629 lines
		
	
	
		
			24 KiB
		
	
	
	
		
			C++
		
	
	
	
			
		
		
	
	
			629 lines
		
	
	
		
			24 KiB
		
	
	
	
		
			C++
		
	
	
	
| // © 2018 and later: Unicode, Inc. and others.
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| // License & terms of use: http://www.unicode.org/copyright.html
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| //
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| // From the double-conversion library. Original license:
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| //
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| // Copyright 2010 the V8 project authors. All rights reserved.
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| // Redistribution and use in source and binary forms, with or without
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| // modification, are permitted provided that the following conditions are
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| // met:
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| //
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| //     * Redistributions of source code must retain the above copyright
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| //       notice, this list of conditions and the following disclaimer.
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| //     * Redistributions in binary form must reproduce the above
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| //       copyright notice, this list of conditions and the following
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| //       disclaimer in the documentation and/or other materials provided
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| //       with the distribution.
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| //     * Neither the name of Google Inc. nor the names of its
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| //       contributors may be used to endorse or promote products derived
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| //       from this software without specific prior written permission.
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| //
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| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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| // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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| // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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| // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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| // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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| // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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| // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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| // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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| // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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| // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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| // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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| 
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| // ICU PATCH: ifdef around UCONFIG_NO_FORMATTING
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| #include "unicode/utypes.h"
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| #if !UCONFIG_NO_FORMATTING
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| 
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| #include <climits>
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| #include <cstdarg>
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| 
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| // ICU PATCH: Customize header file paths for ICU.
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| 
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| #include "double-conversion-bignum.h"
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| #include "double-conversion-cached-powers.h"
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| #include "double-conversion-ieee.h"
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| #include "double-conversion-strtod.h"
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| 
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| // ICU PATCH: Wrap in ICU namespace
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| U_NAMESPACE_BEGIN
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| 
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| namespace double_conversion {
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| 
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| #if defined(DOUBLE_CONVERSION_CORRECT_DOUBLE_OPERATIONS)
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| // 2^53 = 9007199254740992.
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| // Any integer with at most 15 decimal digits will hence fit into a double
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| // (which has a 53bit significand) without loss of precision.
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| static const int kMaxExactDoubleIntegerDecimalDigits = 15;
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| #endif // #if defined(DOUBLE_CONVERSION_CORRECT_DOUBLE_OPERATIONS)
