LCOV - code coverage report
Current view: directory - xpcom/io - nsSegmentedBuffer.h (source / functions) Found Hit Coverage
Test: app.info Lines: 23 23 100.0 %
Date: 2012-06-02 Functions: 9 9 100.0 %

       1                 : /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
       2                 : /* ***** BEGIN LICENSE BLOCK *****
       3                 :  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
       4                 :  *
       5                 :  * The contents of this file are subject to the Mozilla Public License Version
       6                 :  * 1.1 (the "License"); you may not use this file except in compliance with
       7                 :  * the License. You may obtain a copy of the License at
       8                 :  * http://www.mozilla.org/MPL/
       9                 :  *
      10                 :  * Software distributed under the License is distributed on an "AS IS" basis,
      11                 :  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
      12                 :  * for the specific language governing rights and limitations under the
      13                 :  * License.
      14                 :  *
      15                 :  * The Original Code is mozilla.org code.
      16                 :  *
      17                 :  * The Initial Developer of the Original Code is
      18                 :  * Netscape Communications Corporation.
      19                 :  * Portions created by the Initial Developer are Copyright (C) 1998
      20                 :  * the Initial Developer. All Rights Reserved.
      21                 :  *
      22                 :  * Contributor(s):
      23                 :  *
      24                 :  * Alternatively, the contents of this file may be used under the terms of
      25                 :  * either of the GNU General Public License Version 2 or later (the "GPL"),
      26                 :  * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
      27                 :  * in which case the provisions of the GPL or the LGPL are applicable instead
      28                 :  * of those above. If you wish to allow use of your version of this file only
      29                 :  * under the terms of either the GPL or the LGPL, and not to allow others to
      30                 :  * use your version of this file under the terms of the MPL, indicate your
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      32                 :  * and other provisions required by the GPL or the LGPL. If you do not delete
      33                 :  * the provisions above, a recipient may use your version of this file under
      34                 :  * the terms of any one of the MPL, the GPL or the LGPL.
      35                 :  *
      36                 :  * ***** END LICENSE BLOCK ***** */
      37                 : 
      38                 : #ifndef nsSegmentedBuffer_h__
      39                 : #define nsSegmentedBuffer_h__
      40                 : 
      41                 : #include "nsMemory.h"
      42                 : #include "prclist.h"
      43                 : 
      44                 : class nsSegmentedBuffer
      45                 : {
      46                 : public:
      47           26452 :     nsSegmentedBuffer()
      48                 :         : mSegmentSize(0), mMaxSize(0), 
      49                 :           mSegAllocator(nsnull), mSegmentArray(nsnull),
      50                 :           mSegmentArrayCount(0),
      51           26452 :           mFirstSegmentIndex(0), mLastSegmentIndex(0) {}
      52                 : 
      53           26437 :     ~nsSegmentedBuffer() {
      54           26437 :         Empty();
      55           26437 :         NS_IF_RELEASE(mSegAllocator);
      56           26437 :     }
      57                 : 
      58                 : 
      59                 :     nsresult Init(PRUint32 segmentSize, PRUint32 maxSize,
      60                 :                   nsIMemory* allocator = nsnull);
      61                 : 
      62                 :     char* AppendNewSegment();   // pushes at end
      63                 : 
      64                 :     // returns true if no more segments remain:
      65                 :     bool DeleteFirstSegment();  // pops from beginning
      66                 : 
      67                 :     // returns true if no more segments remain:
      68                 :     bool DeleteLastSegment();  // pops from beginning
      69                 : 
      70                 :     // Call Realloc() on last segment.  This is used to reduce memory
      71                 :     // consumption when data is not an exact multiple of segment size.
      72                 :     bool ReallocLastSegment(size_t newSize);
      73                 : 
      74                 :     void Empty();               // frees all segments
      75                 : 
      76         7591639 :     inline PRUint32 GetSegmentCount() {
      77         7591639 :         if (mFirstSegmentIndex <= mLastSegmentIndex)
      78         7591282 :             return mLastSegmentIndex - mFirstSegmentIndex;
      79                 :         else 
      80             357 :             return mSegmentArrayCount + mLastSegmentIndex - mFirstSegmentIndex;
      81                 :     }
      82                 : 
      83           40112 :     inline PRUint32 GetSegmentSize() { return mSegmentSize; }
      84            1148 :     inline PRUint32 GetMaxSize() { return mMaxSize; }
      85         3684177 :     inline PRUint32 GetSize() { return GetSegmentCount() * mSegmentSize; }
      86                 : 
      87         3694576 :     inline char* GetSegment(PRUint32 indx) {
      88         3694576 :         NS_ASSERTION(indx < GetSegmentCount(), "index out of bounds");
      89         3694576 :         PRInt32 i = ModSegArraySize(mFirstSegmentIndex + (PRInt32)indx);
      90         3694576 :         return mSegmentArray[i];
      91                 :     }
      92                 : 
      93                 : protected:
      94        11071095 :     inline PRInt32 ModSegArraySize(PRInt32 n) {
      95        11071095 :         PRUint32 result = n & (mSegmentArrayCount - 1);
      96        11071095 :         NS_ASSERTION(result == n % mSegmentArrayCount,
      97                 :                      "non-power-of-2 mSegmentArrayCount");
      98        11071095 :         return result;
      99                 :     }
     100                 : 
     101         3682998 :    inline bool IsFull() {
     102         3682998 :         return ModSegArraySize(mLastSegmentIndex + 1) == mFirstSegmentIndex;
     103                 :     }
     104                 : 
     105                 : protected:
     106                 :     PRUint32            mSegmentSize;
     107                 :     PRUint32            mMaxSize;
     108                 :     nsIMemory*       mSegAllocator;
     109                 :     char**              mSegmentArray;
     110                 :     PRUint32            mSegmentArrayCount;
     111                 :     PRInt32             mFirstSegmentIndex;
     112                 :     PRInt32             mLastSegmentIndex;
     113                 : };
     114                 : 
     115                 : // NS_SEGMENTARRAY_INITIAL_SIZE: This number needs to start out as a
     116                 : // power of 2 given how it gets used. We double the segment array
     117                 : // when we overflow it, and use that fact that it's a power of 2 
     118                 : // to compute a fast modulus operation in IsFull.
     119                 : //
     120                 : // 32 segment array entries can accommodate 128k of data if segments
     121                 : // are 4k in size. That seems like a reasonable amount that will avoid
     122                 : // needing to grow the segment array.
     123                 : #define NS_SEGMENTARRAY_INITIAL_COUNT 32
     124                 : 
     125                 : #endif // nsSegmentedBuffer_h__

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