michael@0: /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* vim: set ts=8 sts=2 et sw=2 tw=80: */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: /*
michael@0:  * An allocation policy concept, usable for structures and algorithms to
michael@0:  * control how memory is allocated and how failures are handled.
michael@0:  */
michael@0: 
michael@0: #ifndef mozilla_AllocPolicy_h
michael@0: #define mozilla_AllocPolicy_h
michael@0: 
michael@0: #include <stddef.h>
michael@0: #include <stdlib.h>
michael@0: 
michael@0: namespace mozilla {
michael@0: 
michael@0: /*
michael@0:  * Allocation policies are used to implement the standard allocation behaviors
michael@0:  * in a customizable way.  Additionally, custom behaviors may be added to these
michael@0:  * behaviors, such as additionally reporting an error through an out-of-band
michael@0:  * mechanism when OOM occurs.  The concept modeled here is as follows:
michael@0:  *
michael@0:  *  - public copy constructor, assignment, destructor
michael@0:  *  - void* malloc_(size_t)
michael@0:  *      Responsible for OOM reporting when null is returned.
michael@0:  *  - void* calloc_(size_t)
michael@0:  *      Responsible for OOM reporting when null is returned.
michael@0:  *  - void* realloc_(void*, size_t, size_t)
michael@0:  *      Responsible for OOM reporting when null is returned.  The *used* bytes
michael@0:  *      of the previous buffer is passed in (rather than the old allocation
michael@0:  *      size), in addition to the *new* allocation size requested.
michael@0:  *  - void free_(void*)
michael@0:  *  - void reportAllocOverflow() const
michael@0:  *      Called on allocation overflow (that is, an allocation implicitly tried
michael@0:  *      to allocate more than the available memory space -- think allocating an
michael@0:  *      array of large-size objects, where N * size overflows) before null is
michael@0:  *      returned.
michael@0:  *
michael@0:  * mfbt provides (and typically uses by default) only MallocAllocPolicy, which
michael@0:  * does nothing more than delegate to the malloc/alloc/free functions.
michael@0:  */
michael@0: 
michael@0: /*
michael@0:  * A policy that straightforwardly uses malloc/calloc/realloc/free and adds no
michael@0:  * extra behaviors.
michael@0:  */
michael@0: class MallocAllocPolicy
michael@0: {
michael@0:   public:
michael@0:     void* malloc_(size_t bytes) { return malloc(bytes); }
michael@0:     void* calloc_(size_t bytes) { return calloc(bytes, 1); }
michael@0:     void* realloc_(void* p, size_t oldBytes, size_t bytes) { return realloc(p, bytes); }
michael@0:     void free_(void* p) { free(p); }
michael@0:     void reportAllocOverflow() const {}
michael@0: };
michael@0: 
michael@0: 
michael@0: } // namespace mozilla
michael@0: 
michael@0: #endif /* mozilla_AllocPolicy_h */