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| // 2^64 = 18446744073709551616 > 10^19
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| static const int kMaxUint64DecimalDigits = 19;
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| 
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| // Max double: 1.7976931348623157 x 10^308
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| // Min non-zero double: 4.9406564584124654 x 10^-324
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| // Any x >= 10^309 is interpreted as +infinity.
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| // Any x <= 10^-324 is interpreted as 0.
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| // Note that 2.5e-324 (despite being smaller than the min double) will be read
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| // as non-zero (equal to the min non-zero double).
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| static const int kMaxDecimalPower = 309;
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| static const int kMinDecimalPower = -324;
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| 
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| // 2^64 = 18446744073709551616
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| static const uint64_t kMaxUint64 = DOUBLE_CONVERSION_UINT64_2PART_C(0xFFFFFFFF, FFFFFFFF);
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| 
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| 
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| #if defined(DOUBLE_CONVERSION_CORRECT_DOUBLE_OPERATIONS)
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| static const double exact_powers_of_ten[] = {
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|   1.0,  // 10^0
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|   10.0,
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|   100.0,
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|   1000.0,
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|   10000.0,
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|   100000.0,
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|   1000000.0,
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|   10000000.0,
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|   100000000.0,
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|   1000000000.0,
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|   10000000000.0,  // 10^10
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|   100000000000.0,
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|   1000000000000.0,
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|   10000000000000.0,
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|   100000000000000.0,
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|   1000000000000000.0,
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|   10000000000000000.0,
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|   100000000000000000.0,
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|   1000000000000000000.0,
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|   10000000000000000000.0,
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|   100000000000000000000.0,  // 10^20
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|   1000000000000000000000.0,
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|   // 10^22 = 0x21e19e0c9bab2400000 = 0x878678326eac9 * 2^22
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|   10000000000000000000000.0
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| };
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| static const int kExactPowersOfTenSize = DOUBLE_CONVERSION_ARRAY_SIZE(exact_powers_of_ten);
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| #endif // #if defined(DOUBLE_CONVERSION_CORRECT_DOUBLE_OPERATIONS)
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| 
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| // Maximum number of significant digits in the decimal representation.
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| // In fact the value is 772 (see conversions.cc), but to give us some margin
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| // we round up to 780.
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| static const int kMaxSignificantDecimalDigits = 780;
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| 
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| static Vector<const char> TrimLeadingZeros(Vector<const char> buffer) {
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|   for (int i = 0; i < buffer.length(); i++) {
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|     if (buffer[i] != '0') {
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|       return buffer.SubVector(i, buffer.length());
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|     }
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|   }
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|   return Vector<const char>(buffer.start(), 0);
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| }
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| 
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| static void CutToMaxSignificantDigits(Vector<const char> buffer,
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|                                        int exponent,
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|                                        char* significant_buffer,
