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1 // © 2018 and later: Unicode, Inc. and others.
2 // License & terms of use: http://www.unicode.org/copyright.html
3 //
4 // From the double-conversion library. Original license:
5 //
6 // Copyright 2012 the V8 project authors. All rights reserved.
7 // Redistribution and use in source and binary forms, with or without
8 // modification, are permitted provided that the following conditions are
9 // met:
10 //
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12 //       notice, this list of conditions and the following disclaimer.
13 //     * Redistributions in binary form must reproduce the above
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15 //       disclaimer in the documentation and/or other materials provided
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18 //       contributors may be used to endorse or promote products derived
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20 //
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32 
33 // ICU PATCH: ifdef around UCONFIG_NO_FORMATTING
34 #include "unicode/utypes.h"
35 #if !UCONFIG_NO_FORMATTING
36 
37 #ifndef DOUBLE_CONVERSION_DOUBLE_TO_STRING_H_
38 #define DOUBLE_CONVERSION_DOUBLE_TO_STRING_H_
39 
40 // ICU PATCH: Customize header file paths for ICU.
41 
42 #include "double-conversion-utils.h"
43 
44 // ICU PATCH: Wrap in ICU namespace
45 U_NAMESPACE_BEGIN
46 
47 namespace double_conversion {
48 
49 class DoubleToStringConverter {
50  public:
51   // When calling ToFixed with a double > 10^kMaxFixedDigitsBeforePoint
52   // or a requested_digits parameter > kMaxFixedDigitsAfterPoint then the
53   // function returns false.
54   static const int kMaxFixedDigitsBeforePoint = 60;
55   static const int kMaxFixedDigitsAfterPoint = 100;
56 
57   // When calling ToExponential with a requested_digits
58   // parameter > kMaxExponentialDigits then the function returns false.
59   static const int kMaxExponentialDigits = 120;
60 
61   // When calling ToPrecision with a requested_digits
62   // parameter < kMinPrecisionDigits or requested_digits > kMaxPrecisionDigits
63   // then the function returns false.
64   static const int kMinPrecisionDigits = 1;
65   static const int kMaxPrecisionDigits = 120;
66 
67   // The maximal number of digits that are needed to emit a double in base 10.
68   // A higher precision can be achieved by using more digits, but the shortest
69   // accurate representation of any double will never use more digits than
70   // kBase10MaximalLength.
71   // Note that DoubleToAscii null-terminates its input. So the given buffer
72   // should be at least kBase10MaximalLength + 1 characters long.
73   static const int kBase10MaximalLength = 17;
74 
75   // The maximal number of digits that are needed to emit a single in base 10.
76   // A higher precision can be achieved by using more digits, but the shortest
77   // accurate representation of any single will never use more digits than
78   // kBase10MaximalLengthSingle.
79   static const int kBase10MaximalLengthSingle = 9;
80 
81   // The length of the longest string that 'ToShortest' can produce when the
82   // converter is instantiated with EcmaScript defaults (see
83   // 'EcmaScriptConverter')
84   // This value does not include the trailing '\0' character.
85   // This amount of characters is needed for negative values that hit the
86   // 'decimal_in_shortest_low' limit. For example: "-0.0000033333333333333333"
87   static const int kMaxCharsEcmaScriptShortest = 25;
88 
89 #if 0 // not needed for ICU
90   enum Flags {
91     NO_FLAGS = 0,
92     EMIT_POSITIVE_EXPONENT_SIGN = 1,
93     EMIT_TRAILING_DECIMAL_POINT = 2,
94     EMIT_TRAILING_ZERO_AFTER_POINT = 4,
95     UNIQUE_ZERO = 8,
96     NO_TRAILING_ZERO = 16,
97     EMIT_TRAILING_DECIMAL_POINT_IN_EXPONENTIAL = 32,
98     EMIT_TRAILING_ZERO_AFTER_POINT_IN_EXPONENTIAL = 64
99   };
100 
101   // Flags should be a bit-or combination of the possible Flags-enum.
