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nsDiskCacheBlockFile.h
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00001 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
00002  *
00003  * ***** BEGIN LICENSE BLOCK *****
00004  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
00005  *
00006  * The contents of this file are subject to the Mozilla Public License Version
00007  * 1.1 (the "License"); you may not use this file except in compliance with
00008  * the License. You may obtain a copy of the License at
00009  * http://www.mozilla.org/MPL/
00010  *
00011  * Software distributed under the License is distributed on an "AS IS" basis,
00012  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
00013  * for the specific language governing rights and limitations under the
00014  * License.
00015  *
00016  * The Original Code is nsDiskCacheBlockFile.h, released
00017  * April 12, 2001.
00018  *
00019  * The Initial Developer of the Original Code is
00020  * Netscape Communications Corporation.
00021  * Portions created by the Initial Developer are Copyright (C) 2001
00022  * the Initial Developer. All Rights Reserved.
00023  *
00024  * Contributor(s):
00025  *   Gordon Sheridan  <gordon@netscape.com>
00026  *
00027  * Alternatively, the contents of this file may be used under the terms of
00028  * either the GNU General Public License Version 2 or later (the "GPL"), or
00029  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
00030  * in which case the provisions of the GPL or the LGPL are applicable instead
00031  * of those above. If you wish to allow use of your version of this file only
00032  * under the terms of either the GPL or the LGPL, and not to allow others to
00033  * use your version of this file under the terms of the MPL, indicate your
00034  * decision by deleting the provisions above and replace them with the notice
00035  * and other provisions required by the GPL or the LGPL. If you do not delete
00036  * the provisions above, a recipient may use your version of this file under
00037  * the terms of any one of the MPL, the GPL or the LGPL.
00038  *
00039  * ***** END LICENSE BLOCK ***** */
00040 
00041 #ifndef _nsDiskCacheBlockFile_h_
00042 #define _nsDiskCacheBlockFile_h_
00043 
00044 #include "nsILocalFile.h"
00045 #include "nspr.h"
00046 
00047 const unsigned short kBitMapBytes = 4096;
00048 
00049 /******************************************************************************
00050  *  nsDiskCacheBlockFile
00051  *
00052  *  The structure of a cache block file is a 4096 bytes bit map, followed by
00053  *  some number of blocks of mBlockSize.  The creator of a
00054  *  nsDiskCacheBlockFile object must provide the block size for a given file.
00055  *
00056  *****************************************************************************/
00057 class nsDiskCacheBlockFile {
00058 public:
00059     nsDiskCacheBlockFile()
00060            : mFD(nsnull)
00061            , mBlockSize(0)
00062            , mEndOfFile(0)
00063            , mBitMap(nsnull)
00064            , mBitMapDirty(PR_FALSE)
00065             {}
00066     ~nsDiskCacheBlockFile() { (void) Close(PR_TRUE); }
00067     
00068     nsresult  Open( nsILocalFile *  blockFile, PRUint32  blockSize);
00069     nsresult  Close(PRBool flush);
00070     nsresult  Trim();
00071     PRInt32   AllocateBlocks( PRInt32  numBlocks);
00072     nsresult  DeallocateBlocks( PRInt32  startBlock, PRInt32  numBlocks);
00073     nsresult  WriteBlocks( void * buffer, PRInt32  startBlock, PRInt32  numBlocks);
00074     nsresult  ReadBlocks(  void * buffer, PRInt32  startBlock, PRInt32  numBlocks);
00075     
00076 private:
00077     nsresult  FlushBitMap();
00078     nsresult  ValidateFile();   // called by Open()
00079     nsresult  VerifyAllocation( PRInt32 startBlock, PRInt32 numBLocks);
00080     PRInt32   LastBlock();
00081 
00085     PRFileDesc *                mFD;
00086     PRUint32                    mBlockSize;
00087     PRUint32                    mEndOfFile;
00088     PRUint8 *                   mBitMap;      // XXX future: array of bit map blocks
00089     PRBool                      mBitMapDirty;
00090 };
00091 
00092 #endif // _nsDiskCacheBlockFile_h_