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ed14879a19
pybind11/include/pybind11/cast.h
Jason Rhinelander ed14879a19 Move support for return values of called Python functions 
Currently pybind11 always translates values returned by Python functions
invoked from C++ code by copying, even when moving is feasible--and,
more importantly, even when moving is required.

The first, and relatively minor, concern is that moving may be
considerably more efficient for some types.  The second problem,
however, is more serious: there's currently no way python code can
return a non-copyable type to C++ code.

I ran into this while trying to add a PYBIND11_OVERLOAD of a virtual
method that returns just such a type: it simply fails to compile because
this:

    overload = ...
    overload(args).template cast<ret_type>();

involves a copy: overload(args) returns an object instance, and the
invoked object::cast() loads the returned value, then returns a copy of
the loaded value.

We can, however, safely move that returned value *if* the object has the
only reference to it (i.e. if ref_count() == 1) and the object is
itself temporary (i.e. if it's an rvalue).

This commit does that by adding an rvalue-qualified object::cast()
method that allows the returned value to be move-constructed out of the
stored instance when feasible.

This basically comes down to three cases:

- For objects that are movable but not copyable, we always try the move,
  with a runtime exception raised if this would involve moving a value
  with multiple references.
- When the type is both movable and non-trivially copyable, the move
  happens only if the invoked object has a ref_count of 1, otherwise the
  object is copied.  (Trivially copyable types are excluded from this
  case because they are typically just collections of primitive types,
  which can be copied just as easily as they can be moved.)
- Non-movable and trivially copy constructible objects are simply
  copied.

This also adds examples to example-virtual-functions that shows both a
non-copyable object and a movable/copyable object in action: the former
raises an exception if returned while holding a reference, the latter
invokes a move constructor if unreferenced, or a copy constructor if
referenced.

Basically this allows code such as:

    class MyClass(Pybind11Class):
        def somemethod(self, whatever):
            mt = MovableType(whatever)
            # ...
            return mt

which allows the MovableType instance to be returned to the C++ code
via its move constructor.

Of course if you attempt to violate this by doing something like:

    self.value = MovableType(whatever)
    return self.value

you get an exception--but right now, the pybind11-side of that code
won't compile at all.
2016-08-08 13:47:37 -04:00

