gecko/mfbt/AllocPolicy.h

64 lines
2.3 KiB
C++

/* -*- 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 <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
* - void* malloc_(size_t)
* Responsible for OOM reporting when null is returned.
* - void* calloc_(size_t)
* Responsible for OOM reporting when null is returned.
* - void* realloc_(void*, size_t, size_t)
* Responsible for OOM reporting when null is returned. The *used* bytes
* of the previous buffer is passed in (rather than the old allocation
* size), 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:
void* malloc_(size_t bytes) { return malloc(bytes); }
void* calloc_(size_t bytes) { return calloc(bytes, 1); }
void* realloc_(void* p, size_t oldBytes, size_t bytes) { return realloc(p, bytes); }
void free_(void* p) { free(p); }
void reportAllocOverflow() const {}
};
} // namespace mozilla
#endif /* mozilla_AllocPolicy_h */