// @(#)root/io:$Id: TFilePrefetch.h 41698 2011-11-01 21:22:54Z pcanal $
// Author: Elvin Sindrilaru   19/05/2011

/*************************************************************************
 * Copyright (C) 1995-2011, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/

#ifndef ROOT_TFilePrefetch
#define ROOT_TFilePrefetch

//////////////////////////////////////////////////////////////////////////
//                                                                      //
// TFilePrefetch                                                        //
//                                                                      //
// The prefetching mechanism uses two classes (TFilePrefetch and        //
// TFPBlock) to prefetch in advance a block of tree entries. There is   //
// a thread which takes care of actually transferring the blocks and    //
// making them available to the main requesting thread. Therefore,      //
// the time spent by the main thread waiting for the data before        //
// processing considerably decreases. Besides the prefetching           //
// mechanisms there is also a local caching option which can be         //
// enabled by the user. Both capabilities are disabled by default       //
// and must be explicitly enabled by the user.                          //
//                                                                      //
//////////////////////////////////////////////////////////////////////////

#ifndef ROOT_TFile
#include "TFile.h"
#endif
#ifndef ROOT_TThread
#include "TThread.h"
#endif
#ifndef ROOT_TFPBlock
#include "TFPBlock.h"
#endif
#ifndef ROOT_TCondition
#include "TCondition.h"
#endif
#ifndef ROOT_TSemaphore
#include "TSemaphore.h"
#endif
#ifndef ROOT_TMD5
#include "TMD5.h"
#endif
#ifndef ROOT_TObject
#include "TObject.h"
#endif
#ifndef ROOT_TString
#include "TString.h"
#endif
#ifndef ROOT_TObjString
#include "TObjString.h"
#endif
#ifndef ROOT_TMutex
#include "TMutex.h"
#endif
#ifndef ROOT_TObjArray
#include "TObjArray.h"
#endif
#ifndef ROOT_TStopwatch
#include "TStopwatch.h"
#endif


class TFilePrefetch : public TObject {

private:
   TFile      *fFile;              // reference to the file
   TList      *fPendingBlocks;     // list of pending block to be read
   TList      *fReadBlocks;        // list of block read
   TThread    *fConsumer;          // consumer thread
   TMutex     *fMutexPendingList;  // mutex for the pending list
   TMutex     *fMutexReadList;     // mutex for the list of read blocks
   TMutex     *fMutexSynch;        // mutex for synchronisation between working and main thread
   TCondition *fNewBlockAdded;     // condition used to signal the addition of a new pending block
   TCondition *fReadBlockAdded;    // condition usd to signal the addition of a new red block
   TSemaphore *fSem;               // semaphore used to kill the consumer thread
   TString     fPathCache;         // path to the cache directory
   TStopwatch  fWaitTime;          // time wating to prefetch a buffer (in usec)

   static TThread::VoidRtnFunc_t ThreadProc(void*);  //create a joinable worker thread

public:
   TFilePrefetch(TFile*);
   virtual ~TFilePrefetch();

   void      ReadAsync(TFPBlock*, Bool_t&);
   void      ReadListOfBlocks();

   void      AddPendingBlock(TFPBlock*);
   TFPBlock *GetPendingBlock();

   void      AddReadBlock(TFPBlock*);
   Bool_t    ReadBuffer(char*, Long64_t, Int_t);
   void      ReadBlock(Long64_t*, Int_t*, Int_t);
   TFPBlock *CreateBlockObj(Long64_t*, Int_t*, Int_t);

   TThread  *GetThread() const;
   Int_t     ThreadStart();

   Bool_t    SetCache(const char*);
   Bool_t    CheckCachePath(const char*);
   Bool_t    CheckBlockInCache(char*&, TFPBlock*);
   char     *GetBlockFromCache(const char*, Int_t);
   void      SaveBlockInCache(TFPBlock*);

   Int_t     SumHex(const char*);
   Bool_t    BinarySearchReadList(TFPBlock*, Long64_t, Int_t, Int_t*);
   Long64_t  GetWaitTime();

   void      SetFile(TFile*);
   TMutex*   GetMutexSynch() const { return fMutexSynch; };

   ClassDef(TFilePrefetch, 0);  // File block prefetcher
};

#endif