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|                                        int* significant_exponent) {
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|   for (int i = 0; i < kMaxSignificantDecimalDigits - 1; ++i) {
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|     significant_buffer[i] = buffer[i];
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|   }
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|   // The input buffer has been trimmed. Therefore the last digit must be
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|   // different from '0'.
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|   DOUBLE_CONVERSION_ASSERT(buffer[buffer.length() - 1] != '0');
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|   // Set the last digit to be non-zero. This is sufficient to guarantee
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|   // correct rounding.
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|   significant_buffer[kMaxSignificantDecimalDigits - 1] = '1';
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|   *significant_exponent =
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|       exponent + (buffer.length() - kMaxSignificantDecimalDigits);
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| }
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| 
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| 
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| // Trims the buffer and cuts it to at most kMaxSignificantDecimalDigits.
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| // If possible the input-buffer is reused, but if the buffer needs to be
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| // modified (due to cutting), then the input needs to be copied into the
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| // buffer_copy_space.
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| static void TrimAndCut(Vector<const char> buffer, int exponent,
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|                        char* buffer_copy_space, int space_size,
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|                        Vector<const char>* trimmed, int* updated_exponent) {
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|   Vector<const char> left_trimmed = TrimLeadingZeros(buffer);
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|   Vector<const char> right_trimmed = TrimTrailingZeros(left_trimmed);
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|   exponent += left_trimmed.length() - right_trimmed.length();
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|   if (right_trimmed.length() > kMaxSignificantDecimalDigits) {
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|     (void) space_size;  // Mark variable as used.
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|     DOUBLE_CONVERSION_ASSERT(space_size >= kMaxSignificantDecimalDigits);
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|     CutToMaxSignificantDigits(right_trimmed, exponent,
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|                               buffer_copy_space, updated_exponent);
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|     *trimmed = Vector<const char>(buffer_copy_space,
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|                                  kMaxSignificantDecimalDigits);
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|   } else {
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|     *trimmed = right_trimmed;
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|     *updated_exponent = exponent;
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|   }
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| }
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| 
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| 
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| // Reads digits from the buffer and converts them to a uint64.
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| // Reads in as many digits as fit into a uint64.
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| // When the string starts with "1844674407370955161" no further digit is read.
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| // Since 2^64 = 18446744073709551616 it would still be possible read another
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| // digit if it was less or equal than 6, but this would complicate the code.
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| static uint64_t ReadUint64(Vector<const char> buffer,
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|                            int* number_of_read_digits) {
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|   uint64_t result = 0;
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|   int i = 0;
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|   while (i < buffer.length() && result <= (kMaxUint64 / 10 - 1)) {
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|     int digit = buffer[i++] - '0';
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|     DOUBLE_CONVERSION_ASSERT(0 <= digit && digit <= 9);
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|     result = 10 * result + digit;
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|   }
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|   *number_of_read_digits = i;
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|   return result;
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| }
