root/OpenSceneGraph/trunk/include/osg/fast_back_stack @ 13041

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1/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield
2 *
3 * This library is open source and may be redistributed and/or modified under
4 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or
5 * (at your option) any later version.  The full license is in LICENSE file
6 * included with this distribution, and on the openscenegraph.org website.
7 *
8 * This library is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
11 * OpenSceneGraph Public License for more details.
12*/
13
14#ifndef OSG_FAST_BACK_STACK
15#define OSG_FAST_BACK_STACK 1
16
17#include <vector>
18
19namespace osg {
20
21/** Simple stack implementation that keeps the back() cached locally for fast access
22  * rather than at the back of the vector which is the traditional stack implementation.
23  * A conventional std::vector<> stores the rest of the stack. Although fast_back_stack
24  *  contains a stl container it only implements the back push_back(),pop_back()
25  * and back() methods so is not as general purpose as stl stack implementation.
26  * The focus of the fast_back_stack is purely to maximize the speed at which the
27  * back can be accessed.*/
28
29template<class T>
30class fast_back_stack
31{
32    public:
33
34        inline fast_back_stack():_value(),_stack(),_size(0) {}
35
36        inline fast_back_stack(const fast_back_stack& fbs):_value(fbs._value),_stack(fbs._stack),_size(fbs._size) {}
37
38        inline fast_back_stack(const T& value):_value(value),_stack(),_size(1) {}
39
40        fast_back_stack& operator = (const fast_back_stack& fbs)
41        {
42            _value = fbs._value;
43            _stack = fbs._stack;
44            _size = fbs._size;
45            return *this;
46        }
47
48        inline void clear() { _stack.clear(); _size = 0; }
49
50        inline bool empty() const { return _size==0; }
51
52        inline unsigned int size() const { return _size; }
53
54        inline T& back() { return _value; }
55
56        inline const T& back() const { return _value; }
57
58        inline void push_back()
59        {
60            if (_size>0)
61            {
62                _stack.push_back(_value);
63            }
64            ++_size;
65        }
66
67        inline void push_back(const T& value)
68        {
69            if (_size>0)
70            {
71                _stack.push_back(_value);
72            }
73            _value = value;
74            ++_size;
75        }
76
77        inline void pop_back()
78        {
79            if (_size>0)
80            {
81                if (!_stack.empty())
82                {
83                    _value = _stack.back();
84                    _stack.pop_back();
85                }
86                --_size;
87            } // else error condition.
88        }
89
90        T              _value;
91        std::vector<T> _stack;
92        unsigned int   _size;
93};
94
95}
96
97#endif
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