102   //  - NO_FLAGS: no special flags.
103   //  - EMIT_POSITIVE_EXPONENT_SIGN: when the number is converted into exponent
104   //    form, emits a '+' for positive exponents. Example: 1.2e+2.
105   //  - EMIT_TRAILING_DECIMAL_POINT: when the input number is an integer and is
106   //    converted into decimal format then a trailing decimal point is appended.
107   //    Example: 2345.0 is converted to "2345.".
108   //  - EMIT_TRAILING_ZERO_AFTER_POINT: in addition to a trailing decimal point
109   //    emits a trailing '0'-character. This flag requires the
110   //    EMIT_TRAILING_DECIMAL_POINT flag.
111   //    Example: 2345.0 is converted to "2345.0".
112   //  - UNIQUE_ZERO: "-0.0" is converted to "0.0".
113   //  - NO_TRAILING_ZERO: Trailing zeros are removed from the fractional portion
114   //    of the result in precision mode. Matches printf's %g.
115   //    When EMIT_TRAILING_ZERO_AFTER_POINT is also given, one trailing zero is
116   //    preserved.
117   //  - EMIT_TRAILING_DECIMAL_POINT_IN_EXPONENTIAL: when the input number has
118   //    exactly one significant digit and is converted into exponent form then a
119   //    trailing decimal point is appended to the significand in shortest mode
120   //    or in precision mode with one requested digit.
121   //  - EMIT_TRAILING_ZERO_AFTER_POINT_IN_EXPONENTIAL: in addition to a trailing
122   //    decimal point emits a trailing '0'-character. This flag requires the
123   //    EMIT_TRAILING_DECIMAL_POINT_IN_EXPONENTIAL flag.
124   //
125   // Infinity symbol and nan_symbol provide the string representation for these
126   // special values. If the string is nullptr and the special value is encountered
127   // then the conversion functions return false.
128   //
129   // The exponent_character is used in exponential representations. It is
130   // usually 'e' or 'E'.
131   //
132   // When converting to the shortest representation the converter will
133   // represent input numbers in decimal format if they are in the interval
134   // [10^decimal_in_shortest_low; 10^decimal_in_shortest_high[
135   //    (lower boundary included, greater boundary excluded).
136   // Example: with decimal_in_shortest_low = -6 and
137   //               decimal_in_shortest_high = 21:
138   //   ToShortest(0.000001)  -> "0.000001"
139   //   ToShortest(0.0000001) -> "1e-7"
140   //   ToShortest(111111111111111111111.0)  -> "111111111111111110000"
141   //   ToShortest(100000000000000000000.0)  -> "100000000000000000000"
142   //   ToShortest(1111111111111111111111.0) -> "1.1111111111111111e+21"
143   //
144   // When converting to precision mode the converter may add
145   // max_leading_padding_zeroes before returning the number in exponential
146   // format.
147   // Example with max_leading_padding_zeroes_in_precision_mode = 6.
148   //   ToPrecision(0.0000012345, 2) -> "0.0000012"
149   //   ToPrecision(0.00000012345, 2) -> "1.2e-7"
150   // Similarly the converter may add up to
151   // max_trailing_padding_zeroes_in_precision_mode in precision mode to avoid
152   // returning an exponential representation. A zero added by the
153   // EMIT_TRAILING_ZERO_AFTER_POINT flag is counted for this limit.
154   // Examples for max_trailing_padding_zeroes_in_precision_mode = 1:
155   //   ToPrecision(230.0, 2) -> "230"
156   //   ToPrecision(230.0, 2) -> "230."  with EMIT_TRAILING_DECIMAL_POINT.
157   //   ToPrecision(230.0, 2) -> "2.3e2" with EMIT_TRAILING_ZERO_AFTER_POINT.
