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third_party/WebKit/Source/wtf/dtoa/fixed-dtoa.cc

Index: third_party/WebKit/Source/wtf/dtoa/fixed-dtoa.cc
diff --git a/third_party/WebKit/Source/wtf/dtoa/fixed-dtoa.cc b/third_party/WebKit/Source/wtf/dtoa/fixed-dtoa.cc
index f01d3d9a93251882e7c007bce3251d9fd2e71df4..2111e20ba1b08b65a04cd1e5cda8a7533adb35bd 100644
--- a/third_party/WebKit/Source/wtf/dtoa/fixed-dtoa.cc
+++ b/third_party/WebKit/Source/wtf/dtoa/fixed-dtoa.cc
@@ -27,380 +27,380 @@
 
 #include "fixed-dtoa.h"
 
-#include "double.h"
 #include <math.h>
+#include "double.h"
 
 namespace WTF {
 
 namespace double_conversion {
 
-    // Represents a 128bit type. This class should be replaced by a native type on
-    // platforms that support 128bit integers.
-    class UInt128 {
-    public:
-        UInt128() : high_bits_(0), low_bits_(0) { }
-        UInt128(uint64_t high, uint64_t low) : high_bits_(high), low_bits_(low) { }
-
-        void Multiply(uint32_t multiplicand) {
-            uint64_t accumulator;
-
-            accumulator = (low_bits_ & kMask32) * multiplicand;
-            uint32_t part = static_cast<uint32_t>(accumulator & kMask32);
-            accumulator >>= 32;
-            accumulator = accumulator + (low_bits_ >> 32) * multiplicand;
-            low_bits_ = (accumulator << 32) + part;
-            accumulator >>= 32;
-            accumulator = accumulator + (high_bits_ & kMask32) * multiplicand;
-            part = static_cast<uint32_t>(accumulator & kMask32);
-            accumulator >>= 32;
-            accumulator = accumulator + (high_bits_ >> 32) * multiplicand;
-            high_bits_ = (accumulator << 32) + part;
-            ASSERT((accumulator >> 32) == 0);
-        }
-
-        void Shift(int shift_amount) {
-            ASSERT(-64 <= shift_amount && shift_amount <= 64);
-            if (shift_amount == 0) {
-                return;
-            } else if (shift_amount == -64) {
-                high_bits_ = low_bits_;
-                low_bits_ = 0;
-            } else if (shift_amount == 64) {
-                low_bits_ = high_bits_;
-                high_bits_ = 0;
-            } else if (shift_amount <= 0) {
-                high_bits_ <<= -shift_amount;
-                high_bits_ += low_bits_ >> (64 + shift_amount);
-                low_bits_ <<= -shift_amount;
-            } else {
-                low_bits_ >>= shift_amount;
-                low_bits_ += high_bits_ << (64 - shift_amount);
-                high_bits_ >>= shift_amount;
-            }
-        }
-
-        // Modifies *this to *this MOD (2^power).
-        // Returns *this DIV (2^power).
-        int DivModPowerOf2(int power) {
-            if (power >= 64) {
-                int result = static_cast<int>(high_bits_ >> (power - 64));
-                high_bits_ -= static_cast<uint64_t>(result) << (power - 64);
-                return result;
-            } else {
-                uint64_t part_low = low_bits_ >> power;
-                uint64_t part_high = high_bits_ << (64 - power);
-                int result = static_cast<int>(part_low + part_high);
-                high_bits_ = 0;
-                low_bits_ -= part_low << power;
-                return result;
-            }
-        }
-
-        bool IsZero() const {
-            return high_bits_ == 0 && low_bits_ == 0;
-        }
-
-        int BitAt(int position) {
-            if (position >= 64) {
-                return static_cast<int>(high_bits_ >> (position - 64)) & 1;
-            } else {
-                return static_cast<int>(low_bits_ >> position) & 1;
-            }
-        }
-
-    private:
-        static const uint64_t kMask32 = 0xFFFFFFFF;
-        // Value == (high_bits_ << 64) + low_bits_
-        uint64_t high_bits_;
-        uint64_t low_bits_;
-    };
-
-
-    static const int kDoubleSignificandSize = 53;  // Includes the hidden bit.
