TPyClassGenerator.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 "PythonLimitedAPI.h"
 
#include "TPyClassGenerator.h"
#include "TPyReturn.h"
 
// ROOT
#include "TClass.h"
#include "TInterpreter.h"
#include "TROOT.h"
#include "TList.h"
 
// Standard
#include <sstream>
#include <string>
#include <typeinfo>
 
namespace {
 
class PyGILRAII {
   PyGILState_STATE m_GILState;
 
public:
   PyGILRAII() : m_GILState(PyGILState_Ensure()) {}
   ~PyGILRAII() { PyGILState_Release(m_GILState); }
};
 
#if (defined(Py_LIMITED_API) || PY_VERSION_HEX < 0x30d00f0)
 
// Implementation of PyObject_GetOptionalAttr and
// PyObject_GetOptionalAttrString from
// https://github.com/python/pythoncapi-compat/, since the function is not part
// of the limited API.
 
inline int PyObject_GetOptionalAttr(PyObject *obj, PyObject *attr_name, PyObject **result)
{
   *result = PyObject_GetAttr(obj, attr_name);
   if (*result != NULL) {
      return 1;
   }
   if (!PyErr_Occurred()) {
      return 0;
   }
   if (PyErr_ExceptionMatches(PyExc_AttributeError)) {
      PyErr_Clear();
      return 0;
   }
   return -1;
}
 
inline int PyObject_GetOptionalAttrString(PyObject *obj, const char *attr_name, PyObject **result)
{
   PyObject *name_obj;
   int rc;
   name_obj = PyUnicode_FromString(attr_name);
   if (name_obj == NULL) {
      *result = NULL;
      return -1;
   }
   rc = PyObject_GetOptionalAttr(obj, name_obj, result);
   Py_DECREF(name_obj);
   return rc;
}
 
#endif
 
} // namespace
 
//- public members -----------------------------------------------------------
TClass *TPyClassGenerator::GetClass(const char *name, Bool_t load)
{
   // Just forward.
   return GetClass(name, load, kFALSE);
}
 
//- public members -----------------------------------------------------------
TClass *TPyClassGenerator::GetClass(const char *name, Bool_t load, Bool_t silent)
{
   // Class generator to make python classes available to Cling
 
   if (!load || !name)
      return 0;
 
   PyGILRAII thePyGILRAII;
 
   // first, check whether the name is of a module
   PyObject *modules = PySys_GetObject(const_cast<char *>("modules"));
   PyObject *pyname = PyUnicode_FromString(name);
   PyObject *keys = PyDict_Keys(modules);
   Bool_t isModule = PySequence_Contains(keys, pyname);
   Py_DecRef(keys);
   Py_DecRef(pyname);
 
   if (isModule) {
      // the normal TClass::GetClass mechanism doesn't allow direct returns, so
      // do our own check
      TClass *cl = (TClass *)gROOT->GetListOfClasses()->FindObject(name);
      if (cl)
         return cl;
 
      std::ostringstream nsCode;
      nsCode << "namespace " << name << " {\n";
 
      // add all free functions
      PyObject *bases = PyUnicode_FromString("__bases__");
      PyObject *mod = PyDict_GetItemString(modules, const_cast<char *>(name));
      PyObject *dct = PyModule_GetDict(mod);
      keys = PyDict_Keys(dct);
 
      for (int i = 0; i < PyList_Size(keys); ++i) {
         // borrowed references
         PyObject *key = PyList_GetItem(keys, i);
         PyObject *attr = PyDict_GetItem(dct, key);
 
         // TODO: refactor the code below with the class method code
         if (PyCallable_Check(attr) && !(PyType_Check(attr) || PyObject_HasAttr(attr, bases))) {
            const char *func_name = PyUnicode_AsUTF8AndSize(key, nullptr);
            if (!func_name) {
                Py_DecRef(keys);
                Py_DecRef(bases);
                return nullptr; // propagate possible error
            }
 
