TFilePrefetch.h

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// @(#)root/io:$Id$
// 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
 
#include "TObject.h"
#include "TString.h"
#include "TStopwatch.h"
#include "TThread.h"
#include "TFile.h"
 
#include <atomic>
#include <condition_variable>
#include <mutex>
 
#ifdef R__LESS_INCLUDES
class TSemaphore;
class TFPBlock;
#else
#include "TSemaphore.h"
#include "TFPBlock.h"
#endif
 
class TFilePrefetch : public TObject {
 
private:
   TFile      *fFile;                       ///< reference to the file
   TList      *fPendingBlocks;              ///< list of pending blocks to be read
   TList      *fReadBlocks;                 ///< list of blocks read
   TThread    *fConsumer;                   ///< consumer thread
   std::mutex fMutexPendingList;            ///< mutex for the pending list
   std::mutex fMutexReadList;               ///< mutex for the list of read blocks
   std::condition_variable fNewBlockAdded;  ///< signal the addition of a new pending block
   std::condition_variable fReadBlockAdded; ///< signal the addition of a new red block
   TSemaphore *fSemChangeFile;              ///< semaphore used when changing a file in TChain
   TString     fPathCache;                  ///< path to the cache directory
   TStopwatch  fWaitTime;                   ///< time waiting to prefetch a buffer (in usec)
   Bool_t      fThreadJoined;               ///< mark if async thread was joined
   std::atomic<Bool_t> fPrefetchFinished;   ///< true if prefetching is over
 
   static TThread::VoidRtnFunc_t ThreadProc(void*);  //create a joinable worker thread
 
public:
   TFilePrefetch(TFile*);
   ~TFilePrefetch() override;
 
   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    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* file, TFile::ECacheAction action = TFile::kDisconnect);
   std::condition_variable &GetCondNewBlock() { return fNewBlockAdded; };
   void      WaitFinishPrefetch();
   Bool_t    IsPrefetchFinished() const { return fPrefetchFinished; }
 
   ClassDefOverride(TFilePrefetch, 0);  // File block prefetcher
};
 
#endif