TTreeCacheUnzip.cxx

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// @(#)root/tree:$Id$
// Author: Leandro Franco   10/04/2008

/*************************************************************************
 * Copyright (C) 1995-2000, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/

/** \class TTreeCacheUnzip
\ingroup tree

Specialization of TTreeCache for parallel Unzipping.

Fabrizio Furano (CERN) Aug 2009
Core TTree-related code borrowed from the previous version
 by Leandro Franco and Rene Brun

## Parallel Unzipping

TTreeCache has been specialised in order to let additional threads
free to unzip in advance its content. In this implementation we
support up to 10 threads, but right now it makes more sense to
limit their number to 1-2

The application reading data is carefully synchronized, in order to:
 - if the block it wants is not unzipped, it self-unzips it without
   waiting
 - if the block is being unzipped in parallel, it waits only
   for that unzip to finish
 - if the block has already been unzipped, it takes it

This is supposed to cancel a part of the unzipping latency, at the
expenses of cpu time.

The default parameters are the same of the prev version, i.e. 20%
of the TTreeCache cache size. To change it use
TTreeCache::SetUnzipBufferSize(Long64_t bufferSize)
where bufferSize must be passed in bytes.
*/

#include "TTreeCacheUnzip.h"
#include "TChain.h"
#include "TBranch.h"
#include "TFile.h"
#include "TEventList.h"
#include "TMutex.h"
#include "TVirtualMutex.h"
#include "TThread.h"
#include "TCondition.h"
#include "TMath.h"
#include "Bytes.h"

#include "TEnv.h"

#define THREADCNT 2
extern "C" void R__unzip(Int_t *nin, UChar_t *bufin, Int_t *lout, char *bufout, Int_t *nout);
extern "C" int R__unzip_header(Int_t *nin, UChar_t *bufin, Int_t *lout);

TTreeCacheUnzip::EParUnzipMode TTreeCacheUnzip::fgParallel = TTreeCacheUnzip::kDisable;

// The unzip cache does not consume memory by itself, it just allocates in advance
// mem blocks which are then picked as they are by the baskets.
// Hence there is no good reason to limit it too much
Double_t TTreeCacheUnzip::fgRelBuffSize = .5;

ClassImp(TTreeCacheUnzip);

////////////////////////////////////////////////////////////////////////////////

TTreeCacheUnzip::TTreeCacheUnzip() : TTreeCache(),

   fActiveThread(kFALSE),
   fAsyncReading(kFALSE),
   fCycle(0),
   fLastReadPos(0),
   fBlocksToGo(0),
   fUnzipLen(0),
   fUnzipChunks(0),
   fUnzipStatus(0),
   fTotalUnzipBytes(0),
   fNseekMax(0),
   fUnzipBufferSize(0),
   fNUnzip(0),
   fNFound(0),
   fNStalls(0),
   fNMissed(0)

{
   // Default Constructor.

   Init();
}

////////////////////////////////////////////////////////////////////////////////
/// Constructor.

TTreeCacheUnzip::TTreeCacheUnzip(TTree *tree, Int_t buffersize) : TTreeCache(tree,buffersize),
   fActiveThread(kFALSE),
   fAsyncReading(kFALSE),
   fCycle(0),
   fLastReadPos(0),
   fBlocksToGo(0),
   fUnzipLen(0),
   fUnzipChunks(0),
   fUnzipStatus(0),
   fTotalUnzipBytes(0),
   fNseekMax(0),
   fUnzipBufferSize(0),
   fNUnzip(0),
   fNFound(0),
   fNStalls(0),
   fNMissed(0)
{
   Init();
}

////////////////////////////////////////////////////////////////////////////////
/// Initialization procedure common to all the constructors.

void TTreeCacheUnzip::Init()
{
   fMutexList        = new TMutex(kTRUE);
   fIOMutex          = new TMutex(kTRUE);

   fUnzipStartCondition   = new TCondition(fMutexList);
   fUnzipDoneCondition   = new TCondition(fMutexList);

   fTotalUnzipBytes = 0;

   fCompBuffer = new char[16384];
   fCompBufferSize = 16384;

   if (fgParallel == kDisable) {
      fParallel = kFALSE;
   }
   else if(fgParallel == kEnable || fgParallel == kForce) {
      SysInfo_t info;
      gSystem->GetSysInfo(&info);

      fUnzipBufferSize = Long64_t(fgRelBuffSize * GetBufferSize());

      if(gDebug > 0)
         Info("TTreeCacheUnzip", "Enabling Parallel Unzipping");

      fParallel = kTRUE;

      for (Int_t i = 0; i < 10; i++) fUnzipThread[i] = 0;

      StartThreadUnzip(THREADCNT);

   }
   else {
      Warning("TTreeCacheUnzip", "Parallel Option unknown");
   }

   // Check if asynchronous reading is supported by this TFile specialization
   if (gEnv->GetValue("TFile.AsyncReading", 1)) {
      if (fFile && !(fFile->ReadBufferAsync(0, 0)))
         fAsyncReading = kTRUE;
   }

}

////////////////////////////////////////////////////////////////////////////////
/// Destructor. (in general called by the TFile destructor)

TTreeCacheUnzip::~TTreeCacheUnzip()
{
   ResetCache();

   if (IsActiveThread())
      StopThreadUnzip();

   delete [] fUnzipLen;

   delete fUnzipStartCondition;
   delete fUnzipDoneCondition;

   delete fMutexList;
   delete fIOMutex;

   delete [] fUnzipStatus;
   delete [] fUnzipChunks;
}

////////////////////////////////////////////////////////////////////////////////
/// Add a branch to the list of branches to be stored in the cache
/// this function is called by TBranch::GetBasket
/// Returns:
///  - 0 branch added or already included
///  - -1 on error