-
-
-    static void FillDigits32FixedLength(uint32_t number, int requested_length,
-                                        Vector<char> buffer, int* length) {
-        for (int i = requested_length - 1; i >= 0; --i) {
-            buffer[(*length) + i] = '0' + number % 10;
-            number /= 10;
-        }
-        *length += requested_length;
+// Represents a 128bit type. This class should be replaced by a native type on
+// platforms that support 128bit integers.
+class UInt128 {
+ public:
+  UInt128() : high_bits_(0), low_bits_(0) {}
+  UInt128(uint64_t high, uint64_t low) : high_bits_(high), low_bits_(low) {}
+
+  void Multiply(uint32_t multiplicand) {
+    uint64_t accumulator;
+
+    accumulator = (low_bits_ & kMask32) * multiplicand;
+    uint32_t part = static_cast<uint32_t>(accumulator & kMask32);
+    accumulator >>= 32;
+    accumulator = accumulator + (low_bits_ >> 32) * multiplicand;
+    low_bits_ = (accumulator << 32) + part;
+    accumulator >>= 32;
+    accumulator = accumulator + (high_bits_ & kMask32) * multiplicand;
+    part = static_cast<uint32_t>(accumulator & kMask32);
+    accumulator >>= 32;
+    accumulator = accumulator + (high_bits_ >> 32) * multiplicand;
+    high_bits_ = (accumulator << 32) + part;
+    ASSERT((accumulator >> 32) == 0);
+  }
+
+  void Shift(int shift_amount) {
+    ASSERT(-64 <= shift_amount && shift_amount <= 64);
+    if (shift_amount == 0) {
+      return;
+    } else if (shift_amount == -64) {
+      high_bits_ = low_bits_;
+      low_bits_ = 0;
+    } else if (shift_amount == 64) {
+      low_bits_ = high_bits_;
+      high_bits_ = 0;
+    } else if (shift_amount <= 0) {
+      high_bits_ <<= -shift_amount;
+      high_bits_ += low_bits_ >> (64 + shift_amount);
+      low_bits_ <<= -shift_amount;
+    } else {
+      low_bits_ >>= shift_amount;
+      low_bits_ += high_bits_ << (64 - shift_amount);
+      high_bits_ >>= shift_amount;
     }
-
-
-    static void FillDigits32(uint32_t number, Vector<char> buffer, int* length) {
-        int number_length = 0;
-        // We fill the digits in reverse order and exchange them afterwards.
-        while (number != 0) {
-            char digit = number % 10;
-            number /= 10;
-            buffer[(*length) + number_length] = '0' + digit;
-            number_length++;
-        }
-        // Exchange the digits.
-        int i = *length;
-        int j = *length + number_length - 1;
-        while (i < j) {
-            char tmp = buffer[i];
-            buffer[i] = buffer[j];
-            buffer[j] = tmp;
-            i++;
-            j--;
-        }
-        *length += number_length;
+  }
+
+  // Modifies *this to *this MOD (2^power).
+  // Returns *this DIV (2^power).
+  int DivModPowerOf2(int power) {
+    if (power >= 64) {
+      int result = static_cast<int>(high_bits_ >> (power - 64));
+      high_bits_ -= static_cast<uint64_t>(result) << (power - 64);
+      return result;
+    } else {
+      uint64_t part_low = low_bits_ >> power;
+      uint64_t part_high = high_bits_ << (64 - power);
+      int result = static_cast<int>(part_low + part_high);
+      high_bits_ = 0;
+      low_bits_ -= part_low << power;
+      return result;
     }
+  }
 
+  bool IsZero() const { return high_bits_ == 0 && low_bits_ == 0; }
 
-    static void FillDigits64FixedLength(uint64_t number, int,
-                                        Vector<char> buffer, int* length) {
-        const uint32_t kTen7 = 10000000;
-        // For efficiency cut the number into 3 uint32_t parts, and print those.
