gecko-dev/xpcom/io/nsStorageStream.h

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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* The contents of this file are subject to the Netscape 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/NPL/
*
* 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 Communicator client code, released
* March 31, 1998.
*
* The Initial Developer of the Original Code is Netscape
* Communications Corporation. Portions created by Netscape are
* Copyright (C) 1998-1999 Netscape Communications Corporation. All
* Rights Reserved.
*
*/
/*
* The storage stream provides an internal buffer that can be filled by a
* client using a single output stream. One or more independent input streams
* can be created to read the data out non-destructively. The implementation
* uses a segmented buffer internally to avoid realloc'ing of large buffers,
* with the attendant performance loss and heap fragmentation.
*/
#ifndef _nsStorageStream_h_
#define _nsStorageStream_h_
#include "nsIStorageStream.h"
#include "nsIOutputStream.h"
#include "nsMemory.h"
class nsSegmentedBuffer;
class NS_COM nsStorageStream : public nsIStorageStream,
public nsIOutputStream
{
public:
nsStorageStream();
virtual ~nsStorageStream();
NS_METHOD Init(PRUint32 segmentSize, PRUint32 maxSize, nsIMemory *segmentAllocator = 0);
NS_DECL_ISUPPORTS
NS_DECL_NSISTORAGESTREAM
NS_DECL_NSIOUTPUTSTREAM
friend class nsStorageInputStream;
private:
nsSegmentedBuffer* mSegmentedBuffer;
PRUint32 mSegmentSize; // All segments, except possibly the last, are of this size
// Must be power-of-2
PRUint32 mSegmentSizeLog2; // log2(mSegmentSize)
PRBool mWriteInProgress; // true, if an un-Close'ed output stream exists
PRInt32 mLastSegmentNum; // Last segment # in use, -1 initially
char* mWriteCursor; // Pointer to next byte to be written
char* mSegmentEnd; // Pointer to one byte after end of segment
// containing the write cursor
PRUint32 mLogicalLength; // Number of bytes written to stream
NS_METHOD Seek(PRInt32 aPosition);
PRUint32 SegNum(PRUint32 aPosition) {return aPosition >> mSegmentSizeLog2;}
PRUint32 SegOffset(PRUint32 aPosition) {return aPosition & (mSegmentSize - 1);}
};
#endif // _nsStorageStream_h_