Restoring authorship annotation for <mcheshkov@yandex-team.ru>. Commit 1 of 2.

1 files changed, 659 insertions, 659 deletions

diff --git a/contrib/libs/icu/i18n/double-conversion-bignum-dtoa.cpp b/contrib/libs/icu/i18n/double-conversion-bignum-dtoa.cpp
index a95910df04..bc7e408f68 100644
--- a/contrib/libs/icu/i18n/double-conversion-bignum-dtoa.cpp
+++ b/contrib/libs/icu/i18n/double-conversion-bignum-dtoa.cpp
@@ -1,659 +1,659 @@
-// © 2018 and later: Unicode, Inc. and others.
-// License & terms of use: http://www.unicode.org/copyright.html
-//
-// From the double-conversion library. Original license:
-//
-// Copyright 2010 the V8 project authors. 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.
-
-// ICU PATCH: ifdef around UCONFIG_NO_FORMATTING
-#include "unicode/utypes.h"
-#if !UCONFIG_NO_FORMATTING
-
-#include <cmath>
-
-// ICU PATCH: Customize header file paths for ICU.
-
-#include "double-conversion-bignum-dtoa.h"
-
-#include "double-conversion-bignum.h"
-#include "double-conversion-ieee.h"
-
-// ICU PATCH: Wrap in ICU namespace
-U_NAMESPACE_BEGIN
-
-namespace double_conversion {
-
-static int NormalizedExponent(uint64_t significand, int exponent) {
-  DOUBLE_CONVERSION_ASSERT(significand != 0);
-  while ((significand & Double::kHiddenBit) == 0) {
-    significand = significand << 1;
-    exponent = exponent - 1;
-  }
-  return exponent;
-}
-
-
-// Forward declarations:
-// Returns an estimation of k such that 10^(k-1) <= v < 10^k.
-static int EstimatePower(int exponent);
-// Computes v / 10^estimated_power exactly, as a ratio of two bignums, numerator
-// and denominator.
-static void InitialScaledStartValues(uint64_t significand,
-                                     int exponent,
-                                     bool lower_boundary_is_closer,
-                                     int estimated_power,
-                                     bool need_boundary_deltas,
-                                     Bignum* numerator,
-                                     Bignum* denominator,
-                                     Bignum* delta_minus,
-                                     Bignum* delta_plus);
-// Multiplies numerator/denominator so that its values lies in the range 1-10.
-// Returns decimal_point s.t.
-//  v = numerator'/denominator' * 10^(decimal_point-1)
-//     where numerator' and denominator' are the values of numerator and
-//     denominator after the call to this function.
-static void FixupMultiply10(int estimated_power, bool is_even,
-                            int* decimal_point,
-                            Bignum* numerator, Bignum* denominator,
-                            Bignum* delta_minus, Bignum* delta_plus);
-// Generates digits from the left to the right and stops when the generated
-// digits yield the shortest decimal representation of v.
-static void GenerateShortestDigits(Bignum* numerator, Bignum* denominator,
-                                   Bignum* delta_minus, Bignum* delta_plus,
-                                   bool is_even,
-                                   Vector<char> buffer, int* length);
-// Generates 'requested_digits' after the decimal point.
-static void BignumToFixed(int requested_digits, int* decimal_point,
-                          Bignum* numerator, Bignum* denominator,
-                          Vector<char> buffer, int* length);
-// Generates 'count' digits of numerator/denominator.
-// Once 'count' digits have been produced rounds the result depending on the
-// remainder (remainders of exactly .5 round upwards). Might update the
-// decimal_point when rounding up (for example for 0.9999).
-static void GenerateCountedDigits(int count, int* decimal_point,
-                                  Bignum* numerator, Bignum* denominator,
-                                  Vector<char> buffer, int* length);
-
-
-void BignumDtoa(double v, BignumDtoaMode mode, int requested_digits,
-                Vector<char> buffer, int* length, int* decimal_point) {
-  DOUBLE_CONVERSION_ASSERT(v > 0);
-  DOUBLE_CONVERSION_ASSERT(!Double(v).IsSpecial());
-  uint64_t significand;
-  int exponent;
-  bool lower_boundary_is_closer;
-  if (mode == BIGNUM_DTOA_SHORTEST_SINGLE) {
-    float f = static_cast<float>(v);
-    DOUBLE_CONVERSION_ASSERT(f == v);
-    significand = Single(f).Significand();
-    exponent = Single(f).Exponent();
-    lower_boundary_is_closer = Single(f).LowerBoundaryIsCloser();
-  } else {
-    significand = Double(v).Significand();
-    exponent = Double(v).Exponent();
-    lower_boundary_is_closer = Double(v).LowerBoundaryIsCloser();
-  }
-  bool need_boundary_deltas =
-      (mode == BIGNUM_DTOA_SHORTEST || mode == BIGNUM_DTOA_SHORTEST_SINGLE);
-
-  bool is_even = (significand & 1) == 0;
-  int normalized_exponent = NormalizedExponent(significand, exponent);
-  // estimated_power might be too low by 1.
-  int estimated_power = EstimatePower(normalized_exponent);
-
-  // Shortcut for Fixed.
-  // The requested digits correspond to the digits after the point. If the
-  // number is much too small, then there is no need in trying to get any
-  // digits.
-  if (mode == BIGNUM_DTOA_FIXED && -estimated_power - 1 > requested_digits) {
-    buffer[0] = '\0';
-    *length = 0;
-    // Set decimal-point to -requested_digits. This is what Gay does.
-    // Note that it should not have any effect anyways since the string is
-    // empty.
-    *decimal_point = -requested_digits;
-    return;
-  }
-
-  Bignum numerator;
-  Bignum denominator;
-  Bignum delta_minus;
-  Bignum delta_plus;
-  // Make sure the bignum can grow large enough. The smallest double equals
-  // 4e-324. In this case the denominator needs fewer than 324*4 binary digits.
-  // The maximum double is 1.7976931348623157e308 which needs fewer than
-  // 308*4 binary digits.
-  DOUBLE_CONVERSION_ASSERT(Bignum::kMaxSignificantBits >= 324*4);
-  InitialScaledStartValues(significand, exponent, lower_boundary_is_closer,
-                           estimated_power, need_boundary_deltas,
-                           &numerator, &denominator,
-                           &delta_minus, &delta_plus);
-  // We now have v = (numerator / denominator) * 10^estimated_power.
-  FixupMultiply10(estimated_power, is_even, decimal_point,
-                  &numerator, &denominator,
-                  &delta_minus, &delta_plus);
-  // We now have v = (numerator / denominator) * 10^(decimal_point-1), and
-  //  1 <= (numerator + delta_plus) / denominator < 10
-  switch (mode) {
-    case BIGNUM_DTOA_SHORTEST:
-    case BIGNUM_DTOA_SHORTEST_SINGLE:
-      GenerateShortestDigits(&numerator, &denominator,
-                             &delta_minus, &delta_plus,
-                             is_even, buffer, length);
-      break;
-    case BIGNUM_DTOA_FIXED:
-      BignumToFixed(requested_digits, decimal_point,
-                    &numerator, &denominator,
-                    buffer, length);
-      break;
-    case BIGNUM_DTOA_PRECISION:
-      GenerateCountedDigits(requested_digits, decimal_point,
-                            &numerator, &denominator,
-                            buffer, length);
-      break;
-    default:
-      DOUBLE_CONVERSION_UNREACHABLE();
-  }
-  buffer[*length] = '\0';
-}
-
-
-// The procedure starts generating digits from the left to the right and stops
-// when the generated digits yield the shortest decimal representation of v. A
-// decimal representation of v is a number lying closer to v than to any other
-// double, so it converts to v when read.
