RDisplay.hxx

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// Author: Enrico Guiraud, Danilo Piparo CERN, Massimo Tumolo Politecnico di Torino  08/2018
 
/*************************************************************************
 * Copyright (C) 1995-2018, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/
 
#ifndef ROOT_RDFDISPLAYER
#define ROOT_RDFDISPLAYER
 
#include "ROOT/RDF/Utils.hxx"  // IsDataContainer, InterpreterCalc
#include "ROOT/RVec.hxx"
#include "ROOT/TypeTraits.hxx"
#include "TClassEdit.h"
 
#include <vector>
#include <string>
#include <sstream>
 
namespace ROOT {
namespace Internal {
namespace RDF {
 
template<typename T>
class DisplayHelper;
std::string PrettyPrintAddr(const void *const addr);
 
class RDisplayElement {
private:
   enum class PrintingAction { ToBePrinted, ToBeIgnored, ToBeDotted };
   std::string fRepresentation;
   PrintingAction fPrintingAction;
 
public:
   RDisplayElement(const std::string &representation);
   RDisplayElement();
   void SetPrint();
   void SetIgnore();
   void SetDots();
   bool IsPrint() const;
   bool IsIgnore() const;
   bool IsDot() const;
   const std::string &GetRepresentation() const;
   bool IsEmpty() const;
};
} // namespace RDF
} // namespace Internal
 
namespace RDF {
 
/**
 * \class ROOT::RDF::RDisplay
 * \ingroup dataframe
 * This class is the textual representation of the content of a columnar dataset.
 *
 * This class is provided to the user, and it can be used to print on screen
 * the entries of the dataset requested through the Display action in a compact
 * representation or to return the full representation of the events as a string.
 * In order to apply proper formatting the content is buffered in memory as strings.
 */
class RDisplay {
   template<typename T>
   friend class ROOT::Internal::RDF::DisplayHelper;
private:
   using VecStr_t = std::vector<std::string>;
   using DElement_t = ROOT::Internal::RDF::RDisplayElement;
   static constexpr char fgSeparator = ' '; ///< Spacing used to align the table entries
   static constexpr unsigned fgMaxWidth = 100; ///< Maximum width of the table that Print() displays
 
   VecStr_t fTypes; ///< This attribute stores the type of each column. It is needed by the interpreter to print it.
   std::vector<bool> fIsCollection; ///< True if the column contains a collection. Collections are treated differently
                                    ///< during the printing.
   std::vector<std::vector<DElement_t>> fTable; ///< String representation of the data to be printed.
   std::vector<unsigned short> fWidths; ///< Tracks the maximum width of each column, based on the largest element.
 
   VecStr_t fRepresentations; ///< Used by the JITted code to store the string representation of the data.
   std::vector<VecStr_t> fCollectionsRepresentations; ///< Used by the JITted code to store the string representation of
                                                      ///< the data in case of collection. Each row corresponds to a
                                                      ///< column, each column to a value of the collection.
 
   size_t fNColumns; ///< Number of columns to be printed
 
   size_t fCurrentRow = 0;    ///< Row that is being filled
   size_t fNextRow = 1;       ///< Next row to be filled.
   size_t fCurrentColumn = 0; ///< Column that is being filled.
 
   size_t fNMaxCollectionElements = 10; // threshold on number of elements in collections to be Print()
 
   ////////////////////////////////////////////////////////////////////////////
   /// Appends a cling::printValue call to the stringstream.
   /// \tparam T the type of the event to convert
   /// \param[in] stream Where the conversion function call will be chained.
   /// \param[in] element The event to convert to its string representation
   /// \param[in] index To which column the event belongs to
   /// \return false, the event is not a collection
   template <typename T, std::enable_if_t<!ROOT::Internal::RDF::IsDataContainer<T>::value, int> = 0>
   bool AddInterpreterString(std::stringstream &stream, T &element, const int &index)
   {
      stream << "*((std::string*)" << ROOT::Internal::RDF::PrettyPrintAddr(&(fRepresentations[index]))
             << ") = cling::printValue((" << fTypes[index] << "*)" << ROOT::Internal::RDF::PrettyPrintAddr(&element) << ");";
      return false;
   }
 
   ////////////////////////////////////////////////////////////////////////////
   /// Appends collection.size() cling::printValue calls to the stringstream.
   /// \tparam T the type of the event to convert
   /// \param[in] stream Where the conversion function call will be chained.
   /// \param[in] collection The event to convert to its string representation
   /// \param[in] index To which column the event belongs to
   /// \return true, the event is a collection
   /// This function chains a sequence of call to cling::printValue, one for each element of the collection.
   template <typename T, std::enable_if_t<ROOT::Internal::RDF::IsDataContainer<T>::value, int> = 0>
   bool AddInterpreterString(std::stringstream &stream, T &collection, const int &index)
   {
      size_t collectionSize = std::distance(std::begin(collection), std::end(collection));
      // Prepare the row to contain as many elements as the number of elements in the collection
      fCollectionsRepresentations[index] = VecStr_t(collectionSize);
 