Int_t TTreeCacheUnzip::AddBranch(TBranch *b, Bool_t subbranches /*= kFALSE*/)
{
   R__LOCKGUARD(fMutexList);

   return TTreeCache::AddBranch(b, subbranches);
}

////////////////////////////////////////////////////////////////////////////////
/// Add a branch to the list of branches to be stored in the cache
/// this function is called by TBranch::GetBasket
/// Returns:
///  - 0 branch added or already included
///  - -1 on error

Int_t TTreeCacheUnzip::AddBranch(const char *branch, Bool_t subbranches /*= kFALSE*/)
{
   R__LOCKGUARD(fMutexList);

   return TTreeCache::AddBranch(branch, subbranches);
}

////////////////////////////////////////////////////////////////////////////////

Bool_t TTreeCacheUnzip::FillBuffer()
{
   if (fNbranches <= 0) return kFALSE;
   {
      // Fill the cache buffer with the branches in the cache.
      R__LOCKGUARD(fMutexList);
      fIsTransferred = kFALSE;

      TTree *tree = ((TBranch*)fBranches->UncheckedAt(0))->GetTree();
      Long64_t entry = tree->GetReadEntry();

      // If the entry is in the range we previously prefetched, there is
      // no point in retrying.   Note that this will also return false
      // during the training phase (fEntryNext is then set intentional to
      // the end of the training phase).
      if (fEntryCurrent <= entry  && entry < fEntryNext) return kFALSE;

      // Triggered by the user, not the learning phase
      if (entry == -1)  entry=0;

      TTree::TClusterIterator clusterIter = tree->GetClusterIterator(entry);
      fEntryCurrent = clusterIter();
      fEntryNext = clusterIter.GetNextEntry();

      if (fEntryCurrent < fEntryMin) fEntryCurrent = fEntryMin;
      if (fEntryMax <= 0) fEntryMax = tree->GetEntries();
      if (fEntryNext > fEntryMax) fEntryNext = fEntryMax;

      // Check if owner has a TEventList set. If yes we optimize for this
      // Special case reading only the baskets containing entries in the
      // list.
      TEventList *elist = fTree->GetEventList();
      Long64_t chainOffset = 0;
      if (elist) {
         if (fTree->IsA() ==TChain::Class()) {
            TChain *chain = (TChain*)fTree;
            Int_t t = chain->GetTreeNumber();
            chainOffset = chain->GetTreeOffset()[t];
         }
      }

      //clear cache buffer
      TFileCacheRead::Prefetch(0,0);

      //store baskets
      for (Int_t i=0;i<fNbranches;i++) {
         TBranch *b = (TBranch*)fBranches->UncheckedAt(i);
         if (b->GetDirectory()==0) continue;
         if (b->GetDirectory()->GetFile() != fFile) continue;
         Int_t nb = b->GetMaxBaskets();
         Int_t *lbaskets   = b->GetBasketBytes();
         Long64_t *entries = b->GetBasketEntry();
         if (!lbaskets || !entries) continue;
         //we have found the branch. We now register all its baskets
         //from the requested offset to the basket below fEntrymax
         Int_t blistsize = b->GetListOfBaskets()->GetSize();
         for (Int_t j=0;j<nb;j++) {
            // This basket has already been read, skip it
            if (j<blistsize && b->GetListOfBaskets()->UncheckedAt(j)) continue;

            Long64_t pos = b->GetBasketSeek(j);
            Int_t len = lbaskets[j];
            if (pos <= 0 || len <= 0) continue;
            //important: do not try to read fEntryNext, otherwise you jump to the next autoflush
            if (entries[j] >= fEntryNext) continue;
            if (entries[j] < entry && (j<nb-1 && entries[j+1] <= entry)) continue;
            if (elist) {
               Long64_t emax = fEntryMax;
               if (j<nb-1) emax = entries[j+1]-1;
               if (!elist->ContainsRange(entries[j]+chainOffset,emax+chainOffset)) continue;
            }
            fNReadPref++;

            TFileCacheRead::Prefetch(pos,len);
         }
         if (gDebug > 0) printf("Entry: %lld, registering baskets branch %s, fEntryNext=%lld, fNseek=%d, fNtot=%d\n",entry,((TBranch*)fBranches->UncheckedAt(i))->GetName(),fEntryNext,fNseek,fNtot);
      }

      // Now fix the size of the status arrays
      ResetCache();

      fIsLearning = kFALSE;

   }

   return kTRUE;
}

////////////////////////////////////////////////////////////////////////////////
/// Change the underlying buffer size of the cache.
/// Returns:
///  - 0 if the buffer content is still available
///  - 1 if some or all of the buffer content has been made unavailable
///  - -1 on error

Int_t TTreeCacheUnzip::SetBufferSize(Int_t buffersize)
{
   R__LOCKGUARD(fMutexList);

   Int_t res = TTreeCache::SetBufferSize(buffersize);
   if (res < 0) {
      return res;
   }
   fUnzipBufferSize = Long64_t(fgRelBuffSize * GetBufferSize());
   ResetCache();
   return 1;
}

////////////////////////////////////////////////////////////////////////////////
/// Set the minimum and maximum entry number to be processed
/// this information helps to optimize the number of baskets to read
/// when prefetching the branch buffers.

void TTreeCacheUnzip::SetEntryRange(Long64_t emin, Long64_t emax)
{
   R__LOCKGUARD(fMutexList);