-//
-// This is true if d, the decimal representation, is between m- and m+, the
-// upper and lower boundaries. d must be strictly between them if !is_even.
-//           m- := (numerator - delta_minus) / denominator
-//           m+ := (numerator + delta_plus) / denominator
-//
-// Precondition: 0 <= (numerator+delta_plus) / denominator < 10.
-//   If 1 <= (numerator+delta_plus) / denominator < 10 then no leading 0 digit
-//   will be produced. This should be the standard precondition.
-static void GenerateShortestDigits(Bignum* numerator, Bignum* denominator,
-                                   Bignum* delta_minus, Bignum* delta_plus,
-                                   bool is_even,
-                                   Vector<char> buffer, int* length) {
-  // Small optimization: if delta_minus and delta_plus are the same just reuse
-  // one of the two bignums.
-  if (Bignum::Equal(*delta_minus, *delta_plus)) {
-    delta_plus = delta_minus;
-  }
-  *length = 0;
-  for (;;) {
-    uint16_t digit;
-    digit = numerator->DivideModuloIntBignum(*denominator);
-    DOUBLE_CONVERSION_ASSERT(digit <= 9);  // digit is a uint16_t and therefore always positive.
-    // digit = numerator / denominator (integer division).
-    // numerator = numerator % denominator.
-    buffer[(*length)++] = static_cast<char>(digit + '0');
-
-    // Can we stop already?
-    // If the remainder of the division is less than the distance to the lower
-    // boundary we can stop. In this case we simply round down (discarding the
-    // remainder).
-    // Similarly we test if we can round up (using the upper boundary).
-    bool in_delta_room_minus;
-    bool in_delta_room_plus;
-    if (is_even) {
-      in_delta_room_minus = Bignum::LessEqual(*numerator, *delta_minus);
-    } else {
-      in_delta_room_minus = Bignum::Less(*numerator, *delta_minus);
-    }
-    if (is_even) {
-      in_delta_room_plus =
-          Bignum::PlusCompare(*numerator, *delta_plus, *denominator) >= 0;
-    } else {
-      in_delta_room_plus =
-          Bignum::PlusCompare(*numerator, *delta_plus, *denominator) > 0;
-    }
-    if (!in_delta_room_minus && !in_delta_room_plus) {
-      // Prepare for next iteration.
-      numerator->Times10();
-      delta_minus->Times10();
-      // We optimized delta_plus to be equal to delta_minus (if they share the
-      // same value). So don't multiply delta_plus if they point to the same
-      // object.
-      if (delta_minus != delta_plus) {
-        delta_plus->Times10();
-      }
-    } else if (in_delta_room_minus && in_delta_room_plus) {
-      // Let's see if 2*numerator < denominator.
-      // If yes, then the next digit would be < 5 and we can round down.
-      int compare = Bignum::PlusCompare(*numerator, *numerator, *denominator);
-      if (compare < 0) {
-        // Remaining digits are less than .5. -> Round down (== do nothing).
-      } else if (compare > 0) {
-        // Remaining digits are more than .5 of denominator. -> Round up.
-        // Note that the last digit could not be a '9' as otherwise the whole
-        // loop would have stopped earlier.
-        // We still have an assert here in case the preconditions were not
-        // satisfied.
-        DOUBLE_CONVERSION_ASSERT(buffer[(*length) - 1] != '9');
-        buffer[(*length) - 1]++;
-      } else {
-        // Halfway case.
-        // TODO(floitsch): need a way to solve half-way cases.
-        //   For now let's round towards even (since this is what Gay seems to
-        //   do).
-
-        if ((buffer[(*length) - 1] - '0') % 2 == 0) {
-          // Round down => Do nothing.
-        } else {
-          DOUBLE_CONVERSION_ASSERT(buffer[(*length) - 1] != '9');
-          buffer[(*length) - 1]++;
-        }
-      }
-      return;
-    } else if (in_delta_room_minus) {
-      // Round down (== do nothing).
-      return;
-    } else {  // in_delta_room_plus
-      // Round up.
-      // Note again that the last digit could not be '9' since this would have
-      // stopped the loop earlier.
-      // We still have an DOUBLE_CONVERSION_ASSERT here, in case the preconditions were not
-      // satisfied.
-      DOUBLE_CONVERSION_ASSERT(buffer[(*length) -1] != '9');
-      buffer[(*length) - 1]++;
-      return;
-    }
-  }
-}
-
-
-// Let v = numerator / denominator < 10.
-// Then we generate 'count' digits of d = x.xxxxx... (without the decimal point)
-// from left to right. Once 'count' digits have been produced we decide wether
-// to round up or down. Remainders of exactly .5 round upwards. Numbers such
-// as 9.999999 propagate a carry all the way, and change the
-// exponent (decimal_point), when rounding upwards.
-static void GenerateCountedDigits(int count, int* decimal_point,
-                                  Bignum* numerator, Bignum* denominator,
-                                  Vector<char> buffer, int* length) {
-  DOUBLE_CONVERSION_ASSERT(count >= 0);
-  for (int i = 0; i < count - 1; ++i) {
-    uint16_t digit;
-    digit = numerator->DivideModuloIntBignum(*denominator);
-    DOUBLE_CONVERSION_ASSERT(digit <= 9);  // digit is a uint16_t and therefore always positive.
-    // digit = numerator / denominator (integer division).
-    // numerator = numerator % denominator.
-    buffer[i] = static_cast<char>(digit + '0');
-    // Prepare for next iteration.
-    numerator->Times10();
-  }
-  // Generate the last digit.
-  uint16_t digit;
-  digit = numerator->DivideModuloIntBignum(*denominator);
-  if (Bignum::PlusCompare(*numerator, *numerator, *denominator) >= 0) {
-    digit++;
-  }
-  DOUBLE_CONVERSION_ASSERT(digit <= 10);
-  buffer[count - 1] = static_cast<char>(digit + '0');
-  // Correct bad digits (in case we had a sequence of '9's). Propagate the
-  // carry until we hat a non-'9' or til we reach the first digit.
-  for (int i = count - 1; i > 0; --i) {
-    if (buffer[i] != '0' + 10) break;
-    buffer[i] = '0';
-    buffer[i - 1]++;
-  }
-  if (buffer[0] == '0' + 10) {
-    // Propagate a carry past the top place.
-    buffer[0] = '1';
-    (*decimal_point)++;
-  }
-  *length = count;
-}
-
-
-// Generates 'requested_digits' after the decimal point. It might omit
-// trailing '0's. If the input number is too small then no digits at all are
-// generated (ex.: 2 fixed digits for 0.00001).
-//
-// Input verifies:  1 <= (numerator + delta) / denominator < 10.
-static void BignumToFixed(int requested_digits, int* decimal_point,
-                          Bignum* numerator, Bignum* denominator,
-                          Vector<char> buffer, int* length) {
-  // Note that we have to look at more than just the requested_digits, since
-  // a number could be rounded up. Example: v=0.5 with requested_digits=0.
