TBranch.cxx

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// @(#)root/tree:$Id$
// Author: Rene Brun   12/01/96

/*************************************************************************
 * 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.             *
 *************************************************************************/

#include "TBranchCacheInfo.h"

#include "TBranch.h"

#include "Bytes.h"
#include "Compression.h"
#include "TBasket.h"
#include "TBranchBrowsable.h"
#include "TBrowser.h"
#include "TBuffer.h"
#include "TClass.h"
#include "TBufferFile.h"
#include "TClonesArray.h"
#include "TFile.h"
#include "TLeaf.h"
#include "TLeafB.h"
#include "TLeafC.h"
#include "TLeafD.h"
#include "TLeafD32.h"
#include "TLeafF.h"
#include "TLeafF16.h"
#include "TLeafI.h"
#include "TLeafL.h"
#include "TLeafO.h"
#include "TLeafObject.h"
#include "TLeafS.h"
#include "TMessage.h"
#include "TROOT.h"
#include "TSystem.h"
#include "TMath.h"
#include "TTree.h"
#include "TTreeCache.h"
#include "TTreeCacheUnzip.h"
#include "TVirtualMutex.h"
#include "TVirtualPad.h"
#include "TVirtualPerfStats.h"

#include "TBranchIMTHelper.h"

#include "ROOT/TIOFeatures.hxx"

#include <atomic>
#include <cstddef>
#include <string.h>
#include <stdio.h>


Int_t TBranch::fgCount = 0;

/** \class TBranch
\ingroup tree

A TTree is a list of TBranches

A TBranch supports:
 - The list of TLeaf describing this branch.
 - The list of TBasket (branch buffers).

See TBranch structure in TTree.

See also specialized branches:
 - TBranchObject in case the branch is one object
 - TBranchClones in case the branch is an array of clone objects
*/

ClassImp(TBranch);



////////////////////////////////////////////////////////////////////////////////
/// Default constructor.  Used for I/O by default.

TBranch::TBranch()
: TNamed()
, TAttFill(0, 1001)
, fCompress(0)
, fBasketSize(32000)
, fEntryOffsetLen(1000)
, fWriteBasket(0)
, fEntryNumber(0)
, fExtraBasket(nullptr)
, fOffset(0)
, fMaxBaskets(10)
, fNBaskets(0)
, fSplitLevel(0)
, fNleaves(0)
, fReadBasket(0)
, fReadEntry(-1)
, fFirstBasketEntry(-1)
, fNextBasketEntry(-1)
, fCurrentBasket(0)
, fEntries(0)
, fFirstEntry(0)
, fTotBytes(0)
, fZipBytes(0)
, fBranches()
, fLeaves()
, fBaskets(fMaxBaskets)
, fBasketBytes(0)
, fBasketEntry(0)
, fBasketSeek(0)
, fTree(0)
, fMother(0)
, fParent(0)
, fAddress(0)
, fDirectory(0)
, fFileName("")
, fEntryBuffer(0)
, fTransientBuffer(0)
, fBrowsables(0)
, fBulk(*this)
, fSkipZip(kFALSE)
, fReadLeaves(&TBranch::ReadLeavesImpl)
, fFillLeaves(&TBranch::FillLeavesImpl)
{
   SetBit(TBranch::kDoNotUseBufferMap);
}

////////////////////////////////////////////////////////////////////////////////
/// Create a Branch as a child of a Tree
///
///       * address is the address of the first item of a structure
///         or the address of a pointer to an object (see example in TTree.cxx).
///       * leaflist is the concatenation of all the variable names and types
///         separated by a colon character :
///         The variable name and the variable type are separated by a
///         slash (/). The variable type must be 1 character. (Characters
///         after the first are legal and will be appended to the visible
///         name of the leaf, but have no effect.) If no type is given, the
///         type of the variable is assumed to be the same as the previous
///         variable. If the first variable does not have a type, it is
///         assumed of type F by default. The list of currently supported
///         types is given below:
///            - `C` : a character string terminated by the 0 character
///            - `B` : an 8 bit signed integer (`Char_t`)
///            - `b` : an 8 bit unsigned integer (`UChar_t`)
///            - `S` : a 16 bit signed integer (`Short_t`)
///            - `s` : a 16 bit unsigned integer (`UShort_t`)
///            - `I` : a 32 bit signed integer (`Int_t`)
///            - `i` : a 32 bit unsigned integer (`UInt_t`)
///            - `F` : a 32 bit floating point (`Float_t`)
///            - `f` : a 24 bit floating point with truncated mantissa (`Float16_t`)
///            - `D` : a 64 bit floating point (`Double_t`)
///            - `d` : a 24 bit truncated floating point (`Double32_t`)
///            - `L` : a 64 bit signed integer (`Long64_t`)
///            - `l` : a 64 bit unsigned integer (`ULong64_t`)
///            - `O` : [the letter `o`, not a zero] a boolean (`Bool_t`)
///
///         Arrays of values are supported with the following syntax:
///         - If leaf name has the form var[nelem], where nelem is alphanumeric, then
///              if nelem is a leaf name, it is used as the variable size of the array,
///              otherwise return 0.
///              The leaf referred to by nelem **MUST** be an int (/I),
///         - If leaf name has the form var[nelem], where nelem is a non-negative integers, then
///              it is used as the fixed size of the array.
///         - If leaf name has the form of a multi dimension array (e.g. var[nelem][nelem2])
///              where nelem and nelem2 are non-negative integers) then
///              it is used as a 2 dimensional array of fixed size.
///         - In case of the truncated floating point types (Float16_t and Double32_t) you can
///              furthermore specify the range in the style [xmin,xmax] or [xmin,xmax,nbits] after
///              the type character. See `TStreamerElement::GetRange()` for further information.
///         - Any of other form is not supported.
///
///    Note that the TTree will assume that all the item are contiguous in memory.
///    On some platform, this is not always true of the member of a struct or a class,
///    due to padding and alignment.  Sorting your data member in order of decreasing
///    sizeof usually leads to their being contiguous in memory.
///
///       * bufsize is the buffer size in bytes for this branch
///         The default value is 32000 bytes and should be ok for most cases.
///         You can specify a larger value (e.g. 256000) if your Tree is not split
///         and each entry is large (Megabytes)
///         A small value for bufsize is optimum if you intend to access
///         the entries in the Tree randomly and your Tree is in split mode.
///
///   See an example of a Branch definition in the TTree constructor.
///
///   Note that in case the data type is an object, this branch can contain
///   only this object.
///
///    Note that this function is invoked by TTree::Branch

TBranch::TBranch(TTree *tree, const char *name, void *address, const char *leaflist, Int_t basketsize, Int_t compress)
   : TNamed(name, leaflist)
, TAttFill(0, 1001)
, fCompress(compress)
, fBasketSize((basketsize < 100) ? 100 : basketsize)
, fEntryOffsetLen(0)
, fWriteBasket(0)
, fEntryNumber(0)
, fExtraBasket(nullptr)
, fIOFeatures(tree ? tree->GetIOFeatures().GetFeatures() : 0)
, fOffset(0)
, fMaxBaskets(10)
, fNBaskets(0)
, fSplitLevel(0)
, fNleaves(0)
, fReadBasket(0)
, fReadEntry(-1)
, fFirstBasketEntry(-1)
, fNextBasketEntry(-1)
, fCurrentBasket(0)
, fEntries(0)
, fFirstEntry(0)
, fTotBytes(0)
, fZipBytes(0)
, fBranches()
, fLeaves()
, fBaskets(fMaxBaskets)
, fBasketBytes(0)
, fBasketEntry(0)
, fBasketSeek(0)
, fTree(tree)
, fMother(0)
, fParent(0)
, fAddress((char *)address)
, fDirectory(fTree->GetDirectory())
, fFileName("")
, fEntryBuffer(0)
, fTransientBuffer(0)
, fBrowsables(0)
, fBulk(*this)
, fSkipZip(kFALSE)
, fReadLeaves(&TBranch::ReadLeavesImpl)
, fFillLeaves(&TBranch::FillLeavesImpl)
{
   Init(name,leaflist,compress);
}

////////////////////////////////////////////////////////////////////////////////
/// Create a Branch as a child of another Branch
///
/// See documentation for
/// TBranch::TBranch(TTree *, const char *, void *, const char *, Int_t, Int_t)

TBranch::TBranch(TBranch *parent, const char *name, void *address, const char *leaflist, Int_t basketsize,
                 Int_t compress)
: TNamed(name, leaflist)
, TAttFill(0, 1001)
, fCompress(compress)
, fBasketSize((basketsize < 100) ? 100 : basketsize)
, fEntryOffsetLen(0)
, fWriteBasket(0)
, fEntryNumber(0)
, fExtraBasket(nullptr)
, fIOFeatures(parent->fIOFeatures)
, fOffset(0)
, fMaxBaskets(10)
, fNBaskets(0)
, fSplitLevel(0)
, fNleaves(0)
, fReadBasket(0)
, fReadEntry(-1)
, fFirstBasketEntry(-1)
, fNextBasketEntry(-1)
, fCurrentBasket(0)
, fEntries(0)
, fFirstEntry(0)
, fTotBytes(0)
, fZipBytes(0)
, fBranches()
, fLeaves()
, fBaskets(fMaxBaskets)
, fBasketBytes(0)
, fBasketEntry(0)
, fBasketSeek(0)
, fTree(parent ? parent->GetTree() : 0)
, fMother(parent ? parent->GetMother() : 0)
, fParent(parent)
, fAddress((char *)address)
, fDirectory(fTree ? fTree->GetDirectory() : 0)
, fFileName("")
, fEntryBuffer(0)
, fTransientBuffer(0)
, fBrowsables(0)
, fBulk(*this)
, fSkipZip(kFALSE)
, fReadLeaves(&TBranch::ReadLeavesImpl)
, fFillLeaves(&TBranch::FillLeavesImpl)
{
   Init(name,leaflist,compress);
}

void TBranch::Init(const char* name, const char* leaflist, Int_t compress)
{
   // Initialization routine called from the constructor.  This should NOT be made virtual.

   SetBit(TBranch::kDoNotUseBufferMap);
   if ((compress == -1) && fTree->GetDirectory()) {
      TFile* bfile = fTree->GetDirectory()->GetFile();
      if (bfile) {
         fCompress = bfile->GetCompressionSettings();
      }
   }

   fBasketBytes = new Int_t[fMaxBaskets];
   fBasketEntry = new Long64_t[fMaxBaskets];
   fBasketSeek  = new Long64_t[fMaxBaskets];

   for (Int_t i = 0; i < fMaxBaskets; ++i) {
      fBasketBytes[i] = 0;
      fBasketEntry[i] = 0;
      fBasketSeek[i] = 0;
   }

   //
   // Decode the leaflist (search for : as separator).
   //

   char* nameBegin = const_cast<char*>(leaflist);
   Int_t offset = 0;
   auto len = strlen(leaflist);
   // FIXME: Make these string streams instead.
   char* leafname = new char[len + 1];
   char* leaftype = new char[320];
   // Note: The default leaf type is a float.
   strlcpy(leaftype, "F",320);
   char* pos = const_cast<char*>(leaflist);
   const char* leaflistEnd = leaflist + len;
   for (; pos <= leaflistEnd; ++pos) {
      // -- Scan leaf specification and create leaves.
      if ((*pos == ':') || (*pos == 0)) {
         // -- Reached end of a leaf spec, create a leaf.
         Int_t lenName = pos - nameBegin;
         char* ctype = 0;
         if (lenName) {
            strncpy(leafname, nameBegin, lenName);
            leafname[lenName] = 0;
            ctype = strstr(leafname, "/");
            if (ctype) {
               *ctype = 0;
               strlcpy(leaftype, ctype + 1,320);
            }
         }
         if (lenName == 0 || ctype == leafname) {
            Warning("TBranch","No name was given to the leaf number '%d' in the leaflist of the branch '%s'.",fNleaves,name);
            snprintf(leafname,640,"__noname%d",fNleaves);
         }
         TLeaf* leaf = 0;
         if (leaftype[1] == '[' && !strchr(leaftype, ',')) {
            Warning("TBranch", "Array size for branch '%s' must be specified after leaf name, not after the type name!", name);
            // and continue for backward compatibility?
          } else if (leaftype[1] && !strchr(leaftype, ',')) {
            Warning("TBranch", "Extra characters after type tag '%s' for branch '%s'; must be one character.", leaftype, name);
            // and continue for backward compatibility?
         }
         if (*leaftype == 'C') {
            leaf = new TLeafC(this, leafname, leaftype);
         } else if (*leaftype == 'O') {
            leaf = new TLeafO(this, leafname, leaftype);
         } else if (*leaftype == 'B') {
            leaf = new TLeafB(this, leafname, leaftype);
         } else if (*leaftype == 'b') {
            leaf = new TLeafB(this, leafname, leaftype);
            leaf->SetUnsigned();
         } else if (*leaftype == 'S') {
            leaf = new TLeafS(this, leafname, leaftype);
         } else if (*leaftype == 's') {
            leaf = new TLeafS(this, leafname, leaftype);
            leaf->SetUnsigned();
         } else if (*leaftype == 'I') {
            leaf = new TLeafI(this, leafname, leaftype);
         } else if (*leaftype == 'i') {
            leaf = new TLeafI(this, leafname, leaftype);
            leaf->SetUnsigned();
         } else if (*leaftype == 'F') {
            leaf = new TLeafF(this, leafname, leaftype);
         } else if (*leaftype == 'f') {
            leaf = new TLeafF16(this, leafname, leaftype);
         } else if (*leaftype == 'L') {
            leaf = new TLeafL(this, leafname, leaftype);
         } else if (*leaftype == 'l') {
            leaf = new TLeafL(this, leafname, leaftype);
            leaf->SetUnsigned();
         } else if (*leaftype == 'D') {
            leaf = new TLeafD(this, leafname, leaftype);
         } else if (*leaftype == 'd') {
            leaf = new TLeafD32(this, leafname, leaftype);
         }
         if (!leaf) {
            Error("TLeaf", "Illegal data type for %s/%s", name, leaflist);
            delete[] leaftype;
            delete [] leafname;
            MakeZombie();
            return;
         }
         if (leaf->IsZombie()) {
            delete leaf;
            leaf = 0;
            auto msg = "Illegal leaf: %s/%s. If this is a variable size C array it's possible that the branch holding the size is not available.";
            Error("TBranch", msg, name, leaflist);
            delete [] leafname;
            delete[] leaftype;
            MakeZombie();
            return;
         }
         leaf->SetBranch(this);
         leaf->SetAddress((char*) (fAddress + offset));
         leaf->SetOffset(offset);
         if (leaf->GetLeafCount()) {
            // -- Leaf is a varying length array, we need an offset array.
            fEntryOffsetLen = 1000;
         }
         if (leaf->InheritsFrom(TLeafC::Class())) {
            // -- Leaf is a character string, we need an offset array.
            fEntryOffsetLen = 1000;
         }
         ++fNleaves;
         fLeaves.Add(leaf);
         fTree->GetListOfLeaves()->Add(leaf);
         if (*pos == 0) {
            // -- We reached the end of the leaf specification.
            break;
         }
         nameBegin = pos + 1;
         offset += leaf->GetLenType() * leaf->GetLen();
      }
   }
   delete[] leafname;
   leafname = 0;
   delete[] leaftype;
   leaftype = 0;

}

////////////////////////////////////////////////////////////////////////////////
/// Destructor.

