API.cxx

// Bindings
#include "CPyCppyy.h"
#define CPYCPPYY_INTERNAL 1
#include "CPyCppyy/API.h"
#undef CPYCPPYY_INTERNAL

#include "CPPInstance.h"
#include "CPPOverload.h"
#include "CPPScope.h"
#include "ProxyWrappers.h"
#include "PyStrings.h"

// Standard
#include <stdio.h>
#include <iostream>
#include <string>

//______________________________________________________________________________
//                  CPyCppyy API: Interpreter and Proxy Access
//                  ==========================================
//
// Access to cppyy Python objects from Cling and C++: allows conversion for
// instances and type checking for scopes, instances, etc.
// Adds a few convenience functions to call Python from Cling and expose Python
// classes to Cling for use in inheritance etc.


//- data ---------------------------------------------------------------------
static PyObject* gMainDict = nullptr;

namespace CPyCppyy {
    extern PyObject* gThisModule;
}


//- private helpers ----------------------------------------------------------
namespace {

static bool Initialize()
{
// Private initialization method: setup the python interpreter and load the
// cppyy module.
    static bool isInitialized = false;
    if (isInitialized)
        return true;

    if (!Py_IsInitialized()) {
    // this happens if Cling comes in first
#if PY_VERSION_HEX < 0x03020000
        PyEval_InitThreads();
#endif
#if PY_VERSION_HEX < 0x03080000
        Py_Initialize();
#else
        PyConfig config;
        PyConfig_InitPythonConfig(&config);
        PyConfig_SetString(&config, &config.program_name, L"cppyy");
        Py_InitializeFromConfig(&config);
#endif
#if PY_VERSION_HEX >= 0x03020000
#if PY_VERSION_HEX < 0x03090000
        PyEval_InitThreads();
#endif
#endif

    // try again to see if the interpreter is initialized
        if (!Py_IsInitialized()) {
        // give up ...
            std::cerr << "Error: python has not been initialized; returning." << std::endl;
            return false;
        }

   // set the command line arguments on python's sys.argv
#if PY_VERSION_HEX < 0x03000000
        char* argv[] = {const_cast<char*>("cppyy")};
#elif PY_VERSION_HEX < 0x03080000
        wchar_t* argv[] = {const_cast<wchar_t*>(L"cppyy")};
#endif
#if PY_VERSION_HEX < 0x03080000
        PySys_SetArgv(sizeof(argv)/sizeof(argv[0]), argv);
#endif

    // force loading of the cppyy module
        PyRun_SimpleString(const_cast<char*>("import cppyy"));
    }

    if (!gMainDict) {
    // retrieve the main dictionary
        gMainDict = PyModule_GetDict(
            PyImport_AddModule(const_cast<char*>("__main__")));
    // The gMainDict is borrowed, i.e. we are not calling Py_INCREF(gMainDict).
    // Like this, we avoid unexpectedly affecting how long __main__ is kept
    // alive. The gMainDict is only used in Exec(), ExecScript(), and Eval(),
    // which should not be called after __main__ is garbage collected anyway.
    }

// declare success ...
    isInitialized = true;
    return true;
}

} // unnamed namespace


//- C++ access to cppyy objects ---------------------------------------------
void* CPyCppyy::Instance_AsVoidPtr(PyObject* pyobject)
{
// Extract the object pointer held by the CPPInstance pyobject.
    if (!Initialize())
        return nullptr;

// check validity of cast
    if (!CPPInstance_Check(pyobject))
        return nullptr;

// get held object (may be null)
    return ((CPPInstance*)pyobject)->GetObject();
}

//-----------------------------------------------------------------------------
PyObject* CPyCppyy::Instance_FromVoidPtr(
    void* addr, const std::string& classname, bool python_owns)
{
// Bind the addr to a python object of class defined by classname.
    if (!Initialize())
        return nullptr;

// perform cast (the call will check TClass and addr, and set python errors)
    PyObject* pyobject = BindCppObjectNoCast(addr, Cppyy::GetScope(classname), false);

// give ownership, for ref-counting, to the python side, if so requested
    if (python_owns && CPPInstance_Check(pyobject))
        ((CPPInstance*)pyobject)->PythonOwns();

    return pyobject;
}

namespace CPyCppyy {
// version with C type arguments only for use with Numba
PyObject* Instance_FromVoidPtr(void* addr, const char* classname, int python_owns) {
    return Instance_FromVoidPtr(addr, std::string(classname), (bool)python_owns);
}
} // namespace CPyCppyy