-  // Even though the power of v equals 0 we can't just stop here.
-  if (-(*decimal_point) > requested_digits) {
-    // The number is definitively too small.
-    // Ex: 0.001 with requested_digits == 1.
-    // Set decimal-point to -requested_digits. This is what Gay does.
-    // Note that it should not have any effect anyways since the string is
-    // empty.
-    *decimal_point = -requested_digits;
-    *length = 0;
-    return;
-  } else if (-(*decimal_point) == requested_digits) {
-    // We only need to verify if the number rounds down or up.
-    // Ex: 0.04 and 0.06 with requested_digits == 1.
-    DOUBLE_CONVERSION_ASSERT(*decimal_point == -requested_digits);
-    // Initially the fraction lies in range (1, 10]. Multiply the denominator
-    // by 10 so that we can compare more easily.
-    denominator->Times10();
-    if (Bignum::PlusCompare(*numerator, *numerator, *denominator) >= 0) {
-      // If the fraction is >= 0.5 then we have to include the rounded
-      // digit.
-      buffer[0] = '1';
-      *length = 1;
-      (*decimal_point)++;
-    } else {
-      // Note that we caught most of similar cases earlier.
-      *length = 0;
-    }
-    return;
-  } else {
-    // The requested digits correspond to the digits after the point.
-    // The variable 'needed_digits' includes the digits before the point.
-    int needed_digits = (*decimal_point) + requested_digits;
-    GenerateCountedDigits(needed_digits, decimal_point,
-                          numerator, denominator,
-                          buffer, length);
-  }
-}
-
-
-// Returns an estimation of k such that 10^(k-1) <= v < 10^k where
-// v = f * 2^exponent and 2^52 <= f < 2^53.
-// v is hence a normalized double with the given exponent. The output is an
-// approximation for the exponent of the decimal approimation .digits * 10^k.
-//
-// The result might undershoot by 1 in which case 10^k <= v < 10^k+1.
-// Note: this property holds for v's upper boundary m+ too.
-//    10^k <= m+ < 10^k+1.
-//   (see explanation below).
-//
-// Examples:
-//  EstimatePower(0)   => 16
-//  EstimatePower(-52) => 0
-//
-// Note: e >= 0 => EstimatedPower(e) > 0. No similar claim can be made for e<0.
-static int EstimatePower(int exponent) {
-  // This function estimates log10 of v where v = f*2^e (with e == exponent).
-  // Note that 10^floor(log10(v)) <= v, but v <= 10^ceil(log10(v)).
-  // Note that f is bounded by its container size. Let p = 53 (the double's
-  // significand size). Then 2^(p-1) <= f < 2^p.
-  //
-  // Given that log10(v) == log2(v)/log2(10) and e+(len(f)-1) is quite close
-  // to log2(v) the function is simplified to (e+(len(f)-1)/log2(10)).
-  // The computed number undershoots by less than 0.631 (when we compute log3
-  // and not log10).
-  //
-  // Optimization: since we only need an approximated result this computation
-  // can be performed on 64 bit integers. On x86/x64 architecture the speedup is
-  // not really measurable, though.
-  //
-  // Since we want to avoid overshooting we decrement by 1e10 so that
-  // floating-point imprecisions don't affect us.
-  //
-  // Explanation for v's boundary m+: the computation takes advantage of
-  // the fact that 2^(p-1) <= f < 2^p. Boundaries still satisfy this requirement
-  // (even for denormals where the delta can be much more important).
-
-  const double k1Log10 = 0.30102999566398114;  // 1/lg(10)
-
-  // For doubles len(f) == 53 (don't forget the hidden bit).
-  const int kSignificandSize = Double::kSignificandSize;
-  double estimate = ceil((exponent + kSignificandSize - 1) * k1Log10 - 1e-10);
-  return static_cast<int>(estimate);
-}
-
-
-// See comments for InitialScaledStartValues.
-static void InitialScaledStartValuesPositiveExponent(
-    uint64_t significand, int exponent,
-    int estimated_power, bool need_boundary_deltas,
-    Bignum* numerator, Bignum* denominator,
-    Bignum* delta_minus, Bignum* delta_plus) {
-  // A positive exponent implies a positive power.
-  DOUBLE_CONVERSION_ASSERT(estimated_power >= 0);
-  // Since the estimated_power is positive we simply multiply the denominator
-  // by 10^estimated_power.
-
-  // numerator = v.
-  numerator->AssignUInt64(significand);
-  numerator->ShiftLeft(exponent);
-  // denominator = 10^estimated_power.
-  denominator->AssignPowerUInt16(10, estimated_power);
-
-  if (need_boundary_deltas) {
-    // Introduce a common denominator so that the deltas to the boundaries are
-    // integers.
-    denominator->ShiftLeft(1);
-    numerator->ShiftLeft(1);
-    // Let v = f * 2^e, then m+ - v = 1/2 * 2^e; With the common
-    // denominator (of 2) delta_plus equals 2^e.
-    delta_plus->AssignUInt16(1);
-    delta_plus->ShiftLeft(exponent);
-    // Same for delta_minus. The adjustments if f == 2^p-1 are done later.
-    delta_minus->AssignUInt16(1);
-    delta_minus->ShiftLeft(exponent);
-  }
-}
-
-
-// See comments for InitialScaledStartValues
-static void InitialScaledStartValuesNegativeExponentPositivePower(
-    uint64_t significand, int exponent,
-    int estimated_power, bool need_boundary_deltas,
-    Bignum* numerator, Bignum* denominator,
-    Bignum* delta_minus, Bignum* delta_plus) {
-  // v = f * 2^e with e < 0, and with estimated_power >= 0.
-  // This means that e is close to 0 (have a look at how estimated_power is
-  // computed).
-
-  // numerator = significand
-  //  since v = significand * 2^exponent this is equivalent to
-  //  numerator = v * / 2^-exponent
-  numerator->AssignUInt64(significand);
-  // denominator = 10^estimated_power * 2^-exponent (with exponent < 0)
-  denominator->AssignPowerUInt16(10, estimated_power);
-  denominator->ShiftLeft(-exponent);
-
-  if (need_boundary_deltas) {
-    // Introduce a common denominator so that the deltas to the boundaries are
-    // integers.
-    denominator->ShiftLeft(1);
-    numerator->ShiftLeft(1);
-    // Let v = f * 2^e, then m+ - v = 1/2 * 2^e; With the common
-    // denominator (of 2) delta_plus equals 2^e.
-    // Given that the denominator already includes v's exponent the distance
-    // to the boundaries is simply 1.
-    delta_plus->AssignUInt16(1);
-    // Same for delta_minus. The adjustments if f == 2^p-1 are done later.
-    delta_minus->AssignUInt16(1);
-  }
-}
-
-
-// See comments for InitialScaledStartValues
-static void InitialScaledStartValuesNegativeExponentNegativePower(
-    uint64_t significand, int exponent,
-    int estimated_power, bool need_boundary_deltas,
-    Bignum* numerator, Bignum* denominator,
-    Bignum* delta_minus, Bignum* delta_plus) {
-  // Instead of multiplying the denominator with 10^estimated_power we
-  // multiply all values (numerator and deltas) by 10^-estimated_power.
-
-  // Use numerator as temporary container for power_ten.
