The Tor Browser: mfbt/decimal/Decimal.cpp@925c144e1f1f (annotated)

mfbt/decimal/Decimal.cpp@925c144e1f1f (annotated)

mfbt/decimal/Decimal.cpp

Fri, 16 Jan 2015 18:13:44 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Fri, 16 Jan 2015 18:13:44 +0100
branch: TOR_BUG_9701
changeset 14: 925c144e1f1f
permissions: -rw-r--r--

Integrate suggestion from review to improve consistency with existing code.

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * 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
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 #include "Decimal.h"
 #include "moz-decimal-utils.h"
 #include <algorithm>
 #include <float.h>
 using namespace moz_decimal_utils;
 namespace WebCore {
 namespace DecimalPrivate {
 static int const ExponentMax = 1023;
 static int const ExponentMin = -1023;
 static int const Precision = 18;
 static const uint64_t MaxCoefficient = UINT64_C(0x16345785D89FFFF); // 999999999999999999 == 18 9's
 // This class handles Decimal special values.
 class SpecialValueHandler {
     WTF_MAKE_NONCOPYABLE(SpecialValueHandler);
 public:
     enum HandleResult {
         BothFinite,
         BothInfinity,
         EitherNaN,
         LHSIsInfinity,
         RHSIsInfinity,
     };
     SpecialValueHandler(const Decimal& lhs, const Decimal& rhs);
     HandleResult handle();
     Decimal value() const;
 private:
     enum Result {
         ResultIsLHS,
         ResultIsRHS,
         ResultIsUnknown,
     };
     const Decimal& m_lhs;
     const Decimal& m_rhs;
     Result m_result;
 };
 SpecialValueHandler::SpecialValueHandler(const Decimal& lhs, const Decimal& rhs)
     : m_lhs(lhs), m_rhs(rhs), m_result(ResultIsUnknown)
 {
 }
 SpecialValueHandler::HandleResult SpecialValueHandler::handle()
 {
     if (m_lhs.isFinite() && m_rhs.isFinite())
         return BothFinite;
     const Decimal::EncodedData::FormatClass lhsClass = m_lhs.value().formatClass();
     const Decimal::EncodedData::FormatClass rhsClass = m_rhs.value().formatClass();
     if (lhsClass == Decimal::EncodedData::ClassNaN) {
         m_result = ResultIsLHS;
         return EitherNaN;
      }
     if (rhsClass == Decimal::EncodedData::ClassNaN) {
         m_result = ResultIsRHS;
         return EitherNaN;
      }
     if (lhsClass == Decimal::EncodedData::ClassInfinity)
         return rhsClass == Decimal::EncodedData::ClassInfinity ? BothInfinity : LHSIsInfinity;
     if (rhsClass == Decimal::EncodedData::ClassInfinity)
         return RHSIsInfinity;
     ASSERT_NOT_REACHED();
     return BothFinite;
 }
 Decimal SpecialValueHandler::value() const
 {
     switch (m_result) {
     case ResultIsLHS:
         return m_lhs;
     case ResultIsRHS:
         return m_rhs;
     case ResultIsUnknown:
     default:
         ASSERT_NOT_REACHED();
         return m_lhs;
     }
 }
 // This class is used for 128 bit unsigned integer arithmetic.
 class UInt128 {
 public:
     UInt128(uint64_t low, uint64_t high)
         : m_high(high), m_low(low)
     {
     }
     UInt128& operator/=(uint32_t);
     uint64_t high() const { return m_high; }
     uint64_t low() const { return m_low; }
     static UInt128 multiply(uint64_t u, uint64_t v) { return UInt128(u * v, multiplyHigh(u, v)); }
 private:
     static uint32_t highUInt32(uint64_t x) { return static_cast<uint32_t>(x >> 32); }
     static uint32_t lowUInt32(uint64_t x) { return static_cast<uint32_t>(x & ((static_cast<uint64_t>(1) << 32) - 1)); }
     bool isZero() const { return !m_low && !m_high; }
     static uint64_t makeUInt64(uint32_t low, uint32_t high) { return low | (static_cast<uint64_t>(high) << 32); }
     static uint64_t multiplyHigh(uint64_t, uint64_t);
     uint64_t m_high;
     uint64_t m_low;
 };
 UInt128& UInt128::operator/=(const uint32_t divisor)
 {
     ASSERT(divisor);
     if (!m_high) {
         m_low /= divisor;
         return *this;
     }
     uint32_t dividend[4];
     dividend[0] = lowUInt32(m_low);
     dividend[1] = highUInt32(m_low);
     dividend[2] = lowUInt32(m_high);
     dividend[3] = highUInt32(m_high);
     uint32_t quotient[4];
     uint32_t remainder = 0;
     for (int i = 3; i >= 0; --i) {
         const uint64_t work = makeUInt64(dividend[i], remainder);
         remainder = static_cast<uint32_t>(work % divisor);
         quotient[i] = static_cast<uint32_t>(work / divisor);
     }
     m_low = makeUInt64(quotient[0], quotient[1]);
     m_high = makeUInt64(quotient[2], quotient[3]);
     return *this;
 }
 // Returns high 64bit of 128bit product.
