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88 lines
2.7 KiB
C++
88 lines
2.7 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/NullPtr.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* 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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* - void* realloc_(void*, size_t, size_t)
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* Responsible for OOM reporting when null is returned. The *used* bytes
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* of the previous buffer is passed in (rather than the old allocation
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* size), 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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*
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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* 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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return static_cast<T*>(malloc(aNumElems * sizeof(T)));
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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 static_cast<T*>(calloc(aNumElems, sizeof(T)));
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}
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void* realloc_(void* aPtr, size_t aOldBytes, size_t aBytes)
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{
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return realloc(aPtr, aBytes);
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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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};
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} // namespace mozilla
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#endif /* mozilla_AllocPolicy_h */
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