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/*
pybind11/cast.h: Partial template specializations to cast between
C++ and Python types
Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
All rights reserved. Use of this source code is governed by a
BSD-style license that can be found in the LICENSE file.
*/
#pragma once
#include "pytypes.h"
#include "typeid.h"
#include "descr.h"
#include <array>
#include <limits>
#include <iostream>
NAMESPACE_BEGIN(pybind11)
NAMESPACE_BEGIN(detail)
/// Additional type information which does not fit into the PyTypeObject
struct type_info {
PyTypeObject *type;
size_t type_size;
void (*init_holder)(PyObject *, const void *);
std::vector<PyObject *(*)(PyObject *, PyTypeObject *) > implicit_conversions;
buffer_info *(*get_buffer)(PyObject *, void *) = nullptr;
void *get_buffer_data = nullptr;
};
PYBIND11_NOINLINE inline internals &get_internals() {
static internals *internals_ptr = nullptr;
if (internals_ptr)
return *internals_ptr;
handle builtins(PyEval_GetBuiltins());
const char *id = PYBIND11_INTERNALS_ID;
capsule caps(builtins[id]);
if (caps.check()) {
internals_ptr = caps;
} else {
internals_ptr = new internals();
#if defined(WITH_THREAD)
PyEval_InitThreads();
PyThreadState *tstate = PyThreadState_Get();
internals_ptr->tstate = PyThread_create_key();
PyThread_set_key_value(internals_ptr->tstate, tstate);
internals_ptr->istate = tstate->interp;
#endif
builtins[id] = capsule(internals_ptr);
internals_ptr->registered_exception_translators.push_front(
[](std::exception_ptr p) -> void {
try {
if (p) std::rethrow_exception(p);
} catch (const error_already_set &) { return;
} catch (const index_error &e) { PyErr_SetString(PyExc_IndexError, e.what()); return;
} catch (const value_error &e) { PyErr_SetString(PyExc_ValueError, e.what()); return;
} catch (const stop_iteration &e) { PyErr_SetString(PyExc_StopIteration, e.what()); return;
} catch (const std::bad_alloc &e) { PyErr_SetString(PyExc_MemoryError, e.what()); return;
} catch (const std::domain_error &e) { PyErr_SetString(PyExc_ValueError, e.what()); return;
} catch (const std::invalid_argument &e) { PyErr_SetString(PyExc_ValueError, e.what()); return;
} catch (const std::length_error &e) { PyErr_SetString(PyExc_ValueError, e.what()); return;
} catch (const std::out_of_range &e) { PyErr_SetString(PyExc_IndexError, e.what()); return;
} catch (const std::range_error &e) { PyErr_SetString(PyExc_ValueError, e.what()); return;
} catch (const std::exception &e) { PyErr_SetString(PyExc_RuntimeError, e.what()); return;
} catch (...) {
PyErr_SetString(PyExc_RuntimeError, "Caught an unknown exception!");
return;
}
}
);
}
return *internals_ptr;
}
PYBIND11_NOINLINE inline detail::type_info* get_type_info(PyTypeObject *type, bool throw_if_missing = true) {
auto const &type_dict = get_internals().registered_types_py;
do {
auto it = type_dict.find(type);
if (it != type_dict.end())
return (detail::type_info *) it->second;
type = type->tp_base;
if (!type) {
if (throw_if_missing)
pybind11_fail("pybind11::detail::get_type_info: unable to find type object!");
return nullptr;
}
} while (true);
}
PYBIND11_NOINLINE inline detail::type_info *get_type_info(const std::type_info &tp) {
auto &types = get_internals().registered_types_cpp;
auto it = types.find(std::type_index(tp));
if (it != types.end())
return (detail::type_info *) it->second;
return nullptr;
}
PYBIND11_NOINLINE inline handle get_type_handle(const std::type_info &tp) {
detail::type_info *type_info = get_type_info(tp);
return handle(type_info ? ((PyObject *) type_info->type) : nullptr);
}
PYBIND11_NOINLINE inline std::string error_string() {
PyObject *type, *value, *traceback;
PyErr_Fetch(&type, &value, &traceback);
std::string errorString;
if (type) {
errorString += (std::string) handle(type).str();
errorString += ": ";
}
if (value)
errorString += (std::string) handle(value).str();
PyErr_Restore(type, value, traceback);
return errorString;
}
PYBIND11_NOINLINE inline handle get_object_handle(const void *ptr) {
auto instances = get_internals().registered_instances;
auto it = instances.find(ptr);
if (it == instances.end())
return handle();
return handle((PyObject *) it->second);
}
inline PyThreadState *get_thread_state_unchecked() {
#if PY_VERSION_HEX < 0x03000000
return _PyThreadState_Current;
#elif PY_VERSION_HEX < 0x03050000
return (PyThreadState*) _Py_atomic_load_relaxed(&_PyThreadState_Current);
#elif PY_VERSION_HEX < 0x03050200
return (PyThreadState*) _PyThreadState_Current.value;
#else
return _PyThreadState_UncheckedGet();
#endif
}
class type_caster_generic {
public:
PYBIND11_NOINLINE type_caster_generic(const std::type_info &type_info)
: typeinfo(get_type_info(type_info)) { }
PYBIND11_NOINLINE bool load(handle src, bool convert) {
if (!src || !typeinfo)
return false;
if (src.ptr() == Py_None) {
value = nullptr;
return true;
} else if (PyType_IsSubtype(Py_TYPE(src.ptr()), typeinfo->type)) {
value = ((instance<void> *) src.ptr())->value;
return true;
