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      1 /*
      2  * Copyright (C) 2012 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 are
      6  * met:
      7  *
      8  *     * Redistributions of source code must retain the above copyright
      9  * notice, this list of conditions and the following disclaimer.
     10  *     * Redistributions in binary form must reproduce the above
     11  * copyright notice, this list of conditions and the following disclaimer
     12  * in the documentation and/or other materials provided with the
     13  * distribution.
     14  *     * Neither the name of Google Inc. nor the names of its
     15  * contributors may be used to endorse or promote products derived from
     16  * this software without specific prior written permission.
     17  *
     18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     19  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     21  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     22  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     23  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     24  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     28  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     29  */
     30 
     31 #ifndef Decimal_h
     32 #define Decimal_h
     33 
     34 #include "platform/PlatformExport.h"
     35 #include "wtf/Assertions.h"
     36 #include "wtf/text/WTFString.h"
     37 #include <stdint.h>
     38 
     39 namespace WebCore {
     40 
     41 namespace DecimalPrivate {
     42 class SpecialValueHandler;
     43 }
     44 
     45 // This class represents decimal base floating point number.
     46 //
     47 // FIXME: Once all C++ compiler support decimal type, we should replace this
     48 // class to compiler supported one. See below URI for current status of decimal
     49 // type for C++: // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n1977.html
     50 class PLATFORM_EXPORT Decimal {
     51     WTF_MAKE_FAST_ALLOCATED;
     52 public:
     53     enum Sign {
     54         Positive,
     55         Negative,
     56     };
     57 
     58     // You should not use EncodedData other than unit testing.
     59     class EncodedData {
     60         // For accessing FormatClass.
     61         friend class Decimal;
     62         friend class DecimalPrivate::SpecialValueHandler;
     63     public:
     64         EncodedData(Sign, int exponent, uint64_t coefficient);
     65 
     66         bool operator==(const EncodedData&) const;
     67         bool operator!=(const EncodedData& another) const { return !operator==(another); }
     68 
     69         uint64_t coefficient() const { return m_coefficient; }
     70         int countDigits() const;
     71         int exponent() const { return m_exponent; }
     72         bool isFinite() const { return !isSpecial(); }
     73         bool isInfinity() const { return m_formatClass == ClassInfinity; }
     74         bool isNaN() const { return m_formatClass == ClassNaN; }
     75         bool isSpecial() const { return m_formatClass == ClassInfinity || m_formatClass == ClassNaN; }
     76         bool isZero() const { return m_formatClass == ClassZero; }
     77         Sign sign() const { return m_sign; }
     78         void setSign(Sign sign) { m_sign = sign; }
     79 
     80     private:
     81         enum FormatClass {
     82             ClassInfinity,
     83             ClassNormal,
     84             ClassNaN,
     85             ClassZero,
     86         };
     87 
     88         EncodedData(Sign, FormatClass);
     89         FormatClass formatClass() const { return m_formatClass; }
     90 
     91         uint64_t m_coefficient;
     92         int16_t m_exponent;
     93         FormatClass m_formatClass;
     94         Sign m_sign;
     95     };
     96 
     97     Decimal(int32_t = 0);
     98     Decimal(Sign, int exponent, uint64_t coefficient);
     99     Decimal(const Decimal&);
    100 
    101     Decimal& operator=(const Decimal&);
    102     Decimal& operator+=(const Decimal&);
    103     Decimal& operator-=(const Decimal&);
    104     Decimal& operator*=(const Decimal&);
    105     Decimal& operator/=(const Decimal&);
    106 
    107     Decimal operator-() const;
    108 
    109     bool operator==(const Decimal&) const;
    110     bool operator!=(const Decimal&) const;
    111     bool operator<(const Decimal&) const;
    112     bool operator<=(const Decimal&) const;
    113     bool operator>(const Decimal&) const;
    114     bool operator>=(const Decimal&) const;
    115 
    116     Decimal operator+(const Decimal&) const;
    117     Decimal operator-(const Decimal&) const;
    118     Decimal operator*(const Decimal&) const;
    119     Decimal operator/(const Decimal&) const;
    120 
    121     int exponent() const
    122     {
    123         ASSERT(isFinite());
    124         return m_data.exponent();
    125     }
    126 
    127     bool isFinite() const { return m_data.isFinite(); }
    128     bool isInfinity() const { return m_data.isInfinity(); }
    129     bool isNaN() const { return m_data.isNaN(); }
    130     bool isNegative() const { return sign() == Negative; }
    131     bool isPositive() const { return sign() == Positive; }
    132     bool isSpecial() const { return m_data.isSpecial(); }
    133     bool isZero() const { return m_data.isZero(); }
    134 
    135     Decimal abs() const;
    136     Decimal ceiling() const;
    137     Decimal floor() const;
    138     Decimal remainder(const Decimal&) const;
    139     Decimal round() const;
    140 
    141     double toDouble() const;
    142     // Note: toString method supports infinity and nan but fromString not.
    143     String toString() const;
    144 
    145     static Decimal fromDouble(double);
    146     // fromString supports following syntax EBNF:
    147     //  number ::= sign? digit+ ('.' digit*) (exponent-marker sign? digit+)?
    148     //          | sign? '.' digit+ (exponent-marker sign? digit+)?
    149     //  sign ::= '+' | '-'
    150     //  exponent-marker ::= 'e' | 'E'
    151     //  digit ::= '0' | '1' | ... | '9'
    152     // Note: fromString doesn't support "infinity" and "nan".
    153     static Decimal fromString(const String&);
    154     static Decimal infinity(Sign);
    155     static Decimal nan();
    156     static Decimal zero(Sign);
    157 
    158     // You should not use below methods. We expose them for unit testing.
    159     explicit Decimal(const EncodedData&);
    160     const EncodedData& value() const { return m_data; }
    161 
    162 private:
    163     struct AlignedOperands {
    164         uint64_t lhsCoefficient;
    165         uint64_t rhsCoefficient;
    166         int exponent;
    167     };
    168 
    169     Decimal(double);
    170     Decimal compareTo(const Decimal&) const;
    171 
    172     static AlignedOperands alignOperands(const Decimal& lhs, const Decimal& rhs);
    173     static inline Sign invertSign(Sign sign) { return sign == Negative ? Positive : Negative; }
    174 
    175     Sign sign() const { return m_data.sign(); }
    176 
    177     EncodedData m_data;
    178 };
    179 
    180 } // namespace WebCore
    181 
    182 #endif // Decimal_h
    183