-        uint32_t part2 = static_cast<uint32_t>(number % kTen7);
-        number /= kTen7;
-        uint32_t part1 = static_cast<uint32_t>(number % kTen7);
-        uint32_t part0 = static_cast<uint32_t>(number / kTen7);
-
-        FillDigits32FixedLength(part0, 3, buffer, length);
-        FillDigits32FixedLength(part1, 7, buffer, length);
-        FillDigits32FixedLength(part2, 7, buffer, length);
+  int BitAt(int position) {
+    if (position >= 64) {
+      return static_cast<int>(high_bits_ >> (position - 64)) & 1;
+    } else {
+      return static_cast<int>(low_bits_ >> position) & 1;
     }
-
-
-    static void FillDigits64(uint64_t number, Vector<char> buffer, int* length) {
-        const uint32_t kTen7 = 10000000;
-        // For efficiency cut the number into 3 uint32_t parts, and print those.
-        uint32_t part2 = static_cast<uint32_t>(number % kTen7);
-        number /= kTen7;
-        uint32_t part1 = static_cast<uint32_t>(number % kTen7);
-        uint32_t part0 = static_cast<uint32_t>(number / kTen7);
-
-        if (part0 != 0) {
-            FillDigits32(part0, buffer, length);
-            FillDigits32FixedLength(part1, 7, buffer, length);
-            FillDigits32FixedLength(part2, 7, buffer, length);
-        } else if (part1 != 0) {
-            FillDigits32(part1, buffer, length);
-            FillDigits32FixedLength(part2, 7, buffer, length);
-        } else {
-            FillDigits32(part2, buffer, length);
-        }
+  }
+
+ private:
+  static const uint64_t kMask32 = 0xFFFFFFFF;
+  // Value == (high_bits_ << 64) + low_bits_
+  uint64_t high_bits_;
+  uint64_t low_bits_;
+};
+
+static const int kDoubleSignificandSize = 53;  // Includes the hidden bit.
+
+static void FillDigits32FixedLength(uint32_t number,
+                                    int requested_length,
+                                    Vector<char> buffer,
+                                    int* length) {
+  for (int i = requested_length - 1; i >= 0; --i) {
+    buffer[(*length) + i] = '0' + number % 10;
+    number /= 10;
+  }
+  *length += requested_length;
+}
+
+static void FillDigits32(uint32_t number, Vector<char> buffer, int* length) {
+  int number_length = 0;
+  // We fill the digits in reverse order and exchange them afterwards.
+  while (number != 0) {
+    char digit = number % 10;
+    number /= 10;
+    buffer[(*length) + number_length] = '0' + digit;
+    number_length++;
+  }
+  // Exchange the digits.
+  int i = *length;
+  int j = *length + number_length - 1;
+  while (i < j) {
+    char tmp = buffer[i];
+    buffer[i] = buffer[j];
+    buffer[j] = tmp;
+    i++;
+    j--;
+  }
+  *length += number_length;
+}
+
+static void FillDigits64FixedLength(uint64_t number,
+                                    int,
+                                    Vector<char> buffer,
+                                    int* length) {
+  const uint32_t kTen7 = 10000000;
+  // For efficiency cut the number into 3 uint32_t parts, and print those.
+  uint32_t part2 = static_cast<uint32_t>(number % kTen7);
+  number /= kTen7;
+  uint32_t part1 = static_cast<uint32_t>(number % kTen7);
+  uint32_t part0 = static_cast<uint32_t>(number / kTen7);
+
+  FillDigits32FixedLength(part0, 3, buffer, length);
+  FillDigits32FixedLength(part1, 7, buffer, length);
+  FillDigits32FixedLength(part2, 7, buffer, length);
+}
+
+static void FillDigits64(uint64_t number, Vector<char> buffer, int* length) {
+  const uint32_t kTen7 = 10000000;
+  // For efficiency cut the number into 3 uint32_t parts, and print those.