 uint64_t UInt128::multiplyHigh(uint64_t u, uint64_t v)
 {
     const uint64_t uLow = lowUInt32(u);
     const uint64_t uHigh = highUInt32(u);
     const uint64_t vLow = lowUInt32(v);
     const uint64_t vHigh = highUInt32(v);
     const uint64_t partialProduct = uHigh * vLow + highUInt32(uLow * vLow);
     return uHigh * vHigh + highUInt32(partialProduct) + highUInt32(uLow * vHigh + lowUInt32(partialProduct));
 }
 static int countDigits(uint64_t x)
 {
     int numberOfDigits = 0;
     for (uint64_t powerOfTen = 1; x >= powerOfTen; powerOfTen *= 10) {
         ++numberOfDigits;
         if (powerOfTen >= std::numeric_limits<uint64_t>::max() / 10)
             break;
     }
     return numberOfDigits;
 }
 static uint64_t scaleDown(uint64_t x, int n)
 {
     ASSERT(n >= 0);
     while (n > 0 && x) {
         x /= 10;
         --n;
     }
     return x;
 }
 static uint64_t scaleUp(uint64_t x, int n)
 {
     ASSERT(n >= 0);
     ASSERT(n < Precision);
     uint64_t y = 1;
     uint64_t z = 10;
     for (;;) {
         if (n & 1)
             y = y * z;
         n >>= 1;
         if (!n)
             return x * y;
         z = z * z;
     }
 }
 } // namespace DecimalPrivate
 using namespace DecimalPrivate;
 Decimal::EncodedData::EncodedData(Sign sign, FormatClass formatClass)
     : m_coefficient(0)
     , m_exponent(0)
     , m_formatClass(formatClass)
     , m_sign(sign)
 {
 }
 Decimal::EncodedData::EncodedData(Sign sign, int exponent, uint64_t coefficient)
     : m_formatClass(coefficient ? ClassNormal : ClassZero)
     , m_sign(sign)
 {
     if (exponent >= ExponentMin && exponent <= ExponentMax) {
         while (coefficient > MaxCoefficient) {
             coefficient /= 10;
             ++exponent;
         }
     }
     if (exponent > ExponentMax) {
         m_coefficient = 0;
         m_exponent = 0;
         m_formatClass = ClassInfinity;
         return;
     }
     if (exponent < ExponentMin) {
         m_coefficient = 0;
         m_exponent = 0;
         m_formatClass = ClassZero;
         return;
     }
     m_coefficient = coefficient;
     m_exponent = static_cast<int16_t>(exponent);
 }
 bool Decimal::EncodedData::operator==(const EncodedData& another) const
 {
     return m_sign == another.m_sign
         && m_formatClass == another.m_formatClass
         && m_exponent == another.m_exponent
         && m_coefficient == another.m_coefficient;
 }
 Decimal::Decimal(int32_t i32)
     : m_data(i32 < 0 ? Negative : Positive, 0, i32 < 0 ? static_cast<uint64_t>(-static_cast<int64_t>(i32)) : static_cast<uint64_t>(i32))
 {
 }
 Decimal::Decimal(Sign sign, int exponent, uint64_t coefficient)
     : m_data(sign, coefficient ? exponent : 0, coefficient)
 {
 }
 Decimal::Decimal(const EncodedData& data)
     : m_data(data)
 {
 }
 Decimal::Decimal(const Decimal& other)
     : m_data(other.m_data)
 {
 }
 Decimal& Decimal::operator=(const Decimal& other)
 {
     m_data = other.m_data;
     return *this;
 }
 Decimal& Decimal::operator+=(const Decimal& other)
 {
     m_data = (*this + other).m_data;
     return *this;
 }
 Decimal& Decimal::operator-=(const Decimal& other)
 {
     m_data = (*this - other).m_data;
     return *this;
 }
 Decimal& Decimal::operator*=(const Decimal& other)
 {
     m_data = (*this * other).m_data;
     return *this;
 }
 Decimal& Decimal::operator/=(const Decimal& other)
 {
     m_data = (*this / other).m_data;
     return *this;
 }
 Decimal Decimal::operator-() const
 {
     if (isNaN())
         return *this;
     Decimal result(*this);
     result.m_data.setSign(invertSign(m_data.sign()));
     return result;
 }
 Decimal Decimal::operator+(const Decimal& rhs) const
 {
     const Decimal& lhs = *this;
     const Sign lhsSign = lhs.sign();
     const Sign rhsSign = rhs.sign();
     SpecialValueHandler handler(lhs, rhs);
     switch (handler.handle()) {
     case SpecialValueHandler::BothFinite:
         break;
     case SpecialValueHandler::BothInfinity:
         return lhsSign == rhsSign ? lhs : nan();
     case SpecialValueHandler::EitherNaN:
         return handler.value();
     case SpecialValueHandler::LHSIsInfinity:
