| // Copyright 2014 The Chromium Authors |
| // 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 <type_traits> |
| #include <utility> |
| |
| #include "base/check.h" |
| #include "base/functional/callback.h" |
| #include "base/memory/raw_ptr.h" |
| #include "base/observer_list.h" |
| #include "base/strings/strcat.h" |
| #include "gin/arguments.h" |
| #include "gin/converter.h" |
| #include "gin/gin_export.h" |
| #include "gin/per_isolate_data.h" |
| #include "v8/include/v8-external.h" |
| #include "v8/include/v8-forward.h" |
| #include "v8/include/v8-persistent-handle.h" |
| #include "v8/include/v8-template.h" |
| |
| namespace gin { |
| |
| struct InvokerOptions { |
| bool holder_is_first_argument = false; |
| const char* holder_type = nullptr; // Null if unknown or not applicable. |
| }; |
| |
| 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::RepeatingCallback from CreateFunctionTemplate through v8 (via |
| // v8::FunctionTemplate) to DispatchToCallback, where it is invoked. |
| |
| // CallbackHolder will clean up the callback in two different scenarios: |
| // - If the garbage collector finds that it's garbage and collects it. (But note |
| // that even _if_ we become garbage, we might never get collected!) |
| // - If the isolate gets disposed. |
| // |
| // TODO(crbug.com/40210365): When gin::Wrappable gets migrated over to using |
| // cppgc, this class should also be considered for migration. |
| |
| // This simple base class is used so that we can share a single object template |
| // among every CallbackHolder instance. |
| class GIN_EXPORT CallbackHolderBase { |
| public: |
| CallbackHolderBase(const CallbackHolderBase&) = delete; |
| CallbackHolderBase& operator=(const CallbackHolderBase&) = delete; |
| |
| v8::Local<v8::External> GetHandle(v8::Isolate* isolate); |
| |
| protected: |
| explicit CallbackHolderBase(v8::Isolate* isolate); |
| virtual ~CallbackHolderBase(); |
| |
| private: |
| class DisposeObserver : gin::PerIsolateData::DisposeObserver { |
| public: |
| DisposeObserver(gin::PerIsolateData* per_isolate_data, |
| CallbackHolderBase* holder); |
| ~DisposeObserver() override; |
| void OnBeforeDispose(v8::Isolate* isolate) override; |
| void OnDisposed() override; |
| |
| private: |
| const raw_ref<gin::PerIsolateData> per_isolate_data_; |
| const raw_ref<CallbackHolderBase> holder_; |
| }; |
| |
| static void FirstWeakCallback( |
| const v8::WeakCallbackInfo<CallbackHolderBase>& data); |
| static void SecondWeakCallback( |
| const v8::WeakCallbackInfo<CallbackHolderBase>& data); |
| |
| v8::Global<v8::External> v8_ref_; |
| DisposeObserver dispose_observer_; |
| }; |
| |
| template<typename Sig> |
| class CallbackHolder : public CallbackHolderBase { |
| public: |
| CallbackHolder(v8::Isolate* isolate, |
| base::RepeatingCallback<Sig> callback, |
| InvokerOptions invoker_options) |
| : CallbackHolderBase(isolate), |
| callback(std::move(callback)), |
| invoker_options(std::move(invoker_options)) {} |
| CallbackHolder(const CallbackHolder&) = delete; |
| CallbackHolder& operator=(const CallbackHolder&) = delete; |
| |
| base::RepeatingCallback<Sig> callback; |
| InvokerOptions invoker_options; |
| |
| private: |
| ~CallbackHolder() override = default; |
| }; |
| |
| template <typename T> |
| bool GetNextArgument(Arguments* args, |
| const InvokerOptions& invoker_options, |
| bool is_first, |
| T* result) { |
| if (is_first && invoker_options.holder_is_first_argument) { |
| 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, |
| const InvokerOptions& invoker_options, |
| bool is_first, |
| Arguments* result) { |
| *result = *args; |
| return true; |
| } |
| inline bool GetNextArgument(Arguments* args, |
| const InvokerOptions& invoker_options, |
| 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, |
| const InvokerOptions& invoker_options, |
| bool is_first, |
| v8::Isolate** result) { |
| *result = args->isolate(); |
| return true; |
| } |
| |
| // Throws an error indicating conversion failure. |
| GIN_EXPORT void ThrowConversionError(Arguments* args, |
| const InvokerOptions& invoker_options, |
| size_t index); |
| |
| // Class template for extracting and storing single argument for callback |
| // at position |index|. |
| template <size_t index, typename ArgType, typename = void> |
| struct ArgumentHolder { |
| using ArgLocalType = typename CallbackParamTraits<ArgType>::LocalType; |
| |
| ArgLocalType value; |
| bool ok; |
| |
| ArgumentHolder(Arguments* args, const InvokerOptions& invoker_options) |
| : ok(GetNextArgument(args, invoker_options, index == 0, &value)) { |
| if (!ok) |
| ThrowConversionError(args, invoker_options, index); |
| } |
| }; |
| |
| // This is required for types such as v8::LocalVector<T>, which don't have |
| // a default constructor. To create an element of such a type, the isolate |
| // has to be provided. |
| template <size_t index, typename ArgType> |
| struct ArgumentHolder< |
| index, |
| ArgType, |
| std::enable_if_t<!std::is_default_constructible_v< |
| typename CallbackParamTraits<ArgType>::LocalType> && |
| std::is_constructible_v< |