}
if (convert) {
for (auto &converter : typeinfo->implicit_conversions) {
temp = object(converter(src.ptr(), typeinfo->type), false);
if (load(temp, false))
return true;
}
}
return false;
}
PYBIND11_NOINLINE static handle cast(const void *_src, return_value_policy policy, handle parent,
const std::type_info *type_info,
const std::type_info *type_info_backup,
void *(*copy_constructor)(const void *),
void *(*move_constructor)(const void *),
const void *existing_holder = nullptr) {
void *src = const_cast<void *>(_src);
if (src == nullptr)
return handle(Py_None).inc_ref();
// avoid an issue with internal references matching their parent's address
bool dont_cache = policy == return_value_policy::reference_internal &&
parent && ((instance<void> *) parent.ptr())->value == (void *) src;
auto& internals = get_internals();
auto it_instance = internals.registered_instances.find(src);
if (it_instance != internals.registered_instances.end() && !dont_cache)
return handle((PyObject *) it_instance->second).inc_ref();
auto it = internals.registered_types_cpp.find(std::type_index(*type_info));
if (it == internals.registered_types_cpp.end()) {
type_info = type_info_backup;
it = internals.registered_types_cpp.find(std::type_index(*type_info));
}
if (it == internals.registered_types_cpp.end()) {
std::string tname = type_info->name();
detail::clean_type_id(tname);
std::string msg = "Unregistered type : " + tname;
PyErr_SetString(PyExc_TypeError, msg.c_str());
return handle();
}
auto tinfo = (const detail::type_info *) it->second;
object inst(PyType_GenericAlloc(tinfo->type, 0), false);
auto wrapper = (instance<void> *) inst.ptr();
wrapper->value = src;
wrapper->owned = true;
wrapper->parent = nullptr;
if (policy == return_value_policy::automatic)
policy = return_value_policy::take_ownership;
else if (policy == return_value_policy::automatic_reference)
policy = return_value_policy::reference;
if (policy == return_value_policy::copy) {
wrapper->value = copy_constructor(wrapper->value);
if (wrapper->value == nullptr)
throw cast_error("return_value_policy = copy, but the object is non-copyable!");
} else if (policy == return_value_policy::move) {
wrapper->value = move_constructor(wrapper->value);
if (wrapper->value == nullptr)
wrapper->value = copy_constructor(wrapper->value);
if (wrapper->value == nullptr)
throw cast_error("return_value_policy = move, but the object is neither movable nor copyable!");
} else if (policy == return_value_policy::reference) {
wrapper->owned = false;
} else if (policy == return_value_policy::reference_internal) {
wrapper->owned = false;
wrapper->parent = parent.inc_ref().ptr();
}
tinfo->init_holder(inst.ptr(), existing_holder);
if (!dont_cache)
internals.registered_instances[wrapper->value] = inst.ptr();
return inst.release();
}
protected:
const type_info *typeinfo = nullptr;
void *value = nullptr;
object temp;
};
/* Determine suitable casting operator */
template <typename T>
using cast_op_type = typename std::conditional<std::is_pointer<typename std::remove_reference<T>::type>::value,
typename std::add_pointer<typename intrinsic_type<T>::type>::type,
typename std::add_lvalue_reference<typename intrinsic_type<T>::type>::type>::type;
/// Generic type caster for objects stored on the heap
template <typename type> class type_caster_base : public type_caster_generic {
public:
static PYBIND11_DESCR name() { return type_descr(_<type>()); }
type_caster_base() : type_caster_generic(typeid(type)) { }
static handle cast(const type &src, return_value_policy policy, handle parent) {
if (policy == return_value_policy::automatic || policy == return_value_policy::automatic_reference)
policy = return_value_policy::copy;
return cast(&src, policy, parent);
}
static handle cast(type &&src, return_value_policy policy, handle parent) {
if (policy == return_value_policy::automatic || policy == return_value_policy::automatic_reference)
policy = return_value_policy::move;
return cast(&src, policy, parent);
}
static handle cast(const type *src, return_value_policy policy, handle parent) {
return type_caster_generic::cast(
src, policy, parent, src ? &typeid(*src) : nullptr, &typeid(type),
make_copy_constructor(src), make_move_constructor(src));
}
template <typename T> using cast_op_type = pybind11::detail::cast_op_type<T>;
operator type*() { return (type *) value; }
operator type&() { if (!value) throw reference_cast_error(); return *((type *) value); }
protected:
typedef void *(*Constructor)(const void *stream);
#if !defined(_MSC_VER)
/* Only enabled when the types are {copy,move}-constructible *and* when the type
does not have a private operator new implementaton. */
template <typename T = type> static auto make_copy_constructor(const T *value) -> decltype(new T(*value), Constructor(nullptr)) {
return [](const void *arg) -> void * { return new T(*((const T *) arg)); }; }
template <typename T = type> static auto make_move_constructor(const T *value) -> decltype(new T(std::move(*((T *) value))), Constructor(nullptr)) {