-  Bignum* power_ten = numerator;
-  power_ten->AssignPowerUInt16(10, -estimated_power);
-
-  if (need_boundary_deltas) {
-    // Since power_ten == numerator we must make a copy of 10^estimated_power
-    // before we complete the computation of the numerator.
-    // delta_plus = delta_minus = 10^estimated_power
-    delta_plus->AssignBignum(*power_ten);
-    delta_minus->AssignBignum(*power_ten);
-  }
-
-  // numerator = significand * 2 * 10^-estimated_power
-  //  since v = significand * 2^exponent this is equivalent to
-  // numerator = v * 10^-estimated_power * 2 * 2^-exponent.
-  // Remember: numerator has been abused as power_ten. So no need to assign it
-  //  to itself.
-  DOUBLE_CONVERSION_ASSERT(numerator == power_ten);
-  numerator->MultiplyByUInt64(significand);
-
-  // denominator = 2 * 2^-exponent with exponent < 0.
-  denominator->AssignUInt16(1);
-  denominator->ShiftLeft(-exponent);
-
-  if (need_boundary_deltas) {
-    // Introduce a common denominator so that the deltas to the boundaries are
-    // integers.
-    numerator->ShiftLeft(1);
-    denominator->ShiftLeft(1);
-    // With this shift the boundaries have their correct value, since
-    // delta_plus = 10^-estimated_power, and
-    // delta_minus = 10^-estimated_power.
-    // These assignments have been done earlier.
-    // The adjustments if f == 2^p-1 (lower boundary is closer) are done later.
-  }
-}
-
-
-// Let v = significand * 2^exponent.
-// Computes v / 10^estimated_power exactly, as a ratio of two bignums, numerator
-// and denominator. The functions GenerateShortestDigits and
-// GenerateCountedDigits will then convert this ratio to its decimal
-// representation d, with the required accuracy.
-// Then d * 10^estimated_power is the representation of v.
-// (Note: the fraction and the estimated_power might get adjusted before
-// generating the decimal representation.)
-//
-// The initial start values consist of:
-//  - a scaled numerator: s.t. numerator/denominator == v / 10^estimated_power.
-//  - a scaled (common) denominator.
-//  optionally (used by GenerateShortestDigits to decide if it has the shortest
-//  decimal converting back to v):
-//  - v - m-: the distance to the lower boundary.
-//  - m+ - v: the distance to the upper boundary.
-//
-// v, m+, m-, and therefore v - m- and m+ - v all share the same denominator.
-//
-// Let ep == estimated_power, then the returned values will satisfy:
-//  v / 10^ep = numerator / denominator.
-//  v's boundarys m- and m+:
-//    m- / 10^ep == v / 10^ep - delta_minus / denominator
-//    m+ / 10^ep == v / 10^ep + delta_plus / denominator
-//  Or in other words:
-//    m- == v - delta_minus * 10^ep / denominator;
-//    m+ == v + delta_plus * 10^ep / denominator;
-//
-// Since 10^(k-1) <= v < 10^k    (with k == estimated_power)
-//  or       10^k <= v < 10^(k+1)
-//  we then have 0.1 <= numerator/denominator < 1
-//           or    1 <= numerator/denominator < 10
-//
-// It is then easy to kickstart the digit-generation routine.
-//
-// The boundary-deltas are only filled if the mode equals BIGNUM_DTOA_SHORTEST
-// or BIGNUM_DTOA_SHORTEST_SINGLE.
-
-static void InitialScaledStartValues(uint64_t significand,
-                                     int exponent,
-                                     bool lower_boundary_is_closer,
-                                     int estimated_power,
-                                     bool need_boundary_deltas,
-                                     Bignum* numerator,
-                                     Bignum* denominator,
-                                     Bignum* delta_minus,
-                                     Bignum* delta_plus) {
-  if (exponent >= 0) {
-    InitialScaledStartValuesPositiveExponent(
-        significand, exponent, estimated_power, need_boundary_deltas,
-        numerator, denominator, delta_minus, delta_plus);
-  } else if (estimated_power >= 0) {
-    InitialScaledStartValuesNegativeExponentPositivePower(
-        significand, exponent, estimated_power, need_boundary_deltas,
-        numerator, denominator, delta_minus, delta_plus);
-  } else {
-    InitialScaledStartValuesNegativeExponentNegativePower(
-        significand, exponent, estimated_power, need_boundary_deltas,
-        numerator, denominator, delta_minus, delta_plus);
-  }
-
-  if (need_boundary_deltas && lower_boundary_is_closer) {
-    // The lower boundary is closer at half the distance of "normal" numbers.
-    // Increase the common denominator and adapt all but the delta_minus.
-    denominator->ShiftLeft(1);  // *2
-    numerator->ShiftLeft(1);    // *2
-    delta_plus->ShiftLeft(1);   // *2
-  }
-}
-
-
-// This routine multiplies numerator/denominator so that its values lies in the
-// range 1-10. That is after a call to this function we have:
-//    1 <= (numerator + delta_plus) /denominator < 10.
-// Let numerator the input before modification and numerator' the argument
-// after modification, then the output-parameter decimal_point is such that
-//  numerator / denominator * 10^estimated_power ==
-//    numerator' / denominator' * 10^(decimal_point - 1)
-// In some cases estimated_power was too low, and this is already the case. We
-// then simply adjust the power so that 10^(k-1) <= v < 10^k (with k ==
-// estimated_power) but do not touch the numerator or denominator.
-// Otherwise the routine multiplies the numerator and the deltas by 10.
-static void FixupMultiply10(int estimated_power, bool is_even,
-                            int* decimal_point,
-                            Bignum* numerator, Bignum* denominator,
-                            Bignum* delta_minus, Bignum* delta_plus) {
-  bool in_range;
-  if (is_even) {
-    // For IEEE doubles half-way cases (in decimal system numbers ending with 5)
-    // are rounded to the closest floating-point number with even significand.
-    in_range = Bignum::PlusCompare(*numerator, *delta_plus, *denominator) >= 0;
-  } else {
-    in_range = Bignum::PlusCompare(*numerator, *delta_plus, *denominator) > 0;
-  }
-  if (in_range) {
-    // Since numerator + delta_plus >= denominator we already have
-    // 1 <= numerator/denominator < 10. Simply update the estimated_power.
-    *decimal_point = estimated_power + 1;
-  } else {
-    *decimal_point = estimated_power;
-    numerator->Times10();
-    if (Bignum::Equal(*delta_minus, *delta_plus)) {
-      delta_minus->Times10();
-      delta_plus->AssignBignum(*delta_minus);
-    } else {
-      delta_minus->Times10();
-      delta_plus->Times10();
-    }
-  }
-}
-
-}  // namespace double_conversion
-
-// ICU PATCH: Close ICU namespace
-U_NAMESPACE_END
-#endif // ICU PATCH: close #if !UCONFIG_NO_FORMATTING
+// © 2018 and later: Unicode, Inc. and others. 
+// License & terms of use: http://www.unicode.org/copyright.html 
+// 
+// From the double-conversion library. Original license: 
+// 
+// Copyright 2010 the V8 project authors. 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. 
+ 
+// ICU PATCH: ifdef around UCONFIG_NO_FORMATTING 
+#include "unicode/utypes.h" 
+#if !UCONFIG_NO_FORMATTING 
+ 
+#include <cmath> 
+ 
+// ICU PATCH: Customize header file paths for ICU. 
