| 1 | /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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| 2 | /* ***** BEGIN LICENSE BLOCK *****
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| 3 | * Version: MPL 1.1/GPL 2.0/LGPL 2.1
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| 4 | *
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| 5 | * The contents of this file are subject to the Mozilla Public License Version
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| 6 | * 1.1 (the "License"); you may not use this file except in compliance with
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| 7 | * the License. You may obtain a copy of the License at
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| 8 | * http://www.mozilla.org/MPL/
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| 9 | *
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| 10 | * Software distributed under the License is distributed on an "AS IS" basis,
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| 11 | * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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| 12 | * for the specific language governing rights and limitations under the
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| 13 | * License.
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| 14 | *
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| 15 | * The Original Code is mozilla.org code.
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| 16 | *
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| 17 | * The Initial Developer of the Original Code is
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| 18 | * Netscape Communications Corporation.
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| 19 | * Portions created by the Initial Developer are Copyright (C) 1998
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| 20 | * the Initial Developer. All Rights Reserved.
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| 21 | *
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| 22 | * Contributor(s):
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| 23 | *
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| 24 | * Alternatively, the contents of this file may be used under the terms of
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| 25 | * either of the GNU General Public License Version 2 or later (the "GPL"),
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| 26 | * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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| 27 | * in which case the provisions of the GPL or the LGPL are applicable instead
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| 28 | * of those above. If you wish to allow use of your version of this file only
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| 29 | * under the terms of either the GPL or the LGPL, and not to allow others to
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| 30 | * use your version of this file under the terms of the MPL, indicate your
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| 31 | * decision by deleting the provisions above and replace them with the notice
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| 32 | * and other provisions required by the GPL or the LGPL. If you do not delete
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| 33 | * the provisions above, a recipient may use your version of this file under
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| 34 | * the terms of any one of the MPL, the GPL or the LGPL.
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| 35 | *
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| 36 | * ***** END LICENSE BLOCK ***** */
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| 37 |
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| 38 | #ifndef nsSegmentedBuffer_h__
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| 39 | #define nsSegmentedBuffer_h__
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| 40 |
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| 41 | #include "nsMemory.h"
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| 42 | #include "prclist.h"
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| 43 |
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| 44 | class nsSegmentedBuffer
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| 45 | {
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| 46 | public:
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| 47 | nsSegmentedBuffer()
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| 48 | : mSegmentSize(0), mMaxSize(0),
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| 49 | mSegAllocator(nsnull), mSegmentArray(nsnull),
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| 50 | mSegmentArrayCount(0),
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| 51 | mFirstSegmentIndex(0), mLastSegmentIndex(0) {}
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| 52 |
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| 53 | ~nsSegmentedBuffer() {
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| 54 | Empty();
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| 55 | NS_IF_RELEASE(mSegAllocator);
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| 56 | }
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| 57 |
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| 58 |
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| 59 | NS_COM nsresult Init(PRUint32 segmentSize, PRUint32 maxSize,
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| 60 | nsIMemory* allocator = nsnull);
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| 61 |
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| 62 | NS_COM char* AppendNewSegment(); // pushes at end
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| 63 |
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| 64 | // returns true if no more segments remain:
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| 65 | PRBool DeleteFirstSegment(); // pops from beginning
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| 66 |
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| 67 | // returns true if no more segments remain:
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| 68 | PRBool DeleteLastSegment(); // pops from beginning
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| 69 |
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| 70 | // Call Realloc() on last segment. This is used to reduce memory
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| 71 | // consumption when data is not an exact multiple of segment size.
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| 72 | PRBool ReallocLastSegment(size_t newSize);
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| 73 |
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| 74 | NS_COM void Empty(); // frees all segments
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| 75 |
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| 76 | inline PRUint32 GetSegmentCount() {
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| 77 | if (mFirstSegmentIndex <= mLastSegmentIndex)
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| 78 | return mLastSegmentIndex - mFirstSegmentIndex;
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| 79 | else
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| 80 | return mSegmentArrayCount + mLastSegmentIndex - mFirstSegmentIndex;
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| 81 | }
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| 82 |
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| 83 | inline PRUint32 GetSegmentSize() { return mSegmentSize; }
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| 84 | inline PRUint32 GetMaxSize() { return mMaxSize; }
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| 85 | inline PRUint32 GetSize() { return GetSegmentCount() * mSegmentSize; }
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| 86 |
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| 87 | inline char* GetSegment(PRUint32 indx) {
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| 88 | NS_ASSERTION(indx < GetSegmentCount(), "index out of bounds");
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| 89 | PRInt32 i = ModSegArraySize(mFirstSegmentIndex + (PRInt32)indx);
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| 90 | return mSegmentArray[i];
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| 91 | }
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| 92 |
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| 93 | protected:
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| 94 | inline PRInt32 ModSegArraySize(PRInt32 n) {
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| 95 | PRUint32 result = n & (mSegmentArrayCount - 1);
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| 96 | NS_ASSERTION(result == n % mSegmentArrayCount,
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| 97 | "non-power-of-2 mSegmentArrayCount");
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| 98 | return result;
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| 99 | }
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| 100 |
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| 101 | inline PRBool IsFull() {
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| 102 | return ModSegArraySize(mLastSegmentIndex + 1) == mFirstSegmentIndex;
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| 103 | }
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| 104 |
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| 105 | protected:
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| 106 | PRUint32 mSegmentSize;
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| 107 | PRUint32 mMaxSize;
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| 108 | nsIMemory* mSegAllocator;
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| 109 | char** mSegmentArray;
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| 110 | PRUint32 mSegmentArrayCount;
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| 111 | PRInt32 mFirstSegmentIndex;
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| 112 | PRInt32 mLastSegmentIndex;
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| 113 | };
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| 114 |
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| 115 | // NS_SEGMENTARRAY_INITIAL_SIZE: This number needs to start out as a
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| 116 | // power of 2 given how it gets used. We double the segment array
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| 117 | // when we overflow it, and use that fact that it's a power of 2
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| 118 | // to compute a fast modulus operation in IsFull.
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| 119 | //
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| 120 | // 32 segment array entries can accommodate 128k of data if segments
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| 121 | // are 4k in size. That seems like a reasonable amount that will avoid
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| 122 | // needing to grow the segment array.
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| 123 | #define NS_SEGMENTARRAY_INITIAL_COUNT 32
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| 124 |
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| 125 | #endif // nsSegmentedBuffer_h__
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