wtf/DecimalNumber.h

   1 /*
   2  * Copyright (C) 2010 Apple 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. ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #ifndef DecimalNumber_h
  27 #define DecimalNumber_h
  28
  29 #include <math.h>
  30 #include <wtf/dtoa.h>
  31 #include <wtf/MathExtras.h>
  32 #include <wtf/text/WTFString.h>
  33
  34 namespace WTF {
  35
  36 enum RoundingSignificantFiguresType { RoundingSignificantFigures };
  37 enum RoundingDecimalPlacesType { RoundingDecimalPlaces };
  38
  39 class DecimalNumber {
  40 public:
  41     DecimalNumber(double d)
  42     {
  43         ASSERT(!isnan(d) && !isinf(d));
  44         dtoa(m_significand, d, m_sign, m_exponent, m_precision);
  45
  46         ASSERT(m_precision);
  47         // Zero should always have exponent 0.
  48         ASSERT(m_significand[0] != '0' || !m_exponent);
  49         // No values other than zero should have a leading zero.
  50         ASSERT(m_significand[0] != '0' || m_precision == 1);
  51         // No values other than zero should have trailing zeros.
  52         ASSERT(m_significand[0] == '0' || m_significand[m_precision - 1] != '0');
  53     }
  54
  55     DecimalNumber(double d, RoundingSignificantFiguresType, unsigned significantFigures)
  56     {
  57         ASSERT(!isnan(d) && !isinf(d));
  58         dtoaRoundSF(m_significand, d, significantFigures, m_sign, m_exponent, m_precision);
  59
  60         ASSERT(significantFigures && significantFigures <= sizeof(DtoaBuffer));
  61         while (m_precision < significantFigures)
  62             m_significand[m_precision++] = '0';
  63
  64         ASSERT(m_precision);
  65         // Zero should always have exponent 0.
  66         ASSERT(m_significand[0] != '0' || !m_exponent);
  67     }
  68
  69     DecimalNumber(double d, RoundingDecimalPlacesType, unsigned decimalPlaces)
  70     {
  71         ASSERT(!isnan(d) && !isinf(d));
  72         dtoaRoundDP(m_significand, d, decimalPlaces, m_sign, m_exponent, m_precision);
  73
  74         unsigned significantFigures = 1 + m_exponent + decimalPlaces;
  75         ASSERT(significantFigures && significantFigures <= sizeof(DtoaBuffer));
  76         while (m_precision < significantFigures)
  77             m_significand[m_precision++] = '0';
  78
  79         ASSERT(m_precision);
  80         // Zero should always have exponent 0.
  81         ASSERT(m_significand[0] != '0' || !m_exponent);
  82     }
  83
  84     unsigned bufferLengthForStringDecimal() const;
  85     unsigned bufferLengthForStringExponential() const;
  86
  87     unsigned toStringDecimal(UChar* buffer, unsigned bufferLength) const;
  88     unsigned toStringExponential(UChar* buffer, unsigned bufferLength) const;
  89
  90     bool sign() const { return m_sign; }
  91     int exponent() const { return m_exponent; }
  92     const char* significand() const { return m_significand; } // significand contains precision characters, is not null-terminated.
  93     unsigned precision() const { return m_precision; }
  94
  95 private:
  96     bool m_sign;
  97     int m_exponent;
  98     DtoaBuffer m_significand;
  99     unsigned m_precision;
 100 };
 101
 102 } // namespace WTF
 103
 104 using WTF::DecimalNumber;
 105 using WTF::RoundingSignificantFigures;
 106 using WTF::RoundingDecimalPlaces;
 107
 108 #endif // DecimalNumber_h