TBranch::~TBranch()
{
   delete fBrowsables;
   fBrowsables = 0;

   // Note: We do *not* have ownership of the buffer.
   fEntryBuffer = 0;

   delete [] fBasketSeek;
   fBasketSeek  = 0;

   delete [] fBasketEntry;
   fBasketEntry = 0;

   delete [] fBasketBytes;
   fBasketBytes = 0;

   fBaskets.Delete();
   fNBaskets = 0;
   fCurrentBasket = 0;
   fFirstBasketEntry = -1;
   fNextBasketEntry = -1;

   // Remove our leaves from our tree's list of leaves.
   if (fTree) {
      TObjArray* lst = fTree->GetListOfLeaves();
      if (lst && lst->GetLast()!=-1) {
         lst->RemoveAll(&fLeaves);
      }
   }
   // And delete our leaves.
   fLeaves.Delete();

   fBranches.Delete();

   // If we are in a directory and that directory is not the same
   // directory that our tree is in, then try to find an open file
   // with the name fFileName.  If we find one, delete that file.
   // We are attempting to close any alternate file which we have
   // been directed to write our baskets to.
   // FIXME: We make no attempt to check if someone else might be
   //        using this file.  This is very user hostile.  A violation
   //        of the principle of least surprises.
   //
   // Warning. Must use FindObject by name instead of fDirectory->GetFile()
   // because two branches may point to the same file and the file
   // may have already been deleted in the previous branch.
   if (fDirectory && (!fTree || fDirectory != fTree->GetDirectory())) {
      TString bFileName( GetRealFileName() );

      R__LOCKGUARD(gROOTMutex);
      TFile* file = (TFile*)gROOT->GetListOfFiles()->FindObject(bFileName);
      if (file){
         file->Close();
         delete file;
         file = 0;
      }
   }

   fTree = 0;
   fDirectory = 0;

   if (fTransientBuffer) {
      delete fTransientBuffer;
      fTransientBuffer = 0;
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Returns the transient buffer currently used by this TBranch for reading/writing baskets.

TBuffer* TBranch::GetTransientBuffer(Int_t size)
{
   if (fTransientBuffer) {
      if (fTransientBuffer->BufferSize() < size) {
         fTransientBuffer->Expand(size);
      }
      return fTransientBuffer;
   }
   fTransientBuffer = new TBufferFile(TBuffer::kRead, size);
   return fTransientBuffer;
}

////////////////////////////////////////////////////////////////////////////////
/// Add the basket to this branch.
///
/// Warning: if the basket are not 'flushed/copied' in the same
/// order as they were created, this will induce a slow down in
/// the insert (since we'll need to move all the record that are
/// entere 'too early').
/// Warning we also assume that the __current__ write basket is
/// not present (aka has been removed).

void TBranch::AddBasket(TBasket& b, Bool_t ondisk, Long64_t startEntry)
{
   TBasket *basket = &b;

   basket->SetBranch(this);

   if (fWriteBasket >= fMaxBaskets) {
      ExpandBasketArrays();
   }
   Int_t where = fWriteBasket;

   if (where && startEntry < fBasketEntry[where-1]) {
      // Need to find the right location and move the possible baskets

      if (!ondisk) {
         Warning("AddBasket","The assumption that out-of-order basket only comes from disk based ntuple is false.");
      }

      if (startEntry < fBasketEntry[0]) {
         where = 0;
      } else {
         for(Int_t i=fWriteBasket-1; i>=0; --i) {
            if (fBasketEntry[i] < startEntry) {
               where = i+1;
               break;
            } else if (fBasketEntry[i] == startEntry) {
               Error("AddBasket","An out-of-order basket matches the entry number of an existing basket.");
            }
         }
      }

      if (where < fWriteBasket) {
         // We shall move the content of the array
         for (Int_t j=fWriteBasket; j > where; --j) {
            fBasketEntry[j] = fBasketEntry[j-1];
            fBasketBytes[j] = fBasketBytes[j-1];
            fBasketSeek[j]  = fBasketSeek[j-1];
         }
      }
   }
   fBasketEntry[where] = startEntry;

   if (ondisk) {
      fBasketBytes[where] = basket->GetNbytes();  // not for in mem
      fBasketSeek[where] = basket->GetSeekKey();  // not for in mem
      fBaskets.AddAtAndExpand(0,fWriteBasket);
      ++fWriteBasket;
   } else {
      ++fNBaskets;
      fBaskets.AddAtAndExpand(basket,fWriteBasket);
      fTree->IncrementTotalBuffers(basket->GetBufferSize());
   }

   fEntries += basket->GetNevBuf();
   fEntryNumber += basket->GetNevBuf();
   if (ondisk) {
      fTotBytes += basket->GetObjlen() + basket->GetKeylen() ;
      fZipBytes += basket->GetNbytes();
      fTree->AddTotBytes(basket->GetObjlen() + basket->GetKeylen());
      fTree->AddZipBytes(basket->GetNbytes());
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Add the start entry of the write basket (not yet created)

void TBranch::AddLastBasket(Long64_t startEntry)
{
   if (fWriteBasket >= fMaxBaskets) {
      ExpandBasketArrays();
   }
   Int_t where = fWriteBasket;

   if (where && startEntry < fBasketEntry[where-1]) {
      // Need to find the right location and move the possible baskets

      Fatal("AddBasket","The last basket must have the highest entry number (%s/%lld/%d).",GetName(),startEntry,fWriteBasket);

   }
   fBasketEntry[where] = startEntry;
   fBaskets.AddAtAndExpand(0,fWriteBasket);
}

////////////////////////////////////////////////////////////////////////////////
/// Loop on all leaves of this branch to back fill Basket buffer.
///
/// Use this routine instead of TBranch::Fill when filling a branch individually
/// to catch up with the number of entries already in the TTree.
///
/// First it calls TBranch::Fill and then if the number of entries of the branch
/// reach one of TTree cluster's boundary, the basket is flushed.
///
/// The function returns the number of bytes committed to the memory basket.
/// If a write error occurs, the number of bytes returned is -1.
/// If no data are written, because e.g. the branch is disabled,
/// the number of bytes returned is 0.
///
/// To insure that the baskets of each cluster are located close by in the
/// file, when back-filling multiple branches make sure to call BackFill
/// for the same entry for all the branches consecutively
/// ~~~ {.cpp}
///   for( auto e = 0; e < tree->GetEntries(); ++e ) { // loop over entries.
///     for( auto branch : branchCollection) {
///        ... Make change to the data associated with the branch ...
///        branch->BackFill();
///     }
///   }
///   // Since we loop over all the branches for each new entry
///   // all the baskets for a cluster are consecutive in the file.
/// ~~~
/// rather than doing all the entries of one branch at a time.
/// ~~~ {.cpp}
///   // Do NOT do things in the following order, it will lead to
///   // poorly clustered files.
///   for(auto branch : branchCollection) {
///     for( auto e = 0; e < tree->GetEntries(); ++e ) { // loop over entries.
///        ... Make change to the data associated with the branch ...
///        branch->BackFill();
///     }
///   }
///   // Since we loop over all the entries for one branch
///   // all the baskets for that branch are consecutive.
/// ~~~

Int_t TBranch::BackFill() {

   // Get the end of the next cluster.
   auto cluster  = GetTree()->GetClusterIterator( GetEntries() );
   cluster.Next();
   auto endCluster = cluster.GetNextEntry();

   auto result = FillImpl(nullptr);

   if ( result && GetEntries() >= endCluster ) {
      FlushBaskets();
   }

   return result;
}

////////////////////////////////////////////////////////////////////////////////
/// Browser interface.

void TBranch::Browse(TBrowser* b)
{
   if (fNleaves > 1) {
      fLeaves.Browse(b);
   } else {
      // Get the name and strip any extra brackets
      // in order to get the full arrays.
      TString name = GetName();
      Int_t pos = name.First('[');
      if (pos!=kNPOS) name.Remove(pos);

      GetTree()->Draw(name, "", b ? b->GetDrawOption() : "");
      if (gPad) gPad->Update();
   }
}

 ///////////////////////////////////////////////////////////////////////////////
 /// Loop on all branch baskets. If the file where branch buffers reside is
 /// writable, free the disk space associated to the baskets of the branch,
 /// then call Reset(). If the option contains "all", delete also the baskets
 /// for the subbranches.
 /// The branch is reset.
 ///
 /// NOTE that this function must be used with extreme care. Deleting branch baskets
 /// fragments the file and may introduce inefficiencies when adding new entries
 /// in the Tree or later on when reading the Tree.

void TBranch::DeleteBaskets(Option_t* option)
{
   TString opt = option;
   opt.ToLower();
   TFile *file = GetFile(0);

   if(fDirectory && (fDirectory != gROOT) && fDirectory->IsWritable()) {
      for(Int_t i=0; i<fWriteBasket; i++) {
         if (fBasketSeek[i]) file->MakeFree(fBasketSeek[i],fBasketSeek[i]+fBasketBytes[i]-1);
      }
   }

   // process subbranches
   if (opt.Contains("all")) {
      TObjArray *lb = GetListOfBranches();
      Int_t nb = lb->GetEntriesFast();
      for (Int_t j = 0; j < nb; j++) {
         TBranch* branch = (TBranch*) lb->UncheckedAt(j);
         if (branch) branch->DeleteBaskets("all");
      }
   }
   DropBaskets("all");
   Reset();
}

////////////////////////////////////////////////////////////////////////////////
/// Loop on all branch baskets. Drop all baskets from memory except readbasket.
/// If the option contains "all", drop all baskets including
/// read- and write-baskets (unless they are not stored individually on disk).
/// The option "all" also lead to DropBaskets being called on the sub-branches.

void TBranch::DropBaskets(Option_t* options)
{
   Bool_t all = kFALSE;
   if (options && options[0]) {
      TString opt = options;
      opt.ToLower();
      if (opt.Contains("all")) all = kTRUE;
   }

   TBasket *basket;
   Int_t nbaskets = fBaskets.GetEntriesFast();

   if ( (fNBaskets>1) || all ) {
      //slow case
      for (Int_t i=0;i<nbaskets;i++) {
         basket = (TBasket*)fBaskets.UncheckedAt(i);
         if (!basket) continue;
         if ((i == fReadBasket || i == fWriteBasket) && !all) continue;
         // if the basket is not yet on file but already has event in it
         // we must continue to avoid dropping the basket (and thus losing data)
         if (fBasketBytes[i]==0 && basket->GetNevBuf() > 0) continue;
         basket->DropBuffers();
         --fNBaskets;
         fBaskets.RemoveAt(i);
         if (basket == fCurrentBasket) {
            fCurrentBasket    = 0;
            fFirstBasketEntry = -1;
            fNextBasketEntry  = -1;
         }
         delete basket;
      }

      // process subbranches
      if (all) {
         TObjArray *lb = GetListOfBranches();
         Int_t nb = lb->GetEntriesFast();
         for (Int_t j = 0; j < nb; j++) {
            TBranch* branch = (TBranch*) lb->UncheckedAt(j);
            if (!branch) continue;
            branch->DropBaskets("all");
         }
      }
   } else {
      //fast case
      if (nbaskets > 0) {
         Int_t i = fBaskets.GetLast();
         basket = (TBasket*)fBaskets.UncheckedAt(i);
         if (basket && fBasketBytes[i]!=0) {
            basket->DropBuffers();
            if (basket == fCurrentBasket) {
               fCurrentBasket    = 0;
               fFirstBasketEntry = -1;
               fNextBasketEntry  = -1;
            }
            delete basket;
            fBaskets.AddAt(0,i);
            fBaskets.SetLast(-1);
            fNBaskets = 0;
         }
      }
   }

}

////////////////////////////////////////////////////////////////////////////////
/// Increase BasketEntry buffer of a minimum of 10 locations
/// and a maximum of 50 per cent of current size.

void TBranch::ExpandBasketArrays()
{
   Int_t newsize = TMath::Max(10,Int_t(1.5*fMaxBaskets));
   fBasketBytes  = TStorage::ReAllocInt(fBasketBytes, newsize, fMaxBaskets);
   fBasketEntry  = (Long64_t*)TStorage::ReAlloc(fBasketEntry,
                                                newsize*sizeof(Long64_t),fMaxBaskets*sizeof(Long64_t));
   fBasketSeek   = (Long64_t*)TStorage::ReAlloc(fBasketSeek,
                                                newsize*sizeof(Long64_t),fMaxBaskets*sizeof(Long64_t));

   fMaxBaskets   = newsize;

   fBaskets.Expand(newsize);

   for (Int_t i=fWriteBasket;i<fMaxBaskets;i++) {
      fBasketBytes[i] = 0;
      fBasketEntry[i] = 0;
      fBasketSeek[i]  = 0;
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Loop on all leaves of this branch to fill Basket buffer.
///
/// If TBranchIMTHelper is non-null and it is time to WriteBasket, then we will
/// use TBB to compress in parallel.
///
/// The function returns the number of bytes committed to the memory basket.
/// If a write error occurs, the number of bytes returned is -1.
/// If no data are written, because e.g. the branch is disabled,
/// the number of bytes returned is 0.