| typename CallbackParamTraits<ArgType>::LocalType, |
| v8::Isolate*>>> { |
| using ArgLocalType = typename CallbackParamTraits<ArgType>::LocalType; |
| |
| ArgLocalType value; |
| bool ok; |
| |
| ArgumentHolder(Arguments* args, const InvokerOptions& invoker_options) |
| : value(args->isolate()), |
| ok(GetNextArgument(args, invoker_options, index == 0, &value)) { |
| if (!ok) { |
| ThrowConversionError(args, invoker_options, index); |
| } |
| } |
| }; |
| |
| // 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<std::index_sequence<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, const InvokerOptions& invoker_options) |
| : ArgumentHolder<indices, ArgTypes>(args, invoker_options)..., |
| args_(args) {} |
| |
| bool IsOK() { |
| return And(ArgumentHolder<indices, ArgTypes>::ok...); |
| } |
| |
| template <typename ReturnType> |
| void DispatchToCallback( |
| base::RepeatingCallback<ReturnType(ArgTypes...)> callback) { |
| args_->Return( |
| callback.Run(std::move(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::RepeatingCallback<void(ArgTypes...)> callback) { |
| callback.Run(std::move(ArgumentHolder<indices, ArgTypes>::value)...); |
| } |
| |
| private: |
| static bool And() { return true; } |
| template <typename... T> |
| static bool And(bool arg1, T... args) { |
| return arg1 && And(args...); |
| } |
| |
| raw_ptr<Arguments> args_; |
| }; |
| |
| // DispatchToCallback converts all the JavaScript arguments to C++ types and |
| // invokes the base::RepeatingCallback. |
| template <typename Sig> |
| struct Dispatcher {}; |
| |
| template <typename ReturnType, typename... ArgTypes> |
| struct Dispatcher<ReturnType(ArgTypes...)> { |
| static void DispatchToCallbackImpl(Arguments* args) { |
| 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 = std::index_sequence_for<ArgTypes...>; |
| Invoker<Indices, ArgTypes...> invoker(args, holder->invoker_options); |
| if (invoker.IsOK()) |
| invoker.DispatchToCallback(holder->callback); |
| } |
| |
| static void DispatchToCallback( |
| const v8::FunctionCallbackInfo<v8::Value>& info) { |
| Arguments args(info); |
| DispatchToCallbackImpl(&args); |
| } |
| |
| static void DispatchToCallbackForProperty( |
| v8::Local<v8::Name>, |
| const v8::PropertyCallbackInfo<v8::Value>& info) { |
| Arguments args(info); |
| DispatchToCallbackImpl(&args); |
| } |
| }; |
| |
| } // namespace internal |
| |
| // CreateFunctionTemplate creates a v8::FunctionTemplate that will create |
| // JavaScript functions that execute a provided C++ function or |
| // base::RepeatingCallback. JavaScript arguments are automatically converted via |
| // gin::Converter, as is the return value of the C++ function, if any. |
| // |invoker_options| contains additional parameters. If it contains a |
| // holder_type, it will be used to provide a useful conversion error if the |
| // holder is the first argument. If not provided, a generic invocation error |
| // will be used. |
| // |
| // 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. |
| // |
| // The callback will be destroyed if either the function template gets garbage |
| // collected or _after_ the isolate is disposed. Garbage collection can never be |
| // relied upon. As such, any destructors for objects bound to the callback must |
| // not depend on the isolate being alive at the point they are called. The order |
| // in which callbacks are destroyed is not guaranteed. |
| template <typename Sig> |
| v8::Local<v8::FunctionTemplate> CreateFunctionTemplate( |
| v8::Isolate* isolate, |
| base::RepeatingCallback<Sig> callback, |
| InvokerOptions invoker_options = {}) { |
| typedef internal::CallbackHolder<Sig> HolderT; |
| HolderT* holder = |
| new HolderT(isolate, std::move(callback), std::move(invoker_options)); |
| |
| v8::Local<v8::FunctionTemplate> tmpl = v8::FunctionTemplate::New( |
| isolate, &internal::Dispatcher<Sig>::DispatchToCallback, |
| ConvertToV8<v8::Local<v8::External>>(isolate, holder->GetHandle(isolate)), |
| v8::Local<v8::Signature>(), 0, v8::ConstructorBehavior::kThrow); |
| return tmpl; |
| } |
| |
| // CreateDataPropertyCallback creates a v8::AccessorNameGetterCallback and |
| // corresponding data value that will hold and execute the provided |
| // base::RepeatingCallback, using automatic conversions similar to |
| // |CreateFunctionTemplate|. |
| // |
| // It is expected that these will be passed to v8::Template::SetLazyDataProperty |
| // or another similar function. |
| template <typename Sig> |
| std::pair<v8::AccessorNameGetterCallback, v8::Local<v8::Value>> |
| CreateDataPropertyCallback(v8::Isolate* isolate, |
| base::RepeatingCallback<Sig> callback, |
| InvokerOptions invoker_options = {}) { |
| typedef internal::CallbackHolder<Sig> HolderT; |
| HolderT* holder = |
| new HolderT(isolate, std::move(callback), std::move(invoker_options)); |
| return {&internal::Dispatcher<Sig>::DispatchToCallbackForProperty, |
| ConvertToV8<v8::Local<v8::External>>(isolate, |
| holder->GetHandle(isolate))}; |
| } |
| |
| } // namespace gin |
| |
| #endif // GIN_FUNCTION_TEMPLATE_H_ |