   TTreeCache::SetEntryRange(emin, emax);
}

////////////////////////////////////////////////////////////////////////////////
/// It's the same as TTreeCache::StopLearningPhase but we guarantee that
/// we start the unzipping just after getting the buffers

void TTreeCacheUnzip::StopLearningPhase()
{
   R__LOCKGUARD(fMutexList);

   TTreeCache::StopLearningPhase();

}

////////////////////////////////////////////////////////////////////////////////
///update pointer to current Tree and recompute pointers to the branches in the cache

void TTreeCacheUnzip::UpdateBranches(TTree *tree)
{
   R__LOCKGUARD(fMutexList);

   TTreeCache::UpdateBranches(tree);
}

////////////////////////////////////////////////////////////////////////////////
//                                                                            //
// From now on we have the methods concerning the threading part of the cache //
//                                                                            //
////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////
/// Static function that returns the parallel option
/// (to indicate an additional thread)

TTreeCacheUnzip::EParUnzipMode TTreeCacheUnzip::GetParallelUnzip()
{
   return fgParallel;
}

////////////////////////////////////////////////////////////////////////////////
/// Static function that tells wether the multithreading unzipping is activated

Bool_t TTreeCacheUnzip::IsParallelUnzip()
{
   if (fgParallel == kEnable || fgParallel == kForce)
      return kTRUE;

   return kFALSE;
}

////////////////////////////////////////////////////////////////////////////////
/// This indicates if the thread is active in this moment...
/// this variable is very important because if we change it from true to
/// false the thread will stop... ( see StopThreadTreeCacheUnzip() )

Bool_t TTreeCacheUnzip::IsActiveThread()
{
   R__LOCKGUARD(fMutexList);

   return fActiveThread;
}

////////////////////////////////////////////////////////////////////////////////
/// It says if the queue is empty... useful to see if we have to process it.

Bool_t TTreeCacheUnzip::IsQueueEmpty()
{
   R__LOCKGUARD(fMutexList);

   if ( fIsLearning )
      return kTRUE;

   return kFALSE;
}

void TTreeCacheUnzip::WaitUnzipStartSignal()
{
   // Here the threads sleep waiting for some blocks to unzip

   fUnzipStartCondition->TimedWaitRelative(2000);

}

////////////////////////////////////////////////////////////////////////////////
/// This will send the signal corresponfing to the queue... normally used
/// when we want to start processing the list of buffers.

void TTreeCacheUnzip::SendUnzipStartSignal(Bool_t broadcast)
{
   if (gDebug > 0) Info("SendSignal", " fUnzipCondition->Signal()");

   if (broadcast)
      fUnzipStartCondition->Broadcast();
   else
      fUnzipStartCondition->Signal();
}

////////////////////////////////////////////////////////////////////////////////
/// Static function that (de)activates multithreading unzipping
///
/// The possible options are:
///  - kEnable _Enable_ it, which causes an automatic detection and launches the
///    additional thread if the number of cores in the machine is greater than
///    one
///  - kDisable _Disable_ will not activate the additional thread.
///  - kForce _Force_ will start the additional thread even if there is only one
///    core. the default will be taken as kEnable.
///
/// Returns 0 if there was an error, 1 otherwise.

Int_t TTreeCacheUnzip::SetParallelUnzip(TTreeCacheUnzip::EParUnzipMode option)
{
   if(fgParallel == kEnable || fgParallel == kForce || fgParallel == kDisable) {
      fgParallel = option;
      return 1;
   }
   return 0;
}

class TTreeCacheUnzipData {
public:
   TTreeCacheUnzip *fInstance;
   Int_t            fCount;
};

////////////////////////////////////////////////////////////////////////////////
/// The Thread is only a part of the TTreeCache but it is the part that
/// waits for info in the queue and process it... unfortunatly, a Thread is
/// not an object an we have to deal with it in the old C-Style way
/// Returns 0 if the thread was initialized or 1 if it was already running

Int_t TTreeCacheUnzip::StartThreadUnzip(Int_t nthreads)
{
   Int_t nt = nthreads;
   if (nt > 10) nt = 10;

   if (gDebug > 0)
      Info("StartThreadUnzip", "Going to start %d threads.", nt);

   for (Int_t i = 0; i < nt; i++) {
      if (!fUnzipThread[i]) {
         TString nm("UnzipLoop");
         nm += i;

         if (gDebug > 0)
            Info("StartThreadUnzip", "Going to start thread '%s'", nm.Data());

         TTreeCacheUnzipData *d = new TTreeCacheUnzipData;
         d->fInstance = this;
         d->fCount = i;

         fUnzipThread[i] = new TThread(nm.Data(), UnzipLoop, (void*)d);
         if (!fUnzipThread[i])
            Error("TTreeCacheUnzip::StartThreadUnzip", " Unable to create new thread.");

         fUnzipThread[i]->Run();

         // There is at least one active thread
         fActiveThread=kTRUE;

      }
   }

   return (fActiveThread == kTRUE);
}

////////////////////////////////////////////////////////////////////////////////
/// To stop the thread we only need to change the value of the variable
/// fActiveThread to false and the loop will stop (of course, we will have)
/// to do the cleaning after that.
///
/// Note: The syncronization part is important here or we will try to delete
///       teh object while it's still processing the queue

Int_t TTreeCacheUnzip::StopThreadUnzip()
{
   fActiveThread = kFALSE;

   for (Int_t i = 0; i < 1; i++) {
      if(fUnzipThread[i]){

         SendUnzipStartSignal(kTRUE);

         if (fUnzipThread[i]->Exists()) {
            fUnzipThread[i]->Join();
            delete fUnzipThread[i];
         }
      }