Int_t TBranch::FillImpl(ROOT::Internal::TBranchIMTHelper *imtHelper)
{
   if (TestBit(kDoNotProcess)) {
      return 0;
   }

   TBasket* basket = (TBasket*)fBaskets.UncheckedAt(fWriteBasket);
   if (!basket) {
      basket = fTree->CreateBasket(this); //  create a new basket
      if (!basket) return 0;
      ++fNBaskets;
      fBaskets.AddAtAndExpand(basket,fWriteBasket);
   }
   TBuffer* buf = basket->GetBufferRef();

   // Fill basket buffer.

   Int_t nsize  = 0;

   if (buf->IsReading()) {
      basket->SetWriteMode();
   }

   if (!TestBit(kDoNotUseBufferMap)) {
     buf->ResetMap();
   }

   Int_t lnew = 0;
   Int_t nbytes = 0;

   if (fEntryBuffer) {
      nbytes = FillEntryBuffer(basket,buf,lnew);
   } else {
      Int_t lold = buf->Length();
      basket->Update(lold);
      ++fEntries;
      ++fEntryNumber;
      (this->*fFillLeaves)(*buf);
      if (buf->GetMapCount()) {
         // The map is used.
         ResetBit(TBranch::kDoNotUseBufferMap);
      }
      lnew = buf->Length();
      nbytes = lnew - lold;
   }

   if (fEntryOffsetLen) {
      Int_t nevbuf = basket->GetNevBuf();
      // Total size in bytes of EntryOffset table.
      nsize = nevbuf * sizeof(Int_t);
   } else {
      if (!basket->GetNevBufSize()) {
         basket->SetNevBufSize(nbytes);
      }
   }

   // Should we create a new basket?
   // fSkipZip force one entry per buffer (old stuff still maintained for CDF)
   // Transfer full compressed buffer only

   // If GetAutoFlush() is less than zero, then we are determining the end of the autocluster
   // based upon the number of bytes already flushed.  This is incompatible with one-basket-per-cluster
   // (since we will grow the basket indefinitely and never flush!).  Hence, we wait until the
   // first event cluster is written out and *then* enable one-basket-per-cluster mode.
   bool noFlushAtCluster = !fTree->TestBit(TTree::kOnlyFlushAtCluster) || (fTree->GetAutoFlush() < 0);

   if (noFlushAtCluster && !fTree->TestBit(TTree::kCircular) &&
       ((fSkipZip && (lnew >= TBuffer::kMinimalSize)) || (buf->TestBit(TBufferFile::kNotDecompressed)) ||
        ((lnew + (2 * nsize) + nbytes) >= fBasketSize))) {
      Int_t nout = WriteBasketImpl(basket, fWriteBasket, imtHelper);
      if (nout < 0) Error("TBranch::Fill", "Failed to write out basket.\n");
      return (nout >= 0) ? nbytes : -1;
   }
   return nbytes;
}

////////////////////////////////////////////////////////////////////////////////
/// Copy the data from fEntryBuffer into the current basket.

Int_t TBranch::FillEntryBuffer(TBasket* basket, TBuffer* buf, Int_t& lnew)
{
   Int_t nbytes = 0;
   Int_t objectStart = 0;
   Int_t last = 0;
   Int_t lold = buf->Length();

   // Handle the special case of fEntryBuffer != 0
   if (fEntryBuffer->IsA() == TMessage::Class()) {
      objectStart = 8;
   }
   if (fEntryBuffer->TestBit(TBufferFile::kNotDecompressed)) {
      // The buffer given as input has not been decompressed.
      if (basket->GetNevBuf()) {
         // If the basket already contains entry we need to close it
         // out. (This is because we can only transfer full compressed
         // buffer)
         WriteBasket(basket,fWriteBasket);
         // And restart from scratch
         return Fill();
      }
      Int_t startpos = fEntryBuffer->Length();
      fEntryBuffer->SetBufferOffset(0);
      static TBasket toread_fLast;
      fEntryBuffer->SetReadMode();
      toread_fLast.Streamer(*fEntryBuffer);
      fEntryBuffer->SetWriteMode();
      last = toread_fLast.GetLast();
      // last now contains the decompressed number of bytes.
      fEntryBuffer->SetBufferOffset(startpos);
      buf->SetBufferOffset(0);
      buf->SetBit(TBufferFile::kNotDecompressed);
      basket->Update(lold);
   } else {
      // We are required to copy starting at the version number (so not
      // including the class name.
      // See if byte count is here, if not it class still be a newClass
      const UInt_t kNewClassTag = 0xFFFFFFFF;
      const UInt_t kByteCountMask = 0x40000000;  // OR the byte count with this
      UInt_t tag = 0;
      UInt_t startpos = fEntryBuffer->Length();
      fEntryBuffer->SetBufferOffset(objectStart);
      *fEntryBuffer >> tag;
      if (tag & kByteCountMask) {
         *fEntryBuffer >> tag;
      }
      if (tag == kNewClassTag) {
         UInt_t maxsize = 256;
         char* s = new char[maxsize];
         Int_t name_start = fEntryBuffer->Length();
         fEntryBuffer->ReadString(s, maxsize); // Reads at most maxsize - 1 characters, plus null at end.
         while (strlen(s) == (maxsize - 1)) {
            // The classname is too large, try again with a large buffer.
            fEntryBuffer->SetBufferOffset(name_start);
            maxsize *= 2;
            delete[] s;
            s = new char[maxsize];
            fEntryBuffer->ReadString(s, maxsize); // Reads at most maxsize - 1 characters, plus null at end
         }
      } else {
         fEntryBuffer->SetBufferOffset(objectStart);
      }
      objectStart = fEntryBuffer->Length();
      fEntryBuffer->SetBufferOffset(startpos);
      basket->Update(lold, objectStart - fEntryBuffer->GetBufferDisplacement());
   }
   fEntries++;
   fEntryNumber++;
   UInt_t len = 0;
   UInt_t startpos = fEntryBuffer->Length();
   if (startpos > UInt_t(objectStart)) {
      // We assume this buffer have just been directly filled
      // the current position in the buffer indicates the end of the object!
      len = fEntryBuffer->Length() - objectStart;
   } else {
      // The buffer have been acquired either via TSocket or via
      // TBuffer::SetBuffer(newloc,newsize)
      // Only the actual size of the memory buffer gives us an hint about where
      // the object ends.
      len = fEntryBuffer->BufferSize() - objectStart;
   }
   buf->WriteBuf(fEntryBuffer->Buffer() + objectStart, len);
   if (fEntryBuffer->TestBit(TBufferFile::kNotDecompressed)) {
      // The original buffer came pre-compressed and thus the buffer Length
      // does not really show the really object size
      // lnew = nbytes = basket->GetLast();
      nbytes = last;
      lnew = last;
   } else {
      lnew = buf->Length();
      nbytes = lnew - lold;
   }

   return nbytes;
}

////////////////////////////////////////////////////////////////////////////////
/// Find the immediate sub-branch with passed name.

TBranch* TBranch::FindBranch(const char* name)
{
   // We allow the user to pass only the last dotted component of the name.
   std::string longnm;
   longnm.reserve(fName.Length()+strlen(name)+3);
   longnm = fName.Data();
   if (longnm[longnm.length()-1]==']') {
      std::size_t dim = longnm.find_first_of("[");
      if (dim != std::string::npos) {
         longnm.erase(dim);
      }
   }
   if (longnm[longnm.length()-1] != '.') {
      longnm += '.';
   }
   longnm += name;
   UInt_t namelen = strlen(name);

   Int_t nbranches = fBranches.GetEntries();
   TBranch* branch = 0;
   for(Int_t i = 0; i < nbranches; ++i) {
      branch = (TBranch*) fBranches.UncheckedAt(i);

      const char *brname = branch->fName.Data();
      UInt_t brlen = branch->fName.Length();
      if (brname[brlen-1]==']') {
         const char *dim = strchr(brname,'[');
         if (dim) {
            brlen = dim - brname;
         }
      }
      if (namelen == brlen /* same effective size */
          && strncmp(name,brname,brlen) == 0) {
         return branch;
      }
      if (brlen == (size_t)longnm.length()
          && strncmp(longnm.c_str(),brname,brlen) == 0) {
         return branch;
      }
   }
   return 0;
}

////////////////////////////////////////////////////////////////////////////////
/// Find the leaf corresponding to the name 'searchname'.

TLeaf* TBranch::FindLeaf(const char* searchname)
{
   TString leafname;
   TString leaftitle;
   TString longname;
   TString longtitle;

   // We allow the user to pass only the last dotted component of the name.
   TIter next(GetListOfLeaves());
   TLeaf* leaf = 0;
   while ((leaf = (TLeaf*) next())) {
      leafname = leaf->GetName();
      Ssiz_t dim = leafname.First('[');
      if (dim >= 0) leafname.Remove(dim);

      if (leafname == searchname) return leaf;

      // The leaf element contains the branch name in its name, let's use the title.
      leaftitle = leaf->GetTitle();
      dim = leaftitle.First('[');
      if (dim >= 0) leaftitle.Remove(dim);

      if (leaftitle == searchname) return leaf;

      TBranch* branch = leaf->GetBranch();
      if (branch) {
         longname.Form("%s.%s",branch->GetName(),leafname.Data());
         dim = longname.First('[');
         if (dim>=0) longname.Remove(dim);
         if (longname == searchname) return leaf;

         // The leaf element contains the branch name in its name.
         longname.Form("%s.%s",branch->GetName(),searchname);
         if (longname==leafname) return leaf;

         longtitle.Form("%s.%s",branch->GetName(),leaftitle.Data());
         dim = longtitle.First('[');
         if (dim>=0) longtitle.Remove(dim);
         if (longtitle == searchname) return leaf;

         // The following is for the case where the branch is only
         // a sub-branch.  Since we do not see it through
         // TTree::GetListOfBranches, we need to see it indirectly.
         // This is the less sturdy part of this search ... it may
         // need refining ...
         if (strstr(searchname, ".") && !strcmp(searchname, branch->GetName())) return leaf;
      }
   }
   return 0;
}

////////////////////////////////////////////////////////////////////////////////
/// Flush to disk all the baskets of this branch and any of subbranches.
/// Return the number of bytes written or -1 in case of write error.

Int_t TBranch::FlushBaskets()
{
   UInt_t nerror = 0;
   Int_t nbytes = 0;

   Int_t maxbasket = fWriteBasket + 1;
   // The following protection is not necessary since we should always
   // have fWriteBasket < fBasket.GetSize()
   //if (fBaskets.GetSize() < maxbasket) {
   //   maxbasket = fBaskets.GetSize();
   //}
   for(Int_t i=0; i != maxbasket; ++i) {
      if (fBaskets.UncheckedAt(i)) {
         Int_t nwrite = FlushOneBasket(i);
         if (nwrite<0) {
            ++nerror;
         } else {
            nbytes += nwrite;
         }
      }
   }
   Int_t len = fBranches.GetEntriesFast();
   for (Int_t i = 0; i < len; ++i) {
      TBranch* branch = (TBranch*) fBranches.UncheckedAt(i);
      if (!branch) {
         continue;
      }
      Int_t nwrite = branch->FlushBaskets();
      if (nwrite<0) {
         ++nerror;
      } else {
         nbytes += nwrite;
      }
   }
   if (nerror) {
      return -1;
   } else {
      return nbytes;
   }
}

////////////////////////////////////////////////////////////////////////////////
/// If we have a write basket in memory and it contains some entries and
/// has not yet been written to disk, we write it and delete it from memory.
/// Return the number of bytes written;

Int_t TBranch::FlushOneBasket(UInt_t ibasket)
{
   Int_t nbytes = 0;
   if (fDirectory && fBaskets.GetEntries()) {
      TBasket *basket = (TBasket*)fBaskets.UncheckedAt(ibasket);

      if (basket) {
         if (basket->GetNevBuf()
             && fBasketSeek[ibasket]==0) {
            // If the basket already contains entry we need to close it out.
            // (This is because we can only transfer full compressed buffer)

            if (basket->GetBufferRef()->IsReading()) {
               basket->SetWriteMode();
            }
            nbytes = WriteBasket(basket,ibasket);

         } else {
            // If the basket is empty or has already been written.
            if ((Int_t)ibasket==fWriteBasket) {
               // Nothing to do.
            } else {
               basket->DropBuffers();
               if (basket == fCurrentBasket) {
                  fCurrentBasket    = 0;
                  fFirstBasketEntry = -1;
                  fNextBasketEntry  = -1;
               }
               delete basket;
               --fNBaskets;
               fBaskets[ibasket] = 0;
            }
         }
      }
   }
   return nbytes;
}

////////////////////////////////////////////////////////////////////////////////
/// Return pointer to basket basketnumber in this Branch
///
/// If a new buffer must be created and the user_buffer argument is non-null,
/// then the memory in the user_bufer will be shared with the returned TBasket.