         return lhs;
     case SpecialValueHandler::RHSIsInfinity:
         return rhs;
     }
     const AlignedOperands alignedOperands = alignOperands(lhs, rhs);
     const uint64_t result = lhsSign == rhsSign
         ? alignedOperands.lhsCoefficient + alignedOperands.rhsCoefficient
         : alignedOperands.lhsCoefficient - alignedOperands.rhsCoefficient;
     if (lhsSign == Negative && rhsSign == Positive && !result)
         return Decimal(Positive, alignedOperands.exponent, 0);
     return static_cast<int64_t>(result) >= 0
         ? Decimal(lhsSign, alignedOperands.exponent, result)
         : Decimal(invertSign(lhsSign), alignedOperands.exponent, -static_cast<int64_t>(result));
 }
 Decimal Decimal::operator-(const Decimal& rhs) const
 {
     const Decimal& lhs = *this;
     const Sign lhsSign = lhs.sign();
     const Sign rhsSign = rhs.sign();
     SpecialValueHandler handler(lhs, rhs);
     switch (handler.handle()) {
     case SpecialValueHandler::BothFinite:
         break;
     case SpecialValueHandler::BothInfinity:
         return lhsSign == rhsSign ? nan() : lhs;
     case SpecialValueHandler::EitherNaN:
         return handler.value();
     case SpecialValueHandler::LHSIsInfinity:
         return lhs;
     case SpecialValueHandler::RHSIsInfinity:
         return infinity(invertSign(rhsSign));
     }
     const AlignedOperands alignedOperands = alignOperands(lhs, rhs);
     const uint64_t result = lhsSign == rhsSign
         ? alignedOperands.lhsCoefficient - alignedOperands.rhsCoefficient
         : alignedOperands.lhsCoefficient + alignedOperands.rhsCoefficient;
     if (lhsSign == Negative && rhsSign == Negative && !result)
         return Decimal(Positive, alignedOperands.exponent, 0);
     return static_cast<int64_t>(result) >= 0
         ? Decimal(lhsSign, alignedOperands.exponent, result)
         : Decimal(invertSign(lhsSign), alignedOperands.exponent, -static_cast<int64_t>(result));
 }
 Decimal Decimal::operator*(const Decimal& rhs) const
 {
     const Decimal& lhs = *this;
     const Sign lhsSign = lhs.sign();
     const Sign rhsSign = rhs.sign();
     const Sign resultSign = lhsSign == rhsSign ? Positive : Negative;
     SpecialValueHandler handler(lhs, rhs);
     switch (handler.handle()) {
     case SpecialValueHandler::BothFinite: {
         const uint64_t lhsCoefficient = lhs.m_data.coefficient();
         const uint64_t rhsCoefficient = rhs.m_data.coefficient();
         int resultExponent = lhs.exponent() + rhs.exponent();
         UInt128 work(UInt128::multiply(lhsCoefficient, rhsCoefficient));
         while (work.high()) {
             work /= 10;
             ++resultExponent;
         }
         return Decimal(resultSign, resultExponent, work.low());
     }
     case SpecialValueHandler::BothInfinity:
         return infinity(resultSign);
     case SpecialValueHandler::EitherNaN:
         return handler.value();
     case SpecialValueHandler::LHSIsInfinity:
         return rhs.isZero() ? nan() : infinity(resultSign);
     case SpecialValueHandler::RHSIsInfinity:
         return lhs.isZero() ? nan() : infinity(resultSign);
     }
     ASSERT_NOT_REACHED();
     return nan();
 }
 Decimal Decimal::operator/(const Decimal& rhs) const
 {
     const Decimal& lhs = *this;
     const Sign lhsSign = lhs.sign();
     const Sign rhsSign = rhs.sign();
     const Sign resultSign = lhsSign == rhsSign ? Positive : Negative;
     SpecialValueHandler handler(lhs, rhs);
     switch (handler.handle()) {
     case SpecialValueHandler::BothFinite:
         break;
     case SpecialValueHandler::BothInfinity:
         return nan();
     case SpecialValueHandler::EitherNaN:
         return handler.value();
     case SpecialValueHandler::LHSIsInfinity:
         return infinity(resultSign);
     case SpecialValueHandler::RHSIsInfinity:
         return zero(resultSign);
     }
     ASSERT(lhs.isFinite());
     ASSERT(rhs.isFinite());
     if (rhs.isZero())
         return lhs.isZero() ? nan() : infinity(resultSign);
     int resultExponent = lhs.exponent() - rhs.exponent();
     if (lhs.isZero())