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| 
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| 
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| // Reads a DiyFp from the buffer.
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| // The returned DiyFp is not necessarily normalized.
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| // If remaining_decimals is zero then the returned DiyFp is accurate.
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| // Otherwise it has been rounded and has error of at most 1/2 ulp.
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| static void ReadDiyFp(Vector<const char> buffer,
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|                       DiyFp* result,
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|                       int* remaining_decimals) {
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|   int read_digits;
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|   uint64_t significand = ReadUint64(buffer, &read_digits);
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|   if (buffer.length() == read_digits) {
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|     *result = DiyFp(significand, 0);
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|     *remaining_decimals = 0;
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|   } else {
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|     // Round the significand.
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|     if (buffer[read_digits] >= '5') {
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|       significand++;
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|     }
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|     // Compute the binary exponent.
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|     int exponent = 0;
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|     *result = DiyFp(significand, exponent);
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|     *remaining_decimals = buffer.length() - read_digits;
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|   }
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| }
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| 
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| 
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| static bool DoubleStrtod(Vector<const char> trimmed,
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|                          int exponent,
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|                          double* result) {
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| #if !defined(DOUBLE_CONVERSION_CORRECT_DOUBLE_OPERATIONS)
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|   // Avoid "unused parameter" warnings
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|   (void) trimmed;
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|   (void) exponent;
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|   (void) result;
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|   // On x86 the floating-point stack can be 64 or 80 bits wide. If it is
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|   // 80 bits wide (as is the case on Linux) then double-rounding occurs and the
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|   // result is not accurate.
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|   // We know that Windows32 uses 64 bits and is therefore accurate.
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|   return false;
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| #else
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|   if (trimmed.length() <= kMaxExactDoubleIntegerDecimalDigits) {
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|     int read_digits;
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|     // The trimmed input fits into a double.
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|     // If the 10^exponent (resp. 10^-exponent) fits into a double too then we
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|     // can compute the result-double simply by multiplying (resp. dividing) the
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|     // two numbers.
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|     // This is possible because IEEE guarantees that floating-point operations
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|     // return the best possible approximation.
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|     if (exponent < 0 && -exponent < kExactPowersOfTenSize) {
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|       // 10^-exponent fits into a double.
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|       *result = static_cast<double>(ReadUint64(trimmed, &read_digits));
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|       DOUBLE_CONVERSION_ASSERT(read_digits == trimmed.length());
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|       *result /= exact_powers_of_ten[-exponent];
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|       return true;
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|     }
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|     if (0 <= exponent && exponent < kExactPowersOfTenSize) {
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|       // 10^exponent fits into a double.
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|       *result = static_cast<double>(ReadUint64(trimmed, &read_digits));