return [](const void *arg) -> void * { return (void *) new T(std::move(*((T *) arg))); }; }
#else
/* Visual Studio 2015's SFINAE implementation doesn't yet handle the above robustly in all situations.
Use a workaround that only tests for constructibility for now. */
template <typename T = type, typename = typename std::enable_if<std::is_copy_constructible<T>::value>::type>
static Constructor make_copy_constructor(const T *value) {
return [](const void *arg) -> void * { return new T(*((const T *)arg)); }; }
template <typename T = type, typename = typename std::enable_if<std::is_move_constructible<T>::value>::type>
static Constructor make_move_constructor(const T *value) {
return [](const void *arg) -> void * { return (void *) new T(std::move(*((T *)arg))); }; }
#endif
static Constructor make_copy_constructor(...) { return nullptr; }
static Constructor make_move_constructor(...) { return nullptr; }
};
template <typename type, typename SFINAE = void> class type_caster : public type_caster_base<type> { };
template <typename type> class type_caster<std::reference_wrapper<type>> : public type_caster_base<type> {
public:
static handle cast(const std::reference_wrapper<type> &src, return_value_policy policy, handle parent) {
return type_caster_base<type>::cast(&src.get(), policy, parent);
}
template <typename T> using cast_op_type = std::reference_wrapper<type>;
operator std::reference_wrapper<type>() { return std::ref(*((type *) this->value)); }
};
#define PYBIND11_TYPE_CASTER(type, py_name) \
protected: \
type value; \
public: \
static PYBIND11_DESCR name() { return type_descr(py_name); } \
static handle cast(const type *src, return_value_policy policy, handle parent) { \
return cast(*src, policy, parent); \
} \
operator type*() { return &value; } \
operator type&() { return value; } \
template <typename _T> using cast_op_type = pybind11::detail::cast_op_type<_T>
#define PYBIND11_DECLARE_HOLDER_TYPE(type, holder_type) \
namespace pybind11 { namespace detail { \
template <typename type> class type_caster<holder_type> \
: public type_caster_holder<type, holder_type> { }; \
}}
template <typename T>
struct type_caster<
T, typename std::enable_if<std::is_integral<T>::value ||
std::is_floating_point<T>::value>::type> {
typedef typename std::conditional<sizeof(T) <= sizeof(long), long, long long>::type _py_type_0;
typedef typename std::conditional<std::is_signed<T>::value, _py_type_0, typename std::make_unsigned<_py_type_0>::type>::type _py_type_1;
typedef typename std::conditional<std::is_floating_point<T>::value, double, _py_type_1>::type py_type;
public:
bool load(handle src, bool) {
py_type py_value;
if (!src) {
return false;
} if (std::is_floating_point<T>::value) {
py_value = (py_type) PyFloat_AsDouble(src.ptr());
} else if (sizeof(T) <= sizeof(long)) {
if (PyFloat_Check(src.ptr()))
return false;
if (std::is_signed<T>::value)
py_value = (py_type) PyLong_AsLong(src.ptr());
else
py_value = (py_type) PyLong_AsUnsignedLong(src.ptr());
} else {
if (PyFloat_Check(src.ptr()))
return false;
if (std::is_signed<T>::value)
py_value = (py_type) PYBIND11_LONG_AS_LONGLONG(src.ptr());
else
py_value = (py_type) PYBIND11_LONG_AS_UNSIGNED_LONGLONG(src.ptr());
}
if ((py_value == (py_type) -1 && PyErr_Occurred()) ||
(std::is_integral<T>::value && sizeof(py_type) != sizeof(T) &&
(py_value < (py_type) std::numeric_limits<T>::min() ||
py_value > (py_type) std::numeric_limits<T>::max()))) {
PyErr_Clear();
return false;
}
value = (T) py_value;
return true;
}
static handle cast(T src, return_value_policy /* policy */, handle /* parent */) {
if (std::is_floating_point<T>::value) {
return PyFloat_FromDouble((double) src);
} else if (sizeof(T) <= sizeof(long)) {
if (std::is_signed<T>::value)
return PyLong_FromLong((long) src);
else
return PyLong_FromUnsignedLong((unsigned long) src);
} else {
if (std::is_signed<T>::value)
return PyLong_FromLongLong((long long) src);
else
return PyLong_FromUnsignedLongLong((unsigned long long) src);
}
}
PYBIND11_TYPE_CASTER(T, _<std::is_integral<T>::value>("int", "float"));
};
template <> class type_caster<void_type> {
public:
bool load(handle, bool) { return false; }
static handle cast(void_type, return_value_policy /* policy */, handle /* parent */) {
return handle(Py_None).inc_ref();
}
PYBIND11_TYPE_CASTER(void_type, _("None"));
};
template <> class type_caster<void> : public type_caster<void_type> {
public:
using type_caster<void_type>::cast;
bool load(handle h, bool) {
if (!h) {
return false;
} else if (h.ptr() == Py_None) {
value = nullptr;
return true;
}
/* Check if this is a capsule */
capsule c(h, true);
if (c.check()) {
value = (void *) c;
return true;
}
/* Check if this is a C++ type */
if (get_type_info((PyTypeObject *) h.get_type().ptr(), false)) {
value = ((instance<void> *) h.ptr())->value;
return true;
}
/* Fail */
return false;
}
static handle cast(const void *ptr, return_value_policy /* policy */, handle /* parent */) {
if (ptr)