         return Decimal(resultSign, resultExponent, 0);
     uint64_t remainder = lhs.m_data.coefficient();
     const uint64_t divisor = rhs.m_data.coefficient();
     uint64_t result = 0;
     while (result < MaxCoefficient / 100) {
         while (remainder < divisor) {
             remainder *= 10;
             result *= 10;
             --resultExponent;
         }
         result += remainder / divisor;
         remainder %= divisor;
         if (!remainder)
             break;
     }
     if (remainder > divisor / 2)
         ++result;
     return Decimal(resultSign, resultExponent, result);
 }
 bool Decimal::operator==(const Decimal& rhs) const
 {
     if (isNaN() || rhs.isNaN())
         return false;
     return m_data == rhs.m_data || compareTo(rhs).isZero();
 }
 bool Decimal::operator!=(const Decimal& rhs) const
 {
     if (isNaN() || rhs.isNaN())
         return true;
     if (m_data == rhs.m_data)
         return false;
     const Decimal result = compareTo(rhs);
     if (result.isNaN())
         return false;
     return !result.isZero();
 }
 bool Decimal::operator<(const Decimal& rhs) const
 {
     const Decimal result = compareTo(rhs);
     if (result.isNaN())
         return false;
     return !result.isZero() && result.isNegative();
 }
 bool Decimal::operator<=(const Decimal& rhs) const
 {
     if (isNaN() || rhs.isNaN())
         return false;
     if (m_data == rhs.m_data)
         return true;
     const Decimal result = compareTo(rhs);
     if (result.isNaN())
         return false;
     return result.isZero() || result.isNegative();
 }
 bool Decimal::operator>(const Decimal& rhs) const
 {
     const Decimal result = compareTo(rhs);
     if (result.isNaN())
         return false;
     return !result.isZero() && result.isPositive();
 }
 bool Decimal::operator>=(const Decimal& rhs) const
 {
     if (isNaN() || rhs.isNaN())
         return false;
     if (m_data == rhs.m_data)
         return true;
     const Decimal result = compareTo(rhs);
     if (result.isNaN())
         return false;
     return result.isZero() || !result.isNegative();
 }
 Decimal Decimal::abs() const
 {
     Decimal result(*this);
     result.m_data.setSign(Positive);
     return result;
 }
 Decimal::AlignedOperands Decimal::alignOperands(const Decimal& lhs, const Decimal& rhs)
 {
     ASSERT(lhs.isFinite());
     ASSERT(rhs.isFinite());
     const int lhsExponent = lhs.exponent();
     const int rhsExponent = rhs.exponent();
     int exponent = std::min(lhsExponent, rhsExponent);
     uint64_t lhsCoefficient = lhs.m_data.coefficient();
     uint64_t rhsCoefficient = rhs.m_data.coefficient();
     if (lhsExponent > rhsExponent) {
         const int numberOfLHSDigits = countDigits(lhsCoefficient);
         if (numberOfLHSDigits) {
             const int lhsShiftAmount = lhsExponent - rhsExponent;
             const int overflow = numberOfLHSDigits + lhsShiftAmount - Precision;
             if (overflow <= 0)
                 lhsCoefficient = scaleUp(lhsCoefficient, lhsShiftAmount);
             else {
                 lhsCoefficient = scaleUp(lhsCoefficient, lhsShiftAmount - overflow);
                 rhsCoefficient = scaleDown(rhsCoefficient, overflow);
                 exponent += overflow;
             }
         }
     } else if (lhsExponent < rhsExponent) {
         const int numberOfRHSDigits = countDigits(rhsCoefficient);
         if (numberOfRHSDigits) {
             const int rhsShiftAmount = rhsExponent - lhsExponent;
             const int overflow = numberOfRHSDigits + rhsShiftAmount - Precision;
             if (overflow <= 0)
                 rhsCoefficient = scaleUp(rhsCoefficient, rhsShiftAmount);
             else {
                 rhsCoefficient = scaleUp(rhsCoefficient, rhsShiftAmount - overflow);
                 lhsCoefficient = scaleDown(lhsCoefficient, overflow);
                 exponent += overflow;
             }
         }
     }
     AlignedOperands alignedOperands;
     alignedOperands.exponent = exponent;
     alignedOperands.lhsCoefficient = lhsCoefficient;
     alignedOperands.rhsCoefficient = rhsCoefficient;
