mfbt/AllocPolicy.h
author Boris Zbarsky <bzbarsky@mit.edu>
Wed, 24 Jun 2015 00:42:46 -0700
changeset 250045 4267b74ee795e8127ffce4d45d00384cd8170130
parent 223144 3928ee1b0381453833c00fbe1e1b72a26143f13a
child 265171 b75024c49a129410f8414f73cb4dfd914d0041ee
permissions -rw-r--r--
Bug 1176083. Remove the now-dead code for the XPCOM version of setTimeout/setInterval. r=smaug I claim this code is dead because on the one hand it's no longer called from JS (because Window is always on WebIDL bindings, but on the other hand it can't really be called from C++ because it depends on examining the XPConnect call information. I think removing this completely, including from the IDL, is safe, because nothing directly returns nsIDOMJSWindow, so anyone using its vtable would have to QI to it and we're changing the IID.

/* -*- 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/. */

/*
 * An allocation policy concept, usable for structures and algorithms to
 * control how memory is allocated and how failures are handled.
 */

#ifndef mozilla_AllocPolicy_h
#define mozilla_AllocPolicy_h

#include "mozilla/TemplateLib.h"

#include <stddef.h>
#include <stdlib.h>

namespace mozilla {

/*
 * Allocation policies are used to implement the standard allocation behaviors
 * in a customizable way.  Additionally, custom behaviors may be added to these
 * behaviors, such as additionally reporting an error through an out-of-band
 * mechanism when OOM occurs.  The concept modeled here is as follows:
 *
 *  - public copy constructor, assignment, destructor
 *  - template <typename T> T* pod_malloc(size_t)
 *      Responsible for OOM reporting when null is returned.
 *  - template <typename T> T* pod_calloc(size_t)
 *      Responsible for OOM reporting when null is returned.
 *  - template <typename T> T* pod_realloc(T*, size_t, size_t)
 *      Responsible for OOM reporting when null is returned.  The old allocation
 *      size is passed in, in addition to the new allocation size requested.
 *  - void free_(void*)
 *  - void reportAllocOverflow() const
 *      Called on allocation overflow (that is, an allocation implicitly tried
 *      to allocate more than the available memory space -- think allocating an
 *      array of large-size objects, where N * size overflows) before null is
 *      returned.
 *
 * mfbt provides (and typically uses by default) only MallocAllocPolicy, which
 * does nothing more than delegate to the malloc/alloc/free functions.
 */

/*
 * A policy that straightforwardly uses malloc/calloc/realloc/free and adds no
 * extra behaviors.
 */
class MallocAllocPolicy
{
public:
  template <typename T>
  T* pod_malloc(size_t aNumElems)
  {
    if (aNumElems & mozilla::tl::MulOverflowMask<sizeof(T)>::value) {
      return nullptr;
    }
    return static_cast<T*>(malloc(aNumElems * sizeof(T)));
  }

  template <typename T>
  T* pod_calloc(size_t aNumElems)
  {
    return static_cast<T*>(calloc(aNumElems, sizeof(T)));
  }

  template <typename T>
  T* pod_realloc(T* aPtr, size_t aOldSize, size_t aNewSize)
  {
    if (aNewSize & mozilla::tl::MulOverflowMask<sizeof(T)>::value) {
      return nullptr;
    }
    return static_cast<T*>(realloc(aPtr, aNewSize * sizeof(T)));
  }

  void free_(void* aPtr)
  {
    free(aPtr);
  }

  void reportAllocOverflow() const
  {
  }
};

} // namespace mozilla

#endif /* mozilla_AllocPolicy_h */