return capsule(ptr).release();
else
return handle(Py_None).inc_ref();
}
template <typename T> using cast_op_type = void*&;
operator void *&() { return value; }
static PYBIND11_DESCR name() { return type_descr(_("capsule")); }
private:
void *value = nullptr;
};
template <> class type_caster<std::nullptr_t> : public type_caster<void_type> { };
template <> class type_caster<bool> {
public:
bool load(handle src, bool) {
if (!src) return false;
else if (src.ptr() == Py_True) { value = true; return true; }
else if (src.ptr() == Py_False) { value = false; return true; }
else return false;
}
static handle cast(bool src, return_value_policy /* policy */, handle /* parent */) {
return handle(src ? Py_True : Py_False).inc_ref();
}
PYBIND11_TYPE_CASTER(bool, _("bool"));
};
template <> class type_caster<std::string> {
public:
bool load(handle src, bool) {
object temp;
handle load_src = src;
if (!src) {
return false;
} else if (PyUnicode_Check(load_src.ptr())) {
temp = object(PyUnicode_AsUTF8String(load_src.ptr()), false);
if (!temp) { PyErr_Clear(); return false; } // UnicodeEncodeError
load_src = temp;
}
char *buffer;
ssize_t length;
int err = PYBIND11_BYTES_AS_STRING_AND_SIZE(load_src.ptr(), &buffer, &length);
if (err == -1) { PyErr_Clear(); return false; } // TypeError
value = std::string(buffer, (size_t) length);
success = true;
return true;
}
static handle cast(const std::string &src, return_value_policy /* policy */, handle /* parent */) {
return PyUnicode_FromStringAndSize(src.c_str(), (ssize_t) src.length());
}
PYBIND11_TYPE_CASTER(std::string, _(PYBIND11_STRING_NAME));
protected:
bool success = false;
};
template <typename type> class type_caster<std::unique_ptr<type>> {
public:
static handle cast(std::unique_ptr<type> &&src, return_value_policy policy, handle parent) {
handle result = type_caster_base<type>::cast(src.get(), policy, parent);
if (result)
src.release();
return result;
}
static PYBIND11_DESCR name() { return type_caster_base<type>::name(); }
};
template <> class type_caster<std::wstring> {
public:
bool load(handle src, bool) {
object temp;
handle load_src = src;
if (!src) {
return false;
} else if (!PyUnicode_Check(load_src.ptr())) {
temp = object(PyUnicode_FromObject(load_src.ptr()), false);
if (!temp) { PyErr_Clear(); return false; }
load_src = temp;
}
wchar_t *buffer = nullptr;
ssize_t length = -1;
#if PY_MAJOR_VERSION >= 3
buffer = PyUnicode_AsWideCharString(load_src.ptr(), &length);
#else
temp = object(
sizeof(wchar_t) == sizeof(short)
? PyUnicode_AsUTF16String(load_src.ptr())
: PyUnicode_AsUTF32String(load_src.ptr()), false);
if (temp) {
int err = PYBIND11_BYTES_AS_STRING_AND_SIZE(temp.ptr(), (char **) &buffer, &length);
if (err == -1) { buffer = nullptr; } // TypeError
length = length / (ssize_t) sizeof(wchar_t) - 1; ++buffer; // Skip BOM
}
#endif
if (!buffer) { PyErr_Clear(); return false; }
value = std::wstring(buffer, (size_t) length);
success = true;
return true;
}
static handle cast(const std::wstring &src, return_value_policy /* policy */, handle /* parent */) {
return PyUnicode_FromWideChar(src.c_str(), (ssize_t) src.length());
}
PYBIND11_TYPE_CASTER(std::wstring, _(PYBIND11_STRING_NAME));
protected:
bool success = false;
};
template <> class type_caster<char> : public type_caster<std::string> {
public:
bool load(handle src, bool convert) {
if (src.ptr() == Py_None) return true;
return type_caster<std::string>::load(src, convert);
}
static handle cast(const char *src, return_value_policy /* policy */, handle /* parent */) {
if (src == nullptr) return handle(Py_None).inc_ref();
return PyUnicode_FromString(src);
}
static handle cast(char src, return_value_policy /* policy */, handle /* parent */) {
char str[2] = { src, '\0' };
return PyUnicode_DecodeLatin1(str, 1, nullptr);
}
operator char*() { return success ? (char *) value.c_str() : nullptr; }
operator char&() { return value[0]; }
static PYBIND11_DESCR name() { return type_descr(_(PYBIND11_STRING_NAME)); }
};
template <> class type_caster<wchar_t> : public type_caster<std::wstring> {
public:
bool load(handle src, bool convert) {
if (src.ptr() == Py_None) return true;
return type_caster<std::wstring>::load(src, convert);
}
static handle cast(const wchar_t *src, return_value_policy /* policy */, handle /* parent */) {
if (src == nullptr) return handle(Py_None).inc_ref();
return PyUnicode_FromWideChar(src, (ssize_t) wcslen(src));
}
static handle cast(wchar_t src, return_value_policy /* policy */, handle /* parent */) {
wchar_t wstr[2] = { src, L'\0' };
return PyUnicode_FromWideChar(wstr, 1);
}
operator wchar_t*() { return success ? (wchar_t *) value.c_str() : nullptr; }
operator wchar_t&() { return value[0]; }
static PYBIND11_DESCR name() { return type_descr(_(PYBIND11_STRING_NAME)); }
};
template <typename T1, typename T2> class type_caster<std::pair<T1, T2>> {
typedef std::pair<T1, T2> type;
public:
bool load(handle src, bool convert) {
if (!src)
return false;
else if (!PyTuple_Check(src.ptr()) || PyTuple_Size(src.ptr()) != 2)