+  uint32_t part2 = static_cast<uint32_t>(number % kTen7);
+  number /= kTen7;
+  uint32_t part1 = static_cast<uint32_t>(number % kTen7);
+  uint32_t part0 = static_cast<uint32_t>(number / kTen7);
+
+  if (part0 != 0) {
+    FillDigits32(part0, buffer, length);
+    FillDigits32FixedLength(part1, 7, buffer, length);
+    FillDigits32FixedLength(part2, 7, buffer, length);
+  } else if (part1 != 0) {
+    FillDigits32(part1, buffer, length);
+    FillDigits32FixedLength(part2, 7, buffer, length);
+  } else {
+    FillDigits32(part2, buffer, length);
+  }
+}
+
+static void RoundUp(Vector<char> buffer, int* length, int* decimal_point) {
+  // An empty buffer represents 0.
+  if (*length == 0) {
+    buffer[0] = '1';
+    *decimal_point = 1;
+    *length = 1;
+    return;
+  }
+  // Round the last digit until we either have a digit that was not '9' or until
+  // we reached the first digit.
+  buffer[(*length) - 1]++;
+  for (int i = (*length) - 1; i > 0; --i) {
+    if (buffer[i] != '0' + 10) {
+      return;
     }
-
-
-    static void RoundUp(Vector<char> buffer, int* length, int* decimal_point) {
-        // An empty buffer represents 0.
-        if (*length == 0) {
-            buffer[0] = '1';
-            *decimal_point = 1;
-            *length = 1;
-            return;
-        }
-        // Round the last digit until we either have a digit that was not '9' or until
-        // we reached the first digit.
-        buffer[(*length) - 1]++;
-        for (int i = (*length) - 1; i > 0; --i) {
-            if (buffer[i] != '0' + 10) {
-                return;
-            }
-            buffer[i] = '0';
-            buffer[i - 1]++;
-        }
-        // If the first digit is now '0' + 10, we would need to set it to '0' and add
-        // a '1' in front. However we reach the first digit only if all following
-        // digits had been '9' before rounding up. Now all trailing digits are '0' and
-        // we simply switch the first digit to '1' and update the decimal-point
-        // (indicating that the point is now one digit to the right).
-        if (buffer[0] == '0' + 10) {
-            buffer[0] = '1';
-            (*decimal_point)++;
-        }
+    buffer[i] = '0';
+    buffer[i - 1]++;
+  }
+  // If the first digit is now '0' + 10, we would need to set it to '0' and add
+  // a '1' in front. However we reach the first digit only if all following
+  // digits had been '9' before rounding up. Now all trailing digits are '0' and
+  // we simply switch the first digit to '1' and update the decimal-point
+  // (indicating that the point is now one digit to the right).
+  if (buffer[0] == '0' + 10) {
+    buffer[0] = '1';
+    (*decimal_point)++;
+  }
+}
+
+// The given fractionals number represents a fixed-point number with binary
+// point at bit (-exponent).
+// Preconditions:
+//   -128 <= exponent <= 0.
+//   0 <= fractionals * 2^exponent < 1
+//   The buffer holds the result.
+// The function will round its result. During the rounding-process digits not
+// generated by this function might be updated, and the decimal-point variable
+// might be updated. If this function generates the digits 99 and the buffer
+// already contained "199" (thus yielding a buffer of "19999") then a
+// rounding-up will change the contents of the buffer to "20000".
+static void FillFractionals(uint64_t fractionals,
+                            int exponent,
+                            int fractional_count,
+                            Vector<char> buffer,
+                            int* length,
+                            int* decimal_point) {
+  ASSERT(-128 <= exponent && exponent <= 0);
+  // 'fractionals' is a fixed-point number, with binary point at bit
+  // (-exponent). Inside the function the non-converted remainder of fractionals
+  // is a fixed-point number, with binary point at bit 'point'.
