blob: a4c22f2f96eed4eadf17c26a1ea613de0dde2d4c [file] [log] [blame]
// 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.
#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 {
v8::Local<v8::External> GetHandle(v8::Isolate* isolate);
explicit CallbackHolderBase(v8::Isolate* isolate);
virtual ~CallbackHolderBase();
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 {
CallbackHolder(v8::Isolate* isolate,
const base::Callback<Sig>& callback,
int flags)
: CallbackHolderBase(isolate), callback(callback), flags(flags) {}
base::Callback<Sig> callback;
int flags;
virtual ~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:
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,
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.
// 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>... {
// 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.
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...);
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;
CallbackHolderBase* holder_base = reinterpret_cast<CallbackHolderBase*>(
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())
} // 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
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,
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);
ConvertToV8<v8::Local<v8::External> >(
isolate, holder->GetHandle(isolate)));
} // namespace gin