   }

   return 1;
}

////////////////////////////////////////////////////////////////////////////////
/// This is a static function.
///
/// This is the call that will be executed in the Thread generated by
/// StartThreadTreeCacheUnzip... what we want to do is to inflate the next
/// series of buffers leaving them in the second cache.
///
/// Returns 0 when it finishes

void* TTreeCacheUnzip::UnzipLoop(void *arg)
{
   TTreeCacheUnzipData *d = (TTreeCacheUnzipData *)arg;
   TTreeCacheUnzip *unzipMng = d->fInstance;

   TThread::SetCancelOn();
   TThread::SetCancelDeferred();

   Int_t thrnum = d->fCount;
   Int_t startindex = thrnum;
   Int_t locbuffsz = 16384;
   char *locbuff = new char[16384];
   Int_t res = 0;
   Int_t myCycle = 0;

   while( unzipMng->IsActiveThread() ) {
      res = 1;

      {
         R__LOCKGUARD(unzipMng->fMutexList);
         if (myCycle != unzipMng->fCycle) startindex = thrnum;
         myCycle = unzipMng->fCycle;
         if (unzipMng->fNseek) startindex = startindex % unzipMng->fNseek;
         else startindex = -1;
      }

      if (startindex >= 0)
         res = unzipMng->UnzipCache(startindex, locbuffsz, locbuff);

      {
         R__LOCKGUARD(unzipMng->fMutexList);

         if(!unzipMng->IsActiveThread()) break;

         if ((res == 1) || (!unzipMng->fIsTransferred)) {
            unzipMng->WaitUnzipStartSignal();
            startindex = unzipMng->fLastReadPos+3+thrnum;
         }
      }

   }

   delete d;
   delete [] locbuff;
   return (void *)0;
}

////////////////////////////////////////////////////////////////////////////////
//                                                                            //
// From now on we have the methods concerning the unzipping part of the cache //
//                                                                            //
////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////
/// Read the logical record header from the buffer buf.
/// That must be the pointer tho the header part not the object by itself and
/// must contain data of at least maxbytes
/// Returns nread;
///
/// In output arguments:
///
/// -  nbytes : number of bytes in record
///             if negative, this is a deleted record
///             if 0, cannot read record, wrong value of argument first
/// -  objlen : uncompressed object size
/// -  keylen : length of logical record header
///
/// Note that the arguments objlen and keylen are returned only
/// if maxbytes >=16
/// Note: This was adapted from TFile... so some things dont apply

Int_t TTreeCacheUnzip::GetRecordHeader(char *buf, Int_t maxbytes, Int_t &nbytes, Int_t &objlen, Int_t &keylen)
{
   Version_t versionkey;
   Short_t klen;
   UInt_t datime;
   Int_t nb = 0,olen;
   Int_t nread = maxbytes;
   frombuf(buf,&nb);
   nbytes = nb;
   if (nb < 0) return nread;
   //   const Int_t headerSize = Int_t(sizeof(nb) +sizeof(versionkey) +sizeof(olen) +sizeof(datime) +sizeof(klen));
   const Int_t headerSize = 16;
   if (nread < headerSize) return nread;
   frombuf(buf, &versionkey);
   frombuf(buf, &olen);
   frombuf(buf, &datime);
   frombuf(buf, &klen);
   if (!olen) olen = nbytes-klen;
   objlen = olen;
   keylen = klen;
   return nread;
}

////////////////////////////////////////////////////////////////////////////////
/// This will delete the list of buffers that are in the unzipping cache
/// and will reset certain values in the cache.
/// This name is ambiguos because the method doesn't reset the whole cache,
/// only the part related to the unzipping
/// Note: This method is completely different from TTreeCache::ResetCache(),
/// in that method we were cleaning the prefetching buffer while here we
/// delete the information about the unzipped buffers

void TTreeCacheUnzip::ResetCache()
{
   {
   R__LOCKGUARD(fMutexList);

   if (gDebug > 0)
      Info("ResetCache", "Thread: %ld -- Resetting the cache. fNseek:%d fNSeekMax:%d fTotalUnzipBytes:%lld", TThread::SelfId(), fNseek, fNseekMax, fTotalUnzipBytes);

   // Reset all the lists and wipe all the chunks
   fCycle++;
   for (Int_t i = 0; i < fNseekMax; i++) {
      if (fUnzipLen) fUnzipLen[i] = 0;
      if (fUnzipChunks) {
         if (fUnzipChunks[i]) delete [] fUnzipChunks[i];
         fUnzipChunks[i] = 0;
      }
      if (fUnzipStatus) fUnzipStatus[i] = 0;

   }

   while (fActiveBlks.size()) fActiveBlks.pop();

   if(fNseekMax < fNseek){
      if (gDebug > 0)
         Info("ResetCache", "Changing fNseekMax from:%d to:%d", fNseekMax, fNseek);

      Byte_t *aUnzipStatus = new Byte_t[fNseek];
      memset(aUnzipStatus, 0, fNseek*sizeof(Byte_t));

