wtf/text/TextPosition.h

   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
  30 namespace 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
  59 template<typename NUMBER>
  60 class TextPosition {
  61 public:
  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
  82 class OneBasedNumber;
  83
  84 // An int wrapper that always reminds you that the number should be 0-based
  85 class ZeroBasedNumber {
  86 public:
  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
 101 private:
 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
 107 class OneBasedNumber {
 108 public:
 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
 122 private:
 123     OneBasedNumber(int value) : m_value(value) {}
 124     int m_value;
 125 };
 126
 127 typedef TextPosition<ZeroBasedNumber> TextPosition0;
 128 typedef TextPosition<OneBasedNumber> TextPosition1;
 129
 130 inline TextPosition0 toZeroBasedTextPosition(const TextPosition1& position)
 131 {
 132     return TextPosition0(position.m_line.convertToZeroBased(), position.m_column.convertToZeroBased());
 133 }
 134
 135 inline TextPosition1 toOneBasedTextPosition(const TextPosition0& position)
 136 {
 137     return TextPosition1(position.m_line.convertToOneBased(), position.m_column.convertToOneBased());
 138 }
 139
 140 inline OneBasedNumber ZeroBasedNumber::convertToOneBased() const
 141 {
 142     return OneBasedNumber::fromOneBasedInt(m_value + 1);
 143 }
 144
 145 }
 146
 147 using WTF::TextPosition0;
 148 using WTF::TextPosition1;
 149
 150 #endif // TextPosition_h