TBasket* TBranch::GetBasketImpl(Int_t basketnumber, TBuffer *user_buffer)
{
   // This counter in the sequential case collects errors coming also from
   // different files (suppose to have a program reading f1.root, f2.root ...)
   // In the mt case, it is made atomic: it safely collects errors from
   // different files processed simultaneously.
   static std::atomic<Int_t> nerrors(0);

      // reference to an existing basket in memory ?
   if (basketnumber <0 || basketnumber > fWriteBasket) return 0;
   TBasket *basket = (TBasket*)fBaskets.UncheckedAt(basketnumber);
   if (basket) return basket;
   if (basketnumber == fWriteBasket) return 0;

   // create/decode basket parameters from buffer
   TFile *file = GetFile(0);
   if (file == 0) {
      return 0;
   }
   // if cluster pre-fetching or retaining is on, do not re-use existing baskets
   // unless a new cluster is used.
   if (fTree->GetMaxVirtualSize() < 0 || fTree->GetClusterPrefetch())
      basket = GetFreshCluster();
   else
      basket = GetFreshBasket(user_buffer);

   // fSkipZip is old stuff still maintained for CDF
   if (fSkipZip) basket->SetBit(TBufferFile::kNotDecompressed);
   if (fBasketBytes[basketnumber] == 0) {
      fBasketBytes[basketnumber] = basket->ReadBasketBytes(fBasketSeek[basketnumber],file);
   }
   //add branch to cache (if any)
   {
      R__LOCKGUARD_IMT(gROOTMutex); // Lock for parallel TTree I/O
      TFileCacheRead *pf = fTree->GetReadCache(file);
      if (pf){
         if (pf->IsLearning()) pf->LearnBranch(this, kFALSE);
         if (fSkipZip) pf->SetSkipZip();
      }
   }

   //now read basket
   Int_t badread = basket->ReadBasketBuffers(fBasketSeek[basketnumber],fBasketBytes[basketnumber],file);
   if (R__unlikely(badread || basket->GetSeekKey() != fBasketSeek[basketnumber] || basket->IsZombie())) {
      nerrors++;
      if (nerrors > 10) return 0;
      if (nerrors == 10) {
         printf(" file probably overwritten: stopping reporting error messages\n");
         if (fBasketSeek[basketnumber] > 2000000000) {
            printf("===>File is more than 2 Gigabytes\n");
            return 0;
         }
         if (fBasketSeek[basketnumber] > 1000000000) {
            printf("===>Your file is may be bigger than the maximum file size allowed on your system\n");
            printf("    Check your AFS maximum file size limit for example\n");
            return 0;
         }
      }
      Error("GetBasket","File: %s at byte:%lld, branch:%s, entry:%lld, badread=%d, nerrors=%d, basketnumber=%d",file->GetName(),basket->GetSeekKey(),GetName(),fReadEntry,badread,nerrors.load(),basketnumber);
      return 0;
   }

   ++fNBaskets;

   fCacheInfo.SetUsed(basketnumber);
   auto perfStats = GetTree()->GetPerfStats();
   if (perfStats)
      perfStats->SetUsed(this, basketnumber);

   fBaskets.AddAt(basket,basketnumber);
   return basket;
}

////////////////////////////////////////////////////////////////////////////////
/// Return address of basket in the file

Long64_t TBranch::GetBasketSeek(Int_t basketnumber) const
{
   if (basketnumber <0 || basketnumber > fWriteBasket) return 0;
   return fBasketSeek[basketnumber];
}

////////////////////////////////////////////////////////////////////////////////
/// Returns (and, if 0, creates) browsable objects for this branch
/// See TVirtualBranchBrowsable::FillListOfBrowsables.

TList* TBranch::GetBrowsables() {
   if (fBrowsables) return fBrowsables;
   fBrowsables=new TList();
   TVirtualBranchBrowsable::FillListOfBrowsables(*fBrowsables, this);
   return fBrowsables;
}

////////////////////////////////////////////////////////////////////////////////
/// Return the name of the user class whose content is stored in this branch,
/// if any.  If this branch was created using the 'leaflist' technique, this
/// function returns an empty string.

const char * TBranch::GetClassName() const
{
   return "";
}

////////////////////////////////////////////////////////////////////////////////
/// Return icon name depending on type of branch.

const char* TBranch::GetIconName() const
{
   if (IsFolder())
      return "TBranchElement-folder";
   else
      return "TBranchElement-leaf";
}

////////////////////////////////////////////////////////////////////////////////
/// A helper function to locate the correct basket - and its first entry.
/// Extracted to a common private function because it is needed by both GetEntry
/// and GetBulkEntries.  It should not be called directly.
///
/// If a new basket must be constructed and the user_buffer is provided, then
/// the user_buffer will back the memory of the newly-constructed basket.
///
/// Assumes that this branch is enabled.
Int_t TBranch::GetBasketAndFirst(TBasket *&basket, Long64_t &first,
                                 TBuffer *user_buffer)
{
   Long64_t updatedNext = fNextBasketEntry;
   Long64_t entry = fReadEntry;
   if (R__likely(fCurrentBasket && fFirstBasketEntry <= entry && entry < fNextBasketEntry)) {
      // We have found the basket containing this entry.
      // make sure basket buffers are in memory.
      basket = fCurrentBasket;
      first = fFirstBasketEntry;
   } else {
      if ((entry < fFirstEntry) || (entry >= fEntryNumber)) {
         return 0;
      }
      first = fFirstBasketEntry;
      Long64_t last = fNextBasketEntry - 1;
      // Are we still in the same ReadBasket?
      if ((entry < first) || (entry > last)) {
         fReadBasket = TMath::BinarySearch(fWriteBasket + 1, fBasketEntry, entry);
         if (fReadBasket < 0) {
            fNextBasketEntry = -1;
            Error("GetBasketAndFirst", "In the branch %s, no basket contains the entry %lld\n", GetName(), entry);
            return -1;
         }
         if (fReadBasket == fWriteBasket) {
            fNextBasketEntry = fEntryNumber;
         } else {
            fNextBasketEntry = fBasketEntry[fReadBasket+1];
         }
         updatedNext = fNextBasketEntry;
         first = fFirstBasketEntry = fBasketEntry[fReadBasket];
      }
      // We have found the basket containing this entry.
      // make sure basket buffers are in memory.
      basket = (TBasket*) fBaskets.UncheckedAt(fReadBasket);
      if (!basket) {
         basket = GetBasketImpl(fReadBasket, user_buffer);
         if (!basket) {
            fCurrentBasket = 0;
            fFirstBasketEntry = -1;
            fNextBasketEntry = -1;
            return -1;
         }
         if (fTree->GetClusterPrefetch()) {
            TTree::TClusterIterator clusterIterator = fTree->GetClusterIterator(entry);
            clusterIterator.Next();
            Int_t nextClusterEntry = clusterIterator.GetNextEntry();
            for (Int_t i = fReadBasket + 1; i < fMaxBaskets && fBasketEntry[i] < nextClusterEntry; i++) {
               GetBasket(i);
            }
         }
         // Getting the next basket might reset the current one and
         // cause a reset of the first / next basket entries back to -1.
         fFirstBasketEntry = first;
         fNextBasketEntry = updatedNext;
      }
      if (user_buffer) {
         // Disassociate basket from memory buffer for bulk IO
         // When the user provides a memory buffer (i.e., for bulk IO), we should
         // make sure to drop all references to that buffer in the TTree afterward.
         fCurrentBasket = nullptr;
         fBaskets[fReadBasket] = nullptr;
      } else {
         fCurrentBasket = basket;
      }
   }
   return 1;
}

////////////////////////////////////////////////////////////////////////////////
/// Returns true if this branch supports bulk IO, false otherwise.
///
/// This will return true if all the various preconditions necessary hold true
/// to perform bulk IO (reasonable type, single TLeaf, etc); the bulk IO may
/// still fail, depending on the contents of the individual TBaskets loaded.
Bool_t TBranch::SupportsBulkRead() const {
   return (fNleaves == 1) &&
          (static_cast<TLeaf*>(fLeaves.UncheckedAt(0))->GetDeserializeType() != TLeaf::DeserializeType::kDestructive);
}

////////////////////////////////////////////////////////////////////////////////
/// Read as many events as possible into the given buffer, using zero-copy
/// mechanisms.
///
/// Returns -1 in case of a failure.  On success, returns a (non-zero) number of
/// events of the type held by this branch currently in the buffer.
///
/// On success, the caller should be able to access the contents of buf as
///
/// static_cast<T*>(buf.GetCurrent())
///
/// where T is the type stored on this branch.  The array's length is the return
/// value of this function.
///
/// NOTES:
/// - This interface is meant to be used by higher-level, type-safe wrappers, not
///   by end-users.
/// - This only returns events 
/// 

Int_t TBranch::GetBulkEntries(Long64_t entry, TBuffer &user_buf)
{
   // TODO: eventually support multiple leaves.
   if (R__unlikely(fNleaves != 1)) return -1;
   TLeaf *leaf = static_cast<TLeaf*>(fLeaves.UncheckedAt(0));
   if (R__unlikely(leaf->GetDeserializeType() == TLeaf::DeserializeType::kDestructive)) {return -1;}

   // Remember which entry we are reading.
   fReadEntry = entry;

   Bool_t enabled = !TestBit(kDoNotProcess);
   if (R__unlikely(!enabled)) return -1;
   TBasket *basket = nullptr;
   Long64_t first;
   Int_t result = GetBasketAndFirst(basket, first, &user_buf);
   if (R__unlikely(result <= 0)) return -1;
   // Only support reading from full clusters.
   if (R__unlikely(entry != first)) {
       //printf("Failed to read from full cluster; first entry is %ld; requested entry is %ld.\n", first, entry);
       return -1;
   }

   basket->PrepareBasket(entry);
   TBuffer* buf = basket->GetBufferRef();

   // Test for very old ROOT files.
   if (R__unlikely(!buf)) {
      Error("GetBulkEntries", "Failed to get a new buffer.\n");
      return -1;
   }
   // Test for displacements, which aren't supported in fast mode.
   if (R__unlikely(basket->GetDisplacement())) {
      Error("GetBulkEntries", "Basket has displacement.\n");
      return -1;
   }

   Int_t bufbegin = basket->GetKeylen();
   buf->SetBufferOffset(bufbegin);

   Int_t N = ((fNextBasketEntry < 0) ? fEntryNumber : fNextBasketEntry) - first;
   //printf("Requesting %d events; fNextBasketEntry=%lld; first=%lld.\n", N, fNextBasketEntry, first);
   if (R__unlikely(!leaf->ReadBasketFast(*buf, N))) {
      Error("GetBulkEntries", "Leaf failed to read.\n");
      return -1;
   }
   user_buf.SetBufferOffset(bufbegin);

   fCurrentBasket = nullptr;
   fBaskets[fReadBasket] = nullptr;
   R__ASSERT(fExtraBasket == nullptr && "fExtraBasket should have been set to nullptr by GetFreshBasket");
   fExtraBasket = basket;
   basket->DisownBuffer();

   return N;
}

// TODO: Template this and the call above; only difference is the TLeaf function (ReadBasketFast vs
// ReadBasketSerialized
Int_t TBranch::GetEntriesSerialized(Long64_t entry, TBuffer &user_buf, TBuffer *count_buf)
{
   // TODO: eventually support multiple leaves.
   if (R__unlikely(fNleaves != 1)) { return -1; }
   TLeaf *leaf = static_cast<TLeaf*>(fLeaves.UncheckedAt(0));
   if (R__unlikely(leaf->GetDeserializeType() == TLeaf::DeserializeType::kDestructive)) {
      Error("GetEntriesSerialized", "Encountered a branch with destructive deserialization; failing.\n");
      return -1;
   }

   // Remember which entry we are reading.
   fReadEntry = entry;

   Bool_t enabled = !TestBit(kDoNotProcess);
   if (R__unlikely(!enabled)) { return -1; }
   TBasket *basket = nullptr;
   Long64_t first;
   Int_t result = GetBasketAndFirst(basket, first, &user_buf);
   if (R__unlikely(result <= 0)) { return -1; }
   // Only support reading from full clusters.
   if (R__unlikely(entry != first)) {
       Error("GetEntriesSerialized", "Failed to read from full cluster; first entry is %lld; requested entry is %lld.\n", first, entry);
       return -1;
   }

   basket->PrepareBasket(entry);
   TBuffer* buf = basket->GetBufferRef();

   // Test for very old ROOT files.
   if (R__unlikely(!buf)) {
      Error("GetEntriesSerialized", "Failed to get a new buffer.\n");
      return -1;
   }
   // Test for displacements, which aren't supported in fast mode.
   if (R__unlikely(basket->GetDisplacement())) {
      Error("GetEntriesSerialized", "Basket has displacement.\n");
      return -1;
   }

   Int_t bufbegin = basket->GetKeylen();
   buf->SetBufferOffset(bufbegin);

   Int_t N = ((fNextBasketEntry < 0) ? fEntryNumber : fNextBasketEntry) - first;
   //Info("GetEntriesSerialized", "Requesting %d events; fNextBasketEntry=%lld; first=%lld.\n", N, fNextBasketEntry, first);

   if (R__unlikely(!leaf->ReadBasketSerialized(*buf, N))) {
      Error("GetEntriesSerialized", "Leaf failed to read.\n");
      return -1;
   }
   user_buf.SetBufferOffset(bufbegin);

   if (count_buf) {
      TLeaf *count_leaf = leaf->GetLeafCount();
      if (count_leaf) {
         //printf("Getting leaf count entries.\n");
         TBranch *count_branch = count_leaf->GetBranch();
         if (R__unlikely(count_branch->GetEntriesSerialized(entry, *count_buf) < 0)) {
            Error("GetEntriesSerialized", "Failed to read count leaf.\n");
            return -1;
         }
      } else {
         // TODO: if you ask for a count on a fixed-size branch, maybe we should
         // just fail?
         Int_t entry_count_serialized;
         char *tmp_ptr = reinterpret_cast<char*>(&entry_count_serialized);
         tobuf(tmp_ptr, leaf->GetLenType() * leaf->GetNdata());
         Int_t cur_offset = count_buf->GetCurrent() - count_buf->Buffer();
         for (int idx=0; idx<N; idx++) {
             *count_buf << entry_count_serialized;
         }
         count_buf->SetBufferOffset(cur_offset);
      }
   }

   return N;
}

////////////////////////////////////////////////////////////////////////////////
/// Read all leaves of entry and return total number of bytes read.
///
/// The input argument "entry" is the entry number in the current tree.
/// In case of a TChain, the entry number in the current Tree must be found
/// before calling this function. For example:
///
///~~~ {.cpp}
///     TChain* chain = ...;
///     Long64_t localEntry = chain->LoadTree(entry);
///     branch->GetEntry(localEntry);
///~~~
///
/// The function returns the number of bytes read from the input buffer.
/// If entry does not exist, the function returns 0.
/// If an I/O error occurs, the function returns -1.
///
/// See IMPORTANT REMARKS in TTree::GetEntry.

