TPyReturn.cxx

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// Author: Enric Tejedor CERN  08/2019
// Original PyROOT code by Wim Lavrijsen, LBL
//
// /*************************************************************************
//  * Copyright (C) 1995-2019, 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 <Python.h>
 
// Bindings
#include "cpyrt/API.h"
#include "TPyReturn.h"
 
// ROOT
#include "TObject.h"
#include "TInterpreter.h"
 
// Standard
#include <stdexcept>
 
//______________________________________________________________________________
//                        Python expression eval result
//                        =============================
//
// Transport class for bringing objects from python (dynamically typed) to Cling
// (statically typed). It is best to immediately cast a TPyReturn to the real
// type, either implicitly (for builtin types) or explicitly (through a void*
// cast for pointers to ROOT objects).
//
// Examples:
//
//  root [0] TBrowser* b = (void*)TPython::Eval( "ROOT.TBrowser()" );
//  root [1] int i = TPython::Eval( "1+1" );
//  root [2] i
//  (int)2
//  root [3] double d = TPython::Eval( "1+3.1415" );
//  root [4] d
//  (double)4.14150000000000063e+00
 
//- data ---------------------------------------------------------------------
 
namespace {
   class PyGILRAII {
      PyGILState_STATE m_GILState;
   public:
      PyGILRAII() : m_GILState(PyGILState_Ensure()) { }
      ~PyGILRAII() { PyGILState_Release(m_GILState); }
   };
}
 
//- constructors/destructor --------------------------------------------------
TPyReturn::TPyReturn()
{
   PyGILRAII gilRaii;
 
   // Construct a TPyReturn object from Py_None.
   Py_IncRef(Py_None);
   fPyObject = Py_None;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Construct a TPyReturn from a python object. The python object may represent
/// a ROOT object. Steals reference to given python object.
 
TPyReturn::TPyReturn(PyObject *pyobject)
{
   PyGILRAII gilRaii;
 
   if (!pyobject) {
      Py_IncRef(Py_None);
      fPyObject = Py_None;
   } else
      fPyObject = pyobject; // steals reference
}
 
////////////////////////////////////////////////////////////////////////////////
/// Copy constructor. Applies python object reference counting.
 
TPyReturn::TPyReturn(const TPyReturn &other)
{
   PyGILRAII gilRaii;
 
   Py_IncRef(other.fPyObject);
   fPyObject = other.fPyObject;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Assignment operator. Applies python object reference counting.
 
TPyReturn &TPyReturn::operator=(const TPyReturn &other)
{
   PyGILRAII gilRaii;
 
   if (this != &other) {
      Py_IncRef(other.fPyObject);
      Py_DecRef(fPyObject);
      fPyObject = other.fPyObject;
   }
 
   return *this;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Destructor. Reference counting for the held python object is in effect.
 
TPyReturn::~TPyReturn()
{
   PyGILRAII gilRaii;
 
   Py_DecRef(fPyObject);
}
 
//- public members -----------------------------------------------------------
TPyReturn::operator char *() const
{
   PyGILRAII gilRaii;
 
   // Cast python return value to C-style string (may fail).
   return (char *)((const char *)*this);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Cast python return value to C-style string (may fail).
 
TPyReturn::operator const char *() const
{
   PyGILRAII gilRaii;
 
   if (fPyObject == Py_None) // for void returns
      return 0;
 
   const char *s = PyUnicode_AsUTF8AndSize(fPyObject, nullptr);
   if (PyErr_Occurred()) {
      PyErr_Print();
      return 0;
   }
 
   return s;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Cast python return value to C++ char (may fail).
 
TPyReturn::operator Char_t() const
{
   PyGILRAII gilRaii;
 
   std::string s = operator const char *();
   if (s.size())
      return s[0];
 
   return '\0';
}
 
////////////////////////////////////////////////////////////////////////////////
/// Cast python return value to C++ long (may fail).
 
TPyReturn::operator Long_t() const
{
   PyGILRAII gilRaii;
 
   Long_t l = PyLong_AsLong(fPyObject);
 
   if (PyErr_Occurred())
      PyErr_Print();
 
   return l;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Cast python return value to C++ unsigned long (may fail).
 
TPyReturn::operator ULong_t() const
{
   PyGILRAII gilRaii;
 
   ULong_t ul = PyLong_AsUnsignedLong(fPyObject);
 
   if (PyErr_Occurred())
      PyErr_Print();
 
   return ul;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Cast python return value to C++ double (may fail).
 
TPyReturn::operator Double_t() const
{
   PyGILRAII gilRaii;
 
   Double_t d = PyFloat_AsDouble(fPyObject);
 
   if (PyErr_Occurred())
      PyErr_Print();
 
   return d;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Cast python return value to ROOT object with dictionary (may fail; note that
/// you have to use the void* converter, as Cling will not call any other).
 
TPyReturn::operator void *() const
{
   PyGILRAII gilRaii;
 
   if (fPyObject == Py_None)
      return nullptr;
 
   if (cppjit::cpyrt::Instance_Check(fPyObject)) {
      cppjit::cpyrt::Instance_SetCppOwns(fPyObject);
      return cppjit::cpyrt::Instance_AsVoidPtr(fPyObject);
   } else
      return fPyObject; // borrows reference
}
 
////////////////////////////////////////////////////////////////////////////////
/// Direct return of the held PyObject; note the new reference.
 
TPyReturn::operator PyObject *() const
{
   PyGILRAII gilRaii;
 
   if (fPyObject == Py_None)
      return 0;
 
   Py_IncRef(fPyObject);
   return fPyObject;
}