[{"id":3371,"web_url":"https://patchwork.libcamera.org/comment/3371/","msgid":"<20200107195706.GP533370@oden.dyn.berto.se>","date":"2020-01-07T19:57:06","subject":"Re: [libcamera-devel] [PATCH 10/14] libcamera: bound_method:\n\tPropagate method return value","submitter":{"id":5,"url":"https://patchwork.libcamera.org/api/people/5/","name":"Niklas Söderlund","email":"niklas.soderlund@ragnatech.se"},"content":"Hi Laurent,\n\nThanks for your work.\n\nOn 2020-01-04 07:09:43 +0200, Laurent Pinchart wrote:\n> Propagate the return value of the bound method all the way to the caller\n> of activate(). The value is stored in the arguments pack for indirect\n> invocation.\n> \n> As C++ doesn't allow instantiating a variable of type void, we need to\n> specialize the template class BoundMethodPack for methods returning\n> void. This in turn requires template specialization for the\n> BoundMethodArgs class in order to store the return value in the pack,\n> and for the BoundMemberMethod class to extract the return value from the\n> pack.\n> \n> Signed-off-by: Laurent Pinchart \n\nI think the penny dropped for me at the end after reading it 10+ times \n;-)\n\nReviewed-by: Niklas Söderlund \n\n> ---\n> include/libcamera/bound_method.h | 99 +++++++++++++++++++++++++++-----\n> include/libcamera/object.h | 6 +-\n> src/libcamera/bound_method.cpp | 23 ++++++--\n> src/libcamera/object.cpp | 6 +-\n> 4 files changed, 113 insertions(+), 21 deletions(-)\n> \n> diff --git a/include/libcamera/bound_method.h b/include/libcamera/bound_method.h\n> index a74d2c503cdb..0a91f44a2054 100644\n> --- a/include/libcamera/bound_method.h\n> +++ b/include/libcamera/bound_method.h\n> @@ -28,7 +28,7 @@ public:\n> \tvirtual ~BoundMethodPackBase() {}\n> };\n> \n> -template\n> +template\n> class BoundMethodPack : public BoundMethodPackBase\n> {\n> public:\n> @@ -37,6 +37,19 @@ public:\n> \t{\n> \t}\n> \n> +\tstd::tuple::type...> args_;\n> +\tR ret_;\n> +};\n> +\n> +template\n> +class BoundMethodPack : public BoundMethodPackBase\n> +{\n> +public:\n> +\tBoundMethodPack(const Args &... args)\n> +\t\t: args_(args...)\n> +\t{\n> +\t}\n> +\n> \tstd::tuple::type...> args_;\n> };\n> \n> @@ -77,7 +90,7 @@ protected:\n> \t};\n> #endif\n> \n> -\tvoid activatePack(std::shared_ptr pack,\n> +\tbool activatePack(std::shared_ptr pack,\n> \t\t\t bool deleteMethod);\n> \n> \tvoid *obj_;\n> @@ -91,7 +104,34 @@ template\n> class BoundMethodArgs : public BoundMethodBase\n> {\n> public:\n> -\tusing PackType = BoundMethodPack;\n> +\tusing PackType = BoundMethodPack;\n> +\n> +private:\n> +\ttemplate\n> +\tvoid invokePack(BoundMethodPackBase *pack, BoundMethodBase::sequence)\n> +\t{\n> +\t\tPackType *args = static_cast(pack);\n> +\t\targs->ret_ = invoke(std::get(args->args_)...);\n> +\t}\n> +\n> +public:\n> +\tBoundMethodArgs(void *obj, Object *object, ConnectionType type)\n> +\t\t: BoundMethodBase(obj, object, type) {}\n> +\n> +\tvoid invokePack(BoundMethodPackBase *pack) override\n> +\t{\n> +\t\tinvokePack(pack, typename BoundMethodBase::generator::type());\n> +\t}\n> +\n> +\tvirtual R activate(Args... args, bool deleteMethod = false) = 0;\n> +\tvirtual R invoke(Args... args) = 0;\n> +};\n> +\n> +template\n> +class BoundMethodArgs : public BoundMethodBase\n> +{\n> +public:\n> +\tusing