+ 
+#include "double-conversion-bignum-dtoa.h" 
+ 
+#include "double-conversion-bignum.h" 
+#include "double-conversion-ieee.h" 
+ 
+// ICU PATCH: Wrap in ICU namespace 
+U_NAMESPACE_BEGIN 
+ 
+namespace double_conversion { 
+ 
+static int NormalizedExponent(uint64_t significand, int exponent) { 
+  DOUBLE_CONVERSION_ASSERT(significand != 0); 
+  while ((significand & Double::kHiddenBit) == 0) { 
+    significand = significand << 1; 
+    exponent = exponent - 1; 
+  } 
+  return exponent; 
+} 
+ 
+ 
+// Forward declarations: 
+// Returns an estimation of k such that 10^(k-1) <= v < 10^k. 
+static int EstimatePower(int exponent); 
+// Computes v / 10^estimated_power exactly, as a ratio of two bignums, numerator 
+// and denominator. 
+static void InitialScaledStartValues(uint64_t significand, 
+                                     int exponent, 
+                                     bool lower_boundary_is_closer, 
+                                     int estimated_power, 
+                                     bool need_boundary_deltas, 
+                                     Bignum* numerator, 
+                                     Bignum* denominator, 
+                                     Bignum* delta_minus, 
+                                     Bignum* delta_plus); 
+// Multiplies numerator/denominator so that its values lies in the range 1-10. 
+// Returns decimal_point s.t. 
+//  v = numerator'/denominator' * 10^(decimal_point-1) 
+//     where numerator' and denominator' are the values of numerator and 
+//     denominator after the call to this function. 
+static void FixupMultiply10(int estimated_power, bool is_even, 
+                            int* decimal_point, 
+                            Bignum* numerator, Bignum* denominator, 
+                            Bignum* delta_minus, Bignum* delta_plus); 
+// Generates digits from the left to the right and stops when the generated 
+// digits yield the shortest decimal representation of v. 
+static void GenerateShortestDigits(Bignum* numerator, Bignum* denominator, 
+                                   Bignum* delta_minus, Bignum* delta_plus, 
+                                   bool is_even, 
+                                   Vector<char> buffer, int* length); 
+// Generates 'requested_digits' after the decimal point. 
+static void BignumToFixed(int requested_digits, int* decimal_point, 
+                          Bignum* numerator, Bignum* denominator, 
+                          Vector<char> buffer, int* length); 
+// Generates 'count' digits of numerator/denominator. 
+// Once 'count' digits have been produced rounds the result depending on the 
+// remainder (remainders of exactly .5 round upwards). Might update the 
+// decimal_point when rounding up (for example for 0.9999). 
+static void GenerateCountedDigits(int count, int* decimal_point, 
+                                  Bignum* numerator, Bignum* denominator, 
+                                  Vector<char> buffer, int* length); 
+ 
+ 
+void BignumDtoa(double v, BignumDtoaMode mode, int requested_digits, 
+                Vector<char> buffer, int* length, int* decimal_point) { 
+  DOUBLE_CONVERSION_ASSERT(v > 0); 
+  DOUBLE_CONVERSION_ASSERT(!Double(v).IsSpecial()); 
+  uint64_t significand; 
+  int exponent; 
+  bool lower_boundary_is_closer; 
+  if (mode == BIGNUM_DTOA_SHORTEST_SINGLE) { 
+    float f = static_cast<float>(v); 
+    DOUBLE_CONVERSION_ASSERT(f == v); 
+    significand = Single(f).Significand(); 
+    exponent = Single(f).Exponent(); 
+    lower_boundary_is_closer = Single(f).LowerBoundaryIsCloser(); 
+  } else { 
+    significand = Double(v).Significand(); 
+    exponent = Double(v).Exponent(); 
+    lower_boundary_is_closer = Double(v).LowerBoundaryIsCloser(); 
+  } 
+  bool need_boundary_deltas = 
+      (mode == BIGNUM_DTOA_SHORTEST || mode == BIGNUM_DTOA_SHORTEST_SINGLE); 
+ 
+  bool is_even = (significand & 1) == 0; 
+  int normalized_exponent = NormalizedExponent(significand, exponent); 
+  // estimated_power might be too low by 1. 
+  int estimated_power = EstimatePower(normalized_exponent); 
+ 
+  // Shortcut for Fixed. 
+  // The requested digits correspond to the digits after the point. If the 
+  // number is much too small, then there is no need in trying to get any 
+  // digits. 
+  if (mode == BIGNUM_DTOA_FIXED && -estimated_power - 1 > requested_digits) { 
+    buffer[0] = '\0'; 
+    *length = 0; 
+    // Set decimal-point to -requested_digits. This is what Gay does. 
+    // Note that it should not have any effect anyways since the string is 
+    // empty. 
+    *decimal_point = -requested_digits; 
+    return; 
+  } 
+ 
+  Bignum numerator; 
+  Bignum denominator; 
+  Bignum delta_minus; 
+  Bignum delta_plus; 
+  // Make sure the bignum can grow large enough. The smallest double equals 
+  // 4e-324. In this case the denominator needs fewer than 324*4 binary digits. 
+  // The maximum double is 1.7976931348623157e308 which needs fewer than 
+  // 308*4 binary digits. 
+  DOUBLE_CONVERSION_ASSERT(Bignum::kMaxSignificantBits >= 324*4); 
+  InitialScaledStartValues(significand, exponent, lower_boundary_is_closer, 
+                           estimated_power, need_boundary_deltas, 
+                           &numerator, &denominator, 
+                           &delta_minus, &delta_plus); 
+  // We now have v = (numerator / denominator) * 10^estimated_power. 
+  FixupMultiply10(estimated_power, is_even, decimal_point, 
+                  &numerator, &denominator, 
+                  &delta_minus, &delta_plus); 
+  // We now have v = (numerator / denominator) * 10^(decimal_point-1), and 
+  //  1 <= (numerator + delta_plus) / denominator < 10 
+  switch (mode) { 
+    case BIGNUM_DTOA_SHORTEST: 
+    case BIGNUM_DTOA_SHORTEST_SINGLE: 
+      GenerateShortestDigits(&numerator, &denominator, 
+                             &delta_minus, &delta_plus, 
+                             is_even, buffer, length); 
+      break; 
+    case BIGNUM_DTOA_FIXED: 
+      BignumToFixed(requested_digits, decimal_point, 
+                    &numerator, &denominator, 
+                    buffer, length); 
+      break; 
+    case BIGNUM_DTOA_PRECISION: 
+      GenerateCountedDigits(requested_digits, decimal_point, 
+                            &numerator, &denominator, 
+                            buffer, length); 
+      break; 
+    default: 
+      DOUBLE_CONVERSION_UNREACHABLE(); 
+  } 
+  buffer[*length] = '\0'; 
+} 
+ 
+ 
+// The procedure starts generating digits from the left to the right and stops 
+// when the generated digits yield the shortest decimal representation of v. A 
+// decimal representation of v is a number lying closer to v than to any other 
+// double, so it converts to v when read. 
+// 
+// This is true if d, the decimal representation, is between m- and m+, the 
+// upper and lower boundaries. d must be strictly between them if !is_even. 
+//           m- := (numerator - delta_minus) / denominator 
+//           m+ := (numerator + delta_plus) / denominator 
+// 
+// Precondition: 0 <= (numerator+delta_plus) / denominator < 10. 
