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/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is mozilla.org code.
*
* The Initial Developer of the Original Code is
* Netscape Communications Corporation.
* Portions created by the Initial Developer are Copyright (C) 2001, 2002
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Suresh Duddi <dp@netscape.com>
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
/*
* nsRecyclingAllocator
*
* This allocator is useful when we cycle through a small set of allocations
* repeatedly with minimal overlap. For eg. something we do for every gif
* file read (or) buffers required for decompression of every file from jar.
*
* What this does is keeps around the first set of memory allocated and
* reuses it subsequently. If all buckets are full, this falls back to
* malloc/free
*
* Uses a timer to release all memory allocated if not used for more than
* 10 secs automatically.
*
* Also there is a 4 byte maintenance overhead on every allocation.
*
* This allocator is thread safe.
*
* CAVEATS: As the number of buckets increases, this allocators performance
* will drop. As a general guideline, dont use this for more
* than NS_MAX_BLOCKS
*/
#ifndef nsRecyclingAllocator_h__
#define nsRecyclingAllocator_h__
#include "nscore.h"
#include "pratom.h"
#include "prlock.h"
#include "nsIRecyclingAllocator.h"
#include "nsIGenericFactory.h"
#define NS_DEFAULT_RECYCLE_TIMEOUT 10 // secs
#define NS_MAX_BLOCKS 24
#define NS_ALLOCATOR_OVERHEAD_BYTES (sizeof(Block)) // bytes
class nsITimer;
class nsIMemory;
class NS_COM nsRecyclingAllocator {
protected:
struct Block {
PRSize bytes;
};
// Make |BlockStoreNode| a |friend| so it can access |Block|.
struct BlockStoreNode;
friend struct BlockStoreNode;
struct BlockStoreNode {
BlockStoreNode() : bytes(0), block(nsnull), next(nsnull) {};
PRSize bytes;
Block *block;
BlockStoreNode *next;
};
#define DATA(block) ((void *)(((char *)block) + NS_ALLOCATOR_OVERHEAD_BYTES))
#define DATA_TO_BLOCK(data) ((Block *)((char *)(data) - NS_ALLOCATOR_OVERHEAD_BYTES))
// mMaxBlocks: Maximum number of blocks that can be allocated
PRUint32 mMaxBlocks;
// mBlocks:
// All blocks used or not.
BlockStoreNode *mBlocks;
// mFreeList
// A linked list of free blocks sorted by increasing order of size
BlockStoreNode* mFreeList;
// mNotUsedList
// A linked list of BlockStoreNodes that are not used to store
// any block information. When we add blocks into mFreeList, we
// take BlockStoreNode from here.
BlockStoreNode* mNotUsedList;
// mLock: Thread safety of mFreeList and mNotUsedList
PRLock *mLock;
// Timer for freeing unused memory
nsITimer *mRecycleTimer;
// mRecycleAfter:
// Allocator should be untouched for this many seconds for freeing
// unused Blocks.
PRUint32 mRecycleAfter;
// mTouched:
// says if the allocator touched any bucket. If allocator didn't touch
// any bucket over a time time interval, timer will call FreeUnusedBuckets()
PRInt32 mTouched;
// mId:
// a string for identifying the user of nsRecyclingAllocator
// User mainly for debug prints
const char *mId;
#ifdef DEBUG
// mNAllocated: Number of blocks allocated
PRInt32 mNAllocated;
#endif
public:
// nbucket : number of buckets to hold. Capped at NS_MAX_BUCKET
// recycleAfter : Try recycling allocated buckets after this many seconds
// id : a string used to identify debug prints. Will not be released.
nsRecyclingAllocator(PRUint32 nbucket = 0, PRUint32 recycleAfter = NS_DEFAULT_RECYCLE_TIMEOUT,
const char *id = NULL);
~nsRecyclingAllocator();
nsresult Init(PRUint32 nbucket, PRUint32 recycleAfter, const char *id);
// Allocation and free routines
void* Malloc(PRSize size, PRBool zeroit = PR_FALSE);
void Free(void *ptr);
void* Calloc(PRUint32 items, PRSize size)
{
return Malloc(items * size, PR_TRUE);
}
// FreeUnusedBuckets - Frees any bucket memory that isn't in use
void FreeUnusedBuckets();
protected:
// Timer callback to trigger unused memory
static void nsRecycleTimerCallback(nsITimer *aTimer, void *aClosure);
// Freelist management
// FindFreeBlock: return a free block that can hold bytes (best fit)
Block* FindFreeBlock(PRSize bytes);
// AddToFreeList: adds block into our freelist for future retrieval.
// Returns PR_TRUE is addition was successful. PR_FALSE otherewise.
PRBool AddToFreeList(Block* block);
// Touch will mark that someone used this allocator
// Timer based release will free unused memory only if allocator
// was not touched for mRecycleAfter seconds.
void Touch() {
if (!mTouched)
PR_AtomicSet(&mTouched, 1);
}
void Untouch() {
PR_AtomicSet(&mTouched, 0);
}
friend void nsRecycleTimerCallback(nsITimer *aTimer, void *aClosure);
};
// ----------------------------------------------------------------------
// Wrapping the recyling allocator with nsIMemory
// ----------------------------------------------------------------------
// Wrapping the nsRecyclingAllocator with nsIMemory
class nsRecyclingAllocatorImpl : public nsRecyclingAllocator, public nsIRecyclingAllocator {
public:
NS_DECL_ISUPPORTS
NS_DECL_NSIMEMORY
NS_DECL_NSIRECYCLINGALLOCATOR
nsRecyclingAllocatorImpl()
{
}
private:
~nsRecyclingAllocatorImpl() {}
};
#endif // nsRecyclingAllocator_h__
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