PackType = BoundMethodPack;\n> \n> private:\n> \ttemplate\n> @@ -129,15 +169,45 @@ public:\n> \n> \tbool match(R (T::*func)(Args...)) const { return func == func_; }\n> \n> +\tR activate(Args... args, bool deleteMethod = false) override\n> +\t{\n> +\t\tif (!this->object_)\n> +\t\t\treturn (static_cast(this->obj_)->*func_)(args...);\n> +\n> +\t\tauto pack = std::make_shared(args...);\n> +\t\tbool sync = BoundMethodBase::activatePack(pack, deleteMethod);\n> +\t\treturn sync ? pack->ret_ : R();\n> +\t}\n> +\n> +\tR invoke(Args... args) override\n> +\t{\n> +\t\treturn (static_cast(this->obj_)->*func_)(args...);\n> +\t}\n> +\n> +private:\n> +\tR (T::*func_)(Args...);\n> +};\n> +\n> +template\n> +class BoundMemberMethod : public BoundMethodArgs\n> +{\n> +public:\n> +\tusing PackType = typename BoundMethodArgs::PackType;\n> +\n> +\tBoundMemberMethod(T *obj, Object *object, void (T::*func)(Args...),\n> +\t\t\t ConnectionType type = ConnectionTypeAuto)\n> +\t\t: BoundMethodArgs(obj, object, type), func_(func)\n> +\t{\n> +\t}\n> +\n> +\tbool match(void (T::*func)(Args...)) const { return func == func_; }\n> +\n> \tvoid activate(Args... args, bool deleteMethod = false) override\n> \t{\n> -\t\tif (!this->object_) {\n> -\t\t\t(static_cast(this->obj_)->*func_)(args...);\n> -\t\t\treturn;\n> -\t\t}\n> +\t\tif (!this->object_)\n> +\t\t\treturn (static_cast(this->obj_)->*func_)(args...);\n> \n> -\t\tstd::shared_ptr pack =\n> -\t\t\tstd::make_shared::PackType>(args...);\n> +\t\tauto pack = std::make_shared(args...);\n> \t\tBoundMethodBase::activatePack(pack, deleteMethod);\n> \t}\n> \n> @@ -147,7 +217,7 @@ public:\n> \t}\n> \n> private:\n> -\tR (T::*func_)(Args...);\n> +\tvoid (T::*func_)(Args...);\n> };\n> \n> template\n> @@ -162,12 +232,15 @@ public:\n> \n> \tbool match(R (*func)(Args...)) const { return func == func_; }\n> \n> -\tvoid activate(Args... args, bool deleteMethod = false) override\n> +\tR activate(Args... args, bool deleteMethod = false) override\n> \t{\n> -\t\t(*func_)(args...);\n> +\t\treturn (*func_)(args...);\n> \t}\n> \n> -\tvoid invoke(Args...) override {}\n> +\tR invoke(Args...) override\n> +\t{\n> +\t\treturn R();\n> +\t}\n> \n> private:\n> \tR (*func_)(Args...);\n> diff --git a/include/libcamera/object.h b/include/libcamera/object.h\n> index 586c2cf6fc70..04aa18394d55 100644\n> --- a/include/libcamera/object.h\n> +++ b/include/libcamera/object.h\n> @@ -31,12 +31,12 @@ public:\n> \n> \ttemplate \t\t typename std::enable_if::value>::type * = nullptr>\n> -\tvoid invokeMethod(R (T::*func)(FuncArgs...), ConnectionType type,\n> -\t\t\t Args... args)\n> +\tR invokeMethod(R (T::*func)(FuncArgs...), ConnectionType type,\n> +\t\t Args... args)\n> \t{\n> \t\tT *obj = static_cast(this);\n> \t\tauto *method = new BoundMemberMethod(obj, this, func, type);\n> -\t\tmethod->activate(args..., true);\n> +\t\treturn method->activate(args..., true);\n> \t}\n> \n> \tThread *thread() const { return thread_; }\n> diff --git a/src/libcamera/bound_method.cpp b/src/libcamera/bound_method.cpp\n> index 82339b7e9c95..8e95c7eec92c 100644\n> --- a/src/libcamera/bound_method.cpp\n> +++ b/src/libcamera/bound_method.cpp\n> @@ -48,7 +48,22 @@ namespace libcamera {\n> * deadlock will occur.