+//   If 1 <= (numerator+delta_plus) / denominator < 10 then no leading 0 digit 
+//   will be produced. This should be the standard precondition. 
+static void GenerateShortestDigits(Bignum* numerator, Bignum* denominator, 
+                                   Bignum* delta_minus, Bignum* delta_plus, 
+                                   bool is_even, 
+                                   Vector<char> buffer, int* length) { 
+  // Small optimization: if delta_minus and delta_plus are the same just reuse 
+  // one of the two bignums. 
+  if (Bignum::Equal(*delta_minus, *delta_plus)) { 
+    delta_plus = delta_minus; 
+  } 
+  *length = 0; 
+  for (;;) { 
+    uint16_t digit; 
+    digit = numerator->DivideModuloIntBignum(*denominator); 
+    DOUBLE_CONVERSION_ASSERT(digit <= 9);  // digit is a uint16_t and therefore always positive. 
+    // digit = numerator / denominator (integer division). 
+    // numerator = numerator % denominator. 
+    buffer[(*length)++] = static_cast<char>(digit + '0'); 
+ 
+    // Can we stop already? 
+    // If the remainder of the division is less than the distance to the lower 
+    // boundary we can stop. In this case we simply round down (discarding the 
+    // remainder). 
+    // Similarly we test if we can round up (using the upper boundary). 
+    bool in_delta_room_minus; 
+    bool in_delta_room_plus; 
+    if (is_even) { 
+      in_delta_room_minus = Bignum::LessEqual(*numerator, *delta_minus); 
+    } else { 
+      in_delta_room_minus = Bignum::Less(*numerator, *delta_minus); 
+    } 
+    if (is_even) { 
+      in_delta_room_plus = 
+          Bignum::PlusCompare(*numerator, *delta_plus, *denominator) >= 0; 
+    } else { 
+      in_delta_room_plus = 
+          Bignum::PlusCompare(*numerator, *delta_plus, *denominator) > 0; 
+    } 
+    if (!in_delta_room_minus && !in_delta_room_plus) { 
+      // Prepare for next iteration. 
+      numerator->Times10(); 
+      delta_minus->Times10(); 
+      // We optimized delta_plus to be equal to delta_minus (if they share the 
+      // same value). So don't multiply delta_plus if they point to the same 
+      // object. 
+      if (delta_minus != delta_plus) { 
+        delta_plus->Times10(); 
+      } 
+    } else if (in_delta_room_minus && in_delta_room_plus) { 
+      // Let's see if 2*numerator < denominator. 
+      // If yes, then the next digit would be < 5 and we can round down. 
+      int compare = Bignum::PlusCompare(*numerator, *numerator, *denominator); 
+      if (compare < 0) { 
+        // Remaining digits are less than .5. -> Round down (== do nothing). 
+      } else if (compare > 0) { 
+        // Remaining digits are more than .5 of denominator. -> Round up. 
+        // Note that the last digit could not be a '9' as otherwise the whole 
+        // loop would have stopped earlier. 
+        // We still have an assert here in case the preconditions were not 
+        // satisfied. 
+        DOUBLE_CONVERSION_ASSERT(buffer[(*length) - 1] != '9'); 
+        buffer[(*length) - 1]++; 
+      } else { 
+        // Halfway case. 
+        // TODO(floitsch): need a way to solve half-way cases. 
+        //   For now let's round towards even (since this is what Gay seems to 
+        //   do). 
+ 
+        if ((buffer[(*length) - 1] - '0') % 2 == 0) { 
+          // Round down => Do nothing. 
+        } else { 
+          DOUBLE_CONVERSION_ASSERT(buffer[(*length) - 1] != '9'); 
+          buffer[(*length) - 1]++; 
+        } 
+      } 
+      return; 
+    } else if (in_delta_room_minus) { 
+      // Round down (== do nothing). 
+      return; 
+    } else {  // in_delta_room_plus 
+      // Round up. 
+      // Note again that the last digit could not be '9' since this would have 
+      // stopped the loop earlier. 
+      // We still have an DOUBLE_CONVERSION_ASSERT here, in case the preconditions were not 
+      // satisfied. 
+      DOUBLE_CONVERSION_ASSERT(buffer[(*length) -1] != '9'); 
+      buffer[(*length) - 1]++; 
+      return; 
+    } 
+  } 
+} 
+ 
+ 
+// Let v = numerator / denominator < 10. 
+// Then we generate 'count' digits of d = x.xxxxx... (without the decimal point) 
+// from left to right. Once 'count' digits have been produced we decide wether 
+// to round up or down. Remainders of exactly .5 round upwards. Numbers such 
+// as 9.999999 propagate a carry all the way, and change the 
+// exponent (decimal_point), when rounding upwards. 
+static void GenerateCountedDigits(int count, int* decimal_point, 
+                                  Bignum* numerator, Bignum* denominator, 
+                                  Vector<char> buffer, int* length) { 
+  DOUBLE_CONVERSION_ASSERT(count >= 0); 
+  for (int i = 0; i < count - 1; ++i) { 
+    uint16_t digit; 
+    digit = numerator->DivideModuloIntBignum(*denominator); 
+    DOUBLE_CONVERSION_ASSERT(digit <= 9);  // digit is a uint16_t and therefore always positive. 
+    // digit = numerator / denominator (integer division). 
+    // numerator = numerator % denominator. 
+    buffer[i] = static_cast<char>(digit + '0'); 
+    // Prepare for next iteration. 
+    numerator->Times10(); 
+  } 
+  // Generate the last digit. 
+  uint16_t digit; 
+  digit = numerator->DivideModuloIntBignum(*denominator); 
+  if (Bignum::PlusCompare(*numerator, *numerator, *denominator) >= 0) { 
+    digit++; 
+  } 
+  DOUBLE_CONVERSION_ASSERT(digit <= 10); 
+  buffer[count - 1] = static_cast<char>(digit + '0'); 
+  // Correct bad digits (in case we had a sequence of '9's). Propagate the 
+  // carry until we hat a non-'9' or til we reach the first digit. 
+  for (int i = count - 1; i > 0; --i) { 
+    if (buffer[i] != '0' + 10) break; 
+    buffer[i] = '0'; 
+    buffer[i - 1]++; 
+  } 
+  if (buffer[0] == '0' + 10) { 
+    // Propagate a carry past the top place. 
+    buffer[0] = '1'; 
+    (*decimal_point)++; 
+  } 
+  *length = count; 
+} 
+ 
+ 
+// Generates 'requested_digits' after the decimal point. It might omit 
+// trailing '0's. If the input number is too small then no digits at all are 
+// generated (ex.: 2 fixed digits for 0.00001). 
+// 
+// Input verifies:  1 <= (numerator + delta) / denominator < 10. 
+static void BignumToFixed(int requested_digits, int* decimal_point, 
+                          Bignum* numerator, Bignum* denominator, 
+                          Vector<char> buffer, int* length) { 
+  // Note that we have to look at more than just the requested_digits, since 
+  // a number could be rounded up. Example: v=0.5 with requested_digits=0. 
+  // Even though the power of v equals 0 we can't just stop here. 
+  if (-(*decimal_point) > requested_digits) { 
+    // The number is definitively too small. 
+    // Ex: 0.001 with requested_digits == 1. 
+    // Set decimal-point to -requested_digits. This is what Gay does. 