//-----------------------------------------------------------------------------
bool CPyCppyy::Scope_Check(PyObject* pyobject)
{
// Test if the given object is of a CPPScope derived type.
    if (!Initialize())
        return false;

    return CPPScope_Check(pyobject);
}

//-----------------------------------------------------------------------------
bool CPyCppyy::Scope_CheckExact(PyObject* pyobject)
{
// Test if the given object is of a CPPScope type.
    if (!Initialize())
        return false;

    return CPPScope_CheckExact(pyobject);
}

//-----------------------------------------------------------------------------
bool CPyCppyy::Instance_Check(PyObject* pyobject)
{
// Test if the given pyobject is of CPPInstance derived type.
    if (!Initialize())
        return false;

// detailed walk through inheritance hierarchy
    return CPPInstance_Check(pyobject);
}

//-----------------------------------------------------------------------------
bool CPyCppyy::Instance_CheckExact(PyObject* pyobject)
{
// Test if the given pyobject is of CPPInstance type.
    if (!Initialize())
        return false;

// direct pointer comparison of type member
    return CPPInstance_CheckExact(pyobject);
}

//-----------------------------------------------------------------------------
bool CPyCppyy::Sequence_Check(PyObject* pyobject)
{
// Extends on PySequence_Check() to determine whether an object can be iterated
// over (technically, all objects can b/c of C++ pointer arithmetic, hence this
// check isn't 100% accurate, but neither is PySequence_Check()).

// Note: simply having the iterator protocol does not constitute a sequence, bc
// PySequence_GetItem() would fail.

// default to PySequence_Check() if called with a non-C++ object
    if (!CPPInstance_Check(pyobject))
        return (bool)PySequence_Check(pyobject);

// all C++ objects should have sq_item defined, but a user-derived class may
// have deleted it, in which case this is not a sequence
    PyTypeObject* t = Py_TYPE(pyobject);
    if (!t->tp_as_sequence || !t->tp_as_sequence->sq_item)
        return false;

// if this is the default getitem, it is only a sequence if it's an array type
    if (t->tp_as_sequence->sq_item == CPPInstance_Type.tp_as_sequence->sq_item) {
        if (((CPPInstance*)pyobject)->fFlags & CPPInstance::kIsArray)
            return true;
        return false;
    }

// TODO: could additionally verify whether __len__ is supported and/or whether
// operator()[] takes an int argument type

    return true;
}

//-----------------------------------------------------------------------------
bool CPyCppyy::Instance_IsLively(PyObject* pyobject)
{
// Test whether the given instance can safely return to C++
    if (!CPPInstance_Check(pyobject))
        return true;    // simply don't know

// the instance fails the lively test if it owns the C++ object while having a
// reference count of 1 (meaning: it could delete the C++ instance any moment)
    if (pyobject->ob_refcnt <= 1 && (((CPPInstance*)pyobject)->fFlags & CPPInstance::kIsOwner))
        return false;

    return true;
}

//-----------------------------------------------------------------------------
bool CPyCppyy::Overload_Check(PyObject* pyobject)
{
// Test if the given pyobject is of CPPOverload derived type.
    if (!Initialize())
        return false;

// detailed walk through inheritance hierarchy
    return CPPOverload_Check(pyobject);
}

//-----------------------------------------------------------------------------
bool CPyCppyy::Overload_CheckExact(PyObject* pyobject)
{
// Test if the given pyobject is of CPPOverload type.
    if (!Initialize())
        return false;

// direct pointer comparison of type member
    return CPPOverload_CheckExact(pyobject);
}


//- access to the python interpreter ----------------------------------------
bool CPyCppyy::Import(const std::string& mod_name)
{
// Import the named python module and create Cling equivalents for its classes.
    if (!Initialize())
        return false;

    PyObject* mod = PyImport_ImportModule(mod_name.c_str());
    if (!mod) {
        PyErr_Print();
        return false;
    }

// allow finding to prevent creation of a python proxy for the C++ proxy
    Py_INCREF(mod);
    PyModule_AddObject(gThisModule, mod_name.c_str(), mod);

// force creation of the module as a namespace
// TODO: the following is broken (and should live in Cppyy.cxx)
//   TClass::GetClass(mod_name, true);

    PyObject* dct = PyModule_GetDict(mod);