\n> */\n> \n> -void BoundMethodBase::activatePack(std::shared_ptr pack,\n> +/**\n> + * \\brief Invoke the bound method with packed arguments\n> + * \\param[in] pack Packed arguments\n> + * \\param[in] deleteMethod True to delete \\a this bound method instance when\n> + * method invocation completes\n> + *\n> + * The bound method stores its return value, if any, in the arguments \\a pack.\n> + * For direct and blocking invocations, this is performed synchronously, and\n> + * the return value contained in the pack may be used. For queued invocations,\n> + * the return value is stored at an undefined point of time and shall thus not\n> + * be used by the caller.\n> + *\n> + * \\return True if the return value contained in the \\a pack may be used by the\n> + * caller, false otherwise\n> + */\n> +bool BoundMethodBase::activatePack(std::shared_ptr pack,\n> \t\t\t\t bool deleteMethod)\n> {\n> \tConnectionType type = connectionType_;\n> @@ -65,13 +80,13 @@ void BoundMethodBase::activatePack(std::shared_ptr pack,\n> \t\tinvokePack(pack.get());\n> \t\tif (deleteMethod)\n> \t\t\tdelete this;\n> -\t\tbreak;\n> +\t\treturn true;\n> \n> \tcase ConnectionTypeQueued: {\n> \t\tstd::unique_ptr msg =\n> \t\t\tutils::make_unique(this, pack, nullptr, deleteMethod);\n> \t\tobject_->postMessage(std::move(msg));\n> -\t\tbreak;\n> +\t\treturn false;\n> \t}\n> \n> \tcase ConnectionTypeBlocking: {\n> @@ -82,7 +97,7 @@ void BoundMethodBase::activatePack(std::shared_ptr pack,\n> \t\tobject_->postMessage(std::move(msg));\n> \n> \t\tsemaphore.acquire();\n> -\t\tbreak;\n> +\t\treturn true;\n> \t}\n> \t}\n> }\n> diff --git a/src/libcamera/object.cpp b/src/libcamera/object.cpp\n> index e76faf48b8ed..21aad5652b38 100644\n> --- a/src/libcamera/object.cpp\n> +++ b/src/libcamera/object.cpp\n> @@ -143,7 +143,7 @@ void Object::message(Message *msg)\n> }\n> \n> /**\n> - * \\fn void Object::invokeMethod()\n> + * \\fn R Object::invokeMethod()\n> * \\brief Invoke a method asynchronously on an Object instance\n> * \\param[in] func The object method to invoke\n> * \\param[in] type Connection type for method invocation\n> @@ -156,6 +156,10 @@ void Object::message(Message *msg)\n> * Arguments \\a args passed by value or reference are copied, while pointers\n> * are passed untouched. The caller shall ensure that any pointer argument\n> * remains valid until the method is invoked.\n> + *\n> + * \\return For connection types ConnectionTypeDirect and\n> + * ConnectionTypeBlocking, return the return value of the invoked method. For\n> + * connection type ConnectionTypeQueued, return a default-constructed R value.\n> */\n> \n> /**\n> -- \n> Regards,\n> \n> Laurent Pinchart\n> \n> _______________________________________________\n> libcamera-devel mailing list\n> libcamera-devel@lists.libcamera.org\n> https://lists.libcamera.org/listinfo/libcamera-devel","headers":{"Return-Path":"","Received":["from mail-lj1-x242.google.com (mail-lj1-x242.google.com\n\t[IPv6:2a00:1450:4864:20::242])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 77B6E6063B\n\tfor ;\n\tTue, 7 Jan 2020 20:57:08 +0100 (CET)","by mail-lj1-x242.google.com with SMTP id y6so889123lji.0\n\tfor ;\n\tTue, 07 Jan 2020 11:57:08 -0800 (PST)","from localhost (h-93-159.A463.priv.bahnhof.se. 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