+    // Note that it should not have any effect anyways since the string is 
+    // empty. 
+    *decimal_point = -requested_digits; 
+    *length = 0; 
+    return; 
+  } else if (-(*decimal_point) == requested_digits) { 
+    // We only need to verify if the number rounds down or up. 
+    // Ex: 0.04 and 0.06 with requested_digits == 1. 
+    DOUBLE_CONVERSION_ASSERT(*decimal_point == -requested_digits); 
+    // Initially the fraction lies in range (1, 10]. Multiply the denominator 
+    // by 10 so that we can compare more easily. 
+    denominator->Times10(); 
+    if (Bignum::PlusCompare(*numerator, *numerator, *denominator) >= 0) { 
+      // If the fraction is >= 0.5 then we have to include the rounded 
+      // digit. 
+      buffer[0] = '1'; 
+      *length = 1; 
+      (*decimal_point)++; 
+    } else { 
+      // Note that we caught most of similar cases earlier. 
+      *length = 0; 
+    } 
+    return; 
+  } else { 
+    // The requested digits correspond to the digits after the point. 
+    // The variable 'needed_digits' includes the digits before the point. 
+    int needed_digits = (*decimal_point) + requested_digits; 
+    GenerateCountedDigits(needed_digits, decimal_point, 
+                          numerator, denominator, 
+                          buffer, length); 
+  } 
+} 
+ 
+ 
+// Returns an estimation of k such that 10^(k-1) <= v < 10^k where 
+// v = f * 2^exponent and 2^52 <= f < 2^53. 
+// v is hence a normalized double with the given exponent. The output is an 
+// approximation for the exponent of the decimal approimation .digits * 10^k. 
+// 
+// The result might undershoot by 1 in which case 10^k <= v < 10^k+1. 
+// Note: this property holds for v's upper boundary m+ too. 
+//    10^k <= m+ < 10^k+1. 
+//   (see explanation below). 
+// 
+// Examples: 
+//  EstimatePower(0)   => 16 
+//  EstimatePower(-52) => 0 
+// 
+// Note: e >= 0 => EstimatedPower(e) > 0. No similar claim can be made for e<0. 
+static int EstimatePower(int exponent) { 
+  // This function estimates log10 of v where v = f*2^e (with e == exponent). 
+  // Note that 10^floor(log10(v)) <= v, but v <= 10^ceil(log10(v)). 
+  // Note that f is bounded by its container size. Let p = 53 (the double's 
+  // significand size). Then 2^(p-1) <= f < 2^p. 
+  // 
+  // Given that log10(v) == log2(v)/log2(10) and e+(len(f)-1) is quite close 
+  // to log2(v) the function is simplified to (e+(len(f)-1)/log2(10)). 
+  // The computed number undershoots by less than 0.631 (when we compute log3 
+  // and not log10). 
+  // 
+  // Optimization: since we only need an approximated result this computation 
+  // can be performed on 64 bit integers. On x86/x64 architecture the speedup is 
+  // not really measurable, though. 
+  // 
+  // Since we want to avoid overshooting we decrement by 1e10 so that 
+  // floating-point imprecisions don't affect us. 
+  // 
+  // Explanation for v's boundary m+: the computation takes advantage of 
+  // the fact that 2^(p-1) <= f < 2^p. Boundaries still satisfy this requirement 
+  // (even for denormals where the delta can be much more important). 
+ 
+  const double k1Log10 = 0.30102999566398114;  // 1/lg(10) 
+ 
+  // For doubles len(f) == 53 (don't forget the hidden bit). 
+  const int kSignificandSize = Double::kSignificandSize; 
+  double estimate = ceil((exponent + kSignificandSize - 1) * k1Log10 - 1e-10); 
+  return static_cast<int>(estimate); 
+} 
+ 
+ 
+// See comments for InitialScaledStartValues. 
+static void InitialScaledStartValuesPositiveExponent( 
+    uint64_t significand, int exponent, 
+    int estimated_power, bool need_boundary_deltas, 
+    Bignum* numerator, Bignum* denominator, 
+    Bignum* delta_minus, Bignum* delta_plus) { 
+  // A positive exponent implies a positive power. 
+  DOUBLE_CONVERSION_ASSERT(estimated_power >= 0); 
+  // Since the estimated_power is positive we simply multiply the denominator 
+  // by 10^estimated_power. 
+ 
+  // numerator = v. 
+  numerator->AssignUInt64(significand); 
+  numerator->ShiftLeft(exponent); 
+  // denominator = 10^estimated_power. 
+  denominator->AssignPowerUInt16(10, estimated_power); 
+ 
+  if (need_boundary_deltas) { 
+    // Introduce a common denominator so that the deltas to the boundaries are 
+    // integers. 
+    denominator->ShiftLeft(1); 
+    numerator->ShiftLeft(1); 
+    // Let v = f * 2^e, then m+ - v = 1/2 * 2^e; With the common 
+    // denominator (of 2) delta_plus equals 2^e. 
+    delta_plus->AssignUInt16(1); 
+    delta_plus->ShiftLeft(exponent); 
+    // Same for delta_minus. The adjustments if f == 2^p-1 are done later. 
+    delta_minus->AssignUInt16(1); 
+    delta_minus->ShiftLeft(exponent); 
+  } 
+} 
+ 
+ 
+// See comments for InitialScaledStartValues 
+static void InitialScaledStartValuesNegativeExponentPositivePower( 
+    uint64_t significand, int exponent, 
+    int estimated_power, bool need_boundary_deltas, 
+    Bignum* numerator, Bignum* denominator, 
+    Bignum* delta_minus, Bignum* delta_plus) { 
+  // v = f * 2^e with e < 0, and with estimated_power >= 0. 
+  // This means that e is close to 0 (have a look at how estimated_power is 
+  // computed). 
+ 
+  // numerator = significand 
+  //  since v = significand * 2^exponent this is equivalent to 
+  //  numerator = v * / 2^-exponent 
+  numerator->AssignUInt64(significand); 
+  // denominator = 10^estimated_power * 2^-exponent (with exponent < 0) 
+  denominator->AssignPowerUInt16(10, estimated_power); 
+  denominator->ShiftLeft(-exponent); 
+ 
+  if (need_boundary_deltas) { 
+    // Introduce a common denominator so that the deltas to the boundaries are 
+    // integers. 
+    denominator->ShiftLeft(1); 
+    numerator->ShiftLeft(1); 
+    // Let v = f * 2^e, then m+ - v = 1/2 * 2^e; With the common 
+    // denominator (of 2) delta_plus equals 2^e. 
+    // Given that the denominator already includes v's exponent the distance 
+    // to the boundaries is simply 1. 
+    delta_plus->AssignUInt16(1); 
+    // Same for delta_minus. The adjustments if f == 2^p-1 are done later. 
+    delta_minus->AssignUInt16(1); 
+  } 
+} 
+ 
+ 
+// See comments for InitialScaledStartValues 
+static void InitialScaledStartValuesNegativeExponentNegativePower( 
+    uint64_t significand, int exponent, 
+    int estimated_power, bool need_boundary_deltas, 
+    Bignum* numerator, Bignum* denominator, 
+    Bignum* delta_minus, Bignum* delta_plus) { 
+  // Instead of multiplying the denominator with 10^estimated_power we 
+  // multiply all values (numerator and deltas) by 10^-estimated_power. 