      Int_t *aUnzipLen = new Int_t[fNseek];
      memset(aUnzipLen, 0, fNseek*sizeof(Int_t));

      char **aUnzipChunks = new char *[fNseek];
      memset(aUnzipChunks, 0, fNseek*sizeof(char *));

      if (fUnzipStatus) delete [] fUnzipStatus;
      if (fUnzipLen) delete [] fUnzipLen;
      if (fUnzipChunks) delete [] fUnzipChunks;

      fUnzipStatus  = aUnzipStatus;
      fUnzipLen  = aUnzipLen;
      fUnzipChunks = aUnzipChunks;

      fNseekMax  = fNseek;
   }

   fLastReadPos = 0;
   fTotalUnzipBytes = 0;
   fBlocksToGo = fNseek;
   }

   SendUnzipStartSignal(kTRUE);

}

////////////////////////////////////////////////////////////////////////////////
/// We try to read a buffer that has already been unzipped
/// Returns -1 in case of read failure, 0 in case it's not in the
/// cache and n>0 in case read from cache (number of bytes copied).
/// pos and len are the original values as were passed to ReadBuffer
/// but instead we will return the inflated buffer.
/// Note!! : If *buf == 0 we will allocate the buffer and it will be the
/// responsability of the caller to free it... it is useful for example
/// to pass it to the creator of TBuffer

Int_t TTreeCacheUnzip::GetUnzipBuffer(char **buf, Long64_t pos, Int_t len, Bool_t *free)
{
   Int_t res = 0;
   Int_t loc = -1;

   {
      R__LOCKGUARD(fMutexList);

      // We go straight to TTreeCache/TfileCacheRead, in order to get the info we need
      //  pointer to the original zipped chunk
      //  its index in the original unsorted offsets lists
      //
      // Actually there are situations in which copying the buffer is not
      // useful. But the choice is among doing once more a small memcpy or a binary search in a large array. I prefer the former.
      // Also, here we prefer not to trigger the (re)population of the chunks in the TFileCacheRead. That is
      // better to be done in the main thread.

      // And now loc is the position of the chunk in the array of the sorted chunks
      Int_t myCycle = fCycle;

      if (fParallel && !fIsLearning) {

         if(fNseekMax < fNseek){
            if (gDebug > 0)
               Info("GetUnzipBuffer", "Changing fNseekMax from:%d to:%d", fNseekMax, fNseek);

            Byte_t *aUnzipStatus = new Byte_t[fNseek];
            memset(aUnzipStatus, 0, fNseek*sizeof(Byte_t));

            Int_t *aUnzipLen = new Int_t[fNseek];
            memset(aUnzipLen, 0, fNseek*sizeof(Int_t));

            char **aUnzipChunks = new char *[fNseek];
            memset(aUnzipChunks, 0, fNseek*sizeof(char *));

            for (Int_t i = 0; i < fNseekMax; i++) {
               aUnzipStatus[i] = fUnzipStatus[i];
               aUnzipLen[i] = fUnzipLen[i];
               aUnzipChunks[i] = fUnzipChunks[i];
            }

            if (fUnzipStatus) delete [] fUnzipStatus;
            if (fUnzipLen) delete [] fUnzipLen;
            if (fUnzipChunks) delete [] fUnzipChunks;

            fUnzipStatus  = aUnzipStatus;
            fUnzipLen  = aUnzipLen;
            fUnzipChunks = aUnzipChunks;

            fNseekMax  = fNseek;
         }

         loc = (Int_t)TMath::BinarySearch(fNseek,fSeekSort,pos);
         if ( (fCycle == myCycle) && (loc >= 0) && (loc < fNseek) && (pos == fSeekSort[loc]) ) {

            // The buffer is, at minimum, in the file cache. We must know its index in the requests list
            // In order to get its info
            Int_t seekidx = fSeekIndex[loc];

            fLastReadPos = seekidx;

            do {

               // If the block is ready we get it immediately.
               // And also we don't have to alloc the blks. This is supposed to be
               // the main thread of the app.
               if ((fUnzipStatus[seekidx] == 2) && (fUnzipChunks[seekidx]) && (fUnzipLen[seekidx] > 0)) {

                  //if (gDebug > 0)
                  //   Info("GetUnzipBuffer", "++++++++++++++++++++ CacheHIT Block wanted: %d  len:%d req_len:%d fNseek:%d", seekidx, fUnzipLen[seekidx], len,  fNseek);

                  if(!(*buf)) {
                     *buf = fUnzipChunks[seekidx];
                     fUnzipChunks[seekidx] = 0;
                     fTotalUnzipBytes -= fUnzipLen[seekidx];
                     SendUnzipStartSignal(kFALSE);
                     *free = kTRUE;
                  }
                  else {
                     memcpy(*buf, fUnzipChunks[seekidx], fUnzipLen[seekidx]);
                     delete fUnzipChunks[seekidx];
                     fTotalUnzipBytes -= fUnzipLen[seekidx];
                     fUnzipChunks[seekidx] = 0;
                     SendUnzipStartSignal(kFALSE);
                     *free = kFALSE;
                  }

                  fNFound++;

                  return fUnzipLen[seekidx];
               }

               // If the status of the unzipped chunk is pending
               // we wait on the condvar, hoping that the next signal is the good one
               if ( fUnzipStatus[seekidx] == 1 ) {
                  //fMutexList->UnLock();
                  fUnzipDoneCondition->TimedWaitRelative(200);
                  //fMutexList->Lock();

                  if ( myCycle != fCycle ) {
                     if (gDebug > 0)
                        Info("GetUnzipBuffer", "Sudden paging Break!!! IsActiveThread(): %d, fNseek: %d, fIsLearning:%d",
                             IsActiveThread(), fNseek, fIsLearning);

                     fLastReadPos = 0;

                     seekidx = -1;
                     break;
                  }

               }

            } while ( fUnzipStatus[seekidx] == 1 );

