| // Copyright 2014 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef GIN_FUNCTION_TEMPLATE_H_ |
| #define GIN_FUNCTION_TEMPLATE_H_ |
| |
| #include <stddef.h> |
| |
| #include "base/callback.h" |
| #include "base/logging.h" |
| #include "base/macros.h" |
| #include "gin/arguments.h" |
| #include "gin/converter.h" |
| #include "gin/gin_export.h" |
| #include "v8/include/v8.h" |
| |
| namespace gin { |
| |
| enum CreateFunctionTemplateFlags { |
| HolderIsFirstArgument = 1 << 0, |
| }; |
| |
| namespace internal { |
| |
| template<typename T> |
| struct CallbackParamTraits { |
| typedef T LocalType; |
| }; |
| template<typename T> |
| struct CallbackParamTraits<const T&> { |
| typedef T LocalType; |
| }; |
| template<typename T> |
| struct CallbackParamTraits<const T*> { |
| typedef T* LocalType; |
| }; |
| |
| |
| // CallbackHolder and CallbackHolderBase are used to pass a base::Callback from |
| // CreateFunctionTemplate through v8 (via v8::FunctionTemplate) to |
| // DispatchToCallback, where it is invoked. |
| |
| // This simple base class is used so that we can share a single object template |
| // among every CallbackHolder instance. |
| class GIN_EXPORT CallbackHolderBase { |
| public: |
| v8::Local<v8::External> GetHandle(v8::Isolate* isolate); |
| |
| protected: |
| explicit CallbackHolderBase(v8::Isolate* isolate); |
| virtual ~CallbackHolderBase(); |
| |
| private: |
| static void FirstWeakCallback( |
| const v8::WeakCallbackInfo<CallbackHolderBase>& data); |
| static void SecondWeakCallback( |
| const v8::WeakCallbackInfo<CallbackHolderBase>& data); |
| |
| v8::Global<v8::External> v8_ref_; |
| |
| DISALLOW_COPY_AND_ASSIGN(CallbackHolderBase); |
| }; |
| |
| template<typename Sig> |
| class CallbackHolder : public CallbackHolderBase { |
| public: |
| CallbackHolder(v8::Isolate* isolate, |
| const base::Callback<Sig>& callback, |
| int flags) |
| : CallbackHolderBase(isolate), callback(callback), flags(flags) {} |
| base::Callback<Sig> callback; |
| int flags; |
| private: |
| virtual ~CallbackHolder() {} |
| |
| DISALLOW_COPY_AND_ASSIGN(CallbackHolder); |
| }; |
| |
| template<typename T> |
| bool GetNextArgument(Arguments* args, int create_flags, bool is_first, |
| T* result) { |
| if (is_first && (create_flags & HolderIsFirstArgument) != 0) { |
| return args->GetHolder(result); |
| } else { |
| return args->GetNext(result); |
| } |
| } |
| |
| // For advanced use cases, we allow callers to request the unparsed Arguments |
| // object and poke around in it directly. |
| inline bool GetNextArgument(Arguments* args, int create_flags, bool is_first, |
| Arguments* result) { |
| *result = *args; |
| return true; |
| } |
| inline bool GetNextArgument(Arguments* args, int create_flags, bool is_first, |
| Arguments** result) { |
| *result = args; |
| return true; |
| } |
| |
| // It's common for clients to just need the isolate, so we make that easy. |
| inline bool GetNextArgument(Arguments* args, int create_flags, |
| bool is_first, v8::Isolate** result) { |
| *result = args->isolate(); |
| return true; |
| } |
| |
| // Classes for generating and storing an argument pack of integer indices |
| // (based on well-known "indices trick", see: http://goo.gl/bKKojn): |
| template <size_t... indices> |
| struct IndicesHolder {}; |
| |
| template <size_t requested_index, size_t... indices> |
| struct IndicesGenerator { |
| using type = typename IndicesGenerator<requested_index - 1, |
| requested_index - 1, |
| indices...>::type; |
| }; |
| template <size_t... indices> |
| struct IndicesGenerator<0, indices...> { |
| using type = IndicesHolder<indices...>; |
| }; |
| |
| // Class template for extracting and storing single argument for callback |
| // at position |index|. |
| template <size_t index, typename ArgType> |
| struct ArgumentHolder { |
| using ArgLocalType = typename CallbackParamTraits<ArgType>::LocalType; |
| |
| ArgLocalType value; |
| bool ok; |
| |
| ArgumentHolder(Arguments* args, int create_flags) |
| : ok(GetNextArgument(args, create_flags, index == 0, &value)) { |
| if (!ok) { |
| // Ideally we would include the expected c++ type in the error |
| // message which we can access via typeid(ArgType).name() |
| // however we compile with no-rtti, which disables typeid. |
| args->ThrowError(); |
| } |
| } |
| }; |
| |
| // Class template for converting arguments from JavaScript to C++ and running |
| // the callback with them. |
| template <typename IndicesType, typename... ArgTypes> |
| class Invoker {}; |
| |
| template <size_t... indices, typename... ArgTypes> |