     return alignedOperands;
 }
 // Round toward positive infinity.
 // Note: Mac ports defines ceil(x) as wtf_ceil(x), so we can't use name "ceil" here.
 Decimal Decimal::ceiling() const
 {
     if (isSpecial())
         return *this;
     if (exponent() >= 0)
         return *this;
     uint64_t coefficient = m_data.coefficient();
     const int numberOfDigits = countDigits(coefficient);
     const int numberOfDropDigits = -exponent();
     if (numberOfDigits < numberOfDropDigits)
         return isPositive() ? Decimal(1) : zero(Positive);
     uint64_t result = scaleDown(coefficient, numberOfDropDigits);
     uint64_t droppedDigits = coefficient - scaleUp(result, numberOfDropDigits);
     if (droppedDigits && isPositive())
         result += 1;
     return Decimal(sign(), 0, result);
 }
 Decimal Decimal::compareTo(const Decimal& rhs) const
 {
     const Decimal result(*this - rhs);
     switch (result.m_data.formatClass()) {
     case EncodedData::ClassInfinity:
         return result.isNegative() ? Decimal(-1) : Decimal(1);
     case EncodedData::ClassNaN:
     case EncodedData::ClassNormal:
         return result;
     case EncodedData::ClassZero:
         return zero(Positive);
     default:
         ASSERT_NOT_REACHED();
         return nan();
     }
 }
 // Round toward negative infinity.
 Decimal Decimal::floor() const
 {
     if (isSpecial())
         return *this;
     if (exponent() >= 0)
         return *this;
     uint64_t coefficient = m_data.coefficient();
     const int numberOfDigits = countDigits(coefficient);
     const int numberOfDropDigits = -exponent();
     if (numberOfDigits < numberOfDropDigits)
         return isPositive() ? zero(Positive) : Decimal(-1);
     uint64_t result = scaleDown(coefficient, numberOfDropDigits);
     uint64_t droppedDigits = coefficient - scaleUp(result, numberOfDropDigits);
     if (droppedDigits && isNegative()) {
         result += 1;
     }
     return Decimal(sign(), 0, result);
 }
 Decimal Decimal::fromDouble(double doubleValue)
 {
     if (std::isfinite(doubleValue))
         return fromString(mozToString(doubleValue));
     if (std::isinf(doubleValue))
         return infinity(doubleValue < 0 ? Negative : Positive);
     return nan();
 }
 Decimal Decimal::fromString(const String& str)
 {
     int exponent = 0;
     Sign exponentSign = Positive;
     int numberOfDigits = 0;
     int numberOfDigitsAfterDot = 0;
     int numberOfExtraDigits = 0;
     Sign sign = Positive;
     enum {
         StateDigit,
         StateDot,
         StateDotDigit,
         StateE,
         StateEDigit,
         StateESign,
         StateSign,
         StateStart,
         StateZero,
     } state = StateStart;
 #define HandleCharAndBreak(expected, nextState) \
     if (ch == expected) { \
         state = nextState; \
         break; \
     }
 #define HandleTwoCharsAndBreak(expected1, expected2, nextState) \
     if (ch == expected1 || ch == expected2) { \
         state = nextState; \
         break; \
     }
     uint64_t accumulator = 0;
     for (unsigned index = 0; index < str.length(); ++index) {
         const int ch = str[index];
         switch (state) {
         case StateDigit:
             if (ch >= '0' && ch <= '9') {
                 if (numberOfDigits < Precision) {
                     ++numberOfDigits;
                     accumulator *= 10;
                     accumulator += ch - '0';
                 } else
                     ++numberOfExtraDigits;
                 break;
             }
             HandleCharAndBreak('.', StateDot);
             HandleTwoCharsAndBreak('E', 'e', StateE);
             return nan();
         case StateDot:
             if (ch >= '0' && ch <= '9') {
                 if (numberOfDigits < Precision) {
                     ++numberOfDigits;
                     ++numberOfDigitsAfterDot;
                     accumulator *= 10;
                     accumulator += ch - '0';
                 }
                 state = StateDotDigit;
                 break;
             }
         case StateDotDigit:
             if (ch >= '0' && ch <= '9') {
