102 lines
3.5 KiB
C++
102 lines
3.5 KiB
C++
/*
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pybind11/functional.h: std::function<> support
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Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
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All rights reserved. Use of this source code is governed by a
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BSD-style license that can be found in the LICENSE file.
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*/
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#pragma once
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#include "pybind11.h"
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#include <functional>
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PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
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PYBIND11_NAMESPACE_BEGIN(detail)
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template <typename Return, typename... Args>
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struct type_caster<std::function<Return(Args...)>> {
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using type = std::function<Return(Args...)>;
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using retval_type = conditional_t<std::is_same<Return, void>::value, void_type, Return>;
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using function_type = Return (*) (Args...);
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public:
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bool load(handle src, bool convert) {
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if (src.is_none()) {
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// Defer accepting None to other overloads (if we aren't in convert mode):
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if (!convert) return false;
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return true;
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}
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if (!isinstance<function>(src))
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return false;
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auto func = reinterpret_borrow<function>(src);
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/*
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When passing a C++ function as an argument to another C++
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function via Python, every function call would normally involve
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a full C++ -> Python -> C++ roundtrip, which can be prohibitive.
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Here, we try to at least detect the case where the function is
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stateless (i.e. function pointer or lambda function without
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captured variables), in which case the roundtrip can be avoided.
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*/
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if (auto cfunc = func.cpp_function()) {
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auto c = reinterpret_borrow<capsule>(PyCFunction_GET_SELF(cfunc.ptr()));
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auto rec = (function_record *) c;
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if (rec && rec->is_stateless &&
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same_type(typeid(function_type), *reinterpret_cast<const std::type_info *>(rec->data[1]))) {
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struct capture { function_type f; };
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value = ((capture *) &rec->data)->f;
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return true;
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}
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}
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// ensure GIL is held during functor destruction
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struct func_handle {
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function f;
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func_handle(function&& f_) : f(std::move(f_)) {}
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func_handle(const func_handle&) = default;
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~func_handle() {
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gil_scoped_acquire acq;
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function kill_f(std::move(f));
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}
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};
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// to emulate 'move initialization capture' in C++11
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struct func_wrapper {
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func_handle hfunc;
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func_wrapper(func_handle&& hf): hfunc(std::move(hf)) {}
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Return operator()(Args... args) const {
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gil_scoped_acquire acq;
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object retval(hfunc.f(std::forward<Args>(args)...));
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/* Visual studio 2015 parser issue: need parentheses around this expression */
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return (retval.template cast<Return>());
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}
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};
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value = func_wrapper(func_handle(std::move(func)));
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return true;
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}
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template <typename Func>
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static handle cast(Func &&f_, return_value_policy policy, handle /* parent */) {
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if (!f_)
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return none().inc_ref();
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auto result = f_.template target<function_type>();
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if (result)
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return cpp_function(*result, policy).release();
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else
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return cpp_function(std::forward<Func>(f_), policy).release();
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}
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PYBIND11_TYPE_CASTER(type, _("Callable[[") + concat(make_caster<Args>::name...) + _("], ")
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+ make_caster<retval_type>::name + _("]"));
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};
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PYBIND11_NAMESPACE_END(detail)
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PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
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