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BlockArray.h
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1 /*
2  This file is part of Konsole, an X terminal.
3  Copyright (C) 2000, 2013 by Stephan Kulow <coolo@kde.org>
4 
5  Rewritten for QT4 by e_k <e_k at users.sourceforge.net>, Copyright (C)2008
6 
7  This program is free software; you can redistribute it and/or modify
8  it under the terms of the GNU General Public License as published by
9  the Free Software Foundation; either version 2 of the License, or
10  (at your option) any later version.
11 
12  This program is distributed in the hope that it will be useful,
13  but WITHOUT ANY WARRANTY; without even the implied warranty of
14  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15  GNU General Public License for more details.
16 
17  You should have received a copy of the GNU General Public License
18  along with this program; if not, write to the Free Software
19  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
20  02110-1301 USA.
21 */
22 
23 #ifndef BLOCKARRAY_H
24 #define BLOCKARRAY_H
25 
26 #include <unistd.h>
27 
28 #define BlockSize (1 << 12)
29 #define ENTRIES ((BlockSize - sizeof(size_t) ) / sizeof(unsigned char))
30 
31 struct Block {
32  Block() { size = 0; }
33  unsigned char data[ENTRIES];
34  size_t size;
35 };
36 
37 // ///////////////////////////////////////////////////////
38 
39 class BlockArray {
40 public:
41  /**
42  * Creates a history file for holding
43  * maximal size blocks. If more blocks
44  * are requested, then it drops earlier
45  * added ones.
46  */
47  BlockArray();
48 
49  /// destructor
50  ~BlockArray();
51 
52  /**
53  * adds the Block at the end of history.
54  * This may drop other blocks.
55  *
56  * The ownership on the block is transfered.
57  * An unique index number is returned for accessing
58  * it later (if not yet dropped then)
59  *
60  * Note, that the block may be dropped completely
61  * if history is turned off.
62  */
63  size_t append(Block *block);
64 
65  /**
66  * gets the block at the index. Function may return
67  * 0 if the block isn't available any more.
68  *
69  * The returned block is strictly readonly as only
70  * maped in memory - and will be invalid on the next
71  * operation on this class.
72  */
73  const Block *at(size_t index);
74 
75  /**
76  * reorders blocks as needed. If newsize is null,
77  * the history is emptied completely. The indices
78  * returned on append won't change their semantic,
79  * but they may not be valid after this call.
80  */
81  bool setHistorySize(size_t newsize);
82 
83  size_t newBlock();
84 
85  Block *lastBlock() const;
86 
87  /**
88  * Convenient function to set the size in KBytes
89  * instead of blocks
90  */
91  bool setSize(size_t newsize);
92 
93  size_t len() const { return length; }
94 
95  bool has(size_t index) const;
96 
97  size_t getCurrent() const { return current; }
98 
99 private:
100  void unmap();
101  void increaseBuffer();
102  void decreaseBuffer(size_t newsize);
103 
104  size_t size;
105  // current always shows to the last inserted block
106  size_t current;
107  size_t index;
108 
112 
113  int ion;
114  size_t length;
115 
116 };
117 
118 #endif