// create Cling classes for all new python classes
    PyObject* values = PyDict_Values(dct);
    for (int i = 0; i < PyList_GET_SIZE(values); ++i) {
        PyObject* value = PyList_GET_ITEM(values, i);
        Py_INCREF(value);

    // collect classes
        if (PyClass_Check(value) || PyObject_HasAttr(value, PyStrings::gBases)) {
        // get full class name (including module)
            PyObject* pyClName = PyObject_GetAttr(value, PyStrings::gName);
            if (PyErr_Occurred())
                PyErr_Clear();

        // build full, qualified name
            std::string fullname = mod_name;
            fullname += ".";
            fullname += CPyCppyy_PyText_AsString(pyClName);

      // force class creation (this will eventually call TPyClassGenerator)
      // TODO: the following is broken (and should live in Cppyy.cxx) to
      //         TClass::GetClass(fullname.c_str(), true);

            Py_XDECREF(pyClName);
        }

        Py_DECREF(value);
    }

    Py_DECREF(values);

// TODO: mod "leaks" here
    if (PyErr_Occurred())
        return false;
    return true;
}

//-----------------------------------------------------------------------------
void CPyCppyy::ExecScript(const std::string& name, const std::vector<std::string>& args)
{
// Execute a python stand-alone script, with argv CLI arguments.
//
// example of use:
//    CPyCppyy::ExecScript("test.py", {"1", "2", "3"});

    if (!Initialize())
        return;

// verify arguments
    if (name.empty()) {
        std::cerr << "Error: no file name specified." << std::endl;
        return;
    }

    FILE* fp = fopen(name.c_str(), "r");
    if (!fp) {
        std::cerr << "Error: could not open file \"" << name << "\"." << std::endl;
        return;
    }

// store a copy of the old cli for restoration
    PyObject* oldargv = PySys_GetObject(const_cast<char*>("argv"));   // borrowed
    if (!oldargv)                                 // e.g. apache
        PyErr_Clear();
    else {
        PyObject* l = PyList_New(PyList_GET_SIZE(oldargv));
        for (int i = 0; i < PyList_GET_SIZE(oldargv); ++i) {
            PyObject* item = PyList_GET_ITEM(oldargv, i);
            Py_INCREF(item);
            PyList_SET_ITEM(l, i, item);          // steals ref
        }
        oldargv = l;
    }

// create and set (add program name) the new command line
    int argc = args.size() + 1;
#if PY_VERSION_HEX < 0x03000000
// This is a legacy implementation for Python 2
    const char** argv = new const char*[argc];
    for (int i = 1; i < argc; ++i) argv[i] = args[i-1].c_str();
    argv[0] = Py_GetProgramName();
    PySys_SetArgv(argc, const_cast<char**>(argv));
    delete [] argv;
#else
// This is a common code block for Python 3. We prefer using objects to
// automatize memory management and not introduce even more preprocessor
// branching for deletion at the end of the method.
//
// FUTURE IMPROVEMENT ONCE OLD PYTHON VERSIONS ARE NOT SUPPORTED BY CPPYY:
// Right now we use C++ objects to automatize memory management. One could use
// RAAI and the Python memory allocation API (PEP 445) once some old Python
// version is deprecated in CPPYY. That new feature is available since version
// 3.4 and the preprocessor branching to also support that would be so
// complicated to make the code unreadable.
   std::vector<std::wstring> argv2;
   argv2.reserve(argc);
   argv2.emplace_back(name.c_str(), &name[name.size()]);

   for (int i = 1; i < argc; ++i) {
      auto iarg = args[i - 1].c_str();
      argv2.emplace_back(iarg, &iarg[strlen(iarg)]);
   }

#if PY_VERSION_HEX < 0x03080000
// Before version 3.8, the code is one simple line
   wchar_t *argv2_arr[argc];
   for (int i = 0; i < argc; ++i) {
      argv2_arr[i] = const_cast<wchar_t *>(argv2[i].c_str());
   }
   PySys_SetArgv(argc, argv2_arr);

#else
// Here we comply to "PEP 587 – Python Initialization Configuration" to avoid
// deprecation warnings at compile time.
   class PyConfigHelperRAAI {
   public:
      PyConfigHelperRAAI(const std::vector<std::wstring> &argv2)
      {
         PyConfig_InitPythonConfig(&fConfig);
         fConfig.parse_argv = 1;
         UpdateArgv(argv2);
         InitFromConfig();
      }
      ~PyConfigHelperRAAI() { PyConfig_Clear(&fConfig); }

   private:
      void InitFromConfig() { Py_InitializeFromConfig(&fConfig); };
      void UpdateArgv(const std::vector<std::wstring> &argv2)
      {
         auto WideStringListAppendHelper = [](PyWideStringList *wslist, const wchar_t *wcstr) {
            PyStatus append_status = PyWideStringList_Append(wslist, wcstr);
            if (PyStatus_IsError(append_status)) {
               std::wcerr << "Error: could not append element " << wcstr << " to arglist - " << append_status.err_msg
                          << std::endl;
            }
         };

