/* -*- 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/Attributes.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* maybe_pod_malloc(size_t) * Fallible, but doesn't report an error on OOM. * - template <typename T> T* maybe_pod_calloc(size_t) * Fallible, but doesn't report an error on OOM. * - template <typename T> T* maybe_pod_realloc(T*, size_t, size_t) * Fallible, but doesn't report an error on OOM. The old allocation * size is passed in, in addition to the new allocation size requested. * - 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. * - bool checkSimulatedOOM() const * Some clients generally allocate memory yet in some circumstances won't * need to do so. For example, appending to a vector with a small amount of * inline storage generally allocates memory, but no allocation occurs * unless appending exceeds inline storage. But for testing purposes, it * can be useful to treat *every* operation as allocating. * Clients (such as this hypothetical append method implementation) should * call this method in situations that don't allocate, but could generally, * to support this. The default behavior should return true; more * complicated behavior might be to return false only after a certain * number of allocations-or-check-simulated-OOMs (coordinating with the * other AllocPolicy methods) have occurred. * * 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* maybe_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* maybe_pod_calloc(size_t aNumElems) { return static_cast<T*>(calloc(aNumElems, sizeof(T))); } template <typename T> T* maybe_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))); } template <typename T> T* pod_malloc(size_t aNumElems) { return maybe_pod_malloc<T>(aNumElems); } template <typename T> T* pod_calloc(size_t aNumElems) { return maybe_pod_calloc<T>(aNumElems); } template <typename T> T* pod_realloc(T* aPtr, size_t aOldSize, size_t aNewSize) { return maybe_pod_realloc<T>(aPtr, aOldSize, aNewSize); } void free_(void* aPtr) { free(aPtr); } void reportAllocOverflow() const { } MOZ_MUST_USE bool checkSimulatedOOM() const { return true; } }; } // namespace mozilla #endif /* mozilla_AllocPolicy_h */