            //if (gDebug > 0)
            //   Info("GetUnzipBuffer", "------- Block wanted: %d  status: %d len: %d chunk: %llx ", seekidx, fUnzipStatus[seekidx], fUnzipLen[seekidx], fUnzipChunks[seekidx]);

            // Here the block is not pending. It could be done or aborted or not yet being processed.
            if ( (seekidx >= 0) && (fUnzipStatus[seekidx] == 2) && (fUnzipChunks[seekidx]) && (fUnzipLen[seekidx] > 0) ) {

               //if (gDebug > 0)
               //   Info("GetUnzipBuffer", "++++++++++++++++++++ CacheLateHIT Block wanted: %d  len:%d fNseek:%d", seekidx, fUnzipLen[seekidx], fNseek);

               if(!(*buf)) {
                  *buf = fUnzipChunks[seekidx];
                  fUnzipChunks[seekidx] = 0;
                  fTotalUnzipBytes -= fUnzipLen[seekidx];
                  SendUnzipStartSignal(kFALSE);
                  *free = kTRUE;
               }
               else {
                  memcpy(*buf, fUnzipChunks[seekidx], fUnzipLen[seekidx]);
                  delete fUnzipChunks[seekidx];
                  fTotalUnzipBytes -= fUnzipLen[seekidx];
                  fUnzipChunks[seekidx] = 0;
                  SendUnzipStartSignal(kFALSE);
                  *free = kFALSE;
               }

               fNStalls++;

               return fUnzipLen[seekidx];
            }
            else {
               // This is a complete miss. We want to avoid the threads
               // to try unzipping this block in the future.
               fUnzipStatus[seekidx] = 2;
               fUnzipChunks[seekidx] = 0;

               if ((fTotalUnzipBytes < fUnzipBufferSize) && fBlocksToGo)
                  SendUnzipStartSignal(kFALSE);

               //if (gDebug > 0)
               //   Info("GetUnzipBuffer", "++++++++++++++++++++ CacheMISS Block wanted: %d  len:%d fNseek:%d", seekidx, len, fNseek);
            }

         } else {
            loc = -1;
            //fLastReadPos = 0;
            fIsTransferred = kFALSE;
         }

      } else {
         // We need to reset it for new transferences...
         //ResetCache();
         //TFileCacheRead::Prefetch(0,0);
      }

   } // scope of the lock!

   if (len > fCompBufferSize) {
      delete [] fCompBuffer;
      fCompBuffer = new char[len];
      fCompBufferSize = len;
   } else {
      if (fCompBufferSize > len*4) {
      delete [] fCompBuffer;
      fCompBuffer = new char[len*2];
      fCompBufferSize = len*2;
      }
   }

   {
      R__LOCKGUARD(fIOMutex);
      // Here we know that the async unzip of the wanted chunk
      // was not done for some reason. We continue.

      res = 0;
      if (!ReadBufferExt(fCompBuffer, pos, len, loc)) {
         //Info("GetUnzipBuffer", "++++++++++++++++++++ CacheMISS %d %d", loc, fNseek);
         fFile->Seek(pos);
         res = fFile->ReadBuffer(fCompBuffer, len);
      }

      if (res) res = -1;

   } // scope of the lock!

   if (!res) {
      res = UnzipBuffer(buf, fCompBuffer);
      *free = kTRUE;
   }

   if (!fIsLearning) {
      fNMissed++;
   }

   return res;

}

////////////////////////////////////////////////////////////////////////////////
/// static function: Sets the unzip relatibe buffer size

void TTreeCacheUnzip::SetUnzipRelBufferSize(Float_t relbufferSize)
{
   fgRelBuffSize = relbufferSize;
}

////////////////////////////////////////////////////////////////////////////////
/// Sets the size for the unzipping cache... by default it should be
/// two times the size of the prefetching cache

void TTreeCacheUnzip::SetUnzipBufferSize(Long64_t bufferSize)
{
   R__LOCKGUARD(fMutexList);

   fUnzipBufferSize = bufferSize;
}

////////////////////////////////////////////////////////////////////////////////
/// Unzips a ROOT specific buffer... by reading the header at the beginning.
/// returns the size of the inflated buffer or -1 if error
/// Note!! : If *dest == 0 we will allocate the buffer and it will be the
/// responsability of the caller to free it... it is useful for example
/// to pass it to the creator of TBuffer
/// src is the original buffer with the record (header+compressed data)
/// *dest is the inflated buffer (including the header)

Int_t TTreeCacheUnzip::UnzipBuffer(char **dest, char *src)
{
   Int_t  uzlen = 0;
   Bool_t alloc = kFALSE;

   // Here we read the header of the buffer
   const Int_t hlen=128;
   Int_t nbytes=0, objlen=0, keylen=0;
   GetRecordHeader(src, hlen, nbytes, objlen, keylen);

   if (!(*dest)) {
      /* early consistency check */
      UChar_t *bufcur = (UChar_t *) (src + keylen);
      Int_t nin, nbuf;
      if(R__unzip_header(&nin, bufcur, &nbuf)!=0) {
         Error("UnzipBuffer", "Inconsistency found in header (nin=%d, nbuf=%d)", nin, nbuf);
         uzlen = -1;
         return uzlen;
      }
      Int_t l = keylen+objlen;
      *dest = new char[l];
      alloc = kTRUE;
   }
   // Must unzip the buffer
   // fSeekPos[ind]; adress of zipped buffer
   // fSeekLen[ind]; len of the zipped buffer
   // &fBuffer[fSeekPos[ind]]; memory address

