1/*
2 * Copyright (C) 2010 Google Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 *
8 * 1.  Redistributions of source code must retain the above copyright
9 *     notice, this list of conditions and the following disclaimer.
10 * 2.  Redistributions in binary form must reproduce the above copyright
11 *     notice, this list of conditions and the following disclaimer in the
12 *     documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
15 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
16 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
17 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
18 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
19 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
20 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
21 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#ifndef PODInterval_h
27#define PODInterval_h
28
29#ifndef NDEBUG
30#include "ValueToString.h"
31#include <wtf/text/StringBuilder.h>
32#endif
33
34namespace WebCore {
35
36// Class representing a closed interval which can hold an arbitrary
37// Plain Old Datatype (POD) as its endpoints and a piece of user
38// data. An important characteristic for the algorithms we use is that
39// if two intervals have identical endpoints but different user data,
40// they are not considered to be equal. This situation can arise when
41// representing the vertical extents of bounding boxes of overlapping
42// triangles, where the pointer to the triangle is the user data of
43// the interval.
44//
45// *Note* that the destructors of type T and UserData will *not* be
46// called by this class. They must not allocate any memory that is
47// required to be cleaned up in their destructors.
48//
49// The following constructors and operators must be implemented on
50// type T:
51//
52//   - Copy constructor (if user data is desired)
53//   - operator<
54//   - operator==
55//   - operator=
56//
57// If the UserData type is specified, it must support a copy
58// constructor and assignment operator.
59//
60// In debug mode, printing of intervals and the data they contain is
61// enabled. This requires the following template specializations to be
62// available:
63//
64//   template<> struct WebCore::ValueToString<T> {
65//       static String string(const T& t);
66//   };
67//   template<> struct WebCore::ValueToString<UserData> {
68//       static String string(const UserData& t);
69//   };
70//
71// Note that this class requires a copy constructor and assignment
72// operator in order to be stored in the red-black tree.
73
74template<class T, class UserData = void*>
75class PODInterval {
76public:
77    // Constructor from endpoints. This constructor only works when the
78    // UserData type is a pointer or other type which can be initialized
79    // with 0.
80    PODInterval(const T& low, const T& high)
81        : m_low(low)
82        , m_high(high)
83        , m_data(0)
84        , m_maxHigh(high)
85    {
86    }
87
88    // Constructor from two endpoints plus explicit user data.
89    PODInterval(const T& low, const T& high, const UserData data)
90        : m_low(low)
91        , m_high(high)
92        , m_data(data)
93        , m_maxHigh(high)
94    {
95    }
96
97    const T& low() const { return m_low; }
98    const T& high() const { return m_high; }
99    const UserData& data() const { return m_data; }
100
101    bool overlaps(const T& low, const T& high) const
102    {
103        if (this->high() < low)
104            return false;
105        if (high < this->low())
106            return false;
107        return true;
108    }
109
110    bool overlaps(const PODInterval& other) const
111    {
112        return overlaps(other.low(), other.high());
113    }
114
115    // Returns true if this interval is "less" than the other. The
116    // comparison is performed on the low endpoints of the intervals.
117    bool operator<(const PODInterval& other) const
118    {
119        return low() < other.low();
120    }
121
122    // Returns true if this interval is strictly equal to the other,
123    // including comparison of the user data.
124    bool operator==(const PODInterval& other) const
125    {
126        return (low() == other.low()
127                && high() == other.high()
128                && data() == other.data());
129    }
130
131    const T& maxHigh() const { return m_maxHigh; }
132    void setMaxHigh(const T& maxHigh) { m_maxHigh = maxHigh; }
133
134#ifndef NDEBUG
135    // Support for printing PODIntervals.
136    String toString() const
137    {
138        StringBuilder builder;
139        builder.append("[PODInterval (");
140        builder.append(ValueToString<T>::string(low()));
141        builder.append(", ");
142        builder.append(ValueToString<T>::string(high()));
143        builder.append("), data=");
144        builder.append(ValueToString<UserData>::string(data()));
145        builder.append(", maxHigh=");
146        builder.append(ValueToString<T>::string(maxHigh()));
147        builder.append("]");
148        return builder.toString();
149    }
150#endif
151
152private:
153    T m_low;
154    T m_high;
155    UserData m_data;
156    T m_maxHigh;
157};
158
159} // namespace WebCore
160
161#endif // PODInterval_h
162