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|       DOUBLE_CONVERSION_ASSERT(read_digits == trimmed.length());
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|       *result *= exact_powers_of_ten[exponent];
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|       return true;
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|     }
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|     int remaining_digits =
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|         kMaxExactDoubleIntegerDecimalDigits - trimmed.length();
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|     if ((0 <= exponent) &&
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|         (exponent - remaining_digits < kExactPowersOfTenSize)) {
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|       // The trimmed string was short and we can multiply it with
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|       // 10^remaining_digits. As a result the remaining exponent now fits
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|       // into a double too.
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|       *result = static_cast<double>(ReadUint64(trimmed, &read_digits));
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|       DOUBLE_CONVERSION_ASSERT(read_digits == trimmed.length());
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|       *result *= exact_powers_of_ten[remaining_digits];
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|       *result *= exact_powers_of_ten[exponent - remaining_digits];
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|       return true;
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|     }
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|   }
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|   return false;
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| #endif
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| }
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| 
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| 
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| // Returns 10^exponent as an exact DiyFp.
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| // The given exponent must be in the range [1; kDecimalExponentDistance[.
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| static DiyFp AdjustmentPowerOfTen(int exponent) {
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|   DOUBLE_CONVERSION_ASSERT(0 < exponent);
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|   DOUBLE_CONVERSION_ASSERT(exponent < PowersOfTenCache::kDecimalExponentDistance);
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|   // Simply hardcode the remaining powers for the given decimal exponent
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|   // distance.
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|   DOUBLE_CONVERSION_ASSERT(PowersOfTenCache::kDecimalExponentDistance == 8);
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|   switch (exponent) {
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|     case 1: return DiyFp(DOUBLE_CONVERSION_UINT64_2PART_C(0xa0000000, 00000000), -60);
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|     case 2: return DiyFp(DOUBLE_CONVERSION_UINT64_2PART_C(0xc8000000, 00000000), -57);
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|     case 3: return DiyFp(DOUBLE_CONVERSION_UINT64_2PART_C(0xfa000000, 00000000), -54);
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|     case 4: return DiyFp(DOUBLE_CONVERSION_UINT64_2PART_C(0x9c400000, 00000000), -50);
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|     case 5: return DiyFp(DOUBLE_CONVERSION_UINT64_2PART_C(0xc3500000, 00000000), -47);
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|     case 6: return DiyFp(DOUBLE_CONVERSION_UINT64_2PART_C(0xf4240000, 00000000), -44);
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|     case 7: return DiyFp(DOUBLE_CONVERSION_UINT64_2PART_C(0x98968000, 00000000), -40);
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|     default:
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|       DOUBLE_CONVERSION_UNREACHABLE();
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|   }
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| }
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| 
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| 
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| // If the function returns true then the result is the correct double.
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| // Otherwise it is either the correct double or the double that is just below
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| // the correct double.
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| static bool DiyFpStrtod(Vector<const char> buffer,
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|                         int exponent,
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|                         double* result) {
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|   DiyFp input;
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|   int remaining_decimals;
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|   ReadDiyFp(buffer, &input, &remaining_decimals);
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|   // Since we may have dropped some digits the input is not accurate.
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|   // If remaining_decimals is different than 0 than the error is at most
