139 lines
4.9 KiB
C++
139 lines
4.9 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) {
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return false;
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}
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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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}
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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 *cfunc_self = PyCFunction_GET_SELF(cfunc.ptr());
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if (cfunc_self == nullptr) {
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PyErr_Clear();
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} else if (isinstance<capsule>(cfunc_self)) {
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auto c = reinterpret_borrow<capsule>(cfunc_self);
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function_record *rec = nullptr;
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// Check that we can safely reinterpret the capsule into a function_record
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if (detail::is_function_record_capsule(c)) {
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rec = c.get_pointer<function_record>();
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}
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while (rec != nullptr) {
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if (rec->is_stateless
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&& same_type(typeid(function_type),
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*reinterpret_cast<const std::type_info *>(rec->data[1]))) {
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struct capture {
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function_type f;
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};
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value = ((capture *) &rec->data)->f;
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return true;
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}
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rec = rec->next;
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}
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}
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// PYPY segfaults here when passing builtin function like sum.
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// Raising an fail exception here works to prevent the segfault, but only on gcc.
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// See PR #1413 for full details
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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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#if !(defined(_MSC_VER) && _MSC_VER == 1916 && defined(PYBIND11_CPP17))
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// This triggers a syntax error under very special conditions (very weird indeed).
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explicit
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#endif
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func_handle(function &&f_) noexcept
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: f(std::move(f_)) {
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}
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func_handle(const func_handle &f_) { operator=(f_); }
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func_handle &operator=(const func_handle &f_) {
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gil_scoped_acquire acq;
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f = f_.f;
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return *this;
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}
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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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explicit func_wrapper(func_handle &&hf) noexcept : 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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// casts the returned object as a rvalue to the return type
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return hfunc.f(std::forward<Args>(args)...).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().release();
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}
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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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}
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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,
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const_name("Callable[[")
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+ ::pybind11::detail::concat(make_caster<Args>::name...)
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+ const_name("], ") + make_caster<retval_type>::name
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+ const_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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