return false;
return first.load(PyTuple_GET_ITEM(src.ptr(), 0), convert) &&
second.load(PyTuple_GET_ITEM(src.ptr(), 1), convert);
}
static handle cast(const type &src, return_value_policy policy, handle parent) {
object o1 = object(type_caster<typename intrinsic_type<T1>::type>::cast(src.first, policy, parent), false);
object o2 = object(type_caster<typename intrinsic_type<T2>::type>::cast(src.second, policy, parent), false);
if (!o1 || !o2)
return handle();
tuple result(2);
PyTuple_SET_ITEM(result.ptr(), 0, o1.release().ptr());
PyTuple_SET_ITEM(result.ptr(), 1, o2.release().ptr());
return result.release();
}
static PYBIND11_DESCR name() {
return type_descr(
_("Tuple[") + type_caster<typename intrinsic_type<T1>::type>::name() +
_(", ") + type_caster<typename intrinsic_type<T2>::type>::name() + _("]"));
}
template <typename T> using cast_op_type = type;
operator type() {
return type(first .operator typename type_caster<typename intrinsic_type<T1>::type>::template cast_op_type<T1>(),
second.operator typename type_caster<typename intrinsic_type<T2>::type>::template cast_op_type<T2>());
}
protected:
type_caster<typename intrinsic_type<T1>::type> first;
type_caster<typename intrinsic_type<T2>::type> second;
};
template <typename... Tuple> class type_caster<std::tuple<Tuple...>> {
typedef std::tuple<Tuple...> type;
typedef std::tuple<typename intrinsic_type<Tuple>::type...> itype;
typedef std::tuple<args> args_type;
typedef std::tuple<args, kwargs> args_kwargs_type;
public:
enum { size = sizeof...(Tuple) };
static constexpr const bool has_kwargs = std::is_same<itype, args_kwargs_type>::value;
static constexpr const bool has_args = has_kwargs || std::is_same<itype, args_type>::value;
bool load(handle src, bool convert) {
if (!src || !PyTuple_Check(src.ptr()) || PyTuple_GET_SIZE(src.ptr()) != size)
return false;
return load(src, convert, typename make_index_sequence<sizeof...(Tuple)>::type());
}
template <typename T = itype, typename std::enable_if<
!std::is_same<T, args_type>::value &&
!std::is_same<T, args_kwargs_type>::value, int>::type = 0>
bool load_args(handle args, handle, bool convert) {
return load(args, convert, typename make_index_sequence<sizeof...(Tuple)>::type());
}
template <typename T = itype, typename std::enable_if<std::is_same<T, args_type>::value, int>::type = 0>
bool load_args(handle args, handle, bool convert) {
std::get<0>(value).load(args, convert);
return true;
}
template <typename T = itype, typename std::enable_if<std::is_same<T, args_kwargs_type>::value, int>::type = 0>
bool load_args(handle args, handle kwargs, bool convert) {
std::get<0>(value).load(args, convert);
std::get<1>(value).load(kwargs, convert);
return true;
}
static handle cast(const type &src, return_value_policy policy, handle parent) {
return cast(src, policy, parent, typename make_index_sequence<size>::type());
}
static PYBIND11_DESCR element_names() {
return detail::concat(type_caster<typename intrinsic_type<Tuple>::type>::name()...);
}
static PYBIND11_DESCR name() {
return type_descr(_("Tuple[") + element_names() + _("]"));
}
template <typename ReturnValue, typename Func> typename std::enable_if<!std::is_void<ReturnValue>::value, ReturnValue>::type call(Func &&f) {
return call<ReturnValue>(std::forward<Func>(f), typename make_index_sequence<sizeof...(Tuple)>::type());
}
template <typename ReturnValue, typename Func> typename std::enable_if<std::is_void<ReturnValue>::value, void_type>::type call(Func &&f) {
call<ReturnValue>(std::forward<Func>(f), typename make_index_sequence<sizeof...(Tuple)>::type());
return void_type();
}
template <typename T> using cast_op_type = type;
operator type() {
return cast(typename make_index_sequence<sizeof...(Tuple)>::type());
}
protected:
template <typename ReturnValue, typename Func, size_t ... Index> ReturnValue call(Func &&f, index_sequence<Index...>) {
return f(std::get<Index>(value)
.operator typename type_caster<typename intrinsic_type<Tuple>::type>::template cast_op_type<Tuple>()...);
}
template <size_t ... Index> type cast(index_sequence<Index...>) {
return type(std::get<Index>(value)
.operator typename type_caster<typename intrinsic_type<Tuple>::type>::template cast_op_type<Tuple>()...);
}
template <size_t ... Indices> bool load(handle src, bool convert, index_sequence<Indices...>) {
std::array<bool, size> success {{
std::get<Indices>(value).load(PyTuple_GET_ITEM(src.ptr(), Indices), convert)...
}};
(void) convert; /* avoid a warning when the tuple is empty */
for (bool r : success)
if (!r)
return false;
return true;
}
/* Implementation: Convert a C++ tuple into a Python tuple */
template <size_t ... Indices> static handle cast(const type &src, return_value_policy policy, handle parent, index_sequence<Indices...>) {
std::array<object, size> entries {{
object(type_caster<typename intrinsic_type<Tuple>::type>::cast(std::get<Indices>(src), policy, parent), false)...
}};
for (const auto &entry: entries)
if (!entry)