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|   // .5 ulp (unit in the last place).
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|   // We don't want to deal with fractions and therefore keep a common
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|   // denominator.
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|   const int kDenominatorLog = 3;
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|   const int kDenominator = 1 << kDenominatorLog;
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|   // Move the remaining decimals into the exponent.
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|   exponent += remaining_decimals;
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|   uint64_t error = (remaining_decimals == 0 ? 0 : kDenominator / 2);
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| 
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|   int old_e = input.e();
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|   input.Normalize();
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|   error <<= old_e - input.e();
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| 
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|   DOUBLE_CONVERSION_ASSERT(exponent <= PowersOfTenCache::kMaxDecimalExponent);
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|   if (exponent < PowersOfTenCache::kMinDecimalExponent) {
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|     *result = 0.0;
 | |
|     return true;
 | |
|   }
 | |
|   DiyFp cached_power;
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|   int cached_decimal_exponent;
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|   PowersOfTenCache::GetCachedPowerForDecimalExponent(exponent,
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|                                                      &cached_power,
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|                                                      &cached_decimal_exponent);
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| 
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|   if (cached_decimal_exponent != exponent) {
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|     int adjustment_exponent = exponent - cached_decimal_exponent;
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|     DiyFp adjustment_power = AdjustmentPowerOfTen(adjustment_exponent);
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|     input.Multiply(adjustment_power);
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|     if (kMaxUint64DecimalDigits - buffer.length() >= adjustment_exponent) {
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|       // The product of input with the adjustment power fits into a 64 bit
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|       // integer.
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|       DOUBLE_CONVERSION_ASSERT(DiyFp::kSignificandSize == 64);
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|     } else {
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|       // The adjustment power is exact. There is hence only an error of 0.5.
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|       error += kDenominator / 2;
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|     }
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|   }
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| 
 | |
|   input.Multiply(cached_power);
 | |
|   // The error introduced by a multiplication of a*b equals
 | |
|   //   error_a + error_b + error_a*error_b/2^64 + 0.5
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|   // Substituting a with 'input' and b with 'cached_power' we have
 | |
|   //   error_b = 0.5  (all cached powers have an error of less than 0.5 ulp),
 | |
|   //   error_ab = 0 or 1 / kDenominator > error_a*error_b/ 2^64
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|   int error_b = kDenominator / 2;
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|   int error_ab = (error == 0 ? 0 : 1);  // We round up to 1.
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|   int fixed_error = kDenominator / 2;
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|   error += error_b + error_ab + fixed_error;
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| 
 | |
|   old_e = input.e();
 | |
|   input.Normalize();
 | |
|   error <<= old_e - input.e();
 | |
| 
 | |
|   // See if the double's significand changes if we add/subtract the error.
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|   int order_of_magnitude = DiyFp::kSignificandSize + input.e();
 | |
|   int effective_significand_size =
 | |
|       Double::SignificandSizeForOrderOfMagnitude(order_of_magnitude);
 | |
|   int precision_digits_count =
 | |
|       DiyFp::kSignificandSize - effective_significand_size;
 | |
|   if (precision_digits_count + kDenominatorLog >= DiyFp::kSignificandSize) {
 | |
|     // This can only happen for very small denormals. In this case the
 | |
|     // half-way multiplied by the denominator exceeds the range of an uint64.
 | |
|     // Simply shift everything to the right.
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|     int shift_amount = (precision_digits_count + kDenominatorLog) -
 | |
|         DiyFp::kSignificandSize + 1;
 | |
|     input.set_f(input.f() >> shift_amount);
 | |
|     input.set_e(input.e() + shift_amount);
 | |
|     // We add 1 for the lost precision of error, and kDenominator for
 | |
|     // the lost precision of input.f().
 | |
|     error = (error >> shift_amount) + 1 + kDenominator;