#if PY_VERSION_HEX < 0x30d00f0
         WideStringListAppendHelper(&fConfig.argv, Py_GetProgramName());
#else
         PyObject* progname = PySys_GetObject("executable");    // borrowed
         wchar_t buf[4096];
         Py_ssize_t sz = CPyCppyy_PyUnicode_AsWideChar(progname, buf, 4095);
         if (0 < sz)
             WideStringListAppendHelper(&fConfig.argv, buf);
#endif
         for (const auto &iarg : argv2) {
            WideStringListAppendHelper(&fConfig.argv, iarg.c_str());
         }
      }
      PyConfig fConfig;
   };

   PyConfigHelperRAAI pych(argv2);

#endif // of the else branch of PY_VERSION_HEX < 0x03080000
#endif // of the else branch of PY_VERSION_HEX < 0x03000000

// actual script execution
    PyObject* gbl = PyDict_Copy(gMainDict);
    PyObject* result =       // PyRun_FileEx closes fp (b/c of last argument "1")
        PyRun_FileEx(fp, const_cast<char*>(name.c_str()), Py_file_input, gbl, gbl, 1);
    if (!result)
        PyErr_Print();
    Py_XDECREF(result);
    Py_DECREF(gbl);

// restore original command line
    if (oldargv) {
        PySys_SetObject(const_cast<char*>("argv"), oldargv);
        Py_DECREF(oldargv);
    }
}

//-----------------------------------------------------------------------------
bool CPyCppyy::Exec(const std::string& cmd)
{
// Execute a python statement (e.g. "import noddy").
    if (!Initialize())
        return false;

// execute the command
    PyObject* result =
        PyRun_String(const_cast<char*>(cmd.c_str()), Py_file_input, gMainDict, gMainDict);

// test for error
    if (result) {
        Py_DECREF(result);
        return true;
    }

    PyErr_Print();
    return false;
}

//-----------------------------------------------------------------------------
const CPyCppyy::PyResult CPyCppyy::Eval(const std::string& expr)
{
// Evaluate a python expression.
//
// Caution: do not hold on to the return value: either store it in a builtin
// type (implicit casting will work), or in a pointer to a cppyy object (explicit
// casting to a void* is required).
    if (!Initialize())
        return PyResult();

// evaluate the expression
    PyObject* result =
        PyRun_String(const_cast<char*>(expr.c_str()), Py_eval_input, gMainDict, gMainDict);

// report errors as appropriate; return void
    if (!result) {
        PyErr_Print();
        return PyResult();
    }

// results that require no conversion
    if (result == Py_None || CPPInstance_Check(result) ||
            PyBytes_Check(result) ||
            PyFloat_Check(result) || PyLong_Check(result) || PyInt_Check(result))
        return PyResult(result);

// explicit conversion for python type required
    PyObject* pyclass = (PyObject*)Py_TYPE(result);

// retrieve class name and the module in which it resides
    PyObject* name = PyObject_GetAttr(pyclass, PyStrings::gName);
    PyObject* module = PyObject_GetAttr(pyclass, PyStrings::gModule);

 // concat name
    std::string qname =
        std::string(CPyCppyy_PyText_AsString(module)) + \
                    '.' + CPyCppyy_PyText_AsString(name);
    Py_DECREF(module);
    Py_DECREF(name);

// locate cppyy style class with this name
    // TODO: use Cppyy.cxx ...
    //TClass* klass = TClass::GetClass(qname.c_str());
    void* klass = nullptr;

// construct general cppyy python object that pretends to be of class 'klass'
    if (klass)
        return PyResult(result);

// no conversion, return null pointer object
    Py_DECREF(result);
    return PyResult();
}

//-----------------------------------------------------------------------------
void CPyCppyy::Prompt() {
// Enter an interactive python session (exit with ^D). State is preserved
// between successive calls.
    if (!Initialize())
        return;

// enter i/o interactive mode
    PyRun_InteractiveLoop(stdin, const_cast<char*>("\0"));
}