+  if (-exponent <= 64) {
+    // One 64 bit number is sufficient.
+    ASSERT(fractionals >> 56 == 0);
+    int point = -exponent;
+    for (int i = 0; i < fractional_count; ++i) {
+      if (fractionals == 0)
+        break;
+      // Instead of multiplying by 10 we multiply by 5 and adjust the point
+      // location. This way the fractionals variable will not overflow.
+      // Invariant at the beginning of the loop: fractionals < 2^point.
+      // Initially we have: point <= 64 and fractionals < 2^56
+      // After each iteration the point is decremented by one.
+      // Note that 5^3 = 125 < 128 = 2^7.
+      // Therefore three iterations of this loop will not overflow fractionals
+      // (even without the subtraction at the end of the loop body). At this
+      // time point will satisfy point <= 61 and therefore fractionals < 2^point
+      // and any further multiplication of fractionals by 5 will not overflow.
+      fractionals *= 5;
+      point--;
+      char digit = static_cast<char>(fractionals >> point);
+      buffer[*length] = '0' + digit;
+      (*length)++;
+      fractionals -= static_cast<uint64_t>(digit) << point;
     }
-
-
-    // The given fractionals number represents a fixed-point number with binary
-    // point at bit (-exponent).
-    // Preconditions:
-    //   -128 <= exponent <= 0.
-    //   0 <= fractionals * 2^exponent < 1
-    //   The buffer holds the result.
-    // The function will round its result. During the rounding-process digits not
-    // generated by this function might be updated, and the decimal-point variable
-    // might be updated. If this function generates the digits 99 and the buffer
-    // already contained "199" (thus yielding a buffer of "19999") then a
-    // rounding-up will change the contents of the buffer to "20000".
-    static void FillFractionals(uint64_t fractionals, int exponent,
-                                int fractional_count, Vector<char> buffer,
-                                int* length, int* decimal_point) {
-        ASSERT(-128 <= exponent && exponent <= 0);
-        // 'fractionals' is a fixed-point number, with binary point at bit
-        // (-exponent). Inside the function the non-converted remainder of fractionals
-        // is a fixed-point number, with binary point at bit 'point'.
-        if (-exponent <= 64) {
-            // One 64 bit number is sufficient.
-            ASSERT(fractionals >> 56 == 0);
-            int point = -exponent;
-            for (int i = 0; i < fractional_count; ++i) {
-                if (fractionals == 0) break;
-                // Instead of multiplying by 10 we multiply by 5 and adjust the point
-                // location. This way the fractionals variable will not overflow.
-                // Invariant at the beginning of the loop: fractionals < 2^point.
-                // Initially we have: point <= 64 and fractionals < 2^56
-                // After each iteration the point is decremented by one.
-                // Note that 5^3 = 125 < 128 = 2^7.
-                // Therefore three iterations of this loop will not overflow fractionals
-                // (even without the subtraction at the end of the loop body). At this
-                // time point will satisfy point <= 61 and therefore fractionals < 2^point
-                // and any further multiplication of fractionals by 5 will not overflow.
-                fractionals *= 5;
-                point--;
-                char digit = static_cast<char>(fractionals >> point);
-                buffer[*length] = '0' + digit;
-                (*length)++;
-                fractionals -= static_cast<uint64_t>(digit) << point;
-            }
-            // If the first bit after the point is set we have to round up.
-            if (((fractionals >> (point - 1)) & 1) == 1) {
-                RoundUp(buffer, length, decimal_point);
-            }
-        } else {  // We need 128 bits.
-            ASSERT(64 < -exponent && -exponent <= 128);
-            UInt128 fractionals128 = UInt128(fractionals, 0);
-            fractionals128.Shift(-exponent - 64);
-            int point = 128;
-            for (int i = 0; i < fractional_count; ++i) {
-                if (fractionals128.IsZero()) break;
-                // As before: instead of multiplying by 10 we multiply by 5 and adjust the
-                // point location.
