pyOverride.h

//
// Copyright 2016 Pixar
//
// Licensed under the terms set forth in the LICENSE.txt file available at
// https://openusd.org/license.
//
#ifndef PXR_BASE_TF_PY_OVERRIDE_H
#define PXR_BASE_TF_PY_OVERRIDE_H
 
#include "pxr/pxr.h"
 
#include "pxr/base/tf/pyLock.h"
#include "pxr/base/tf/pyObjWrapper.h"
 
#include <boost/python/override.hpp>
 
PXR_NAMESPACE_OPEN_SCOPE
 
class TfPyMethodResult
{
private:
    friend class TfPyOverride;
    explicit TfPyMethodResult(PyObject* x)
    : m_obj(x)
    {}
 
public:
    TfPyMethodResult(TfPyMethodResult const &other);
 
    ~TfPyMethodResult();
 
    TfPyMethodResult &operator=(TfPyMethodResult const &other);
 
    template <class T>
    operator T()
    {
        TfPyLock lock;
        boost::python::converter::return_from_python<T> converter;
        return converter(m_obj.release());
    }
 
    template <class T>
    operator T&() const
    {
        TfPyLock lock;
        boost::python::converter::return_from_python<T&> converter;
        return converter(
            const_cast<boost::python::handle<>&>(m_obj).release());
    }
 
    template <class T>
    T as(boost::type<T>* = 0)
    {
        TfPyLock lock;
        boost::python::converter::return_from_python<T> converter;
        return converter(m_obj.release());
    }
 
    template <class T>
    T unchecked(boost::type<T>* = 0)
    {
        TfPyLock lock;
        return boost::python::extract<T>(m_obj)();
    }
 
private:
    mutable boost::python::handle<> m_obj;
};
 
class TfPyOverride : public TfPyObjWrapper
{
    // Helper to generate Py_BuildValue-style format strings at compile time.
    template <typename Arg>
    constexpr static char _PyObjArg()
    {
        return 'O';
    }
 
public:
    TfPyOverride(boost::python::handle<> callable)
        : TfPyObjWrapper(boost::python::object(callable))
    {}
 
    template <typename... Args>
    TfPyMethodResult
    operator()(Args const&... args) const
    {
        TfPyLock lock;
        // Use the Args parameter pack together with the _PyObjArg helper to
        // unpack the right number of 'O' elements into the format string.
        static const char pyCallFormat[] =
            { '(', _PyObjArg<Args>()..., ')', '\0' };
 
        TfPyMethodResult x(
            PyEval_CallFunction(
                this->ptr(),
                const_cast<char*>(pyCallFormat),
                boost::python::converter::arg_to_python<Args>(args).get()...));
        return x;
    }
};
 
PXR_NAMESPACE_CLOSE_SCOPE
 
#endif // PXR_BASE_TF_PY_OVERRIDE_H