ptr since it is not used anymore
		{	
			if(verbose_output)cout<<"Delete file ptr"<<endl;
			delete file;
		}
		cout<<"     File "<<file_name<<" was read successfully"<<endl;
	}
	catch()
	{
		cout<<"Caught an exception while looking at TTree"<<t->GetName()<<endl;
	};	
}