Int_t TBranch::GetEntry(Long64_t entry, Int_t getall)
{
   // Remember which entry we are reading.
   fReadEntry = entry;

   if (R__unlikely(TestBit(kDoNotProcess) && !getall)) { return 0; }

   TBasket *basket; // will be initialized in the if/then clauses.
   Long64_t first;

   Int_t result = GetBasketAndFirst(basket, first, nullptr);
   if (R__unlikely(result <= 0)) { return result; }

   basket->PrepareBasket(entry);
   TBuffer* buf = basket->GetBufferRef();

   // This test necessary to read very old Root files (NvE).
   if (R__unlikely(!buf)) {
      TFile* file = GetFile(0);
      if (!file) return -1;
      basket->ReadBasketBuffers(fBasketSeek[fReadBasket], fBasketBytes[fReadBasket], file);
      buf = basket->GetBufferRef();
   }

   // Set entry offset in buffer.
   if (!TestBit(kDoNotUseBufferMap)) {
      buf->ResetMap();
   }
   if (R__unlikely(!buf->IsReading())) {
      basket->SetReadMode();
   }

   Int_t* entryOffset = basket->GetEntryOffset();
   Int_t bufbegin = 0;
   if (entryOffset) {
      bufbegin = entryOffset[entry-first];
      buf->SetBufferOffset(bufbegin);
      Int_t* displacement = basket->GetDisplacement();
      if (R__unlikely(displacement)) {
         buf->SetBufferDisplacement(displacement[entry-first]);
      }
   } else {
      bufbegin = basket->GetKeylen() + ((entry-first) * basket->GetNevBufSize());
      buf->SetBufferOffset(bufbegin);
   }

   // Int_t bufbegin = buf->Length();
   (this->*fReadLeaves)(*buf);
   return buf->Length() - bufbegin;
}

////////////////////////////////////////////////////////////////////////////////
/// Read all leaves of an entry and export buffers to real objects in a TClonesArray list.
///
/// Returns total number of bytes read.

Int_t TBranch::GetEntryExport(Long64_t entry, Int_t /*getall*/, TClonesArray* li, Int_t nentries)
{
   // Remember which entry we are reading.
   fReadEntry = entry;

   if (TestBit(kDoNotProcess)) {
      return 0;
   }
   if ((entry < 0) || (entry >= fEntryNumber)) {
      return 0;
   }
   Int_t nbytes = 0;
   Long64_t first  = fFirstBasketEntry;
   Long64_t last = fNextBasketEntry - 1;
   // Are we still in the same ReadBasket?
   if ((entry < first) || (entry > last)) {
      fReadBasket = TMath::BinarySearch(fWriteBasket + 1, fBasketEntry, entry);
      if (fReadBasket < 0) {
         fNextBasketEntry = -1;
         Error("In the branch %s, no basket contains the entry %d\n", GetName(), entry);
         return -1;
      }
      if (fReadBasket == fWriteBasket) {
         fNextBasketEntry = fEntryNumber;
      } else {
         fNextBasketEntry = fBasketEntry[fReadBasket+1];
      }
      fFirstBasketEntry = first = fBasketEntry[fReadBasket];
   }

   // We have found the basket containing this entry.
   // Make sure basket buffers are in memory.
   TBasket* basket = GetBasketImpl(fReadBasket, nullptr);
   fCurrentBasket = basket;
   if (!basket) {
      fFirstBasketEntry = -1;
      fNextBasketEntry = -1;
      return 0;
   }
   TBuffer* buf = basket->GetBufferRef();
   // Set entry offset in buffer and read data from all leaves.
   if (!TestBit(kDoNotUseBufferMap)) {
      buf->ResetMap();
   }
   if (R__unlikely(!buf->IsReading())) {
      basket->SetReadMode();
   }
   Int_t* entryOffset = basket->GetEntryOffset();
   Int_t bufbegin = 0;
   if (entryOffset) {
      bufbegin = entryOffset[entry-first];
      buf->SetBufferOffset(bufbegin);
      Int_t* displacement = basket->GetDisplacement();
      if (R__unlikely(displacement)) {
         buf->SetBufferDisplacement(displacement[entry-first]);
      }
   } else {
      bufbegin = basket->GetKeylen() + ((entry-first) * basket->GetNevBufSize());
      buf->SetBufferOffset(bufbegin);
   }
   TLeaf* leaf = (TLeaf*) fLeaves.UncheckedAt(0);
   leaf->ReadBasketExport(*buf, li, nentries);
   nbytes = buf->Length() - bufbegin;
   return nbytes;
}

////////////////////////////////////////////////////////////////////////////////
/// Fill expectedClass and expectedType with information on the data type of the
/// object/values contained in this branch (and thus the type of pointers
/// expected to be passed to Set[Branch]Address
/// return 0 in case of success and > 0 in case of failure.

Int_t TBranch::GetExpectedType(TClass *&expectedClass,EDataType &expectedType)
{
   expectedClass = 0;
   expectedType = kOther_t;
   TLeaf* l = (TLeaf*) GetListOfLeaves()->At(0);
   if (l) {
      expectedType = (EDataType) gROOT->GetType(l->GetTypeName())->GetType();
      return 0;
   } else {
      Error("GetExpectedType", "Did not find any leaves in %s",GetName());
      return 1;
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Return pointer to the file where branch buffers reside, returns 0
/// in case branch buffers reside in the same file as tree header.
/// If mode is 1 the branch buffer file is recreated.

TFile* TBranch::GetFile(Int_t mode)
{
   if (fDirectory) return fDirectory->GetFile();

   // check if a file with this name is in the list of Root files
   TFile *file = 0;
   {
      R__LOCKGUARD(gROOTMutex);
      file = (TFile*)gROOT->GetListOfFiles()->FindObject(fFileName.Data());
      if (file) {
         fDirectory = file;
         return file;
      }
   }

   if (fFileName.Length() == 0) return 0;

   TString bFileName( GetRealFileName() );

   // Open file (new file if mode = 1)
   {
      TDirectory::TContext ctxt;
      if (mode) file = TFile::Open(bFileName, "recreate");
      else      file = TFile::Open(bFileName);
   }
   if (!file) return 0;
   if (file->IsZombie()) {delete file; return 0;}
   fDirectory = (TDirectory*)file;
   return file;
}

////////////////////////////////////////////////////////////////////////////////
/// Return a fresh basket by either resusing an existing basket that needs
/// to be drop (according to TTree::MemoryFull) or create a new one.
///
/// If the user_buffer argument is non-null, then the memory in the
/// user-provided buffer will be utilized by the underlying basket.

TBasket* TBranch::GetFreshBasket(TBuffer* user_buffer)
{
   TBasket *basket = 0;
   if (user_buffer && fExtraBasket) {
      basket = fExtraBasket;
      fExtraBasket = nullptr;
      basket->AdoptBuffer(user_buffer);
   } else {
      if (GetTree()->MemoryFull(0)) {
         if (fNBaskets==1) {
            // Steal the existing basket
            Int_t oldindex = fBaskets.GetLast();
            basket = (TBasket*)fBaskets.UncheckedAt(oldindex);
            if (!basket) {
               fBaskets.SetLast(-2); // For recalculation of Last.
               oldindex = fBaskets.GetLast();
               if (oldindex != fBaskets.LowerBound()-1) {
                  basket = (TBasket*)fBaskets.UncheckedAt(oldindex);
               }
            }
            if (basket && fBasketBytes[oldindex]!=0) {
               if (basket == fCurrentBasket) {
                  fCurrentBasket    = 0;
                  fFirstBasketEntry = -1;
                  fNextBasketEntry  = -1;
               }
               fBaskets.AddAt(0,oldindex);
               fBaskets.SetLast(-1);
               fNBaskets = 0;
            } else {
               basket = fTree->CreateBasket(this);
            }
         } else if (fNBaskets == 0) {
            // There is nothing to drop!
            basket = fTree->CreateBasket(this);
         } else {
            // Memory is full and there is more than one basket,
            // Let DropBaskets do it job.
            DropBaskets();
            basket = fTree->CreateBasket(this);
         }
      } else {
         basket = fTree->CreateBasket(this);
      }
      if (user_buffer)
         basket->AdoptBuffer(user_buffer);
   }
   return basket;
}

////////////////////////////////////////////////////////////////////////////////
/// Drops the cluster two behind the current cluster and returns a fresh basket
/// by either reusing or creating a new one

TBasket *TBranch::GetFreshCluster()
{
   TBasket *basket = 0;

   // If GetClusterIterator is called with a negative entry then GetStartEntry will be 0
   // So we need to check if we reach the zero before we have gone back (1-VirtualSize) clusters
   // if this is the case, we want to keep everything in memory so we return a new basket
   TTree::TClusterIterator iter = fTree->GetClusterIterator(fBasketEntry[fReadBasket]);
   if (iter.GetStartEntry() == 0) {
      return fTree->CreateBasket(this);
   }

   // Iterate backwards (1-VirtualSize) clusters to reach cluster to be unloaded from memory,
   // skipped if VirtualSize > 0.
   for (Int_t j = 0; j < -fTree->GetMaxVirtualSize(); j++) {
      if (iter.Previous() == 0) {
         return fTree->CreateBasket(this);
      }
   }

   Int_t entryToUnload = iter.Previous();
   // Finds the basket to unload from memory. Since the basket should be close to current
   // basket, just iterate backwards until the correct basket is reached. This should
   // be fast as long as the number of baskets per cluster is small
   Int_t basketToUnload = fReadBasket;
   while (fBasketEntry[basketToUnload] != entryToUnload) {
      basketToUnload--;
      if (basketToUnload < 0) {
         return fTree->CreateBasket(this);
      }
   }

   // Retrieves the basket that is going to be unloaded from memory. If the basket did not
   // exist, create a new one
   basket = (TBasket *)fBaskets.UncheckedAt(basketToUnload);
   if (basket) {
      fBaskets.AddAt(0, basketToUnload);
      --fNBaskets;
   } else {
      basket = fTree->CreateBasket(this);
   }
   ++basketToUnload;

   // Clear the rest of the baskets. While it would be ideal to reuse these baskets
   // for other baskets in the new cluster. It would require the function to go
   // beyond its current scope. In the ideal case when each cluster only has 1 basket
   // this will perform well
   iter.Next();
   while (fBasketEntry[basketToUnload] < iter.GetStartEntry()) {
      TBasket *oldbasket = (TBasket *)fBaskets.UncheckedAt(basketToUnload);
      if (oldbasket) {
         oldbasket->DropBuffers();
         delete oldbasket;
         fBaskets.AddAt(0, basketToUnload);
         --fNBaskets;
      }
      ++basketToUnload;
   }
   fBaskets.SetLast(-1);
   return basket;
}

////////////////////////////////////////////////////////////////////////////////
/// Return pointer to the 1st Leaf named name in thisBranch

TLeaf* TBranch::GetLeaf(const char* name) const
{
   Int_t i;
   for (i=0;i<fNleaves;i++) {
      TLeaf *leaf = (TLeaf*)fLeaves.UncheckedAt(i);
      if (!strcmp(leaf->GetName(),name)) return leaf;
   }
   return 0;
}

////////////////////////////////////////////////////////////////////////////////
/// Get real file name

TString TBranch::GetRealFileName() const
{
   if (fFileName.Length()==0) {
      return fFileName;
   }
   TString bFileName = fFileName;

   // check if branch file name is absolute or a URL (e.g. root://host/...)
   char *bname = gSystem->ExpandPathName(fFileName.Data());
   if (!gSystem->IsAbsoluteFileName(bname) && !strstr(bname, ":/") && fTree && fTree->GetCurrentFile()) {

      // if not, get filename where tree header is stored
      const char *tfn = fTree->GetCurrentFile()->GetName();

      // If it is an archive file we need a special treatment
      TUrl arc(tfn);
      if (strlen(arc.GetAnchor()) > 0) {
         arc.SetAnchor(gSystem->BaseName(fFileName));
         bFileName = arc.GetUrl();
      } else {
         // if this is an absolute path or a URL then prepend this path
         // to the branch file name
         char *tname = gSystem->ExpandPathName(tfn);
         if (gSystem->IsAbsoluteFileName(tname) || strstr(tname, ":/")) {
            bFileName = gSystem->DirName(tname);
            bFileName += "/";
            bFileName += fFileName;
         }
         delete [] tname;
      }
   }
   delete [] bname;

   return bFileName;
}

////////////////////////////////////////////////////////////////////////////////
/// Return all elements of one row unpacked in internal array fValues
/// [Actually just returns 1 (?)]