 | |
|     precision_digits_count -= shift_amount;
 | |
|   }
 | |
|   // We use uint64_ts now. This only works if the DiyFp uses uint64_ts too.
 | |
|   DOUBLE_CONVERSION_ASSERT(DiyFp::kSignificandSize == 64);
 | |
|   DOUBLE_CONVERSION_ASSERT(precision_digits_count < 64);
 | |
|   uint64_t one64 = 1;
 | |
|   uint64_t precision_bits_mask = (one64 << precision_digits_count) - 1;
 | |
|   uint64_t precision_bits = input.f() & precision_bits_mask;
 | |
|   uint64_t half_way = one64 << (precision_digits_count - 1);
 | |
|   precision_bits *= kDenominator;
 | |
|   half_way *= kDenominator;
 | |
|   DiyFp rounded_input(input.f() >> precision_digits_count,
 | |
|                       input.e() + precision_digits_count);
 | |
|   if (precision_bits >= half_way + error) {
 | |
|     rounded_input.set_f(rounded_input.f() + 1);
 | |
|   }
 | |
|   // If the last_bits are too close to the half-way case than we are too
 | |
|   // inaccurate and round down. In this case we return false so that we can
 | |
|   // fall back to a more precise algorithm.
 | |
| 
 | |
|   *result = Double(rounded_input).value();
 | |
|   if (half_way - error < precision_bits && precision_bits < half_way + error) {
 | |
|     // Too imprecise. The caller will have to fall back to a slower version.
 | |
|     // However the returned number is guaranteed to be either the correct
 | |
|     // double, or the next-lower double.
 | |
|     return false;
 | |
|   } else {
 | |
|     return true;
 | |
|   }
 | |
| }
 | |
| 
 | |
| 
 | |
| // Returns
 | |
| //   - -1 if buffer*10^exponent < diy_fp.
 | |
| //   -  0 if buffer*10^exponent == diy_fp.
 | |
| //   - +1 if buffer*10^exponent > diy_fp.
 | |
| // Preconditions:
 | |
| //   buffer.length() + exponent <= kMaxDecimalPower + 1
 | |
| //   buffer.length() + exponent > kMinDecimalPower
 | |
| //   buffer.length() <= kMaxDecimalSignificantDigits
 | |
| static int CompareBufferWithDiyFp(Vector<const char> buffer,
 | |
|                                   int exponent,
 | |
|                                   DiyFp diy_fp) {
 | |
|   DOUBLE_CONVERSION_ASSERT(buffer.length() + exponent <= kMaxDecimalPower + 1);
 | |
|   DOUBLE_CONVERSION_ASSERT(buffer.length() + exponent > kMinDecimalPower);
 | |
|   DOUBLE_CONVERSION_ASSERT(buffer.length() <= kMaxSignificantDecimalDigits);
 | |
|   // Make sure that the Bignum will be able to hold all our numbers.
 | |
|   // Our Bignum implementation has a separate field for exponents. Shifts will
 | |
|   // consume at most one bigit (< 64 bits).
 | |
|   // ln(10) == 3.3219...
 | |
|   DOUBLE_CONVERSION_ASSERT(((kMaxDecimalPower + 1) * 333 / 100) < Bignum::kMaxSignificantBits);
 | |
|   Bignum buffer_bignum;
 | |
|   Bignum diy_fp_bignum;
 | |
|   buffer_bignum.AssignDecimalString(buffer);
 | |
|   diy_fp_bignum.AssignUInt64(diy_fp.f());
 | |
|   if (exponent >= 0) {
 | |
|     buffer_bignum.MultiplyByPowerOfTen(exponent);
 | |
|   } else {
 | |
|     diy_fp_bignum.MultiplyByPowerOfTen(-exponent);
 | |
|   }
 | |
|   if (diy_fp.e() > 0) {
 | |
|     diy_fp_bignum.ShiftLeft(diy_fp.e());
 | |
|   } else {
 | |
|     buffer_bignum.ShiftLeft(-diy_fp.e());
 | |
|   }
 | |
|   return Bignum::Compare(buffer_bignum, diy_fp_bignum);
 | |
| }
 | |
| 
 | |
| 
 | |
| // Returns true if the guess is the correct double.
 | |
| // Returns false, when guess is either correct or the next-lower double.
 | |
| static bool ComputeGuess(Vector<const char> trimmed, int exponent,
 | |
|                          double* guess) {
 | |
|   if (trimmed.length() == 0) {
 | |
|     *guess = 0.0;
 | |
|     return true;
 | |
|   }
 | |
|   if (exponent + trimmed.length() - 1 >= kMaxDecimalPower) {
 | |
|     *guess = Double::Infinity();
 | |
|     return true;
 | |
|   }
 | |
|   if (exponent + trimmed.length() <= kMinDecimalPower) {
 | |
|     *guess = 0.0;
 | |
|     return true;
 | |
|   }
 | |
| 
 | |
|   if (DoubleStrtod(trimmed, exponent, guess) ||
 | |
|       DiyFpStrtod(trimmed, exponent, guess)) {
 | |
|     return true;
 | |
|   }
 | |
|   if (*guess == Double::Infinity()) {
 | |
|     return true;
 | |
|   }
 | |
|   return false;
 | |
| }
 | |
| 
 | |
| #if U_DEBUG // needed for ICU only in debug mode
 | |
| static bool IsDigit(const char d) {
 | |
|   return ('0' <= d) && (d <= '9');
 | |
| }
 | |
| 
 | |
| static bool IsNonZeroDigit(const char d) {
 | |
|   return ('1' <= d) && (d <= '9');
 | |
| }
 | |
| 
 | |
| #ifdef __has_cpp_attribute
 | |
| #if __has_cpp_attribute(maybe_unused)
 | |
| [[maybe_unused]]
 | |
| #endif
 | |
| #endif
 | |
| static bool AssertTrimmedDigits(const Vector<const char>& buffer) {
 | |
|   for(int i = 0; i < buffer.length(); ++i) {
 | |
|     if(!IsDigit(buffer[i])) {
 | |
|       return false;
 | |
|     }
 | |
|   }
 | |
|   return (buffer.length() == 0) || (IsNonZeroDigit(buffer[0]) && IsNonZeroDigit(buffer[buffer.length()-1]));
 | |
| }
 | |
| #endif // needed for ICU only in debug mode
 | |
| 
 | |
| double StrtodTrimmed(Vector<const char> trimmed, int exponent) {
 | |
|   DOUBLE_CONVERSION_ASSERT(trimmed.length() <= kMaxSignificantDecimalDigits);
 | |
|   DOUBLE_CONVERSION_ASSERT(AssertTrimmedDigits(trimmed));
 | |
|   double guess;
 | |
|   const bool is_correct = ComputeGuess(trimmed, exponent, &guess);
 | |
|   if (is_correct) {
 | |
|     return guess;
 | |
|   }
 | |
|   DiyFp upper_boundary = Double(guess).UpperBoundary();
 | |
|   int comparison = CompareBufferWithDiyFp(trimmed, exponent, upper_boundary);
 | |
|   if (comparison < 0) {
 | |
|     return guess;
