mirror of
https://github.com/classilla/tenfourfox.git
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133 lines
4.4 KiB
C++
133 lines
4.4 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/*
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* An allocation policy concept, usable for structures and algorithms to
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* control how memory is allocated and how failures are handled.
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*/
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#ifndef mozilla_AllocPolicy_h
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#define mozilla_AllocPolicy_h
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#include "mozilla/TemplateLib.h"
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#include <stddef.h>
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#include <stdlib.h>
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namespace mozilla {
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/*
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* Allocation policies are used to implement the standard allocation behaviors
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* in a customizable way. Additionally, custom behaviors may be added to these
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* behaviors, such as additionally reporting an error through an out-of-band
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* mechanism when OOM occurs. The concept modeled here is as follows:
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*
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* - public copy constructor, assignment, destructor
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* - template <typename T> T* maybe_pod_malloc(size_t)
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* Fallible, but doesn't report an error on OOM.
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* - template <typename T> T* maybe_pod_calloc(size_t)
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* Fallible, but doesn't report an error on OOM.
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* - template <typename T> T* maybe_pod_realloc(T*, size_t, size_t)
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* Fallible, but doesn't report an error on OOM. The old allocation
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* size is passed in, in addition to the new allocation size requested.
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* - template <typename T> T* pod_malloc(size_t)
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* Responsible for OOM reporting when null is returned.
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* - template <typename T> T* pod_calloc(size_t)
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* Responsible for OOM reporting when null is returned.
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* - template <typename T> T* pod_realloc(T*, size_t, size_t)
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* Responsible for OOM reporting when null is returned. The old allocation
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* size is passed in, in addition to the new allocation size requested.
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* - void free_(void*)
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* - void reportAllocOverflow() const
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* Called on allocation overflow (that is, an allocation implicitly tried
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* to allocate more than the available memory space -- think allocating an
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* array of large-size objects, where N * size overflows) before null is
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* returned.
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* - bool checkSimulatedOOM() const
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* Some clients generally allocate memory yet in some circumstances won't
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* need to do so. For example, appending to a vector with a small amount of
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* inline storage generally allocates memory, but no allocation occurs
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* unless appending exceeds inline storage. But for testing purposes, it
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* can be useful to treat *every* operation as allocating.
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* Clients (such as this hypothetical append method implementation) should
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* call this method in situations that don't allocate, but could generally,
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* to support this. The default behavior should return true; more
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* complicated behavior might be to return false only after a certain
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* number of allocations-or-check-simulated-OOMs (coordinating with the
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* other AllocPolicy methods) have occurred.
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*
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* mfbt provides (and typically uses by default) only MallocAllocPolicy, which
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* does nothing more than delegate to the malloc/alloc/free functions.
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*/
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/*
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* A policy that straightforwardly uses malloc/calloc/realloc/free and adds no
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* extra behaviors.
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*/
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class MallocAllocPolicy
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{
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public:
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template <typename T>
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T* maybe_pod_malloc(size_t aNumElems)
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{
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if (aNumElems & mozilla::tl::MulOverflowMask<sizeof(T)>::value) {
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return nullptr;
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}
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return static_cast<T*>(malloc(aNumElems * sizeof(T)));
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}
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template <typename T>
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T* maybe_pod_calloc(size_t aNumElems)
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{
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return static_cast<T*>(calloc(aNumElems, sizeof(T)));
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}
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template <typename T>
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T* maybe_pod_realloc(T* aPtr, size_t aOldSize, size_t aNewSize)
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{
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if (aNewSize & mozilla::tl::MulOverflowMask<sizeof(T)>::value) {
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return nullptr;
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}
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return static_cast<T*>(realloc(aPtr, aNewSize * sizeof(T)));
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}
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template <typename T>
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T* pod_malloc(size_t aNumElems)
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{
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return maybe_pod_malloc<T>(aNumElems);
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}
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template <typename T>
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T* pod_calloc(size_t aNumElems)
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{
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return maybe_pod_calloc<T>(aNumElems);
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}
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template <typename T>
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T* pod_realloc(T* aPtr, size_t aOldSize, size_t aNewSize)
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{
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return maybe_pod_realloc<T>(aPtr, aOldSize, aNewSize);
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}
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void free_(void* aPtr)
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{
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free(aPtr);
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}
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void reportAllocOverflow() const
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{
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}
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bool checkSimulatedOOM() const
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{
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return true;
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}
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};
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} // namespace mozilla
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#endif /* mozilla_AllocPolicy_h */
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