Int_t TBranch::GetRow(Int_t)
{
   return 1;
}

////////////////////////////////////////////////////////////////////////////////
/// Return whether this branch is in a mode where the object are decomposed
/// or not (Also known as MakeClass mode).

Bool_t TBranch::GetMakeClass() const
{
   // Regular TBranch and TBrancObject can not be in makeClass mode

   return kFALSE;
}

////////////////////////////////////////////////////////////////////////////////
/// Get our top-level parent branch in the tree.

TBranch* TBranch::GetMother() const
{
   if (fMother) return fMother;

   const TObjArray* array = fTree->GetListOfBranches();
   Int_t n = array->GetEntriesFast();
   for (Int_t i = 0; i < n; ++i) {
      TBranch* branch = (TBranch*) array->UncheckedAt(i);
      TBranch* parent = branch->GetSubBranch(this);
      if (parent) {
         const_cast<TBranch*>(this)->fMother = branch; // We can not yet use the 'mutable' keyword
         return branch;
      }
   }
   return 0;
}

////////////////////////////////////////////////////////////////////////////////
/// Find the parent branch of child.
/// Return 0 if child is not in this branch hierarchy.

TBranch* TBranch::GetSubBranch(const TBranch* child) const
{
   // Handle error condition, if the parameter is us, we cannot find the parent.
   if (this == child) {
      // Note: We cast away any const-ness of "this".
      return (TBranch*) this;
   }

   if (child->fParent) {
      return child->fParent;
   }

   Int_t len = fBranches.GetEntriesFast();
   for (Int_t i = 0; i < len; ++i) {
      TBranch* branch = (TBranch*) fBranches.UncheckedAt(i);
      if (!branch) {
         continue;
      }
      if (branch == child) {
         // We are the direct parent of child.
         const_cast<TBranch*>(child)->fParent = (TBranch*)this; // We can not yet use the 'mutable' keyword
         // Note: We cast away any const-ness of "this".
         const_cast<TBranch*>(child)->fParent = (TBranch*)this; // We can not yet use the 'mutable' keyword
         return (TBranch*) this;
      }
      // FIXME: This is a tail-recursion!
      TBranch* parent = branch->GetSubBranch(child);
      if (parent) {
         return parent;
      }
   }
   // We failed to find the parent.
   return 0;
}

////////////////////////////////////////////////////////////////////////////////
/// Return total number of bytes in the branch (including current buffer)

Long64_t TBranch::GetTotalSize(Option_t * /*option*/) const
{
   TBufferFile b(TBuffer::kWrite, 10000);
   // This intentionally only store the TBranch part and thus slightly
   // under-estimate the space used.
   // Since the TBranchElement part contains pointers to other branches (branch count),
   // doing regular Streaming would end up including those and thus greatly over-estimate
   // the size used.
   const_cast<TBranch *>(this)->TBranch::Streamer(b);

   Long64_t totbytes = 0;
   if (fZipBytes > 0) totbytes = fTotBytes;
   return totbytes + b.Length();
}

////////////////////////////////////////////////////////////////////////////////
/// Return total number of bytes in the branch (excluding current buffer)
/// if option ="*" includes all sub-branches of this branch too

Long64_t TBranch::GetTotBytes(Option_t *option) const
{
   Long64_t totbytes = fTotBytes;
   if (!option) return totbytes;
   if (option[0] != '*') return totbytes;
   //scan sub-branches
   Int_t len = fBranches.GetEntriesFast();
   for (Int_t i = 0; i < len; ++i) {
      TBranch* branch = (TBranch*) fBranches.UncheckedAt(i);
      if (branch) totbytes += branch->GetTotBytes(option);
   }
   return totbytes;
}

////////////////////////////////////////////////////////////////////////////////
/// Return total number of zip bytes in the branch
/// if option ="*" includes all sub-branches of this branch too

Long64_t TBranch::GetZipBytes(Option_t *option) const
{
   Long64_t zipbytes = fZipBytes;
   if (!option) return zipbytes;
   if (option[0] != '*') return zipbytes;
   //scan sub-branches
   Int_t len = fBranches.GetEntriesFast();
   for (Int_t i = 0; i < len; ++i) {
      TBranch* branch = (TBranch*) fBranches.UncheckedAt(i);
      if (branch) zipbytes += branch->GetZipBytes(option);
   }
   return zipbytes;
}

////////////////////////////////////////////////////////////////////////////////
/// Returns the IO settings currently in use for this branch.

ROOT::TIOFeatures TBranch::GetIOFeatures() const
{
   return fIOFeatures;
}

////////////////////////////////////////////////////////////////////////////////
/// Return kTRUE if an existing object in a TBranchObject must be deleted.

Bool_t TBranch::IsAutoDelete() const
{
   return TestBit(kAutoDelete);
}

////////////////////////////////////////////////////////////////////////////////
/// Return kTRUE if more than one leaf or browsables, kFALSE otherwise.

Bool_t TBranch::IsFolder() const
{
   if (fNleaves > 1) {
      return kTRUE;
   }
   TList* browsables = const_cast<TBranch*>(this)->GetBrowsables();
   return browsables && browsables->GetSize();
}

////////////////////////////////////////////////////////////////////////////////
/// keep a maximum of fMaxEntries in memory

void TBranch::KeepCircular(Long64_t maxEntries)
{
   Int_t dentries = (Int_t) (fEntries - maxEntries);
   TBasket* basket = (TBasket*) fBaskets.UncheckedAt(0);
   if (basket) basket->MoveEntries(dentries);
   fEntries = maxEntries;
   fEntryNumber = maxEntries;
   //loop on sub branches
   Int_t nb = fBranches.GetEntriesFast();
   for (Int_t i = 0; i < nb; ++i)  {
      TBranch* branch = (TBranch*) fBranches.UncheckedAt(i);
      branch->KeepCircular(maxEntries);
   }
}

////////////////////////////////////////////////////////////////////////////////
///  Baskets associated to this branch are forced to be in memory.
///  You can call TTree::SetMaxVirtualSize(maxmemory) to instruct
///  the system that the total size of the imported baskets does not
///  exceed maxmemory bytes.
///
///  The function returns the number of baskets that have been put in memory.
///  This method may be called to force all baskets of one or more branches
///  in memory when random access to entries in this branch is required.
///  See also TTree::LoadBaskets to load all baskets of all branches in memory.

Int_t TBranch::LoadBaskets()
{
   Int_t nimported = 0;
   Int_t nbaskets = fWriteBasket;
   TFile *file = GetFile(0);
   if (!file) return 0;
   TBasket *basket;
   for (Int_t i=0;i<nbaskets;i++) {
      basket = (TBasket*)fBaskets.UncheckedAt(i);
      if (basket) continue;
      basket = GetFreshBasket(nullptr);
      if (fBasketBytes[i] == 0) {
         fBasketBytes[i] = basket->ReadBasketBytes(fBasketSeek[i],file);
      }
      Int_t badread = basket->ReadBasketBuffers(fBasketSeek[i],fBasketBytes[i],file);
      if (badread) {
         Error("Loadbaskets","Error while reading basket buffer %d of branch %s",i,GetName());
         return -1;
      }
      ++fNBaskets;
      fBaskets.AddAt(basket,i);
      nimported++;
   }
   return nimported;
}

////////////////////////////////////////////////////////////////////////////////
/// Print TBranch parameters
///
/// If options contains "basketsInfo" print the entry number, location and size
/// of each baskets.

void TBranch::Print(Option_t *option) const
{
   const int kLINEND = 77;
   Float_t cx = 1;

   TString titleContent(GetTitle());
   if ( titleContent == GetName() ) {
      titleContent.Clear();
   }

   if (fLeaves.GetEntries() == 1) {
      if (titleContent.Length()>=2 && titleContent[titleContent.Length()-2]=='/' && isalpha(titleContent[titleContent.Length()-1])) {
         // The type is already encoded.  Nothing to do.
      } else {
         TLeaf *leaf = (TLeaf*)fLeaves.UncheckedAt(0);
         if (titleContent.Length()) {
            titleContent.Prepend(" ");
         }
         // titleContent.Append("type: ");
         titleContent.Prepend(leaf->GetTypeName());
      }
   }
   Int_t titleLength = titleContent.Length();

   Int_t aLength = titleLength + strlen(GetName());
   aLength += (aLength / 54 + 1) * 80 + 100;
   if (aLength < 200) aLength = 200;
   char *bline = new char[aLength];

   Long64_t totBytes = GetTotalSize();
   if (fZipBytes) cx = (fTotBytes+0.00001)/fZipBytes;
   if (titleLength) snprintf(bline,aLength,"*Br%5d :%-9s : %-54s *",fgCount,GetName(),titleContent.Data());
   else             snprintf(bline,aLength,"*Br%5d :%-9s : %-54s *",fgCount,GetName()," ");
   if (strlen(bline) > UInt_t(kLINEND)) {
      char *tmp = new char[strlen(bline)+1];
      if (titleLength) strlcpy(tmp, titleContent.Data(),strlen(bline)+1);
      snprintf(bline,aLength,"*Br%5d :%-9s : ",fgCount,GetName());
      int pos = strlen (bline);
      int npos = pos;
      int beg=0, end;
      while (beg < titleLength) {
         for (end=beg+1; end < titleLength-1; end ++)
            if (tmp[end] == ':')  break;
         if (npos + end-beg+1 >= 78) {
            while (npos < kLINEND) {
               bline[pos ++] = ' ';
               npos ++;
            }
            bline[pos ++] = '*';
            bline[pos ++] = '\n';
            bline[pos ++] = '*';
            npos = 1;
            for (; npos < 12; npos ++)
               bline[pos ++] = ' ';
            bline[pos-2] = '|';
         }
         for (int n = beg; n <= end; n ++)
            bline[pos+n-beg] = tmp[n];
         pos += end-beg+1;
         npos += end-beg+1;
         beg = end+1;
      }
      while (npos < kLINEND) {
         bline[pos ++] = ' ';
         npos ++;
      }
      bline[pos ++] = '*';
      bline[pos] = '\0';
      delete[] tmp;
   }
   Printf("%s", bline);

   if (fTotBytes > 2000000000) {
      Printf("*Entries :%lld : Total  Size=%11lld bytes  File Size  = %lld *",fEntries,totBytes,fZipBytes);
   } else {
      if (fZipBytes > 0) {
         Printf("*Entries :%9lld : Total  Size=%11lld bytes  File Size  = %10lld *",fEntries,totBytes,fZipBytes);
      } else {
         if (fWriteBasket > 0) {
               Printf("*Entries :%9lld : Total  Size=%11lld bytes  All baskets in memory   *",fEntries,totBytes);
         } else {
               Printf("*Entries :%9lld : Total  Size=%11lld bytes  One basket in memory    *",fEntries,totBytes);
         }
      }
   }
   Printf("*Baskets :%9d : Basket Size=%11d bytes  Compression= %6.2f     *",fWriteBasket,fBasketSize,cx);

   if (strncmp(option,"basketsInfo",strlen("basketsInfo"))==0) {
      Int_t nbaskets = fWriteBasket;
      for (Int_t i=0;i<nbaskets;i++) {
         Printf("*Basket #%4d  entry=%6lld  pos=%6lld  size=%5d",
                i, fBasketEntry[i], fBasketSeek[i], fBasketBytes[i]);
      }
   }

   Printf("*............................................................................*");
   delete [] bline;
   fgCount++;
}

////////////////////////////////////////////////////////////////////////////////
/// Print the information we have about which basket is currently cached and
/// whether they have been 'used'/'read' from the cache.

void TBranch::PrintCacheInfo() const
{
   fCacheInfo.Print(GetName(), fBasketEntry);
}

////////////////////////////////////////////////////////////////////////////////
/// Loop on all leaves of this branch to read Basket buffer.

void TBranch::ReadBasket(TBuffer&)
{
   //   fLeaves->ReadBasket(basket);
}

////////////////////////////////////////////////////////////////////////////////
/// Loop on all leaves of this branch to read Basket buffer.

void TBranch::ReadLeavesImpl(TBuffer& b)
{
   for (Int_t i = 0; i < fNleaves; ++i) {
      TLeaf* leaf = (TLeaf*) fLeaves.UncheckedAt(i);
      leaf->ReadBasket(b);
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Read zero leaves without the overhead of a loop.

void TBranch::ReadLeaves0Impl(TBuffer&)
{
}

////////////////////////////////////////////////////////////////////////////////
/// Read one leaf without the overhead of a loop.

void TBranch::ReadLeaves1Impl(TBuffer& b)
{
   ((TLeaf*) fLeaves.UncheckedAt(0))->ReadBasket(b);
}

////////////////////////////////////////////////////////////////////////////////
/// Read two leaves without the overhead of a loop.

void TBranch::ReadLeaves2Impl(TBuffer& b)
{
   ((TLeaf*) fLeaves.UncheckedAt(0))->ReadBasket(b);
   ((TLeaf*) fLeaves.UncheckedAt(1))->ReadBasket(b);
}

////////////////////////////////////////////////////////////////////////////////
/// Loop on all leaves of this branch to fill Basket buffer.