            // figure out number of variables required
            PyObject *func_code = nullptr;
            PyObject_GetOptionalAttrString(attr, (char *)"func_code", &func_code);
            PyObject *var_names = func_code ? PyObject_GetAttrString(func_code, (char *)"co_varnames") : NULL;
            int nVars = var_names ? PyTuple_Size(var_names) : 0 /* TODO: probably large number, all default? */;
            if (nVars < 0)
               nVars = 0;
            Py_DecRef(var_names);
            Py_DecRef(func_code);
 
            nsCode << " TPyReturn " << func_name << "(";
            for (int ivar = 0; ivar < nVars; ++ivar) {
               nsCode << "const TPyArg& a" << ivar;
               if (ivar != nVars - 1)
                  nsCode << ", ";
            }
            nsCode << ") {\n";
            nsCode << "  std::vector<TPyArg> v; v.reserve(" << nVars << ");\n";
 
            // add the variables
            for (int ivar = 0; ivar < nVars; ++ivar)
               nsCode << "  v.push_back(a" << ivar << ");\n";
 
            // call dispatch (method or class pointer hard-wired)
            nsCode << "  return TPyReturn(TPyArg::CallMethod((PyObject*)" << std::showbase << (uintptr_t)attr << ", v)); }\n";
         }
      }
 
      Py_DecRef(keys);
      Py_DecRef(bases);
 
      nsCode << " }";
 
      if (gInterpreter->LoadText(nsCode.str().c_str())) {
         TClass *klass = new TClass(name, silent);
         TClass::AddClass(klass);
         return klass;
      }
 
      return nullptr;
   }
 
   // determine module and class name part
   std::string clName = name;
   std::string::size_type pos = clName.rfind('.');
 
   if (pos == std::string::npos)
      return 0; // this isn't a python style class
 
   std::string mdName = clName.substr(0, pos);
   clName = clName.substr(pos + 1, std::string::npos);
 
   // create class in namespace, if it exists (no load, silent)
   Bool_t useNS = gROOT->GetListOfClasses()->FindObject(mdName.c_str()) != 0;
   if (!useNS) {
      // the class itself may exist if we're using the global scope
      TClass *cl = (TClass *)gROOT->GetListOfClasses()->FindObject(clName.c_str());
      if (cl)
         return cl;
   }
 
   // locate and get class
   PyObject *mod = PyImport_AddModule(const_cast<char *>(mdName.c_str()));
   if (!mod) {
      PyErr_Clear();
      return 0; // module apparently disappeared
   }
 
   Py_IncRef(mod);
   PyObject *pyclass = PyDict_GetItemString(PyModule_GetDict(mod), const_cast<char *>(clName.c_str()));
   Py_IncRef(pyclass);
   Py_DecRef(mod);
 
   if (!pyclass) {
      PyErr_Clear(); // the class is no longer available?!
      return 0;
   }
 
   // get a listing of all python-side members
   PyObject *attrs = PyObject_Dir(pyclass);
   if (!attrs) {
      PyErr_Clear();
      Py_DecRef(pyclass);
      return 0;
   }
 
   // pre-amble Cling proxy class
   std::ostringstream proxyCode;
   if (useNS)
      proxyCode << "namespace " << mdName << " { ";
   proxyCode << "class " << clName << " {\nprivate:\n PyObject* fPyObject;\npublic:\n";
 
   // loop over and add member functions
   Bool_t hasConstructor = kFALSE, hasDestructor = kFALSE;
   for (int i = 0; i < PyList_Size(attrs); ++i) {
      PyObject *label = PyList_GetItem(attrs, i);
      Py_IncRef(label);
      PyObject *attr = PyObject_GetAttr(pyclass, label);
 
      // collect only member functions (i.e. callable elements in __dict__)
      if (PyCallable_Check(attr)) {
         const char *mtNameCStr = PyUnicode_AsUTF8AndSize(label, nullptr);
         if(!mtNameCStr) {
            return nullptr;
         }
         std::string mtName = mtNameCStr;
 
         if (mtName == "__del__") {
            hasDestructor = kTRUE;
            proxyCode << " ~" << clName << "() { TPyArg::CallDestructor(fPyObject); }\n";
            continue;
         }
 
