зеркало из https://github.com/mozilla/pjs.git
169 строки
5.7 KiB
C++
169 строки
5.7 KiB
C++
/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* ***** BEGIN LICENSE BLOCK *****
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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*
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* The contents of this file are subject to the Mozilla Public License Version
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* 1.1 (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is mozilla.org code.
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*
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* The Initial Developer of the Original Code is
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* Netscape Communications Corporation.
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* Portions created by the Initial Developer are Copyright (C) 2001, 2002
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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* Suresh Duddi <dp@netscape.com>
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*
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* Alternatively, the contents of this file may be used under the terms of
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* either the GNU General Public License Version 2 or later (the "GPL"), or
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* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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* in which case the provisions of the GPL or the LGPL are applicable instead
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* of those above. If you wish to allow use of your version of this file only
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* under the terms of either the GPL or the LGPL, and not to allow others to
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* use your version of this file under the terms of the MPL, indicate your
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* decision by deleting the provisions above and replace them with the notice
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* and other provisions required by the GPL or the LGPL. If you do not delete
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* the provisions above, a recipient may use your version of this file under
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* the terms of any one of the MPL, the GPL or the LGPL.
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*
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* ***** END LICENSE BLOCK ***** */
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/*
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* nsRecyclingAllocator
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*
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* This allocator is useful when we cycle through a small set of allocations
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* repeatedly with minimal overlap. For eg. something we do for every gif
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* file read (or) buffers required for decompression of every file from jar.
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*
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* What this does is keeps around the first set of memory allocated and
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* reuses it subsequently. If all buckets are full, this falls back to
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* malloc/free
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*
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* Uses a timer to release all memory allocated if not used for more than
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* 10 secs automatically.
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*
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* Also there is a 4 byte maintenance overhead on every allocation.
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*
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* This allocator is thread safe.
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*
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* CAVEATS: As the number of buckets increases, this allocators performance
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* will drop, as the list of freed items is a linked list sorted on size.
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*/
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#ifndef nsRecyclingAllocator_h__
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#define nsRecyclingAllocator_h__
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#include "mozilla/Mutex.h"
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#include "nscore.h"
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#include "nsIRecyclingAllocator.h"
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#define NS_DEFAULT_RECYCLE_TIMEOUT 10 // secs
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#define NS_ALLOCATOR_OVERHEAD_BYTES (sizeof(PRSize)) // bytes
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class nsITimer;
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class nsIMemory;
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class nsRecyclingAllocator {
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protected:
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struct Block {
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PRSize bytes;
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Block *next;
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};
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#define DATA(block) ((void *)(((char *)block) + NS_ALLOCATOR_OVERHEAD_BYTES))
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#define DATA_TO_BLOCK(data) ((Block *)((char *)(data) - NS_ALLOCATOR_OVERHEAD_BYTES))
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// mMaxBlocks: Maximum number of blocks that are kept in the mFreeList for recycling
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PRUint32 mMaxBlocks;
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// mFreeListCount: Current number of blocks in the mFreeList
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PRUint32 mFreeListCount;
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// mFreeList: linked list of free blocks sorted by increasing order of size
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Block* mFreeList;
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// mLock: Thread safety for the member variables:
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// mFreeList, mFreeListCount, mRecycleTimer, and mTouched
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mozilla::Mutex mLock;
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// Timer for freeing unused memory
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nsITimer *mRecycleTimer;
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// mRecycleAfter:
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// Allocator should be untouched for this many seconds for freeing
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// unused Blocks.
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PRUint32 mRecycleAfter;
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// mTouched:
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// says if the allocator touched the freelist. If allocator didn't touch
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// the freelist over a time time interval, timer will call ClearFreeList()
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PRBool mTouched;
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#ifdef DEBUG
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// mId:
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// a string for identifying the user of nsRecyclingAllocator
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// User mainly for debug prints
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const char *mId;
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// mNAllocated: Number of blocks allocated
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PRInt32 mNAllocated;
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#endif
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public:
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// nbucket : number of buckets to hold. Capped at NS_MAX_BUCKET
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// recycleAfter : Try recycling allocated buckets after this many seconds
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// id : a string used to identify debug prints. Will not be released.
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nsRecyclingAllocator(PRUint32 nbucket = 0, PRUint32 recycleAfter = NS_DEFAULT_RECYCLE_TIMEOUT,
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const char *id = NULL);
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~nsRecyclingAllocator();
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nsresult Init(PRUint32 nbucket, PRUint32 recycleAfter, const char *id);
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// Allocation and free routines
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void* Malloc(PRSize size, PRBool zeroit = PR_FALSE);
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void Free(void *ptr);
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void* Calloc(PRUint32 items, PRSize size)
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{
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return Malloc(items * size, PR_TRUE);
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}
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// ClearFreeList - Frees all blocks kept by mFreelist, and stops the timer
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void ClearFreeList();
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protected:
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// Timer callback to trigger unused memory
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static void nsRecycleTimerCallback(nsITimer *aTimer, void *aClosure);
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friend void nsRecycleTimerCallback(nsITimer *aTimer, void *aClosure);
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};
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// ----------------------------------------------------------------------
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// Wrapping the recyling allocator with nsIMemory
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// ----------------------------------------------------------------------
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// Wrapping the nsRecyclingAllocator with nsIMemory
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class nsRecyclingAllocatorImpl : public nsRecyclingAllocator, public nsIRecyclingAllocator {
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public:
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NS_DECL_ISUPPORTS
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NS_DECL_NSIMEMORY
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NS_DECL_NSIRECYCLINGALLOCATOR
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nsRecyclingAllocatorImpl()
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{
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}
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private:
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~nsRecyclingAllocatorImpl() {}
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};
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#endif // nsRecyclingAllocator_h__
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