1 /**
2 * \file circulator.h
3 * \brief \todo brief description
4 *
5 * Copyright 2006 MenTaLguY <mental@rydia.net>
6 *
7 * This library is free software; you can redistribute it and/or
8 * modify it either under the terms of the GNU Lesser General Public
9 * License version 2.1 as published by the Free Software Foundation
10 * (the "LGPL") or, at your option, under the terms of the Mozilla
11 * Public License Version 1.1 (the "MPL"). If you do not alter this
12 * notice, a recipient may use your version of this file under either
13 * the MPL or the LGPL.
14 *
15 * You should have received a copy of the LGPL along with this library
16 * in the file COPYING-LGPL-2.1; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18 * You should have received a copy of the MPL along with this library
19 * in the file COPYING-MPL-1.1
20 *
21 * The contents of this file are subject to the Mozilla Public License
22 * Version 1.1 (the "License"); you may not use this file except in
23 * compliance with the License. You may obtain a copy of the License at
24 * http://www.mozilla.org/MPL/
25 *
26 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
27 * OF ANY KIND, either express or implied. See the LGPL or the MPL for
28 * the specific language governing rights and limitations.
29 *
30 */
32 #ifndef SEEN_Circulator_H
33 #define SEEN_Circulator_H
35 #include <iterator>
37 namespace Geom {
39 template <typename Iterator>
40 class Circulator {
41 public:
42 typedef std::random_access_iterator_tag iterator_category;
43 typedef typename std::iterator_traits<Iterator>::value_type value_type;
44 typedef typename std::iterator_traits<Iterator>::difference_type difference_type;
45 typedef typename std::iterator_traits<Iterator>::pointer pointer;
46 typedef typename std::iterator_traits<Iterator>::reference reference;
48 Circulator(Iterator const &first,
49 Iterator const &last,
50 Iterator const &pos)
51 : _first(first), _last(last), _pos(pos)
52 {
53 match_random_access(iterator_category(first));
54 }
56 reference operator*() const {
57 return *_pos;
58 }
59 pointer operator->() const {
60 return &*_pos;
61 }
63 Circulator &operator++() {
64 if ( _first == _last ) return *this;
65 ++_pos;
66 if ( _pos == _last ) _pos = _first;
67 return *this;
68 }
69 Circulator operator++(int) {
70 Circulator saved=*this;
71 ++(*this);
72 return saved;
73 }
75 Circulator &operator--() {
76 if ( _pos == _first ) _pos = _last;
77 --_pos;
78 return *this;
79 }
80 Circulator operator--(int) {
81 Circulator saved=*this;
82 --(*this);
83 return saved;
84 }
86 Circulator &operator+=(int n) {
87 _pos = _offset(n);
88 return *this;
89 }
90 Circulator operator+(int n) const {
91 return Circulator(_first, _last, _offset(n));
92 }
93 Circulator &operator-=(int n) {
94 _pos = _offset(-n);
95 return *this;
96 }
97 Circulator operator-(int n) const {
98 return Circulator(_first, _last, _offset(-n));
99 }
101 difference_type operator-(Circulator const &other) {
102 return _pos - other._pos;
103 }
105 reference operator[](int n) const {
106 return *_offset(n);
107 }
109 private:
110 void match_random_access(iterator_category) {}
112 Iterator _offset(int n) {
113 difference_type range=( _last - _first );
114 difference_type offset=( _pos - _first + n );
116 if ( offset < 0 ) {
117 // modulus not well-defined for negative numbers in C++
118 offset += ( ( -offset / range ) + 1 ) * range;
119 } else if ( offset >= range ) {
120 offset %= range;
121 }
122 return _first + offset;
123 }
125 Iterator _first;
126 Iterator _last;
127 Iterator _pos;
128 };
130 }
132 template <typename T>
133 Geom::Circulator<T> operator+(int n, Geom::Circulator<T> const &c) {
134 return c + n;
135 }
137 #endif // SEEN_Circulator_H
139 /*
140 Local Variables:
141 mode:c++
142 c-file-style:"stroustrup"
143 c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
144 indent-tabs-mode:nil
145 fill-column:99
146 End:
147 */
148 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=99 :