-                // This multiplication will not overflow for the same reasons as before.
-                fractionals128.Multiply(5);
-                point--;
-                char digit = static_cast<char>(fractionals128.DivModPowerOf2(point));
-                buffer[*length] = '0' + digit;
-                (*length)++;
-            }
-            if (fractionals128.BitAt(point - 1) == 1) {
-                RoundUp(buffer, length, decimal_point);
-            }
-        }
+    // If the first bit after the point is set we have to round up.
+    if (((fractionals >> (point - 1)) & 1) == 1) {
+      RoundUp(buffer, length, decimal_point);
     }
-
-
-    // Removes leading and trailing zeros.
-    // If leading zeros are removed then the decimal point position is adjusted.
-    static void TrimZeros(Vector<char> buffer, int* length, int* decimal_point) {
-        while (*length > 0 && buffer[(*length) - 1] == '0') {
-            (*length)--;
-        }
-        int first_non_zero = 0;
-        while (first_non_zero < *length && buffer[first_non_zero] == '0') {
-            first_non_zero++;
-        }
-        if (first_non_zero != 0) {
-            for (int i = first_non_zero; i < *length; ++i) {
-                buffer[i - first_non_zero] = buffer[i];
-            }
-            *length -= first_non_zero;
-            *decimal_point -= first_non_zero;
-        }
+  } else {  // We need 128 bits.
+    ASSERT(64 < -exponent && -exponent <= 128);
+    UInt128 fractionals128 = UInt128(fractionals, 0);
+    fractionals128.Shift(-exponent - 64);
+    int point = 128;
+    for (int i = 0; i < fractional_count; ++i) {
+      if (fractionals128.IsZero())
+        break;
+      // As before: instead of multiplying by 10 we multiply by 5 and adjust the
+      // point location.
+      // This multiplication will not overflow for the same reasons as before.
+      fractionals128.Multiply(5);
+      point--;
+      char digit = static_cast<char>(fractionals128.DivModPowerOf2(point));
+      buffer[*length] = '0' + digit;
+      (*length)++;
     }
-
-
-    bool FastFixedDtoa(double v,
-                       int fractional_count,
-                       Vector<char> buffer,
-                       int* length,
-                       int* decimal_point) {
-        const uint32_t kMaxUInt32 = 0xFFFFFFFF;
-        uint64_t significand = Double(v).Significand();
-        int exponent = Double(v).Exponent();
-        // v = significand * 2^exponent (with significand a 53bit integer).
-        // If the exponent is larger than 20 (i.e. we may have a 73bit number) then we
-        // don't know how to compute the representation. 2^73 ~= 9.5*10^21.
-        // If necessary this limit could probably be increased, but we don't need
-        // more.
-        if (exponent > 20) return false;
-        if (fractional_count > 20) return false;
-        *length = 0;
-        // At most kDoubleSignificandSize bits of the significand are non-zero.
-        // Given a 64 bit integer we have 11 0s followed by 53 potentially non-zero
-        // bits:  0..11*..0xxx..53*..xx
-        if (exponent + kDoubleSignificandSize > 64) {
-            // The exponent must be > 11.
-            //
-            // We know that v = significand * 2^exponent.
-            // And the exponent > 11.
-            // We simplify the task by dividing v by 10^17.
-            // The quotient delivers the first digits, and the remainder fits into a 64
-            // bit number.
-            // Dividing by 10^17 is equivalent to dividing by 5^17*2^17.
-            const uint64_t kFive17 = UINT64_2PART_C(0xB1, A2BC2EC5);  // 5^17
-            uint64_t divisor = kFive17;
-            int divisor_power = 17;
-            uint64_t dividend = significand;
-            uint32_t quotient;
-            uint64_t remainder;
-            // Let v = f * 2^e with f == significand and e == exponent.