   // This is similar to TBasket::ReadBasketBuffers
   Bool_t oldCase = objlen==nbytes-keylen
      && ((TBranch*)fBranches->UncheckedAt(0))->GetCompressionLevel()!=0
      && fFile->GetVersion()<=30401;

   if (objlen > nbytes-keylen || oldCase) {

      // Copy the key
      memcpy(*dest, src, keylen);
      uzlen += keylen;

      char *objbuf = *dest + keylen;
      UChar_t *bufcur = (UChar_t *) (src + keylen);
      Int_t nin, nbuf;
      Int_t nout = 0;
      Int_t noutot = 0;

      while (1) {
         Int_t hc = R__unzip_header(&nin, bufcur, &nbuf);
         if (hc!=0) break;
         if (gDebug > 2)
            Info("UnzipBuffer", " nin:%d, nbuf:%d, bufcur[3] :%d, bufcur[4] :%d, bufcur[5] :%d ",
                 nin, nbuf, bufcur[3], bufcur[4], bufcur[5]);
         if (oldCase && (nin > objlen || nbuf > objlen)) {
            if (gDebug > 2)
               Info("UnzipBuffer", "oldcase objlen :%d ", objlen);

            //buffer was very likely not compressed in an old version
            memcpy( *dest + keylen, src + keylen, objlen);
            uzlen += objlen;
            return uzlen;
         }

         R__unzip(&nin, bufcur, &nbuf, objbuf, &nout);

         if (gDebug > 2)
            Info("UnzipBuffer", "R__unzip nin:%d, bufcur:%p, nbuf:%d, objbuf:%p, nout:%d",
                 nin, bufcur, nbuf, objbuf, nout);

         if (!nout) break;
         noutot += nout;
         if (noutot >= objlen) break;
         bufcur += nin;
         objbuf += nout;
      }

      if (noutot != objlen) {
         Error("UnzipBuffer", "nbytes = %d, keylen = %d, objlen = %d, noutot = %d, nout=%d, nin=%d, nbuf=%d",
               nbytes,keylen,objlen, noutot,nout,nin,nbuf);
         uzlen = -1;
         if(alloc) delete [] *dest;
         *dest = 0;
         return uzlen;
      }
      uzlen += objlen;
   } else {
      memcpy(*dest, src, keylen);
      uzlen += keylen;
      memcpy(*dest + keylen, src + keylen, objlen);
      uzlen += objlen;
   }
   return uzlen;
}

////////////////////////////////////////////////////////////////////////////////
/// This inflates all the buffers in the cache.. passing the data to a new
/// buffer that will only wait there to be read...
/// We can not inflate all the buffers in the cache so we will try to do
/// it until the cache gets full... there is a member called fUnzipBufferSize which will
/// tell us the max size we can allocate for this cache.
///
/// note that we will  unzip in the order they were put into the cache not
/// the order of the transference so it has to be read in that order or the
/// pre-unzipping will be useless.
///
/// startindex is used as start index to check for blks to be unzipped
///
/// returns 0 in normal conditions or -1 if error, 1 if it would like to sleep
///
/// This func is supposed to compete among an indefinite number of threads to get a chunk to inflate
/// in order to accommodate multiple unzippers
/// Since everything is so async, we cannot use a fixed buffer, we are forced to keep
/// the individual chunks as separate blocks, whose summed size does not exceed the maximum
/// allowed. The pointers are kept globally in the array fUnzipChunks

Int_t TTreeCacheUnzip::UnzipCache(Int_t &startindex, Int_t &locbuffsz, char *&locbuff)
{
   Int_t myCycle;
   const Int_t hlen=128;
   Int_t objlen=0, keylen=0;
   Int_t nbytes=0;
   Int_t readbuf = 0;

   Int_t idxtounzip = -1;
   Long64_t rdoffs = 0;
   Int_t rdlen = 0;
   {
      R__LOCKGUARD(fMutexList);

      if (!IsActiveThread() || !fNseek || fIsLearning || !fIsTransferred) {
         if (gDebug > 0)
            Info("UnzipCache", "Sudden Break!!! IsActiveThread(): %d, fNseek: %d, fIsLearning:%d",
                 IsActiveThread(), fNseek, fIsLearning);
         return 1;
      }

      // To synchronize with the 'paging'
      myCycle = fCycle;

      // Try to look for a blk to unzip
      idxtounzip = -1;
      rdoffs = 0;
      rdlen = 0;
      if (fTotalUnzipBytes < fUnzipBufferSize) {

         if (fBlocksToGo > 0) {
            for (Int_t ii=0; ii < fNseek; ii++) {
               Int_t reqi = (startindex+ii) % fNseek;
               if (!fUnzipStatus[reqi] && (fSeekLen[reqi] > 256)   ) {
                  // We found a chunk which is not unzipped nor pending
                  fUnzipStatus[reqi] = 1; // Set it as pending
                  idxtounzip = reqi;

                  rdoffs = fSeek[idxtounzip];
                  rdlen = fSeekLen[idxtounzip];
                  break;
               }
            }
            if (idxtounzip < 0) fBlocksToGo = 0;
         }
      }

   } // lock scope

   if (idxtounzip < 0) {
      if (gDebug > 0)
         Info("UnzipCache", "Nothing to do... startindex:%d fTotalUnzipBytes:%lld fUnzipBufferSize:%lld fNseek:%d",
              startindex, fTotalUnzipBytes, fUnzipBufferSize, fNseek );
      return 1;
   }

