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 * Copyright (C) 2012 Google Inc. All rights reserved.
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 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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 */

#ifndef Decimal_h
#define Decimal_h

#include "platform/PlatformExport.h"
#include "wtf/Allocator.h"
#include "wtf/Assertions.h"
#include "wtf/text/WTFString.h"
#include <stdint.h>

namespace blink {

namespace DecimalPrivate {
class SpecialValueHandler;
}

// This class represents decimal base floating point number.
//
// FIXME: Once all C++ compiler support decimal type, we should replace this
// class to compiler supported one. See below URI for current status of decimal
// type for C++:
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n1977.html
class PLATFORM_EXPORT Decimal {
  USING_FAST_MALLOC(Decimal);

 public:
  enum Sign {
    Positive,
    Negative,
  };

  // You should not use EncodedData other than unit testing.
  class EncodedData {
    DISALLOW_NEW();
    // For accessing FormatClass.
    friend class Decimal;
    friend class DecimalPrivate::SpecialValueHandler;

   public:
    EncodedData(Sign, int exponent, uint64_t coefficient);

    bool operator==(const EncodedData&) const;
    bool operator!=(const EncodedData& another) const {
      return !operator==(another);
    }

    uint64_t coefficient() const { return m_coefficient; }
    int countDigits() const;
    int exponent() const { return m_exponent; }
    bool isFinite() const { return !isSpecial(); }
    bool isInfinity() const { return m_formatClass == ClassInfinity; }
    bool isNaN() const { return m_formatClass == ClassNaN; }
    bool isSpecial() const {
      return m_formatClass == ClassInfinity || m_formatClass == ClassNaN;
    }
    bool isZero() const { return m_formatClass == ClassZero; }
    Sign getSign() const { return m_sign; }
    void setSign(Sign sign) { m_sign = sign; }

   private:
    enum FormatClass {
      ClassInfinity,
      ClassNormal,
      ClassNaN,
      ClassZero,
    };

    EncodedData(Sign, FormatClass);
    FormatClass getFormatClass() const { return m_formatClass; }

    uint64_t m_coefficient;
    int16_t m_exponent;
    FormatClass m_formatClass;
    Sign m_sign;
  };

  Decimal(int32_t = 0);
  Decimal(Sign, int exponent, uint64_t coefficient);
  Decimal(const Decimal&);

  Decimal& operator=(const Decimal&);
  Decimal& operator+=(const Decimal&);
  Decimal& operator-=(const Decimal&);
  Decimal& operator*=(const Decimal&);
  Decimal& operator/=(const Decimal&);

  Decimal operator-() const;

  bool operator==(const Decimal&) const;
  bool operator!=(const Decimal&) const;
  bool operator<(const Decimal&) const;
  bool operator<=(const Decimal&) const;
  bool operator>(const Decimal&) const;
  bool operator>=(const Decimal&) const;

  Decimal operator+(const Decimal&) const;
  Decimal operator-(const Decimal&) const;
  Decimal operator*(const Decimal&)const;
  Decimal operator/(const Decimal&) const;

  int exponent() const {
    ASSERT(isFinite());
    return m_data.exponent();
  }

  bool isFinite() const { return m_data.isFinite(); }
  bool isInfinity() const { return m_data.isInfinity(); }
  bool isNaN() const { return m_data.isNaN(); }
  bool isNegative() const { return getSign() == Negative; }
  bool isPositive() const { return getSign() == Positive; }
  bool isSpecial() const { return m_data.isSpecial(); }
  bool isZero() const { return m_data.isZero(); }

  Decimal abs() const;
  Decimal ceil() const;
  Decimal floor() const;
  Decimal remainder(const Decimal&) const;
  Decimal round() const;

  double toDouble() const;
  // Note: toString method supports infinity and nan but fromString not.
  String toString() const;

  static Decimal fromDouble(double);
  // fromString supports following syntax EBNF:
  //  number ::= sign? digit+ ('.' digit*) (exponent-marker sign? digit+)?
  //          | sign? '.' digit+ (exponent-marker sign? digit+)?
  //  sign ::= '+' | '-'
  //  exponent-marker ::= 'e' | 'E'
  //  digit ::= '0' | '1' | ... | '9'
  // Note: fromString doesn't support "infinity" and "nan".
  static Decimal fromString(const String&);
  static Decimal infinity(Sign);
  static Decimal nan();
  static Decimal zero(Sign);

  // You should not use below methods. We expose them for unit testing.
  explicit Decimal(const EncodedData&);
  const EncodedData& value() const { return m_data; }

 private:
  struct AlignedOperands {
    uint64_t lhsCoefficient;
    uint64_t rhsCoefficient;
    int exponent;
  };

  Decimal(double);
  Decimal compareTo(const Decimal&) const;

  static AlignedOperands alignOperands(const Decimal& lhs, const Decimal& rhs);
  static inline Sign invertSign(Sign sign) {
    return sign == Negative ? Positive : Negative;
  }

  Sign getSign() const { return m_data.getSign(); }

  EncodedData m_data;
};

PLATFORM_EXPORT std::ostream& operator<<(std::ostream&, const Decimal&);

}  // namespace blink

#endif  // Decimal_h