void TBranch::FillLeavesImpl(TBuffer& b)
{
   for (Int_t i = 0; i < fNleaves; ++i) {
      TLeaf* leaf = (TLeaf*) fLeaves.UncheckedAt(i);
      leaf->FillBasket(b);
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Refresh this branch using new information in b
/// This function is called by TTree::Refresh

void TBranch::Refresh(TBranch* b)
{
   if (b==0) return;

   fEntryOffsetLen = b->fEntryOffsetLen;
   fWriteBasket    = b->fWriteBasket;
   fEntryNumber    = b->fEntryNumber;
   fMaxBaskets     = b->fMaxBaskets;
   fEntries        = b->fEntries;
   fTotBytes       = b->fTotBytes;
   fZipBytes       = b->fZipBytes;
   fReadBasket     = 0;
   fReadEntry      = -1;
   fFirstBasketEntry = -1;
   fNextBasketEntry  = -1;
   fCurrentBasket    =  0;
   delete [] fBasketBytes;
   delete [] fBasketEntry;
   delete [] fBasketSeek;
   fBasketBytes = new Int_t[fMaxBaskets];
   fBasketEntry = new Long64_t[fMaxBaskets];
   fBasketSeek  = new Long64_t[fMaxBaskets];
   Int_t i;
   for (i=0;i<fMaxBaskets;i++) {
      fBasketBytes[i] = b->fBasketBytes[i];
      fBasketEntry[i] = b->fBasketEntry[i];
      fBasketSeek[i]  = b->fBasketSeek[i];
   }
   fBaskets.Delete();
   Int_t nbaskets = b->fBaskets.GetSize();
   fBaskets.Expand(nbaskets);
   // If the current fWritebasket is in memory, take it (just swap)
   // from the Tree being read
   TBasket *basket = (TBasket*)b->fBaskets.UncheckedAt(fWriteBasket);
   fBaskets.AddAt(basket,fWriteBasket);
   if (basket) {
      fNBaskets = 1;
      --(b->fNBaskets);
      b->fBaskets.RemoveAt(fWriteBasket);
      basket->SetBranch(this);
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Reset a Branch.
///
/// - Existing buffers are deleted.
/// - Entries, max and min are reset.

void TBranch::Reset(Option_t*)
{
   fReadBasket = 0;
   fReadEntry = -1;
   fFirstBasketEntry = -1;
   fNextBasketEntry = -1;
   fCurrentBasket   = 0;
   fWriteBasket = 0;
   fEntries = 0;
   fTotBytes = 0;
   fZipBytes = 0;
   fEntryNumber = 0;

   if (fBasketBytes) {
      for (Int_t i = 0; i < fMaxBaskets; ++i) {
         fBasketBytes[i] = 0;
      }
   }

   if (fBasketEntry) {
      for (Int_t i = 0; i < fMaxBaskets; ++i) {
         fBasketEntry[i] = 0;
      }
   }

   if (fBasketSeek) {
      for (Int_t i = 0; i < fMaxBaskets; ++i) {
         fBasketSeek[i] = 0;
      }
   }

   fBaskets.Delete();
   fNBaskets = 0;
}

////////////////////////////////////////////////////////////////////////////////
/// Reset a Branch.
///
/// - Existing buffers are deleted.
/// - Entries, max and min are reset.

void TBranch::ResetAfterMerge(TFileMergeInfo *)
{
   fReadBasket       = 0;
   fReadEntry        = -1;
   fFirstBasketEntry = -1;
   fNextBasketEntry  = -1;
   fCurrentBasket    = 0;
   fWriteBasket      = 0;
   fEntries          = 0;
   fTotBytes         = 0;
   fZipBytes         = 0;
   fEntryNumber      = 0;

   if (fBasketBytes) {
      for (Int_t i = 0; i < fMaxBaskets; ++i) {
         fBasketBytes[i] = 0;
      }
   }

   if (fBasketEntry) {
      for (Int_t i = 0; i < fMaxBaskets; ++i) {
         fBasketEntry[i] = 0;
      }
   }

   if (fBasketSeek) {
      for (Int_t i = 0; i < fMaxBaskets; ++i) {
         fBasketSeek[i] = 0;
      }
   }

   TBasket *reusebasket = (TBasket*)fBaskets[fWriteBasket];
   if (reusebasket) {
      fBaskets[fWriteBasket] = 0;
   } else {
      reusebasket = (TBasket*)fBaskets[fReadBasket];
      if (reusebasket) {
         fBaskets[fReadBasket] = 0;
      }
   }
   fBaskets.Delete();
   if (reusebasket) {
      fNBaskets = 1;
      reusebasket->Reset();
      fBaskets[0] = reusebasket;
   } else {
      fNBaskets = 0;
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Reset the address of the branch.

void TBranch::ResetAddress()
{
   fAddress = 0;

   //  Reset last read entry number, we have will had new user object now.
   fReadEntry = -1;

   for (Int_t i = 0; i < fNleaves; ++i) {
      TLeaf* leaf = (TLeaf*) fLeaves.UncheckedAt(i);
      leaf->SetAddress(0);
   }

   Int_t nbranches = fBranches.GetEntriesFast();
   for (Int_t i = 0; i < nbranches; ++i)  {
      TBranch* abranch = (TBranch*) fBranches[i];
      // FIXME: This is a tail recursion.
      abranch->ResetAddress();
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Static function resetting fgCount

void TBranch::ResetCount()
{
   fgCount = 0;
}

////////////////////////////////////////////////////////////////////////////////
/// Set address of this branch.

void TBranch::SetAddress(void* addr)
{
   if (TestBit(kDoNotProcess)) {
      return;
   }
   fReadEntry = -1;
   fFirstBasketEntry = -1;
   fNextBasketEntry  = -1;
   fAddress = (char*) addr;
   for (Int_t i = 0; i < fNleaves; ++i) {
      TLeaf* leaf = (TLeaf*) fLeaves.UncheckedAt(i);
      Int_t offset = leaf->GetOffset();
      if (TestBit(kIsClone)) {
         offset = 0;
      }
      if (fAddress) leaf->SetAddress(fAddress + offset);
      else leaf->SetAddress(0);
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Set the automatic delete bit.
///
/// This bit is used by TBranchObject::ReadBasket to decide if an object
/// referenced by a TBranchObject must be deleted or not before reading
/// a new entry.
///
/// If autodel is kTRUE, this existing object will be deleted, a new object
/// created by the default constructor, then read from disk by the streamer.
///
/// If autodel is kFALSE, the existing object is not deleted.  Root assumes
/// that the user is taking care of deleting any internal object or array
/// (this can be done in the streamer).

void TBranch::SetAutoDelete(Bool_t autodel)
{
   if (autodel) {
      SetBit(kAutoDelete, 1);
   } else {
      SetBit(kAutoDelete, 0);
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Set the basket size
/// The function makes sure that the basket size is greater than fEntryOffsetlen

void TBranch::SetBasketSize(Int_t buffsize)
{
   Int_t minsize = 100 + fName.Length();
   if (buffsize < minsize+fEntryOffsetLen) buffsize = minsize+fEntryOffsetLen;
   fBasketSize = buffsize;
   TBasket *basket = (TBasket*)fBaskets[fWriteBasket];
   if (basket) {
      basket->AdjustSize(fBasketSize);
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Set address of this branch directly from a TBuffer to avoid streaming.
///
/// Note: We do not take ownership of the buffer.

void TBranch::SetBufferAddress(TBuffer* buf)
{
   // Check this is possible
   if ( (fNleaves != 1)
       || (strcmp("TLeafObject",fLeaves.UncheckedAt(0)->ClassName())!=0) ) {
      Error("TBranch::SetAddress","Filling from a TBuffer can only be done with a not split object branch.  Request ignored.");
   } else {
      fReadEntry = -1;
      fNextBasketEntry  = -1;
      fFirstBasketEntry = -1;
      // Note: We do not take ownership of the buffer.
      fEntryBuffer = buf;
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Set compression algorithm.

void TBranch::SetCompressionAlgorithm(Int_t algorithm)
{
   if (algorithm < 0 || algorithm >= ROOT::RCompressionSetting::EAlgorithm::kUndefined) algorithm = 0;
   if (fCompress < 0) {
      fCompress = 100 * algorithm + ROOT::RCompressionSetting::ELevel::kUseMin;
   } else {
      int level = fCompress % 100;
      fCompress = 100 * algorithm + level;
   }

   Int_t nb = fBranches.GetEntriesFast();
   for (Int_t i=0;i<nb;i++) {
      TBranch *branch = (TBranch*)fBranches.UncheckedAt(i);
      branch->SetCompressionAlgorithm(algorithm);
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Set compression level.

void TBranch::SetCompressionLevel(Int_t level)
{
   if (level < 0) level = 0;
   if (level > 99) level = 99;
   if (fCompress < 0) {
      fCompress = level;
   } else {
      int algorithm = fCompress / 100;
      if (algorithm >= ROOT::RCompressionSetting::EAlgorithm::kUndefined) algorithm = 0;
      fCompress = 100 * algorithm + level;
   }

   Int_t nb = fBranches.GetEntriesFast();
   for (Int_t i=0;i<nb;i++) {
      TBranch *branch = (TBranch*)fBranches.UncheckedAt(i);
      branch->SetCompressionLevel(level);
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Set compression settings.

void TBranch::SetCompressionSettings(Int_t settings)
{
   fCompress = settings;

   Int_t nb = fBranches.GetEntriesFast();
   for (Int_t i=0;i<nb;i++) {
      TBranch *branch = (TBranch*)fBranches.UncheckedAt(i);
      branch->SetCompressionSettings(settings);
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Update the default value for the branch's fEntryOffsetLen if and only if
/// it was already non zero (and the new value is not zero)
/// If updateExisting is true, also update all the existing branches.

void TBranch::SetEntryOffsetLen(Int_t newdefault, Bool_t updateExisting)
{
   if (fEntryOffsetLen && newdefault) {
      fEntryOffsetLen = newdefault;
   }
   if (updateExisting) {
      TIter next( GetListOfBranches() );
      TBranch *b;
      while ( ( b = (TBranch*)next() ) ) {
         b->SetEntryOffsetLen( newdefault, kTRUE );
      }
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Set the number of entries in this branch.

void TBranch::SetEntries(Long64_t entries)
{
   fEntries = entries;
   fEntryNumber = entries;
}

////////////////////////////////////////////////////////////////////////////////
/// Set file where this branch writes/reads its buffers.
/// By default the branch buffers reside in the file where the
/// Tree was created.
/// If the file name where the tree was created is an absolute
/// path name or an URL (e.g. or root://host/...)
/// and if the fname is not an absolute path name or an URL then
/// the path of the tree file is prepended to fname to make the
/// branch file relative to the tree file. In this case one can
/// move the tree + all branch files to a different location in
/// the file system and still access the branch files.
/// The ROOT file will be connected only when necessary.
/// If called by TBranch::Fill (via TBasket::WriteFile), the file
/// will be created with the option "recreate".
/// If called by TBranch::GetEntry (via TBranch::GetBasket), the file
/// will be opened in read mode.
/// To open a file in "update" mode or with a certain compression
/// level, use TBranch::SetFile(TFile *file).

void TBranch::SetFile(TFile* file)
{
   if (file == 0) file = fTree->GetCurrentFile();
   fDirectory = (TDirectory*)file;
   if (file == fTree->GetCurrentFile()) fFileName = "";
   else                                 fFileName = file->GetName();

   if (file && fCompress == -1) {
      fCompress = file->GetCompressionLevel();
   }

   // Apply to all existing baskets.
   TIter nextb(GetListOfBaskets());
   TBasket *basket;
   while ((basket = (TBasket*)nextb())) {
      basket->SetParent(file);
   }

   // Apply to sub-branches as well.
   TIter next(GetListOfBranches());
   TBranch *branch;
   while ((branch = (TBranch*)next())) {
      branch->SetFile(file);
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Set file where this branch writes/reads its buffers.
/// By default the branch buffers reside in the file where the
/// Tree was created.
/// If the file name where the tree was created is an absolute
/// path name or an URL (e.g. root://host/...)
/// and if the fname is not an absolute path name or an URL then
/// the path of the tree file is prepended to fname to make the
/// branch file relative to the tree file. In this case one can
/// move the tree + all branch files to a different location in
/// the file system and still access the branch files.
/// The ROOT file will be connected only when necessary.
/// If called by TBranch::Fill (via TBasket::WriteFile), the file
/// will be created with the option "recreate".
/// If called by TBranch::GetEntry (via TBranch::GetBasket), the file
/// will be opened in read mode.
/// To open a file in "update" mode or with a certain compression
/// level, use TBranch::SetFile(TFile *file).

void TBranch::SetFile(const char* fname)
{
   fFileName  = fname;
   fDirectory = 0;

   //apply to sub-branches as well
   TIter next(GetListOfBranches());
   TBranch *branch;
   while ((branch = (TBranch*)next())) {
      branch->SetFile(fname);
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Set the branch in a mode where the object are decomposed
/// (Also known as MakeClass mode).
/// Return whether the setting was possible (it is not possible for
/// TBranch and TBranchObject).