return handle();
tuple result(size);
int counter = 0;
for (auto & entry: entries)
PyTuple_SET_ITEM(result.ptr(), counter++, entry.release().ptr());
return result.release();
}
protected:
std::tuple<type_caster<typename intrinsic_type<Tuple>::type>...> value;
};
/// Type caster for holder types like std::shared_ptr, etc.
template <typename type, typename holder_type> class type_caster_holder : public type_caster_base<type> {
public:
using type_caster_base<type>::cast;
using type_caster_base<type>::typeinfo;
using type_caster_base<type>::value;
using type_caster_base<type>::temp;
bool load(handle src, bool convert) {
if (!src || !typeinfo) {
return false;
} else if (src.ptr() == Py_None) {
value = nullptr;
return true;
} else if (PyType_IsSubtype(Py_TYPE(src.ptr()), typeinfo->type)) {
auto inst = (instance<type, holder_type> *) src.ptr();
value = (void *) inst->value;
holder = inst->holder;
return true;
}
if (convert) {
for (auto &converter : typeinfo->implicit_conversions) {
temp = object(converter(src.ptr(), typeinfo->type), false);
if (load(temp, false))
return true;
}
}
return false;
}
explicit operator type*() { return this->value; }
explicit operator type&() { return *(this->value); }
explicit operator holder_type*() { return &holder; }
// Workaround for Intel compiler bug
// see pybind11 issue 94
#if defined(__ICC) || defined(__INTEL_COMPILER)
operator holder_type&() { return holder; }
#else
explicit operator holder_type&() { return holder; }
#endif
static handle cast(const holder_type &src, return_value_policy, handle) {
return type_caster_generic::cast(
src.get(), return_value_policy::take_ownership, handle(),
src.get() ? &typeid(*src.get()) : nullptr, &typeid(type),
nullptr, nullptr, &src);
}
protected:
holder_type holder;
};
template <typename T> struct handle_type_name { static PYBIND11_DESCR name() { return _<T>(); } };
template <> struct handle_type_name<bytes> { static PYBIND11_DESCR name() { return _(PYBIND11_BYTES_NAME); } };
template <> struct handle_type_name<args> { static PYBIND11_DESCR name() { return _("*args"); } };
template <> struct handle_type_name<kwargs> { static PYBIND11_DESCR name() { return _("**kwargs"); } };
template <typename type>
struct type_caster<type, typename std::enable_if<std::is_base_of<handle, type>::value>::type> {
public:
template <typename T = type, typename std::enable_if<!std::is_base_of<object, T>::value, int>::type = 0>
bool load(handle src, bool /* convert */) { value = type(src); return value.check(); }
template <typename T = type, typename std::enable_if<std::is_base_of<object, T>::value, int>::type = 0>
bool load(handle src, bool /* convert */) { value = type(src, true); return value.check(); }
static handle cast(const handle &src, return_value_policy /* policy */, handle /* parent */) {
return src.inc_ref();
}
PYBIND11_TYPE_CASTER(type, handle_type_name<type>::name());
};
// Our conditions for enabling moving are quite restrictive:
// At compile time:
// - T needs to be a non-const, non-pointer, non-reference type
// - type_caster<T>::operator T&() must exist
// - the type must be move constructible (obviously)
// At run-time:
// - if the type is non-copy-constructible, the object must be the sole owner of the type (i.e. it
// must have ref_count() == 1)h
// If any of the above are not satisfied, we fall back to copying.
template <typename T, typename SFINAE = void> struct move_is_plain_type : std::false_type {};
template <typename T> struct move_is_plain_type<T, typename std::enable_if<
!std::is_void<T>::value && !std::is_pointer<T>::value && !std::is_reference<T>::value && !std::is_const<T>::value
>::type> : std::true_type {};
template <typename T, typename SFINAE = void> struct move_always : std::false_type {};
template <typename T> struct move_always<T, typename std::enable_if<
move_is_plain_type<T>::value &&
!std::is_copy_constructible<T>::value && std::is_move_constructible<T>::value &&
std::is_same<decltype(std::declval<type_caster<T>>().operator T&()), T&>::value
>::type> : std::true_type {};
template <typename T, typename SFINAE = void> struct move_if_unreferenced : std::false_type {};
template <typename T> struct move_if_unreferenced<T, typename std::enable_if<
move_is_plain_type<T>::value &&
!move_always<T>::value && std::is_move_constructible<T>::value &&
std::is_same<decltype(std::declval<type_caster<T>>().operator T&()), T&>::value
>::type> : std::true_type {};
template <typename T> using move_never = std::integral_constant<bool, !move_always<T>::value && !move_if_unreferenced<T>::value>;
NAMESPACE_END(detail)
template <typename T> T cast(const handle &handle) {
typedef detail::type_caster<typename detail::intrinsic_type<T>::type> type_caster;
type_caster conv;
if (!conv.load(handle, true)) {
#if defined(NDEBUG)
throw cast_error("Unable to cast Python instance to C++ type (compile in debug mode for details)");
#else
throw cast_error("Unable to cast Python instance of type " +
