History prior to this date belonged to the now deprecated ISAAC project, and was deleted to save space

python/src/pybind11/functional.h

@@ -0,0 +1,108 @@
+/*
+    pybind11/functional.h: std::function<> support
+
+    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 "pybind11.h"
+#include <functional>
+
+NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+NAMESPACE_BEGIN(detail)
+
+template <typename Return, typename... Args>
+struct type_caster<std::function<Return(Args...)>> {
+    using type = std::function<Return(Args...)>;
+    using retval_type = conditional_t<std::is_same<Return, void>::value, void_type, Return>;
+    using function_type = Return (*) (Args...);
+
+public:
+    bool load(handle src, bool convert) {
+        if (src.is_none()) {
+            // Defer accepting None to other overloads (if we aren't in convert mode):
+            if (!convert) return false;
+            return true;
+        }
+
+        if (!isinstance<function>(src))
+            return false;
+
+        auto func = reinterpret_borrow<function>(src);
+
+        /*
+           When passing a C++ function as an argument to another C++
+           function via Python, every function call would normally involve
+           a full C++ -> Python -> C++ roundtrip, which can be prohibitive.
+           Here, we try to at least detect the case where the function is
+           stateless (i.e. function pointer or lambda function without
+           captured variables), in which case the roundtrip can be avoided.
+         */
+        if (auto cfunc = func.cpp_function()) {
+            auto c = reinterpret_borrow<capsule>(PyCFunction_GET_SELF(cfunc.ptr()));
+            auto rec = (function_record *) c;
+
+            if (rec && rec->is_stateless &&
+                    same_type(typeid(function_type), *reinterpret_cast<const std::type_info *>(rec->data[1]))) {
+                struct capture { function_type f; };
+                value = ((capture *) &rec->data)->f;
+                return true;
+            }
+        }
+
+        // ensure GIL is held during functor destruction
+        struct func_handle {
+            function f;
+            func_handle(function&& f_) : f(std::move(f_)) {}
+            func_handle(const func_handle&) = default;
+            ~func_handle() {
+                gil_scoped_acquire acq;
+                function kill_f(std::move(f));
+            }
+        };
+
+        // value = [hfunc = func_handle(std::move(func))](Args... args) -> Return {
+        //     gil_scoped_acquire acq;
+        //     object retval(hfunc.f(std::forward<Args>(args)...));
+        //     /* Visual studio 2015 parser issue: need parentheses around this expression */
+        //     return (retval.template cast<Return>());
+        // };
+
+        struct func_wrapper {
+            func_handle hfunc;
+            func_wrapper(func_handle&& hf): hfunc(std::move(hf)) {}
+            Return operator()(Args... args) const {
+                gil_scoped_acquire acq;
+                object retval(hfunc.f(std::forward<Args>(args)...));
+                /* Visual studio 2015 parser issue: need parentheses around this expression */
+                return (retval.template cast<Return>());
+            }
+        };
+
+        value = func_wrapper(func_handle(std::move(func)));
+
+        return true;
+    }
+
+    template <typename Func>
+    static handle cast(Func &&f_, return_value_policy policy, handle /* parent */) {
+        if (!f_)
+            return none().inc_ref();
+
+        auto result = f_.template target<function_type>();
+        if (result)
+            return cpp_function(*result, policy).release();
+        else
+            return cpp_function(std::forward<Func>(f_), policy).release();
+    }
+
+    PYBIND11_TYPE_CASTER(type, _("Callable[[") + concat(make_caster<Args>::name...) + _("], ")
+                               + make_caster<retval_type>::name + _("]"));
+};
+
+NAMESPACE_END(detail)
+NAMESPACE_END(PYBIND11_NAMESPACE)