-            // Then need q (quotient) and r (remainder) as follows:
-            //   v            = q * 10^17       + r
-            //   f * 2^e      = q * 10^17       + r
-            //   f * 2^e      = q * 5^17 * 2^17 + r
-            // If e > 17 then
-            //   f * 2^(e-17) = q * 5^17        + r/2^17
-            // else
-            //   f  = q * 5^17 * 2^(17-e) + r/2^e
-            if (exponent > divisor_power) {
-                // We only allow exponents of up to 20 and therefore (17 - e) <= 3
-                dividend <<= exponent - divisor_power;
-                quotient = static_cast<uint32_t>(dividend / divisor);
-                remainder = (dividend % divisor) << divisor_power;
-            } else {
-                divisor <<= divisor_power - exponent;
-                quotient = static_cast<uint32_t>(dividend / divisor);
-                remainder = (dividend % divisor) << exponent;
-            }
-            FillDigits32(quotient, buffer, length);
-            FillDigits64FixedLength(remainder, divisor_power, buffer, length);
-            *decimal_point = *length;
-        } else if (exponent >= 0) {
-            // 0 <= exponent <= 11
-            significand <<= exponent;
-            FillDigits64(significand, buffer, length);
-            *decimal_point = *length;
-        } else if (exponent > -kDoubleSignificandSize) {
-            // We have to cut the number.
-            uint64_t integrals = significand >> -exponent;
-            uint64_t fractionals = significand - (integrals << -exponent);
-            if (integrals > kMaxUInt32) {
-                FillDigits64(integrals, buffer, length);
-            } else {
-                FillDigits32(static_cast<uint32_t>(integrals), buffer, length);
-            }
-            *decimal_point = *length;
-            FillFractionals(fractionals, exponent, fractional_count,
-                            buffer, length, decimal_point);
-        } else if (exponent < -128) {
-            // This configuration (with at most 20 digits) means that all digits must be
-            // 0.
-            ASSERT(fractional_count <= 20);
-            buffer[0] = '\0';
-            *length = 0;
-            *decimal_point = -fractional_count;
-        } else {
-            *decimal_point = 0;
-            FillFractionals(significand, exponent, fractional_count,
-                            buffer, length, decimal_point);
-        }
-        TrimZeros(buffer, length, decimal_point);
-        buffer[*length] = '\0';
-        if ((*length) == 0) {
-            // The string is empty and the decimal_point thus has no importance. Mimick
-            // Gay's dtoa and and set it to -fractional_count.
-            *decimal_point = -fractional_count;
-        }
-        return true;
+    if (fractionals128.BitAt(point - 1) == 1) {
+      RoundUp(buffer, length, decimal_point);
+    }
+  }
+}
+
+// Removes leading and trailing zeros.
+// If leading zeros are removed then the decimal point position is adjusted.
+static void TrimZeros(Vector<char> buffer, int* length, int* decimal_point) {
+  while (*length > 0 && buffer[(*length) - 1] == '0') {
+    (*length)--;
+  }
+  int first_non_zero = 0;
+  while (first_non_zero < *length && buffer[first_non_zero] == '0') {
+    first_non_zero++;
+  }
+  if (first_non_zero != 0) {
+    for (int i = first_non_zero; i < *length; ++i) {
+      buffer[i - first_non_zero] = buffer[i];
+    }
+    *length -= first_non_zero;
+    *decimal_point -= first_non_zero;
+  }
+}
+
+bool FastFixedDtoa(double v,
+                   int fractional_count,
+                   Vector<char> buffer,
+                   int* length,
+                   int* decimal_point) {
+  const uint32_t kMaxUInt32 = 0xFFFFFFFF;
+  uint64_t significand = Double(v).Significand();
+  int exponent = Double(v).Exponent();
+  // v = significand * 2^exponent (with significand a 53bit integer).
