mozglue/misc/DynamicallyLinkedFunctionPtr.h
author Emilio Cobos Álvarez <emilio@crisal.io>
Tue, 02 Jul 2019 18:50:04 +0000
changeset 480995 6525ac41c35455512bc1b681df331a5b74cb75cc
parent 448947 6f3709b3878117466168c40affa7bca0b60cf75b
child 486767 f1c97ef1f9cb83b8a70882ce7047d44e13d8c248
permissions -rw-r--r--
Bug 1562789 - SmallPointerArray should support moves, and have an IsEmpty() helper. r=froydnj This also implicitly deletes its copy-assignment operator and copy-constructor, which is great since it's a huge footgun. Differential Revision: https://phabricator.services.mozilla.com/D36549

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef mozilla_DynamicallyLinkedFunctionPtr_h
#define mozilla_DynamicallyLinkedFunctionPtr_h

#include "mozilla/Move.h"
#include <windows.h>

namespace mozilla {

template <typename T>
class DynamicallyLinkedFunctionPtr;

template <typename R, typename... Args>
class DynamicallyLinkedFunctionPtr<R(__stdcall*)(Args...)> {
  typedef R(__stdcall* FunctionPtrT)(Args...);

 public:
  DynamicallyLinkedFunctionPtr(const wchar_t* aLibName, const char* aFuncName)
      : mModule(NULL), mFunction(nullptr) {
    mModule = ::LoadLibraryW(aLibName);
    if (mModule) {
      mFunction =
          reinterpret_cast<FunctionPtrT>(::GetProcAddress(mModule, aFuncName));

      if (!mFunction) {
        // Since the function doesn't exist, there is no point in holding a
        // reference to mModule anymore.
        ::FreeLibrary(mModule);
        mModule = NULL;
      }
    }
  }

  DynamicallyLinkedFunctionPtr(const DynamicallyLinkedFunctionPtr&) = delete;
  DynamicallyLinkedFunctionPtr& operator=(const DynamicallyLinkedFunctionPtr&) =
      delete;

  DynamicallyLinkedFunctionPtr(DynamicallyLinkedFunctionPtr&&) = delete;
  DynamicallyLinkedFunctionPtr& operator=(DynamicallyLinkedFunctionPtr&&) =
      delete;

  ~DynamicallyLinkedFunctionPtr() {
    if (mModule) {
      ::FreeLibrary(mModule);
    }
  }

  R operator()(Args... args) const {
    return mFunction(std::forward<Args>(args)...);
  }

  explicit operator bool() const { return !!mFunction; }

 private:
  HMODULE mModule;
  FunctionPtrT mFunction;
};

}  // namespace mozilla

#endif  // mozilla_DynamicallyLinkedFunctionPtr_h