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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* ***** 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) 1998
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
*
* Alternatively, the contents of this file may be used under the terms of
* either of 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 ***** */
#ifndef nsSegmentedBuffer_h__
#define nsSegmentedBuffer_h__
#include "nsMemory.h"
#include "prclist.h"
class nsSegmentedBuffer
{
public:
nsSegmentedBuffer()
: mSegmentSize(0), mMaxSize(0),
mSegAllocator(nsnull), mSegmentArray(nsnull),
mSegmentArrayCount(0),
mFirstSegmentIndex(0), mLastSegmentIndex(0) {}
~nsSegmentedBuffer() {
Empty();
NS_IF_RELEASE(mSegAllocator);
}
NS_COM nsresult Init(PRUint32 segmentSize, PRUint32 maxSize,
nsIMemory* allocator = nsnull);
NS_COM char* AppendNewSegment(); // pushes at end
// returns true if no more segments remain:
PRBool DeleteFirstSegment(); // pops from beginning
// returns true if no more segments remain:
PRBool DeleteLastSegment(); // pops from beginning
// Call Realloc() on last segment. This is used to reduce memory
// consumption when data is not an exact multiple of segment size.
PRBool ReallocLastSegment(size_t newSize);
NS_COM void Empty(); // frees all segments
inline PRUint32 GetSegmentCount() {
if (mFirstSegmentIndex <= mLastSegmentIndex)
return mLastSegmentIndex - mFirstSegmentIndex;
else
return mSegmentArrayCount + mLastSegmentIndex - mFirstSegmentIndex;
}
inline PRUint32 GetSegmentSize() { return mSegmentSize; }
inline PRUint32 GetMaxSize() { return mMaxSize; }
inline PRUint32 GetSize() { return GetSegmentCount() * mSegmentSize; }
inline char* GetSegment(PRUint32 indx) {
NS_ASSERTION(indx < GetSegmentCount(), "index out of bounds");
PRInt32 i = ModSegArraySize(mFirstSegmentIndex + (PRInt32)indx);
return mSegmentArray[i];
}
protected:
inline PRInt32 ModSegArraySize(PRInt32 n) {
PRUint32 result = n & (mSegmentArrayCount - 1);
NS_ASSERTION(result == n % mSegmentArrayCount,
"non-power-of-2 mSegmentArrayCount");
return result;
}
inline PRBool IsFull() {
return ModSegArraySize(mLastSegmentIndex + 1) == mFirstSegmentIndex;
}
protected:
PRUint32 mSegmentSize;
PRUint32 mMaxSize;
nsIMemory* mSegAllocator;
char** mSegmentArray;
PRUint32 mSegmentArrayCount;
PRInt32 mFirstSegmentIndex;
PRInt32 mLastSegmentIndex;
};
// NS_SEGMENTARRAY_INITIAL_SIZE: This number needs to start out as a
// power of 2 given how it gets used. We double the segment array
// when we overflow it, and use that fact that it's a power of 2
// to compute a fast modulus operation in IsFull.
//
// 32 segment array entries can accommodate 128k of data if segments
// are 4k in size. That seems like a reasonable amount that will avoid
// needing to grow the segment array.
#define NS_SEGMENTARRAY_INITIAL_COUNT 32
#endif // nsSegmentedBuffer_h__
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