   // And here we have a new blk to unzip
   startindex = idxtounzip+THREADCNT;

   if (!IsActiveThread() || !fNseek || fIsLearning ) {
      if (gDebug > 0)
         Info("UnzipCache", "Sudden Break!!! IsActiveThread(): %d, fNseek: %d, fIsLearning:%d",
              IsActiveThread(), fNseek, fIsLearning);
      return 1;
   }

   Int_t loc = -1;

   // Prepare a static tmp buf of adequate size
   if(locbuffsz < rdlen) {
      if (locbuff) delete [] locbuff;
      locbuffsz = rdlen;
      locbuff = new char[locbuffsz];
      //memset(locbuff, 0, locbuffsz);
   } else if(locbuffsz > rdlen*3) {
      if (locbuff) delete [] locbuff;
      locbuffsz = rdlen*2;
      locbuff = new char[locbuffsz];
      //memset(locbuff, 0, locbuffsz);
   }

   if (gDebug > 0)
     Info("UnzipCache", "Going to unzip block %d", idxtounzip);

   readbuf = ReadBufferExt(locbuff, rdoffs, rdlen, loc);

   {
      R__LOCKGUARD(fMutexList);

      if ( (myCycle != fCycle) || !fIsTransferred )  {
         if (gDebug > 0)
            Info("UnzipCache", "Sudden paging Break!!! IsActiveThread(): %d, fNseek: %d, fIsLearning:%d",
                 IsActiveThread(), fNseek, fIsLearning);

         fUnzipStatus[idxtounzip] = 2; // Set it as not done
         fUnzipChunks[idxtounzip] = 0;
         fUnzipLen[idxtounzip] = 0;
         fUnzipDoneCondition->Signal();

         startindex = 0;
         return 1;
      }

      if (readbuf <= 0) {
         fUnzipStatus[idxtounzip] = 2; // Set it as not done
         fUnzipChunks[idxtounzip] = 0;
         fUnzipLen[idxtounzip] = 0;
         if (gDebug > 0)
            Info("UnzipCache", "Block %d not done. rdoffs=%lld rdlen=%d readbuf=%d", idxtounzip, rdoffs, rdlen, readbuf);
         return -1;
      }

      GetRecordHeader(locbuff, hlen, nbytes, objlen, keylen);

      Int_t len = (objlen > nbytes-keylen)? keylen+objlen : nbytes;

      // If the single unzipped chunk is really too big, reset it to not processable
      // I.e. mark it as done but set the pointer to 0
      // This block will be unzipped synchronously in the main thread
      if (len > 4*fUnzipBufferSize) {

         //if (gDebug > 0)
            Info("UnzipCache", "Block %d is too big, skipping.", idxtounzip);

         fUnzipStatus[idxtounzip] = 2; // Set it as done
         fUnzipChunks[idxtounzip] = 0;
         fUnzipLen[idxtounzip] = 0;

         fUnzipDoneCondition->Signal();
         return 0;
      }

   } // Scope of the lock

   // Unzip it into a new blk
   char *ptr = 0;
   Int_t loclen = 0;

   loclen = UnzipBuffer(&ptr, locbuff);

   if ((loclen > 0) && (loclen == objlen+keylen)) {
      R__LOCKGUARD(fMutexList);

      if ( (myCycle != fCycle)  || !fIsTransferred) {
         if (gDebug > 0)
            Info("UnzipCache", "Sudden paging Break!!! IsActiveThread(): %d, fNseek: %d, fIsLearning:%d",
                 IsActiveThread(), fNseek, fIsLearning);
         delete [] ptr;

         fUnzipStatus[idxtounzip] = 2; // Set it as not done
         fUnzipChunks[idxtounzip] = 0;
         fUnzipLen[idxtounzip] = 0;

         startindex = 0;
         fUnzipDoneCondition->Signal();
         return 1;
      }

      fUnzipStatus[idxtounzip] = 2; // Set it as done
      fUnzipChunks[idxtounzip] = ptr;
      fUnzipLen[idxtounzip] = loclen;
      fTotalUnzipBytes += loclen;

      fActiveBlks.push(idxtounzip);

      if (gDebug > 0)
         Info("UnzipCache", "reqi:%d, rdoffs:%lld, rdlen: %d, loclen:%d",
              idxtounzip, rdoffs, rdlen, loclen);

      fNUnzip++;
   }
   else {
      R__LOCKGUARD(fMutexList);
      Info("argh", "loclen:%d objlen:%d loc:%d readbuf:%d", loclen, objlen, loc, readbuf);
      fUnzipStatus[idxtounzip] = 2; // Set it as done
      fUnzipChunks[idxtounzip] = 0;
      fUnzipLen[idxtounzip] = 0;
   }

   fUnzipDoneCondition->Signal();

   return 0;
}

void  TTreeCacheUnzip::Print(Option_t* option) const {

   printf("******TreeCacheUnzip statistics for file: %s ******\n",fFile->GetName());
   printf("Max allowed mem for pending buffers: %lld\n", fUnzipBufferSize);
   printf("Number of blocks unzipped by threads: %d\n", fNUnzip);
   printf("Number of hits: %d\n", fNFound);
   printf("Number of stalls: %d\n", fNStalls);
   printf("Number of misses: %d\n", fNMissed);

   TTreeCache::Print(option);
}

////////////////////////////////////////////////////////////////////////////////

Int_t TTreeCacheUnzip::ReadBufferExt(char *buf, Long64_t pos, Int_t len, Int_t &loc) {
   R__LOCKGUARD(fIOMutex);
   return TTreeCache::ReadBufferExt(buf, pos, len, loc);

}