+  // If the exponent is larger than 20 (i.e. we may have a 73bit number) then we
+  // don't know how to compute the representation. 2^73 ~= 9.5*10^21.
+  // If necessary this limit could probably be increased, but we don't need
+  // more.
+  if (exponent > 20)
+    return false;
+  if (fractional_count > 20)
+    return false;
+  *length = 0;
+  // At most kDoubleSignificandSize bits of the significand are non-zero.
+  // Given a 64 bit integer we have 11 0s followed by 53 potentially non-zero
+  // bits:  0..11*..0xxx..53*..xx
+  if (exponent + kDoubleSignificandSize > 64) {
+    // The exponent must be > 11.
+    //
+    // We know that v = significand * 2^exponent.
+    // And the exponent > 11.
+    // We simplify the task by dividing v by 10^17.
+    // The quotient delivers the first digits, and the remainder fits into a 64
+    // bit number.
+    // Dividing by 10^17 is equivalent to dividing by 5^17*2^17.
+    const uint64_t kFive17 = UINT64_2PART_C(0xB1, A2BC2EC5);  // 5^17
+    uint64_t divisor = kFive17;
+    int divisor_power = 17;
+    uint64_t dividend = significand;
+    uint32_t quotient;
+    uint64_t remainder;
+    // Let v = f * 2^e with f == significand and e == exponent.
+    // Then need q (quotient) and r (remainder) as follows:
+    //   v            = q * 10^17       + r
+    //   f * 2^e      = q * 10^17       + r
+    //   f * 2^e      = q * 5^17 * 2^17 + r
+    // If e > 17 then
+    //   f * 2^(e-17) = q * 5^17        + r/2^17
+    // else
+    //   f  = q * 5^17 * 2^(17-e) + r/2^e
+    if (exponent > divisor_power) {
+      // We only allow exponents of up to 20 and therefore (17 - e) <= 3
+      dividend <<= exponent - divisor_power;
+      quotient = static_cast<uint32_t>(dividend / divisor);
+      remainder = (dividend % divisor) << divisor_power;
+    } else {
+      divisor <<= divisor_power - exponent;
+      quotient = static_cast<uint32_t>(dividend / divisor);
+      remainder = (dividend % divisor) << exponent;
+    }
+    FillDigits32(quotient, buffer, length);
+    FillDigits64FixedLength(remainder, divisor_power, buffer, length);
+    *decimal_point = *length;
+  } else if (exponent >= 0) {
+    // 0 <= exponent <= 11
+    significand <<= exponent;
+    FillDigits64(significand, buffer, length);
+    *decimal_point = *length;
+  } else if (exponent > -kDoubleSignificandSize) {
+    // We have to cut the number.
+    uint64_t integrals = significand >> -exponent;
+    uint64_t fractionals = significand - (integrals << -exponent);
+    if (integrals > kMaxUInt32) {
+      FillDigits64(integrals, buffer, length);
+    } else {
+      FillDigits32(static_cast<uint32_t>(integrals), buffer, length);
     }
+    *decimal_point = *length;
+    FillFractionals(fractionals, exponent, fractional_count, buffer, length,
+                    decimal_point);
+  } else if (exponent < -128) {
+    // This configuration (with at most 20 digits) means that all digits must be
+    // 0.
+    ASSERT(fractional_count <= 20);
+    buffer[0] = '\0';
+    *length = 0;
+    *decimal_point = -fractional_count;
+  } else {
+    *decimal_point = 0;
+    FillFractionals(significand, exponent, fractional_count, buffer, length,
+                    decimal_point);
+  }
+  TrimZeros(buffer, length, decimal_point);
+  buffer[*length] = '\0';
+  if ((*length) == 0) {
+    // The string is empty and the decimal_point thus has no importance. Mimick
+    // Gay's dtoa and and set it to -fractional_count.
+    *decimal_point = -fractional_count;
+  }
+  return true;
+}
 
 }  // namespace double_conversion
 
-} // namespace WTF
+}  // namespace WTF