         Bool_t isConstructor = mtName == "__init__";
         if (!isConstructor && mtName.find("__", 0, 2) == 0)
            continue; // skip all other python special funcs
 
// figure out number of variables required
         PyObject *func_code = PyObject_GetAttrString(attr, "__code__");
         PyObject *var_names = func_code ? PyObject_GetAttrString(func_code, (char *)"co_varnames") : NULL;
         if (PyErr_Occurred())
            PyErr_Clear(); // happens for slots; default to 0 arguments
 
         int nVars =
            var_names ? PyTuple_Size(var_names) - 1 /* self */ : 0 /* TODO: probably large number, all default? */;
         if (nVars < 0)
            nVars = 0;
         Py_DecRef(var_names);
         Py_DecRef(func_code);
 
         // method declaration as appropriate
         if (isConstructor) {
            hasConstructor = kTRUE;
            proxyCode << " " << clName << "(";
         } else // normal method
            proxyCode << " TPyReturn " << mtName << "(";
         for (int ivar = 0; ivar < nVars; ++ivar) {
            proxyCode << "const TPyArg& a" << ivar;
            if (ivar != nVars - 1)
               proxyCode << ", ";
         }
         proxyCode << ") {\n";
         proxyCode << "  std::vector<TPyArg> v; v.reserve(" << nVars + (isConstructor ? 0 : 1) << ");\n";
 
         // add the 'self' argument as appropriate
         if (!isConstructor)
            proxyCode << "  v.push_back(fPyObject);\n";
 
         // then add the remaining variables
         for (int ivar = 0; ivar < nVars; ++ivar)
            proxyCode << "  v.push_back(a" << ivar << ");\n";
 
         // call dispatch (method or class pointer hard-wired)
         if (!isConstructor)
            proxyCode << "  return TPyReturn(TPyArg::CallMethod((PyObject*)" << std::showbase << (uintptr_t)attr << ", v))";
         else
            proxyCode << "  TPyArg::CallConstructor(fPyObject, (PyObject*)" << std::showbase << (uintptr_t)pyclass << ", v)";
         proxyCode << ";\n }\n";
      }
 
      // no decref of attr for now (b/c of hard-wired ptr); need cleanup somehow
      Py_DecRef(label);
   }
 
   // special case if no constructor or destructor
   if (!hasConstructor)
      proxyCode << " " << clName << "() {\n TPyArg::CallConstructor(fPyObject, (PyObject*)" << std::showbase << (uintptr_t)pyclass
                << "); }\n";
 
   if (!hasDestructor)
      proxyCode << " ~" << clName << "() { TPyArg::CallDestructor(fPyObject); }\n";
 
   // for now, don't allow copying (ref-counting wouldn't work as expected anyway)
   proxyCode << " " << clName << "(const " << clName << "&) = delete;\n";
   proxyCode << " " << clName << "& operator=(const " << clName << "&) = delete;\n";
 
   // closing and building of Cling proxy class
   proxyCode << "};";
   if (useNS)
      proxyCode << " }";
 
   Py_DecRef(attrs);
   // done with pyclass, decref here, assuming module is kept
   Py_DecRef(pyclass);
 
   // body compilation
   if (!gInterpreter->LoadText(proxyCode.str().c_str()))
      return nullptr;
 
   // done, let ROOT manage the new class
   TClass *klass = new TClass(useNS ? (mdName + "::" + clName).c_str() : clName.c_str(), silent);
   TClass::AddClass(klass);
 
   return klass;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Just forward; based on type name only.
 
TClass *TPyClassGenerator::GetClass(const std::type_info &typeinfo, Bool_t load, Bool_t silent)
{
   return GetClass(typeinfo.name(), load, silent);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Just forward; based on type name only
 
TClass *TPyClassGenerator::GetClass(const std::type_info &typeinfo, Bool_t load)
{
   return GetClass(typeinfo.name(), load);
}