python/src/converter/from_python.cpp at python · boostorg/python · GitHub

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// Copyright David Abrahams 2002.

// Distributed under the Boost Software License, Version 1.0. (See

// accompanying file LICENSE_1_0.txt or copy at

// http://www.boost.org/LICENSE_1_0.txt)

#include <boost/python/converter/from_python.hpp>

#include <boost/python/converter/registrations.hpp>

#include <boost/python/converter/rvalue_from_python_data.hpp>

#include <boost/python/object/find_instance.hpp>

#include <boost/python/handle.hpp>

#include <boost/python/detail/raw_pyobject.hpp>

#include <boost/python/cast.hpp>

#include <vector>

#include <algorithm>

namespace boost { namespace python { namespace converter {

// rvalue_from_python_stage1 -- do the first stage of a conversion

// from a Python object to a C++ rvalue.

// source - the Python object to be converted

// converters - the registry entry for the target type T

// Postcondition: where x is the result, one of:

// 1. x.convertible == 0, indicating failure

// 2. x.construct == 0, x.convertible is the address of an object of

// type T. Indicates a successful lvalue conversion

// 3. where y is of type rvalue_from_python_data<T>,

// x.construct(source, y) constructs an object of type T

// in y.storage.bytes and then sets y.convertible == y.storage.bytes,

// or else throws an exception and has no effect.

BOOST_PYTHON_DECL rvalue_from_python_stage1_data rvalue_from_python_stage1(

PyObject* source

, registration const& converters)

{

rvalue_from_python_stage1_data data;

// First check to see if it's embedded in an extension class

// instance, as a special case.

data.convertible = objects::find_instance_impl(source, converters.target_type, converters.is_shared_ptr);

data.construct = 0;

if (!data.convertible)

{

for (rvalue_from_python_chain const* chain = converters.rvalue_chain;

chain != 0;

chain = chain->next)

{

void* r = chain->convertible(source);

if (r != 0)

{

data.convertible = r;

data.construct = chain->construct;

break;

}

return data;

}

// rvalue_result_from_python -- return the address of a C++ object which

// can be used as the result of calling a Python function.

// src - the Python object to be converted

// data - a reference to the base part of a

// rvalue_from_python_data<T> object, where T is the

// target type of the conversion.

// Requires: data.convertible == &registered<T>::converters

BOOST_PYTHON_DECL void* rvalue_result_from_python(

PyObject* src, rvalue_from_python_stage1_data& data)

{

// Retrieve the registration

// Cast in two steps for less-capable compilers

void const* converters_ = data.convertible;

registration const& converters = *static_cast<registration const*>(converters_);

// Look for an eligible converter

data = rvalue_from_python_stage1(src, converters);

return rvalue_from_python_stage2(src, data, converters);

}

BOOST_PYTHON_DECL void* rvalue_from_python_stage2(

PyObject* source, rvalue_from_python_stage1_data& data, registration const& converters)

{

if (!data.convertible)

{

handle<> msg(

#if PY_VERSION_HEX >= 0x03000000

::PyUnicode_FromFormat

#else

::PyString_FromFormat

#endif

(

"No registered converter was able to produce a C++ rvalue of type %s from this Python object of type %s"

, converters.target_type.name()

, source->ob_type->tp_name

));

PyErr_SetObject(PyExc_TypeError, msg.get());

throw_error_already_set();

}

// If a construct function was registered (i.e. we found an

// rvalue conversion), call it now.

if (data.construct != 0)

data.construct(source, &data);

// Return the address of the resulting C++ object

return data.convertible;

}

BOOST_PYTHON_DECL void* get_lvalue_from_python(

PyObject* source

, registration const& converters)

{

// Check to see if it's embedded in a class instance

void* x = objects::find_instance_impl(source, converters.target_type);

if (x)

return x;

lvalue_from_python_chain const* chain = converters.lvalue_chain;

for (;chain != 0; chain = chain->next)

{

void* r = chain->convert(source);

if (r != 0)

return r;

}

return 0;