                 if (numberOfDigits < Precision) {
                     ++numberOfDigits;
                     ++numberOfDigitsAfterDot;
                     accumulator *= 10;
                     accumulator += ch - '0';
                 }
                 break;
             }
             HandleTwoCharsAndBreak('E', 'e', StateE);
             return nan();
         case StateE:
             if (ch == '+') {
                 exponentSign = Positive;
                 state = StateESign;
                 break;
             }
             if (ch == '-') {
                 exponentSign = Negative;
                 state = StateESign;
                 break;
             }
             if (ch >= '0' && ch <= '9') {
                 exponent = ch - '0';
                 state = StateEDigit;
                 break;
             }
             return nan();
         case StateEDigit:
             if (ch >= '0' && ch <= '9') {
                 exponent *= 10;
                 exponent += ch - '0';
                 if (exponent > ExponentMax + Precision) {
                     if (accumulator)
                         return exponentSign == Negative ? zero(Positive) : infinity(sign);
                     return zero(sign);
                 }
                 state = StateEDigit;
                 break;
             }
             return nan();
         case StateESign:
             if (ch >= '0' && ch <= '9') {
                 exponent = ch - '0';
                 state = StateEDigit;
                 break;
             }
             return nan();
         case StateSign:
             if (ch >= '1' && ch <= '9') {
                 accumulator = ch - '0';
                 numberOfDigits = 1;
                 state = StateDigit;
                 break;
             }
             HandleCharAndBreak('0', StateZero);
             return nan();
         case StateStart:
             if (ch >= '1' && ch <= '9') {
                 accumulator = ch - '0';
                 numberOfDigits = 1;
                 state = StateDigit;
                 break;
             }
             if (ch == '-') {
                 sign = Negative;
                 state = StateSign;
                 break;
             }
             if (ch == '+') {
                 sign = Positive;
                 state = StateSign;
                 break;
             }
             HandleCharAndBreak('0', StateZero);
             HandleCharAndBreak('.', StateDot);
             return nan();
         case StateZero:
             if (ch == '0')
                 break;
             if (ch >= '1' && ch <= '9') {
                 accumulator = ch - '0';
                 numberOfDigits = 1;
                 state = StateDigit;
                 break;
             }
             HandleCharAndBreak('.', StateDot);
             HandleTwoCharsAndBreak('E', 'e', StateE);
             return nan();
         default:
             ASSERT_NOT_REACHED();
             return nan();
         }
     }
     if (state == StateZero)
         return zero(sign);
     if (state == StateDigit || state == StateEDigit || state == StateDotDigit) {
         int resultExponent = exponent * (exponentSign == Negative ? -1 : 1) - numberOfDigitsAfterDot + numberOfExtraDigits;
         if (resultExponent < ExponentMin)
             return zero(Positive);
         const int overflow = resultExponent - ExponentMax + 1;
         if (overflow > 0) {
             if (overflow + numberOfDigits - numberOfDigitsAfterDot > Precision)
                 return infinity(sign);
             accumulator = scaleUp(accumulator, overflow);
             resultExponent -= overflow;
         }
         return Decimal(sign, resultExponent, accumulator);
     }
     return nan();
 }
 Decimal Decimal::infinity(const Sign sign)
 {
     return Decimal(EncodedData(sign, EncodedData::ClassInfinity));
 }
 Decimal Decimal::nan()
 {
     return Decimal(EncodedData(Positive, EncodedData::ClassNaN));
 }
 Decimal Decimal::remainder(const Decimal& rhs) const
 {
     const Decimal quotient = *this / rhs;