 | |
|   } else if (comparison > 0) {
 | |
|     return Double(guess).NextDouble();
 | |
|   } else if ((Double(guess).Significand() & 1) == 0) {
 | |
|     // Round towards even.
 | |
|     return guess;
 | |
|   } else {
 | |
|     return Double(guess).NextDouble();
 | |
|   }
 | |
| }
 | |
| 
 | |
| double Strtod(Vector<const char> buffer, int exponent) {
 | |
|   char copy_buffer[kMaxSignificantDecimalDigits];
 | |
|   Vector<const char> trimmed;
 | |
|   int updated_exponent;
 | |
|   TrimAndCut(buffer, exponent, copy_buffer, kMaxSignificantDecimalDigits,
 | |
|              &trimmed, &updated_exponent);
 | |
|   return StrtodTrimmed(trimmed, updated_exponent);
 | |
| }
 | |
| 
 | |
| static float SanitizedDoubletof(double d) {
 | |
|   DOUBLE_CONVERSION_ASSERT(d >= 0.0);
 | |
|   // ASAN has a sanitize check that disallows casting doubles to floats if
 | |
|   // they are too big.
 | |
|   // https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html#available-checks
 | |
|   // The behavior should be covered by IEEE 754, but some projects use this
 | |
|   // flag, so work around it.
 | |
|   float max_finite = 3.4028234663852885981170418348451692544e+38;
 | |
|   // The half-way point between the max-finite and infinity value.
 | |
|   // Since infinity has an even significand everything equal or greater than
 | |
|   // this value should become infinity.
 | |
|   double half_max_finite_infinity =
 | |
|       3.40282356779733661637539395458142568448e+38;
 | |
|   if (d >= max_finite) {
 | |
|     if (d >= half_max_finite_infinity) {
 | |
|       return Single::Infinity();
 | |
|     } else {
 | |
|       return max_finite;
 | |
|     }
 | |
|   } else {
 | |
|     return static_cast<float>(d);
 | |
|   }
 | |
| }
 | |
| 
 | |
| float Strtof(Vector<const char> buffer, int exponent) {
 | |
|   char copy_buffer[kMaxSignificantDecimalDigits];
 | |
|   Vector<const char> trimmed;
 | |
|   int updated_exponent;
 | |
|   TrimAndCut(buffer, exponent, copy_buffer, kMaxSignificantDecimalDigits,
 | |
|              &trimmed, &updated_exponent);
 | |
|   exponent = updated_exponent;
 | |
|   return StrtofTrimmed(trimmed, exponent);
 | |
| }
 | |
| 
 | |
| float StrtofTrimmed(Vector<const char> trimmed, int exponent) {
 | |
|   DOUBLE_CONVERSION_ASSERT(trimmed.length() <= kMaxSignificantDecimalDigits);
 | |
|   DOUBLE_CONVERSION_ASSERT(AssertTrimmedDigits(trimmed));
 | |
| 
 | |
|   double double_guess;
 | |
|   bool is_correct = ComputeGuess(trimmed, exponent, &double_guess);
 | |
| 
 | |
|   float float_guess = SanitizedDoubletof(double_guess);
 | |
|   if (float_guess == double_guess) {
 | |
|     // This shortcut triggers for integer values.
 | |
|     return float_guess;
 | |
|   }
 | |
| 
 | |
|   // We must catch double-rounding. Say the double has been rounded up, and is
 | |
|   // now a boundary of a float, and rounds up again. This is why we have to
 | |
|   // look at previous too.
 | |
|   // Example (in decimal numbers):
 | |
|   //    input: 12349
 | |
|   //    high-precision (4 digits): 1235
 | |
|   //    low-precision (3 digits):
 | |
|   //       when read from input: 123
 | |
|   //       when rounded from high precision: 124.
 | |
|   // To do this we simply look at the neighbors of the correct result and see
 | |
|   // if they would round to the same float. If the guess is not correct we have
 | |
|   // to look at four values (since two different doubles could be the correct
 | |
|   // double).
 | |
| 
 | |
|   double double_next = Double(double_guess).NextDouble();
 | |
|   double double_previous = Double(double_guess).PreviousDouble();
 | |
| 
 | |
|   float f1 = SanitizedDoubletof(double_previous);
 | |
|   float f2 = float_guess;
 | |
|   float f3 = SanitizedDoubletof(double_next);
 | |
|   float f4;
 | |
|   if (is_correct) {
 | |
|     f4 = f3;
 | |
|   } else {
 | |
|     double double_next2 = Double(double_next).NextDouble();
 | |
|     f4 = SanitizedDoubletof(double_next2);
 | |
|   }
 | |
|   (void) f2;  // Mark variable as used.
 | |
|   DOUBLE_CONVERSION_ASSERT(f1 <= f2 && f2 <= f3 && f3 <= f4);
 | |
| 
 | |
|   // If the guess doesn't lie near a single-precision boundary we can simply
 | |
|   // return its float-value.
 | |
|   if (f1 == f4) {
 | |
|     return float_guess;
 | |
|   }
 | |
| 
 | |
|   DOUBLE_CONVERSION_ASSERT((f1 != f2 && f2 == f3 && f3 == f4) ||
 | |
|          (f1 == f2 && f2 != f3 && f3 == f4) ||
 | |
|          (f1 == f2 && f2 == f3 && f3 != f4));
 | |
| 
 | |
|   // guess and next are the two possible candidates (in the same way that
 | |
|   // double_guess was the lower candidate for a double-precision guess).
 | |
|   float guess = f1;
 | |
|   float next = f4;
 | |
|   DiyFp upper_boundary;
 | |
|   if (guess == 0.0f) {
 | |
|     float min_float = 1e-45f;
 | |
|     upper_boundary = Double(static_cast<double>(min_float) / 2).AsDiyFp();
 | |
|   } else {
 | |
|     upper_boundary = Single(guess).UpperBoundary();
 | |
|   }
 | |
|   int comparison = CompareBufferWithDiyFp(trimmed, exponent, upper_boundary);
 | |
|   if (comparison < 0) {
 | |
|     return guess;
 | |
|   } else if (comparison > 0) {
 | |
|     return next;
 | |
|   } else if ((Single(guess).Significand() & 1) == 0) {
 | |
|     // Round towards even.
 | |
|     return guess;
 | |
|   } else {
 | |
|     return next;
 | |
|   }
 | |
| }
 | |
| 
 | |
| }  // namespace double_conversion
 | |
| 
 | |
| // ICU PATCH: Close ICU namespace
 | |
| U_NAMESPACE_END
 | |
| #endif // ICU PATCH: close #if !UCONFIG_NO_FORMATTING
 |