root/ROOT/TBufferMerger.hxx

0001 // @(#)root/io:$Id$
0002 // Author: Philippe Canal, Witold Pokorski, and Guilherme Amadio
0003
0004 /*************************************************************************
0005  * Copyright (C) 1995-2017, Rene Brun and Fons Rademakers.               *
0006  * All rights reserved.                                                  *
0007  *                                                                       *
0008  * For the licensing terms see $ROOTSYS/LICENSE.                         *
0009  * For the list of contributors see $ROOTSYS/README/CREDITS.             *
0010  *************************************************************************/
0011
0012 #ifndef ROOT_TBufferMerger
0013 #define ROOT_TBufferMerger
0014
0015 #include "TFileMerger.h"
0016 #include "TMemFile.h"
0017 #include "ROOT/RConfig.hxx"
0018
0019 #include <functional>
0020 #include <memory>
0021 #include <mutex>
0022 #include <queue>
0023
0024 namespace ROOT {
0025
0026 class TBufferMergerFile;
0027
0028 /**
0029  * \class TBufferMerger TBufferMerger.hxx
0030  * \ingroup IO
0031  *
0032  * TBufferMerger is a class to facilitate writing data in
0033  * parallel from multiple threads, while writing to a single
0034  * output file. Its purpose is similar to TParallelMergingFile,
0035  * but instead of using processes that connect to a network
0036  * socket, TBufferMerger uses threads that each write to a
0037  * TBufferMergerFile, which in turn push data into a queue
0038  * managed by the TBufferMerger.
0039  */
0040
0041 class TBufferMerger {
0042 public:
0043    /** Constructor
0044     * @param name Output file name
0045     * @param option Output file creation options
0046     * @param compress Output file compression level
0047     */
0048    TBufferMerger(const char *name, Option_t *option = "RECREATE",
0049                  Int_t compress = ROOT::RCompressionSetting::EDefaults::kUseCompiledDefault);
0050
0051    /** Constructor
0052     * @param output Output \c TFile
0053     */
0054    TBufferMerger(std::unique_ptr<TFile> output);
0055
0056    /** Destructor */
0057    virtual ~TBufferMerger();
0058
0059    /** Returns a TBufferMergerFile to which data can be written.
0060     *  At the end, all TBufferMergerFiles get merged into the output file.
0061     *  The user is responsible to "cd" into the file to associate objects
0062     *  such as histograms or trees to it.
0063     *
0064     *  After the creation of this file, the user must reset the kMustCleanup
0065     *  bit on any objects attached to it and take care of their deletion, as
0066     *  there is a possibility that a race condition will happen that causes
0067     *  a crash if ROOT manages these objects.
0068     */
0069    std::shared_ptr<TBufferMergerFile> GetFile();
0070
0071    _R__DEPRECATED_LATER("The queuing mechanism in TBufferMerger was removed in ROOT v6.32")
0072    size_t GetQueueSize() const { return 0; }
0073
0074    _R__DEPRECATED_LATER("The queuing mechanism in TBufferMerger was removed in ROOT v6.32")
0075    size_t GetBuffered() const { return 0; }
0076
0077    _R__DEPRECATED_LATER("The queuing mechanism in TBufferMerger was removed in ROOT v6.32")
0078    size_t GetAutoSave() const { return 0; }
0079
0080    /** Returns the current merge options. */
0081    const char* GetMergeOptions();
0082
0083    _R__DEPRECATED_LATER("The queuing mechanism in TBufferMerger was removed in ROOT v6.32")
0084    void SetAutoSave(size_t /*size*/) {}
0085
0086    /** Sets the merge options. SetMergeOptions("fast") will disable
0087     * recompression of input data into the output if they have different
0088     * compression settings.
0089     * @param options TFileMerger/TFileMergeInfo merge options
0090     */
0091    void SetMergeOptions(const TString& options);
0092
0093    /** Indicates that any TTree objects in the file should be skipped
0094     * and thus that steps that are specific to TTree can be skipped */
0095    void SetNotrees(Bool_t notrees=kFALSE)
0096    {
0097       fMerger.SetNotrees(notrees);
0098    }
0099
0100    /** Returns whether the file has been marked as not containing any TTree objects
0101     * and thus that steps that are specific to TTree can be skipped */
0102    Bool_t GetNotrees() const
0103    {
0104       return fMerger.GetNotrees();
0105    }
0106
0107    _R__DEPRECATED_LATER("The queuing mechanism in TBufferMerger was removed in ROOT v6.32")
0108    void SetCompressTemporaryKeys(Bool_t /*request_compression*/ = true) {}
0109
0110    _R__DEPRECATED_LATER("The queuing mechanism in TBufferMerger was removed in ROOT v6.32")
0111    Bool_t GetCompressTemporaryKeys() const { return false; }
0112
0113    friend class TBufferMergerFile;
0114
0115 private:
0116    /** TBufferMerger has no default constructor */
0117    TBufferMerger();
0118
0119    /** TBufferMerger has no copy constructor */
0120    TBufferMerger(const TBufferMerger &);
0121
0122    /** TBufferMerger has no copy operator */
0123    TBufferMerger &operator=(const TBufferMerger &);
0124
0125    void Init(std::unique_ptr<TFile>);
0126
0127    void Merge(TBufferMergerFile *memfile);
0128
0129    TFileMerger fMerger{false, false};                            //< TFileMerger used to merge all buffers
0130    std::mutex fMergeMutex;                                       //< Mutex used to lock fMerger
0131    std::vector<std::weak_ptr<TBufferMergerFile>> fAttachedFiles; //< Attached files
0132 };
0133
0134 /**
0135  * \class TBufferMergerFile TBufferMerger.hxx
0136  * \ingroup IO
0137  *
0138  * A TBufferMergerFile is similar to a TMemFile, but when data
0139  * is written to it, it is appended to the TBufferMerger queue.
0140  * The TBufferMerger merges all data into the output file on disk.
0141  */
0142
0143 class TBufferMergerFile : public TMemFile {
0144 private:
0145    TBufferMerger &fMerger; //< TBufferMerger this file is attached to
0146
0147    /** Constructor. Can only be called by TBufferMerger.
0148     * @param m Merger this file is attached to. */
0149    TBufferMergerFile(TBufferMerger &m);
0150
0151    /** TBufferMergerFile has no default constructor. */
0152    TBufferMergerFile();
0153
0154    /** TBufferMergerFile has no copy constructor. */
0155    TBufferMergerFile(const TBufferMergerFile &);
0156
0157    /** TBufferMergerFile has no copy operator */
0158    TBufferMergerFile &operator=(const TBufferMergerFile &);
0159
0160    friend class TBufferMerger;
0161
0162 public:
0163    /** Destructor */
0164    ~TBufferMergerFile() override;
0165
0166    using TMemFile::Write;
0167
0168    /** Write data into a TBufferFile and append it to TBufferMerger.
0169     * @param name Name
0170     * @param opt  Options
0171     * @param bufsize Buffer size
0172     * This function must be called before the TBufferMergerFile gets destroyed,
0173     * or no data is appended to the TBufferMerger.
0174     */
0175    Int_t Write(const char *name = nullptr, Int_t opt = 0, Int_t bufsize = 0) override;
0176
0177    ClassDefOverride(TBufferMergerFile, 0);
0178 };
0179
0180 } // namespace ROOT
0181
0182 #endif