     return quotient.isSpecial() ? quotient : *this - (quotient.isNegative() ? quotient.ceiling() : quotient.floor()) * rhs;
 }
 Decimal Decimal::round() const
 {
     if (isSpecial())
         return *this;
     if (exponent() >= 0)
         return *this;
     uint64_t result = m_data.coefficient();
     const int numberOfDigits = countDigits(result);
     const int numberOfDropDigits = -exponent();
     if (numberOfDigits < numberOfDropDigits)
         return zero(Positive);
     // We're implementing round-half-away-from-zero, so we only need the one
     // (the most significant) fractional digit:
     result = scaleDown(result, numberOfDropDigits - 1);
     if (result % 10 >= 5)
         result += 10;
     result /= 10;
     return Decimal(sign(), 0, result);
 }
 double Decimal::toDouble() const
 {
     if (isFinite()) {
         bool valid;
         const double doubleValue = mozToDouble(toString(), &valid);
         return valid ? doubleValue : std::numeric_limits<double>::quiet_NaN();
     }
     if (isInfinity())
         return isNegative() ? -std::numeric_limits<double>::infinity() : std::numeric_limits<double>::infinity();
     return std::numeric_limits<double>::quiet_NaN();
 }
 String Decimal::toString() const
 {
     switch (m_data.formatClass()) {
     case EncodedData::ClassInfinity:
         return sign() ? "-Infinity" : "Infinity";
     case EncodedData::ClassNaN:
         return "NaN";
     case EncodedData::ClassNormal:
     case EncodedData::ClassZero:
         break;
     default:
         ASSERT_NOT_REACHED();
         return "";
     }
     StringBuilder builder;
     if (sign())
         builder.append('-');
     int originalExponent = exponent();
     uint64_t coefficient = m_data.coefficient();
     if (originalExponent < 0) {
         const int maxDigits = DBL_DIG;
         uint64_t lastDigit = 0;
         while (countDigits(coefficient) > maxDigits) {
             lastDigit = coefficient % 10;
             coefficient /= 10;
             ++originalExponent;
         }
         if (lastDigit >= 5)
             ++coefficient;
         while (originalExponent < 0 && coefficient && !(coefficient % 10)) {
             coefficient /= 10;
             ++originalExponent;
         }
     }
     const String digits = mozToString(coefficient);
     int coefficientLength = static_cast<int>(digits.length());
     const int adjustedExponent = originalExponent + coefficientLength - 1;
     if (originalExponent <= 0 && adjustedExponent >= -6) {
         if (!originalExponent) {
             builder.append(digits);
             return builder.toString();
         }
         if (adjustedExponent >= 0) {
             for (int i = 0; i < coefficientLength; ++i) {
                 builder.append(digits[i]);
                 if (i == adjustedExponent)
                     builder.append('.');
             }
             return builder.toString();
         }
         builder.appendLiteral("0.");
         for (int i = adjustedExponent + 1; i < 0; ++i)
             builder.append('0');
         builder.append(digits);
     } else {
         builder.append(digits[0]);
         while (coefficientLength >= 2 && digits[coefficientLength - 1] == '0')
             --coefficientLength;
         if (coefficientLength >= 2) {
             builder.append('.');
             for (int i = 1; i < coefficientLength; ++i)
                 builder.append(digits[i]);
         }
         if (adjustedExponent) {
             builder.append(adjustedExponent < 0 ? "e" : "e+");
             builder.appendNumber(adjustedExponent);
         }
     }
     return builder.toString();
 }
 bool Decimal::toString(char* strBuf, size_t bufLength) const
 {
   ASSERT(bufLength > 0);
   String str = toString();
   size_t length = str.copy(strBuf, bufLength);
   if (length < bufLength) {
     strBuf[length] = '\0';
     return true;
   }
   strBuf[bufLength - 1] = '\0';
   return false;
 }
 Decimal Decimal::zero(Sign sign)
 {
     return Decimal(EncodedData(sign, EncodedData::ClassZero));
 }
 } // namespace WebCore

The Tor Browser / annotate

mfbt/decimal/Decimal.cpp@925c144e1f1f (annotated)

mfbt/decimal/Decimal.cpp