| class Invoker<IndicesHolder<indices...>, ArgTypes...> |
| : public ArgumentHolder<indices, ArgTypes>... { |
| public: |
| // Invoker<> inherits from ArgumentHolder<> for each argument. |
| // C++ has always been strict about the class initialization order, |
| // so it is guaranteed ArgumentHolders will be initialized (and thus, will |
| // extract arguments from Arguments) in the right order. |
| Invoker(Arguments* args, int create_flags) |
| : ArgumentHolder<indices, ArgTypes>(args, create_flags)..., args_(args) { |
| // GCC thinks that create_flags is going unused, even though the |
| // expansion above clearly makes use of it. Per jyasskin@, casting |
| // to void is the commonly accepted way to convince the compiler |
| // that you're actually using a parameter/varible. |
| (void)create_flags; |
| } |
| |
| bool IsOK() { |
| return And(ArgumentHolder<indices, ArgTypes>::ok...); |
| } |
| |
| template <typename ReturnType> |
| void DispatchToCallback(base::Callback<ReturnType(ArgTypes...)> callback) { |
| args_->Return(callback.Run(ArgumentHolder<indices, ArgTypes>::value...)); |
| } |
| |
| // In C++, you can declare the function foo(void), but you can't pass a void |
| // expression to foo. As a result, we must specialize the case of Callbacks |
| // that have the void return type. |
| void DispatchToCallback(base::Callback<void(ArgTypes...)> callback) { |
| callback.Run(ArgumentHolder<indices, ArgTypes>::value...); |
| } |
| |
| private: |
| static bool And() { return true; } |
| template <typename... T> |
| static bool And(bool arg1, T... args) { |
| return arg1 && And(args...); |
| } |
| |
| Arguments* args_; |
| }; |
| |
| // DispatchToCallback converts all the JavaScript arguments to C++ types and |
| // invokes the base::Callback. |
| template <typename Sig> |
| struct Dispatcher {}; |
| |
| template <typename ReturnType, typename... ArgTypes> |
| struct Dispatcher<ReturnType(ArgTypes...)> { |
| static void DispatchToCallback( |
| const v8::FunctionCallbackInfo<v8::Value>& info) { |
| Arguments args(info); |
| v8::Local<v8::External> v8_holder; |
| CHECK(args.GetData(&v8_holder)); |
| CallbackHolderBase* holder_base = reinterpret_cast<CallbackHolderBase*>( |
| v8_holder->Value()); |
| |
| typedef CallbackHolder<ReturnType(ArgTypes...)> HolderT; |
| HolderT* holder = static_cast<HolderT*>(holder_base); |
| |
| using Indices = typename IndicesGenerator<sizeof...(ArgTypes)>::type; |
| Invoker<Indices, ArgTypes...> invoker(&args, holder->flags); |
| if (invoker.IsOK()) |
| invoker.DispatchToCallback(holder->callback); |
| } |
| }; |
| |
| } // namespace internal |
| |
| |
| // CreateFunctionTemplate creates a v8::FunctionTemplate that will create |
| // JavaScript functions that execute a provided C++ function or base::Callback. |
| // JavaScript arguments are automatically converted via gin::Converter, as is |
| // the return value of the C++ function, if any. |
| // |
| // NOTE: V8 caches FunctionTemplates for a lifetime of a web page for its own |
| // internal reasons, thus it is generally a good idea to cache the template |
| // returned by this function. Otherwise, repeated method invocations from JS |
| // will create substantial memory leaks. See http://crbug.com/463487. |
| template<typename Sig> |
| v8::Local<v8::FunctionTemplate> CreateFunctionTemplate( |
| v8::Isolate* isolate, const base::Callback<Sig> callback, |
| int callback_flags = 0) { |
| typedef internal::CallbackHolder<Sig> HolderT; |
| HolderT* holder = new HolderT(isolate, callback, callback_flags); |
| |
| v8::Local<v8::FunctionTemplate> tmpl = v8::FunctionTemplate::New( |
| isolate, &internal::Dispatcher<Sig>::DispatchToCallback, |
| ConvertToV8<v8::Local<v8::External>>(isolate, |
| holder->GetHandle(isolate))); |
| tmpl->RemovePrototype(); |
| return tmpl; |
| } |
| |
| // CreateFunctionHandler installs a CallAsFunction handler on the given |
| // object template that forwards to a provided C++ function or base::Callback. |
| template<typename Sig> |
| void CreateFunctionHandler(v8::Isolate* isolate, |
| v8::Local<v8::ObjectTemplate> tmpl, |
| const base::Callback<Sig> callback, |
| int callback_flags = 0) { |
| typedef internal::CallbackHolder<Sig> HolderT; |
| HolderT* holder = new HolderT(isolate, callback, callback_flags); |
| tmpl->SetCallAsFunctionHandler(&internal::Dispatcher<Sig>::DispatchToCallback, |
| ConvertToV8<v8::Local<v8::External> >( |
| isolate, holder->GetHandle(isolate))); |
| } |
| |
| } // namespace gin |
| |
| #endif // GIN_FUNCTION_TEMPLATE_H_ |