+ 
+  // Use numerator as temporary container for power_ten. 
+  Bignum* power_ten = numerator; 
+  power_ten->AssignPowerUInt16(10, -estimated_power); 
+ 
+  if (need_boundary_deltas) { 
+    // Since power_ten == numerator we must make a copy of 10^estimated_power 
+    // before we complete the computation of the numerator. 
+    // delta_plus = delta_minus = 10^estimated_power 
+    delta_plus->AssignBignum(*power_ten); 
+    delta_minus->AssignBignum(*power_ten); 
+  } 
+ 
+  // numerator = significand * 2 * 10^-estimated_power 
+  //  since v = significand * 2^exponent this is equivalent to 
+  // numerator = v * 10^-estimated_power * 2 * 2^-exponent. 
+  // Remember: numerator has been abused as power_ten. So no need to assign it 
+  //  to itself. 
+  DOUBLE_CONVERSION_ASSERT(numerator == power_ten); 
+  numerator->MultiplyByUInt64(significand); 
+ 
+  // denominator = 2 * 2^-exponent with exponent < 0. 
+  denominator->AssignUInt16(1); 
+  denominator->ShiftLeft(-exponent); 
+ 
+  if (need_boundary_deltas) { 
+    // Introduce a common denominator so that the deltas to the boundaries are 
+    // integers. 
+    numerator->ShiftLeft(1); 
+    denominator->ShiftLeft(1); 
+    // With this shift the boundaries have their correct value, since 
+    // delta_plus = 10^-estimated_power, and 
+    // delta_minus = 10^-estimated_power. 
+    // These assignments have been done earlier. 
+    // The adjustments if f == 2^p-1 (lower boundary is closer) are done later. 
+  } 
+} 
+ 
+ 
+// Let v = significand * 2^exponent. 
+// Computes v / 10^estimated_power exactly, as a ratio of two bignums, numerator 
+// and denominator. The functions GenerateShortestDigits and 
+// GenerateCountedDigits will then convert this ratio to its decimal 
+// representation d, with the required accuracy. 
+// Then d * 10^estimated_power is the representation of v. 
+// (Note: the fraction and the estimated_power might get adjusted before 
+// generating the decimal representation.) 
+// 
+// The initial start values consist of: 
+//  - a scaled numerator: s.t. numerator/denominator == v / 10^estimated_power. 
+//  - a scaled (common) denominator. 
+//  optionally (used by GenerateShortestDigits to decide if it has the shortest 
+//  decimal converting back to v): 
+//  - v - m-: the distance to the lower boundary. 
+//  - m+ - v: the distance to the upper boundary. 
+// 
+// v, m+, m-, and therefore v - m- and m+ - v all share the same denominator. 
+// 
+// Let ep == estimated_power, then the returned values will satisfy: 
+//  v / 10^ep = numerator / denominator. 
+//  v's boundarys m- and m+: 
+//    m- / 10^ep == v / 10^ep - delta_minus / denominator 
+//    m+ / 10^ep == v / 10^ep + delta_plus / denominator 
+//  Or in other words: 
+//    m- == v - delta_minus * 10^ep / denominator; 
+//    m+ == v + delta_plus * 10^ep / denominator; 
+// 
+// Since 10^(k-1) <= v < 10^k    (with k == estimated_power) 
+//  or       10^k <= v < 10^(k+1) 
+//  we then have 0.1 <= numerator/denominator < 1 
+//           or    1 <= numerator/denominator < 10 
+// 
+// It is then easy to kickstart the digit-generation routine. 
+// 
+// The boundary-deltas are only filled if the mode equals BIGNUM_DTOA_SHORTEST 
+// or BIGNUM_DTOA_SHORTEST_SINGLE. 
+ 
+static void InitialScaledStartValues(uint64_t significand, 
+                                     int exponent, 
+                                     bool lower_boundary_is_closer, 
+                                     int estimated_power, 
+                                     bool need_boundary_deltas, 
+                                     Bignum* numerator, 
+                                     Bignum* denominator, 
+                                     Bignum* delta_minus, 
+                                     Bignum* delta_plus) { 
+  if (exponent >= 0) { 
+    InitialScaledStartValuesPositiveExponent( 
+        significand, exponent, estimated_power, need_boundary_deltas, 
+        numerator, denominator, delta_minus, delta_plus); 
+  } else if (estimated_power >= 0) { 
+    InitialScaledStartValuesNegativeExponentPositivePower( 
+        significand, exponent, estimated_power, need_boundary_deltas, 
+        numerator, denominator, delta_minus, delta_plus); 
+  } else { 
+    InitialScaledStartValuesNegativeExponentNegativePower( 
+        significand, exponent, estimated_power, need_boundary_deltas, 
+        numerator, denominator, delta_minus, delta_plus); 
+  } 
+ 
+  if (need_boundary_deltas && lower_boundary_is_closer) { 
+    // The lower boundary is closer at half the distance of "normal" numbers. 
+    // Increase the common denominator and adapt all but the delta_minus. 
+    denominator->ShiftLeft(1);  // *2 
+    numerator->ShiftLeft(1);    // *2 
+    delta_plus->ShiftLeft(1);   // *2 
+  } 
+} 
+ 
+ 
+// This routine multiplies numerator/denominator so that its values lies in the 
+// range 1-10. That is after a call to this function we have: 
+//    1 <= (numerator + delta_plus) /denominator < 10. 
+// Let numerator the input before modification and numerator' the argument 
+// after modification, then the output-parameter decimal_point is such that 
+//  numerator / denominator * 10^estimated_power == 
+//    numerator' / denominator' * 10^(decimal_point - 1) 
+// In some cases estimated_power was too low, and this is already the case. We 
+// then simply adjust the power so that 10^(k-1) <= v < 10^k (with k == 
+// estimated_power) but do not touch the numerator or denominator. 
+// Otherwise the routine multiplies the numerator and the deltas by 10. 
+static void FixupMultiply10(int estimated_power, bool is_even, 
+                            int* decimal_point, 
+                            Bignum* numerator, Bignum* denominator, 
+                            Bignum* delta_minus, Bignum* delta_plus) { 
+  bool in_range; 
+  if (is_even) { 
+    // For IEEE doubles half-way cases (in decimal system numbers ending with 5) 
+    // are rounded to the closest floating-point number with even significand. 
+    in_range = Bignum::PlusCompare(*numerator, *delta_plus, *denominator) >= 0; 
+  } else { 
+    in_range = Bignum::PlusCompare(*numerator, *delta_plus, *denominator) > 0; 
+  } 
+  if (in_range) { 
+    // Since numerator + delta_plus >= denominator we already have 
+    // 1 <= numerator/denominator < 10. Simply update the estimated_power. 
+    *decimal_point = estimated_power + 1; 
+  } else { 
+    *decimal_point = estimated_power; 
+    numerator->Times10(); 
+    if (Bignum::Equal(*delta_minus, *delta_plus)) { 
+      delta_minus->Times10(); 
+      delta_plus->AssignBignum(*delta_minus); 
+    } else { 
+      delta_minus->Times10(); 
+      delta_plus->Times10(); 
+    } 
+  } 
+} 
+ 
+}  // namespace double_conversion 
+ 
+// ICU PATCH: Close ICU namespace 
+U_NAMESPACE_END 
+#endif // ICU PATCH: close #if !UCONFIG_NO_FORMATTING