[gin] Use variadic templates in gin/function_template.h

gin/function_template.h.pump

-$$ This is a pump file for generating file templates.  Pump is a python
-$$ script that is part of the Google Test suite of utilities.  Description
-$$ can be found here:
-$$
-$$ http://code.google.com/p/googletest/wiki/PumpManual
-$$
-
-#ifndef GIN_FUNCTION_TEMPLATE_H_
-#define GIN_FUNCTION_TEMPLATE_H_
-
-$var MAX_ARITY = 6
-
-// Copyright 2013 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 "base/callback.h"
-#include "base/logging.h"
-#include "gin/arguments.h"
-#include "gin/converter.h"
-#include "gin/gin_export.h"
-#include "v8/include/v8.h"
-
-namespace gin {
-
-class PerIsolateData;
-
-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::Handle<v8::External> GetHandle(v8::Isolate* isolate);
-
- protected:
-  explicit CallbackHolderBase(v8::Isolate* isolate);
-  virtual ~CallbackHolderBase();
-
- private:
-  static void WeakCallback(
-      const v8::WeakCallbackData<v8::External, CallbackHolderBase>& data);
-
-  v8::Persistent<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);
-};
-
-
-// This set of templates invokes a base::Callback, converts the return type to a
-// JavaScript value, and returns that value to script via the provided
-// gin::Arguments object.
-//
-// 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.
-
-$range ARITY 0..MAX_ARITY
-$for ARITY [[
-$var INV_ARITY = MAX_ARITY - ARITY
-$range ARG 1..INV_ARITY
-$range VOID INV_ARITY+1..MAX_ARITY
-
-$if ARITY == 0 [[
-template<typename R$for ARG [[, typename P$(ARG) = void]]>
-struct Invoker {
-]] $else [[
-template<typename R$for ARG [[, typename P$(ARG)]]>
-struct Invoker<R$for ARG [[, P$(ARG)]]$for VOID [[, void]]> {
-]]
-
-  inline static void Go(
-      Arguments* args,
-      const base::Callback<R($for ARG , [[P$(ARG)]])>& callback$for ARG [[, 
-      const P$(ARG)& a$(ARG)]]) {
-    args->Return(callback.Run($for ARG, [[a$(ARG)]]));
-  }
-};
-template<$for ARG , [[typename P$(ARG)]]>
-struct Invoker<void$for ARG [[, P$(ARG)]]$for VOID [[, void]]> {
-  inline static void Go(
-      Arguments* args,
-      const base::Callback<void($for ARG , [[P$(ARG)]])>& callback$for ARG [[,
-      const P$(ARG)& a$(ARG)]]) {
-    callback.Run($for ARG, [[a$(ARG)]]);
-  }
-};
-
-
-]]
-
-template<typename T>
-bool GetNextArgument(Arguments* args, int create_flags, bool is_first,
-                     T* result) {
-  if (is_first && (create_flags & HolderIsFirstArgument) != 0) {
-    return args->GetHolder(result);
-  } else {
-    return args->GetNext(result);
-  }
-}
-
-// For advanced use cases, we allow callers to request the unparsed Arguments
-// object and poke around in it directly.
-inline bool GetNextArgument(Arguments* args, int create_flags, bool is_first,
-                            Arguments* result) {
-  *result = *args;
-  return true;
-}
-inline bool GetNextArgument(Arguments* args, int create_flags, bool is_first,
-                            Arguments** result) {
-  *result = args;
-  return true;
-}
-
-// It's common for clients to just need the isolate, so we make that easy.
-inline bool GetNextArgument(Arguments* args, int create_flags,
-                            bool is_first, v8::Isolate** result) {
-  *result = args->isolate();
-  return true;
-}
-
-
-// DispatchToCallback converts all the JavaScript arguments to C++ types and
-// invokes the base::Callback.
-template<typename Sig>
-struct Dispatcher {
-};
-
-$range ARITY 0..MAX_ARITY
-$for ARITY [[
-$range ARG 1..ARITY
-
-template<typename R$for ARG [[, typename P$(ARG)]]>
-struct Dispatcher<R($for ARG , [[P$(ARG)]])> {
-  static void DispatchToCallback(
-      const v8::FunctionCallbackInfo<v8::Value>& info) {
-    Arguments args(info);
-    v8::Handle<v8::External> v8_holder;
-    CHECK(args.GetData(&v8_holder));
-    CallbackHolderBase* holder_base = reinterpret_cast<CallbackHolderBase*>(
-        v8_holder->Value());
-
-    typedef CallbackHolder<R($for ARG , [[P$(ARG)]])> HolderT;
-    HolderT* holder = static_cast<HolderT*>(holder_base);
-
-$if ARITY != 0 [[
-
-
-$for ARG [[    typename CallbackParamTraits<P$(ARG)>::LocalType a$(ARG);
-
-]]
-    if ($for ARG  ||
-        [[!GetNextArgument(&args, holder->flags, $if ARG == 1 [[true]] $else [[false]], &a$(ARG))]]) {
-      args.ThrowError();
-      return;
-    }
-
-]]
-
-    Invoker<R$for ARG [[, P$(ARG)]]>::Go(&args, holder->callback$for ARG [[, a$(ARG)]]);
-  }
-};
-
-]]
-
-}  // 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.
-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);
-
-  return v8::FunctionTemplate::New(
-      isolate,
-      &internal::Dispatcher<Sig>::DispatchToCallback,
-      ConvertToV8<v8::Handle<v8::External> >(isolate,
-                                             holder->GetHandle(isolate)));
-}
-
-// 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::Handle<v8::External> >(
-                                     isolate, holder->GetHandle(isolate)));
-}
-
-}  // namespace gin
-
-#endif  // GIN_FUNCTION_TEMPLATE_H_