}

namespace

{

// Prevent looping in implicit conversions. This could/should be

// much more efficient, but will work for now.

typedef std::vector<rvalue_from_python_chain const*> visited_t;

static visited_t visited;

inline bool visit(rvalue_from_python_chain const* chain)

{

visited_t::iterator const p = std::lower_bound(visited.begin(), visited.end(), chain);

if (p != visited.end() && *p == chain)

return false;

visited.insert(p, chain);

return true;

}

// RAII class for managing global visited marks.

struct unvisit

{

unvisit(rvalue_from_python_chain const* chain)

: chain(chain) {}

~unvisit()

{

visited_t::iterator const p = std::lower_bound(visited.begin(), visited.end(), chain);

assert(p != visited.end());

visited.erase(p);

}

private:

rvalue_from_python_chain const* chain;

};

}

BOOST_PYTHON_DECL bool implicit_rvalue_convertible_from_python(

PyObject* source

, registration const& converters)

{

if (objects::find_instance_impl(source, converters.target_type))

return true;

rvalue_from_python_chain const* chain = converters.rvalue_chain;

if (!visit(chain))

return false;

unvisit protect(chain);

for (;chain != 0; chain = chain->next)

{

if (chain->convertible(source))

return true;

}

return false;

}

namespace

{

void throw_no_lvalue_from_python(PyObject* source, registration const& converters, char const* ref_type)

{

handle<> msg(

#if PY_VERSION_HEX >= 0x03000000

::PyUnicode_FromFormat

#else

::PyString_FromFormat

#endif

(

"No registered converter was able to extract a C++ %s to type %s"

" from this Python object of type %s"

, ref_type

, converters.target_type.name()

, source->ob_type->tp_name

));

PyErr_SetObject(PyExc_TypeError, msg.get());

throw_error_already_set();

}

void* lvalue_result_from_python(

PyObject* source

, registration const& converters

, char const* ref_type)

{

handle<> holder(source);

if (

#if PY_VERSION_HEX < 0x03090000

source->ob_refcnt

#else

Py_REFCNT(source)

#endif

<= 1)

{

handle<> msg(

#if PY_VERSION_HEX >= 0x3000000

::PyUnicode_FromFormat

#else

::PyString_FromFormat

#endif

(

"Attempt to return dangling %s to object of type: %s"

, ref_type

, converters.target_type.name()));

PyErr_SetObject(PyExc_ReferenceError, msg.get());

throw_error_already_set();

}

void* result = get_lvalue_from_python(source, converters);

if (!result)

(throw_no_lvalue_from_python)(source, converters, ref_type);

return result;

}

BOOST_PYTHON_DECL void throw_no_pointer_from_python(PyObject* source, registration const& converters)

{

(throw_no_lvalue_from_python)(source, converters, "pointer");

}

BOOST_PYTHON_DECL void throw_no_reference_from_python(PyObject* source, registration const& converters)

{

(throw_no_lvalue_from_python)(source, converters, "reference");

}

BOOST_PYTHON_DECL void* reference_result_from_python(

PyObject* source

, registration const& converters)

{

return (lvalue_result_from_python)(source, converters, "reference");

}

BOOST_PYTHON_DECL void* pointer_result_from_python(

PyObject* source

, registration const& converters)

{

if (source == Py_None)

{

Py_DECREF(source);

return 0;

}

return (lvalue_result_from_python)(source, converters, "pointer");

}

BOOST_PYTHON_DECL void void_result_from_python(PyObject* o)

{

Py_DECREF(expect_non_null(o));

}

} // namespace boost::python::converter

BOOST_PYTHON_DECL PyObject*

pytype_check(PyTypeObject* type_, PyObject* source)

{

if (!PyObject_IsInstance(source, python::upcast<PyObject>(type_)))

{

::PyErr_Format(

PyExc_TypeError

, "Expecting an object of type %s; got an object of type %s instead"

, type_->tp_name

, source->ob_type->tp_name

);

throw_error_already_set();

}

return source;

}

}} // namespace boost::python

python/src/converter/from_python.cpp at python · boostorg/python · GitHub

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