Bool_t TBranch::SetMakeClass(Bool_t /* decomposeObj */)
{
   // Regular TBranch and TBrancObject can not be in makeClass mode
   return kFALSE;
}

////////////////////////////////////////////////////////////////////////////////
/// Set object this branch is pointing to.

void TBranch::SetObject(void * /* obj */)
{
   if (TestBit(kDoNotProcess)) {
      return;
   }
   Warning("SetObject","is not supported in TBranch objects");
}

////////////////////////////////////////////////////////////////////////////////
/// Set branch status to Process or DoNotProcess.

void TBranch::SetStatus(Bool_t status)
{
   if (status) ResetBit(kDoNotProcess);
   else        SetBit(kDoNotProcess);
}

////////////////////////////////////////////////////////////////////////////////
/// Stream a class object

void TBranch::Streamer(TBuffer& b)
{
   if (b.IsReading()) {
      UInt_t R__s, R__c;
      fTree = 0; // Will be set by TTree::Streamer
      fAddress = 0;
      gROOT->SetReadingObject(kTRUE);

      // Reset transients.
      SetBit(TBranch::kDoNotUseBufferMap);
      fCurrentBasket    = 0;
      fFirstBasketEntry = -1;
      fNextBasketEntry  = -1;

      Version_t v = b.ReadVersion(&R__s, &R__c);
      if (v > 9) {
         b.ReadClassBuffer(TBranch::Class(), this, v, R__s, R__c);

         if (fWriteBasket>=fBaskets.GetSize()) {
            fBaskets.Expand(fWriteBasket+1);
         }
         fDirectory = 0;
         fNleaves = fLeaves.GetEntriesFast();
         for (Int_t i=0;i<fNleaves;i++) {
            TLeaf *leaf = (TLeaf*)fLeaves.UncheckedAt(i);
            leaf->SetBranch(this);
         }

         fNBaskets = fBaskets.GetEntries();
         for (Int_t j=fWriteBasket,n=0;j>=0 && n<fNBaskets;--j) {
            TBasket *bk = (TBasket*)fBaskets.UncheckedAt(j);
            if (bk) {
               bk->SetBranch(this);
               // GetTree()->IncrementTotalBuffers(bk->GetBufferSize());
               ++n;
            }
         }
         if (fWriteBasket >= fMaxBaskets) {
            //old versions may need this fix
            ExpandBasketArrays();
            fBasketBytes[fWriteBasket] = fBasketBytes[fWriteBasket-1];
            fBasketEntry[fWriteBasket] = fEntries;
            fBasketSeek [fWriteBasket] = fBasketSeek [fWriteBasket-1];

         }
         if (!fSplitLevel && fBranches.GetEntriesFast()) fSplitLevel = 1;
         gROOT->SetReadingObject(kFALSE);
         if (IsA() == TBranch::Class()) {
            if (fNleaves == 0) {
               fReadLeaves = &TBranch::ReadLeaves0Impl;
            } else if (fNleaves == 1) {
               fReadLeaves = &TBranch::ReadLeaves1Impl;
            } else if (fNleaves == 2) {
               fReadLeaves = &TBranch::ReadLeaves2Impl;
            } else {
               fReadLeaves = &TBranch::ReadLeavesImpl;
            }
         }
         return;
      }
      //====process old versions before automatic schema evolution
      Int_t n,i,j,ijunk;
      if (v > 5) {
         Stat_t djunk;
         TNamed::Streamer(b);
         if (v > 7) TAttFill::Streamer(b);
         b >> fCompress;
         b >> fBasketSize;
         b >> fEntryOffsetLen;
         b >> fWriteBasket;
         b >> ijunk; fEntryNumber = (Long64_t)ijunk;
         b >> fOffset;
         b >> fMaxBaskets;
         if (v > 6) b >> fSplitLevel;
         b >> djunk; fEntries  = (Long64_t)djunk;
         b >> djunk; fTotBytes = (Long64_t)djunk;
         b >> djunk; fZipBytes = (Long64_t)djunk;

         fBranches.Streamer(b);
         fLeaves.Streamer(b);
         fBaskets.Streamer(b);
         fBasketBytes = new Int_t[fMaxBaskets];
         fBasketEntry = new Long64_t[fMaxBaskets];
         fBasketSeek  = new Long64_t[fMaxBaskets];
         Char_t isArray;
         b >> isArray;
         b.ReadFastArray(fBasketBytes,fMaxBaskets);
         b >> isArray;
         for (i=0;i<fMaxBaskets;i++) {b >> ijunk; fBasketEntry[i] = ijunk;}
         b >> isArray;
         for (i=0;i<fMaxBaskets;i++) {
            if (isArray == 2) b >> fBasketSeek[i];
            else              {Int_t bsize; b >> bsize; fBasketSeek[i] = (Long64_t)bsize;};
         }
         fFileName.Streamer(b);
         b.CheckByteCount(R__s, R__c, TBranch::IsA());
         fDirectory = 0;
         fNleaves = fLeaves.GetEntriesFast();
         for (i=0;i<fNleaves;i++) {
            TLeaf *leaf = (TLeaf*)fLeaves.UncheckedAt(i);
            leaf->SetBranch(this);
         }
         fNBaskets = fBaskets.GetEntries();
         for (j=fWriteBasket,n=0;j>=0 && n<fNBaskets;--j) {
            TBasket *bk = (TBasket*)fBaskets.UncheckedAt(j);
            if (bk) {
               bk->SetBranch(this);
               //GetTree()->IncrementTotalBuffers(bk->GetBufferSize());
               ++n;
            }
         }
         if (fWriteBasket >= fMaxBaskets) {
            //old versions may need this fix
            ExpandBasketArrays();
            fBasketBytes[fWriteBasket] = fBasketBytes[fWriteBasket-1];
            fBasketEntry[fWriteBasket] = fEntries;
            fBasketSeek [fWriteBasket] = fBasketSeek [fWriteBasket-1];

         }
         // Check Byte Count is not needed since it was done in ReadBuffer
         if (!fSplitLevel && fBranches.GetEntriesFast()) fSplitLevel = 1;
         gROOT->SetReadingObject(kFALSE);
         b.CheckByteCount(R__s, R__c, TBranch::IsA());
         if (IsA() == TBranch::Class()) {
            if (fNleaves == 0) {
               fReadLeaves = &TBranch::ReadLeaves0Impl;
            } else if (fNleaves == 1) {
               fReadLeaves = &TBranch::ReadLeaves1Impl;
            } else if (fNleaves == 2) {
               fReadLeaves = &TBranch::ReadLeaves2Impl;
            } else {
               fReadLeaves = &TBranch::ReadLeavesImpl;
            }
         }
         return;
      }
      //====process very old versions
      Stat_t djunk;
      TNamed::Streamer(b);
      b >> fCompress;
      b >> fBasketSize;
      b >> fEntryOffsetLen;
      b >> fMaxBaskets;
      b >> fWriteBasket;
      b >> ijunk; fEntryNumber = (Long64_t)ijunk;
      b >> djunk; fEntries  = (Long64_t)djunk;
      b >> djunk; fTotBytes = (Long64_t)djunk;
      b >> djunk; fZipBytes = (Long64_t)djunk;
      b >> fOffset;
      fBranches.Streamer(b);
      fLeaves.Streamer(b);
      fNleaves = fLeaves.GetEntriesFast();
      for (i=0;i<fNleaves;i++) {
         TLeaf *leaf = (TLeaf*)fLeaves.UncheckedAt(i);
         leaf->SetBranch(this);
      }
      fBaskets.Streamer(b);
      Int_t nbaskets = fBaskets.GetEntries();
      for (j=fWriteBasket,n=0;j>0 && n<nbaskets;--j) {
         TBasket *bk = (TBasket*)fBaskets.UncheckedAt(j);
         if (bk) {
            bk->SetBranch(this);
            //GetTree()->IncrementTotalBuffers(bk->GetBufferSize());
            ++n;
         }
      }
      fBasketEntry = new Long64_t[fMaxBaskets];
      b >> n;
      for (i=0;i<n;i++) {b >> ijunk; fBasketEntry[i] = ijunk;}
      fBasketBytes = new Int_t[fMaxBaskets];
      if (v > 4) {
         n  = b.ReadArray(fBasketBytes);
      } else {
         for (n=0;n<fMaxBaskets;n++) fBasketBytes[n] = 0;
      }
      if (v < 2) {
         fBasketSeek = new Long64_t[fMaxBaskets];
         for (n=0;n<fWriteBasket;n++) {
            TBasket *basket = GetBasketImpl(n, nullptr);
            fBasketSeek[n] = basket ? basket->GetSeekKey() : 0;
         }
      } else {
         fBasketSeek = new Long64_t[fMaxBaskets];
         b >> n;
         for (n=0;n<fMaxBaskets;n++) {
            Int_t aseek;
            b >> aseek;
            fBasketSeek[n] = Long64_t(aseek);
         }
      }
      if (v > 2) {
         fFileName.Streamer(b);
      }
      fDirectory = 0;
      if (v < 4) SetAutoDelete(kTRUE);
      if (!fSplitLevel && fBranches.GetEntriesFast()) fSplitLevel = 1;
      gROOT->SetReadingObject(kFALSE);
      b.CheckByteCount(R__s, R__c, TBranch::IsA());
      //====end of old versions
      if (IsA() == TBranch::Class()) {
         if (fNleaves == 0) {
            fReadLeaves = &TBranch::ReadLeaves0Impl;
         } else if (fNleaves == 1) {
            fReadLeaves = &TBranch::ReadLeaves1Impl;
         } else if (fNleaves == 2) {
            fReadLeaves = &TBranch::ReadLeaves2Impl;
         } else {
            fReadLeaves = &TBranch::ReadLeavesImpl;
         }
      }
   } else {
      Int_t maxBaskets = fMaxBaskets;
      fMaxBaskets = fWriteBasket+1;
      Int_t lastBasket = fMaxBaskets;
      if (fMaxBaskets < 10) fMaxBaskets = 10;

      TBasket **stash = new TBasket *[lastBasket];
      for (Int_t i = 0; i < lastBasket; ++i) {
         TBasket *ba = (TBasket *)fBaskets.UncheckedAt(i);
         if (ba && (fBasketBytes[i] || ba->GetNevBuf()==0)) {
            // Already on disk or empty.
            stash[i] = ba;
            fBaskets[i] = nullptr;
         } else {
            stash[i] = nullptr;
         }
      }

      b.WriteClassBuffer(TBranch::Class(), this);

      for (Int_t i = 0; i < lastBasket; ++i) {
         if (stash[i]) fBaskets[i] = stash[i];
      }

      delete[] stash;
      fMaxBaskets = maxBaskets;
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Write the current basket to disk and return the number of bytes
/// written to the file.

Int_t TBranch::WriteBasketImpl(TBasket* basket, Int_t where, ROOT::Internal::TBranchIMTHelper *imtHelper)
{
   Int_t nevbuf = basket->GetNevBuf();
   if (fEntryOffsetLen > 10 &&  (4*nevbuf) < fEntryOffsetLen ) {
      // Make sure that the fEntryOffset array does not stay large unnecessarily.
      fEntryOffsetLen = nevbuf < 3 ? 10 : 4*nevbuf; // assume some fluctuations.
   } else if (fEntryOffsetLen && nevbuf > fEntryOffsetLen) {
      // Increase the array ...
      fEntryOffsetLen = 2*nevbuf; // assume some fluctuations.
   }

   // Note: captures `basket`, `where`, and `this` by value; modifies the TBranch and basket,
   // as we make a copy of the pointer.  We cannot capture `basket` by reference as the pointer
   // itself might be modified after `WriteBasketImpl` exits.
   auto doUpdates = [=]() {
      Int_t nout  = basket->WriteBuffer();    //  Write buffer
      if (nout < 0) Error("TBranch::WriteBasketImpl", "basket's WriteBuffer failed.\n");
      fBasketBytes[where]  = basket->GetNbytes();
      fBasketSeek[where]   = basket->GetSeekKey();
      Int_t addbytes = basket->GetObjlen() + basket->GetKeylen();
      TBasket *reusebasket = 0;
      if (nout>0) {
         // The Basket was written so we can now safely reuse it.
         fBaskets[where] = 0;

         reusebasket = basket;
         reusebasket->Reset();

         fZipBytes += nout;
         fTotBytes += addbytes;
         fTree->AddTotBytes(addbytes);
         fTree->AddZipBytes(nout);
#ifdef R__TRACK_BASKET_ALLOC_TIME
         fTree->AddAllocationTime(reusebasket->GetResetAllocationTime());
#endif
         fTree->AddAllocationCount(reusebasket->GetResetAllocationCount());
      }

      if (where==fWriteBasket) {
         ++fWriteBasket;
         if (fWriteBasket >= fMaxBaskets) {
            ExpandBasketArrays();
         }
         if (reusebasket && reusebasket == fCurrentBasket) {
            // The 'current' basket has Reset, so if we need it we will need
            // to reload it.
            fCurrentBasket    = 0;
            fFirstBasketEntry = -1;
            fNextBasketEntry  = -1;
         }
         fBaskets.AddAtAndExpand(reusebasket,fWriteBasket);
         fBasketEntry[fWriteBasket] = fEntryNumber;
      } else {
         --fNBaskets;
         fBaskets[where] = 0;
         basket->DropBuffers();
         if (basket == fCurrentBasket) {
            fCurrentBasket    = 0;
            fFirstBasketEntry = -1;
            fNextBasketEntry  = -1;
         }
         delete basket;
      }
      return nout;
   };
   if (imtHelper) {
      imtHelper->Run(doUpdates);
      return 0;
   } else {
      return doUpdates();
   }
}

////////////////////////////////////////////////////////////////////////////////
///set the first entry number (case of TBranchSTL)

void TBranch::SetFirstEntry(Long64_t entry)
{
   fFirstEntry = entry;
   fEntries = 0;
   fEntryNumber = entry;
   if( fBasketEntry )
      fBasketEntry[0] = entry;
   for( Int_t i = 0; i < fBranches.GetEntriesFast(); ++i )
      ((TBranch*)fBranches[i])->SetFirstEntry( entry );
}

////////////////////////////////////////////////////////////////////////////////
/// If the branch address is not set,  we set all addresses starting with
/// the top level parent branch.

void TBranch::SetupAddresses()
{
   // Nothing to do for regular branch, the TLeaf already did it.
}

////////////////////////////////////////////////////////////////////////////////
/// Refresh the value of fDirectory (i.e. where this branch writes/reads its buffers)
/// with the current value of fTree->GetCurrentFile unless this branch has been
/// redirected to a different file.  Also update the sub-branches.

void TBranch::UpdateFile()
{
   TFile *file = fTree->GetCurrentFile();
   if (fFileName.Length() == 0) {
      fDirectory = file;

      // Apply to all existing baskets.
      TIter nextb(GetListOfBaskets());
      TBasket *basket;
      while ((basket = (TBasket*)nextb())) {
         basket->SetParent(file);
      }
   }

   // Apply to sub-branches as well.
   TIter next(GetListOfBranches());
   TBranch *branch;
   while ((branch = (TBranch*)next())) {
      branch->UpdateFile();
   }
}