      // Use GetSplit to get the encapsulated type of the collection. For example, GetSplit on
      // std::vector<std::vector<int>> will return std::vector<int>
      VecStr_t output;
      int nestedLoc = 0;
      TClassEdit::GetSplit(fTypes[index].c_str(), output, nestedLoc);
 
      // For each element, append a call and feed the proper type returned by GetSplit
      for (size_t i = 0; i < collectionSize; ++i) {
         stream << "*((std::string*)" << ROOT::Internal::RDF::PrettyPrintAddr(&(fCollectionsRepresentations[index][i]))
                << ") = cling::printValue((" << output[1] << "*)"
                << ROOT::Internal::RDF::PrettyPrintAddr(&(collection[i])) << ");";
      }
      return true;
   }
 
   ////////////////////////////////////////////////////////////////////////////
   /// AddInterpreterString overload for arrays of chars.
   ///
   /// \param[in] charArr The character array to convert to string representation
   /// \param[in] index To which column the event belongs
   /// \return false, the event is not a collection
   ///
   /// This specialization for arrays of characters skips the cling::printValue
   /// (i.e. appends nothing to the stream) and directly writes to fRepresentations the
   /// string representation of the array of chars.
   bool AddInterpreterString(std::stringstream &, ROOT::RVec<char> &charArr, const int &index)
   {
      // if null-terminated char array, do not copy the null terminator into std::string, it makes columns misaligned.
      const auto length = charArr[charArr.size()-1] == '\0' ? charArr.size() - 1 : charArr.size();
      const std::string arrAsStr(charArr.data(), length); // also works for non-null-terminated strings
      fRepresentations[index] = arrAsStr;
      return false; // do not treat this as a collection
   }
 
   ////////////////////////////////////////////////////////////////////////////
   /// AddInterpreterString overload for arrays of booleans.
   ///
   /// \param[in] boolArr The bool array to convert to string representation
   /// \param[in] index To which column the event belongs
   /// \return true, the event is a collection
   ///
   /// This specialization for arrays of booleans skips the cling::printValue
   /// (i.e. appends nothing to the stream) and directly writes to fCollectionsRepresentations the
   /// string representation of the array of chars.
   bool AddInterpreterString(std::stringstream &, ROOT::RVec<bool> &boolArr, const int &index)
   {
      auto &collRepr = fCollectionsRepresentations[index];
      collRepr.clear();
      collRepr.reserve(boolArr.size());
      for (bool b : boolArr)
         collRepr.push_back(b ? "true" : "false");
 
      return true; // treat this as a collection
   }
 
 
   ////////////////////////////////////////////////////////////////////////////
   /// Adds a single element to the next slot in the table
   void AddToRow(const std::string &stringEle);
 
   ////////////////////////////////////////////////////////////////////////////
   /// Adds a collection to the table
   ///
   /// Starting from the slot, the elements are added one under the other, each
   /// one using a single cell of an entire row
   void AddCollectionToRow(const VecStr_t &collection);
 
   ////////////////////////////////////////////////////////////////////////////
   /// Moves to the next cell
   ///
   /// Moves to the next cell, and if the row is full moves to the next row.
   void MovePosition();
 
   ////////////////////////////////////////////////////////////////////////////
   /// Get the number of columns that do NOT fit in the characters limit
   size_t GetNColumnsToShorten() const;
 
   ////////////////////////////////////////////////////////////////////////////
   /// Generate dashes between entries in Print() and AsString() Methods
   std::string DashesBetweenLines(size_t lastColToPrint, bool allColumnsFit) const;
 
   ////////////////////////////////////////////////////////////////////////////
   /// Adds a row of events to the table
   template <typename... Columns>
   void AddRow(Columns &... columns)
   {
      std::stringstream calc; // JITted code
      int columnIndex = 0;
      // Unwrapping the parameters to create the JITted code.
      fIsCollection = {AddInterpreterString(calc, columns, columnIndex++)...};
 
      // Let cling::printValue handle the conversion. This can be done only through cling-compiled code.
      const std::string toJit = calc.str();
      if (!toJit.empty())
         ROOT::Internal::RDF::InterpreterCalc(calc.str(), "Display");
 
      // Populate the fTable using the results of the JITted code.
      for (size_t i = 0; i < fNColumns; ++i) {
         if (fIsCollection[i]) {
            AddCollectionToRow(fCollectionsRepresentations[i]);
         } else {
            AddToRow(fRepresentations[i]);
         }
      }
   }
 
   void EnsureCurrentColumnWidth(size_t w);
 
public:
   ////////////////////////////////////////////////////////////////////////////
   /// Creates an RDisplay to print the event values
   /// \param[in] columnNames Columns to print
   /// \param[in] types The type of each column
   /// \param[in] nMaxCollectionElements Number of maximum elements in collection.
   RDisplay(const VecStr_t &columnNames, const VecStr_t &types, size_t nMaxCollectionElements);
 
   ////////////////////////////////////////////////////////////////////////////
   /// Prints the representation to the standard output
   ///
   /// Collections are shortened to the first and last element. The overall width
   /// is shortened to a fixed number of columns that should fit the screen width.
   void Print() const;
 
   ////////////////////////////////////////////////////////////////////////////
   /// Returns the representation as a string
   std::string AsString() const;
};
 
} // namespace RDF
} // namespace ROOT
 
#endif