100 lines
3.9 KiB
C++
100 lines
3.9 KiB
C++
// Filename: deletedChain.h
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// Created by: drose (01Apr06)
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//
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////////////////////////////////////////////////////////////////////
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//
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// PANDA 3D SOFTWARE
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// Copyright (c) 2001 - 2004, Disney Enterprises, Inc. All rights reserved
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//
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// All use of this software is subject to the terms of the Panda 3d
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// Software license. You should have received a copy of this license
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// along with this source code; you will also find a current copy of
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// the license at http://etc.cmu.edu/panda3d/docs/license/ .
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//
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// To contact the maintainers of this program write to
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// panda3d-general@lists.sourceforge.net .
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//
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////////////////////////////////////////////////////////////////////
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#ifndef DELETEDCHAIN_H
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#define DELETEDCHAIN_H
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#include "dtoolbase.h"
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#include "mutexImpl.h"
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#include "atomicAdjust.h"
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#include <assert.h>
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////////////////////////////////////////////////////////////////////
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// Class : DeletedChain
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// Description : This template class can be used to provide faster
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// allocation/deallocation for many Panda objects. It
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// works by maintaining a linked list of deleted objects
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// that are all of the same type; when a new object is
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// allocated that matches that type, the same space is
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// just reused.
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//
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// This is particularly important to do in the case of a
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// multithreaded pipeline, so we minimize contention
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// between the parallel threads. If we didn't do this,
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// the threads might compete overmuch on the system
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// mutex protecting the malloc() call. This way, there
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// can be a different mutex for each type of object; or on
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// some systems (e.g. i386), no mutex at all.
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//
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// Of course, this trick of maintaining the deleted
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// object chain won't work in the presence of
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// polymorphism, where you might have many classes that
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// derive from a base class, and all of them have a
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// different size--unless you instantiate a DeletedChain
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// for *every* kind of derived class. The
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// ALLOC_DELETED_CHAIN macro, below, is designed to make
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// this easy.
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////////////////////////////////////////////////////////////////////
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template<class Type>
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class DeletedChain {
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public:
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INLINE static Type *allocate(size_t size);
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INLINE static void deallocate(Type *ptr);
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private:
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class ObjectNode {
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public:
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ObjectNode *_next;
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};
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// Ideally, the compiler and linker will unify all references to
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// this static pointer for a given type, as per the C++ spec.
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// However, if the compiler fails to do this (*cough* Microsoft), it
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// won't be a big deal; it just means there will be multiple
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// unrelated chains of deleted objects for a particular type.
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static ObjectNode *_deleted_chain;
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#ifndef HAVE_ATOMIC_COMPARE_AND_EXCHANGE_PTR
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// If we don't have atomic compare-and-exchange, we need to use a
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// Mutex to protect the above linked list.
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static MutexImpl _lock;
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#endif
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};
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// Place this macro within a class definition to define appropriate
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// operator new and delete methods that take advantage of
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// DeletedChain.
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#define ALLOC_DELETED_CHAIN(Type) \
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inline void *operator new(size_t size) { \
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return (void *)DeletedChain< Type >::allocate(size); \
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} \
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inline void *operator new(size_t size, void *ptr) { \
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return ptr; \
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} \
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inline void operator delete(void *ptr) { \
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DeletedChain< Type >::deallocate((Type *)ptr); \
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} \
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inline void operator delete(void *, void *) { \
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}
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#include "deletedChain.T"
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#endif
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