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- // 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 <utility>
- #include "base/callback.h"
- #include "base/check.h"
- #include "base/memory/raw_ptr.h"
- #include "base/strings/strcat.h"
- #include "gin/arguments.h"
- #include "gin/converter.h"
- #include "gin/gin_export.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.
- // 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:
- static void FirstWeakCallback(
- const v8::WeakCallbackInfo<CallbackHolderBase>& data);
- static void SecondWeakCallback(
- const v8::WeakCallbackInfo<CallbackHolderBase>& data);
- v8::Global<v8::External> v8_ref_;
- };
- 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>
- 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);
- }
- };
- // 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.
- 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_
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