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 * 1.  Redistributions of source code must retain the above copyright
8 *     notice, this list of conditions and the following disclaimer.
9 * 2.  Redistributions in binary form must reproduce the above copyright
10 *     notice, this list of conditions and the following disclaimer in the
11 *     documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
15 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
16 * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
17 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
18 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
19 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
20 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
22 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23 */
24
25#ifndef TextPosition_h
26#define TextPosition_h
27
28#include <wtf/Assertions.h>
29
30namespace WTF {
31
32/*
33 * Text Position
34 *
35 * TextPosition structure specifies coordinates within an text resource. It is used mostly
36 * for saving script source position.
37 *
38 * Later TextPosition0 and TextPosition1 and both number types can be merged together quite easily.
39 *
40 * 0-based and 1-based
41 *
42 * Line and column numbers could be interpreted as zero-based or 1-based. Since
43 * both practices coexist in WebKit source base, 'int' type should be replaced with
44 * a dedicated wrapper types, so that compiler helped us with this ambiguity.
45 *
46 * Here we introduce 2 types of numbers: ZeroBasedNumber and OneBasedNumber and
47 * 2 corresponding types of TextPosition structure. While only one type ought to be enough,
48 * this is done to keep transition to the new types as transparent as possible:
49 * e.g. in areas where 0-based integers are used, TextPosition0 should be introduced. This
50 * way all changes will remain trackable.
51 *
52 * Later both number types can be merged in one type quite easily.
53 *
54 * For type safety and for the future type merge it is important that all operations in API
55 * that accept or return integer have a name explicitly defining base of integer. For this reason
56 * int-receiving constructors are hidden from API.
57 */
58
59template<typename NUMBER>
60class TextPosition {
61public:
62    TextPosition(NUMBER line, NUMBER column)
63        : m_line(line)
64        , m_column(column)
65    {
66    }
67    TextPosition() {}
68
69    bool operator==(const TextPosition& other) { return m_line == other.m_line && m_column == other.m_column; }
70    bool operator!=(const TextPosition& other) { return !((*this) == other); }
71
72    // A 'minimum' value of position, used as a default value.
73    static TextPosition<NUMBER> minimumPosition() { return TextPosition<NUMBER>(NUMBER::base(), NUMBER::base()); }
74
75    // A value with line value less than a minimum; used as an impossible position.
76    static TextPosition<NUMBER> belowRangePosition() { return TextPosition<NUMBER>(NUMBER::belowBase(), NUMBER::belowBase()); }
77
78    NUMBER m_line;
79    NUMBER m_column;
80};
81
82class OneBasedNumber;
83
84// An int wrapper that always reminds you that the number should be 0-based
85class ZeroBasedNumber {
86public:
87    static ZeroBasedNumber fromZeroBasedInt(int zeroBasedInt) { return ZeroBasedNumber(zeroBasedInt); }
88
89    ZeroBasedNumber() {}
90
91    int zeroBasedInt() const { return m_value; }
92    int convertAsOneBasedInt() const { return m_value + 1; }
93    OneBasedNumber convertToOneBased() const;
94
95    bool operator==(ZeroBasedNumber other) { return m_value == other.m_value; }
96    bool operator!=(ZeroBasedNumber other) { return !((*this) == other); }
97
98    static ZeroBasedNumber base() { return 0; }
99    static ZeroBasedNumber belowBase() { return -1; }
100
101private:
102    ZeroBasedNumber(int value) : m_value(value) {}
103    int m_value;
104};
105
106// An int wrapper that always reminds you that the number should be 1-based
107class OneBasedNumber {
108public:
109    static OneBasedNumber fromOneBasedInt(int oneBasedInt) { return OneBasedNumber(oneBasedInt); }
110    OneBasedNumber() {}
111
112    int oneBasedInt() const { return m_value; }
113    int convertAsZeroBasedInt() const { return m_value - 1; }
114    ZeroBasedNumber convertToZeroBased() const { return ZeroBasedNumber::fromZeroBasedInt(m_value - 1); }
115
116    bool operator==(OneBasedNumber other) { return m_value == other.m_value; }
117    bool operator!=(OneBasedNumber other) { return !((*this) == other); }
118
119    static OneBasedNumber base() { return 1; }
120    static OneBasedNumber belowBase() { return 0; }
121
122private:
123    OneBasedNumber(int value) : m_value(value) {}
124    int m_value;
125};
126
127typedef TextPosition<ZeroBasedNumber> TextPosition0;
128typedef TextPosition<OneBasedNumber> TextPosition1;
129
130inline TextPosition0 toZeroBasedTextPosition(const TextPosition1& position)
131{
132    return TextPosition0(position.m_line.convertToZeroBased(), position.m_column.convertToZeroBased());
133}
134
135inline TextPosition1 toOneBasedTextPosition(const TextPosition0& position)
136{
137    return TextPosition1(position.m_line.convertToOneBased(), position.m_column.convertToOneBased());
138}
139
140inline OneBasedNumber ZeroBasedNumber::convertToOneBased() const
141{
142    return OneBasedNumber::fromOneBasedInt(m_value + 1);
143}
144
145}
146
147using WTF::TextPosition0;
148using WTF::TextPosition1;
149
150#endif // TextPosition_h
151