(std::string) handle.get_type().str() + " to C++ type '" + type_id<T>() + "''");
#endif
}
return conv.operator typename type_caster::template cast_op_type<T>();
}
template <typename T> object cast(const T &value,
return_value_policy policy = return_value_policy::automatic_reference,
handle parent = handle()) {
if (policy == return_value_policy::automatic)
policy = std::is_pointer<T>::value ? return_value_policy::take_ownership : return_value_policy::copy;
else if (policy == return_value_policy::automatic_reference)
policy = std::is_pointer<T>::value ? return_value_policy::reference : return_value_policy::copy;
return object(detail::type_caster<typename detail::intrinsic_type<T>::type>::cast(value, policy, parent), false);
}
template <typename T> T handle::cast() const { return pybind11::cast<T>(*this); }
template <> inline void handle::cast() const { return; }
template <typename T>
typename std::enable_if<detail::move_always<T>::value || detail::move_if_unreferenced<T>::value, T>::type move(object &&obj) {
if (obj.ref_count() > 1)
#if defined(NDEBUG)
throw cast_error("Unable to cast Python instance to C++ rvalue: instance has multiple references"
" (compile in debug mode for details)");
#else
throw cast_error("Unable to move from Python " + (std::string) obj.get_type().str() +
" instance to C++ " + type_id<T>() + " instance: instance has multiple references");
#endif
typedef detail::type_caster<T> type_caster;
type_caster conv;
if (!conv.load(obj, true))
#if defined(NDEBUG)
throw cast_error("Unable to cast Python instance to C++ type (compile in debug mode for details)");
#else
throw cast_error("Unable to cast Python instance of type " +
(std::string) obj.get_type().str() + " to C++ type '" + type_id<T>() + "''");
#endif
// Move into a temporary and return that, because the reference may be a local value of `conv`
T ret = std::move(conv.operator T&());
return ret;
}
// Calling cast() on an rvalue calls pybind::cast with the object rvalue, which does:
// - If we have to move (because T has no copy constructor), do it. This will fail if the moved
// object has multiple references, but trying to copy will fail to compile.
// - If both movable and copyable, check ref count: if 1, move; otherwise copy
// - Otherwise (not movable), copy.
template <typename T> typename std::enable_if<detail::move_always<T>::value, T>::type cast(object &&object) {
return move<T>(std::move(object));
}
template <typename T> typename std::enable_if<detail::move_if_unreferenced<T>::value, T>::type cast(object &&object) {
if (object.ref_count() > 1)
return cast<T>(object);
else
return move<T>(std::move(object));
}
template <typename T> typename std::enable_if<detail::move_never<T>::value, T>::type cast(object &&object) {
return cast<T>(object);
}
template <typename T> T object::cast() const & { return pybind11::cast<T>(*this); }
template <typename T> T object::cast() && { return pybind11::cast<T>(std::move(*this)); }
template <> inline void object::cast() const & { return; }
template <> inline void object::cast() && { return; }
template <return_value_policy policy = return_value_policy::automatic_reference,
typename... Args> tuple make_tuple(Args&&... args_) {
const size_t size = sizeof...(Args);
std::array<object, size> args {
{ object(detail::type_caster<typename detail::intrinsic_type<Args>::type>::cast(
std::forward<Args>(args_), policy, nullptr), false)... }
};
for (auto &arg_value : args) {
if (!arg_value) {
#if defined(NDEBUG)
throw cast_error("make_tuple(): unable to convert arguments to Python object (compile in debug mode for details)");
#else
throw cast_error("make_tuple(): unable to convert arguments of types '" +
(std::string) type_id<std::tuple<Args...>>() + "' to Python object");
#endif
}
}
tuple result(size);
int counter = 0;
for (auto &arg_value : args)
PyTuple_SET_ITEM(result.ptr(), counter++, arg_value.release().ptr());
return result;
}
template <return_value_policy policy,
typename... Args> object handle::operator()(Args&&... args) const {
tuple args_tuple = pybind11::make_tuple<policy>(std::forward<Args>(args)...);
object result(PyObject_CallObject(m_ptr, args_tuple.ptr()), false);
if (!result)
throw error_already_set();
return result;
}
template <return_value_policy policy,
typename... Args> object handle::call(Args &&... args) const {
return operator()<policy>(std::forward<Args>(args)...);
}
inline object handle::operator()(detail::args_proxy args) const {
object result(PyObject_CallObject(m_ptr, args.ptr()), false);
if (!result)
throw error_already_set();
return result;
}
inline object handle::operator()(detail::args_proxy args, detail::kwargs_proxy kwargs) const {
object result(PyObject_Call(m_ptr, args.ptr(), kwargs.ptr()), false);
if (!result)
throw error_already_set();
return result;
}
#define PYBIND11_MAKE_OPAQUE(Type) \
namespace pybind11 { namespace detail { \
template<> class type_caster<Type> : public type_caster_base<Type> { }; \
}}
NAMESPACE_END(pybind11)
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