158   //
159   // When converting numbers with exactly one significant digit to exponent
160   // form in shortest mode or in precision mode with one requested digit, the
161   // EMIT_TRAILING_DECIMAL_POINT and EMIT_TRAILING_ZERO_AFTER_POINT flags have
162   // no effect. Use the EMIT_TRAILING_DECIMAL_POINT_IN_EXPONENTIAL flag to
163   // append a decimal point in this case and the
164   // EMIT_TRAILING_ZERO_AFTER_POINT_IN_EXPONENTIAL flag to also append a
165   // '0'-character in this case.
166   // Example with decimal_in_shortest_low = 0:
167   //   ToShortest(0.0009) -> "9e-4"
168   //     with EMIT_TRAILING_DECIMAL_POINT_IN_EXPONENTIAL deactivated.
169   //   ToShortest(0.0009) -> "9.e-4"
170   //     with EMIT_TRAILING_DECIMAL_POINT_IN_EXPONENTIAL activated.
171   //   ToShortest(0.0009) -> "9.0e-4"
172   //     with EMIT_TRAILING_DECIMAL_POINT_IN_EXPONENTIAL activated and
173   //     EMIT_TRAILING_ZERO_AFTER_POINT_IN_EXPONENTIAL activated.
174   //
175   // The min_exponent_width is used for exponential representations.
176   // The converter adds leading '0's to the exponent until the exponent
177   // is at least min_exponent_width digits long.
178   // The min_exponent_width is clamped to 5.
179   // As such, the exponent may never have more than 5 digits in total.
180   DoubleToStringConverter(int flags,
181                           const char* infinity_symbol,
182                           const char* nan_symbol,
183                           char exponent_character,
184                           int decimal_in_shortest_low,
185                           int decimal_in_shortest_high,
186                           int max_leading_padding_zeroes_in_precision_mode,
187                           int max_trailing_padding_zeroes_in_precision_mode,
188                           int min_exponent_width = 0)
189       : flags_(flags),
190         infinity_symbol_(infinity_symbol),
191         nan_symbol_(nan_symbol),
192         exponent_character_(exponent_character),
193         decimal_in_shortest_low_(decimal_in_shortest_low),
194         decimal_in_shortest_high_(decimal_in_shortest_high),
195         max_leading_padding_zeroes_in_precision_mode_(
196             max_leading_padding_zeroes_in_precision_mode),
197         max_trailing_padding_zeroes_in_precision_mode_(
198             max_trailing_padding_zeroes_in_precision_mode),
199         min_exponent_width_(min_exponent_width) {
200     // When 'trailing zero after the point' is set, then 'trailing point'
201     // must be set too.
202     DOUBLE_CONVERSION_ASSERT(((flags & EMIT_TRAILING_DECIMAL_POINT) != 0) ||
203         !((flags & EMIT_TRAILING_ZERO_AFTER_POINT) != 0));
204   }
205 
206   // Returns a converter following the EcmaScript specification.
207   //
208   // Flags: UNIQUE_ZERO and EMIT_POSITIVE_EXPONENT_SIGN.
209   // Special values: "Infinity" and "NaN".
210   // Lower case 'e' for exponential values.
211   // decimal_in_shortest_low: -6
212   // decimal_in_shortest_high: 21
213   // max_leading_padding_zeroes_in_precision_mode: 6
214   // max_trailing_padding_zeroes_in_precision_mode: 0
215   static const DoubleToStringConverter& EcmaScriptConverter();
216 
217   // Computes the shortest string of digits that correctly represent the input
218   // number. Depending on decimal_in_shortest_low and decimal_in_shortest_high
219   // (see constructor) it then either returns a decimal representation, or an
220   // exponential representation.
221   // Example with decimal_in_shortest_low = -6,
222   //              decimal_in_shortest_high = 21,
223   //              EMIT_POSITIVE_EXPONENT_SIGN activated, and
224   //              EMIT_TRAILING_DECIMAL_POINT deactivated:
225   //   ToShortest(0.000001)  -> "0.000001"
226   //   ToShortest(0.0000001) -> "1e-7"
227   //   ToShortest(111111111111111111111.0)  -> "111111111111111110000"
228   //   ToShortest(100000000000000000000.0)  -> "100000000000000000000"
229   //   ToShortest(1111111111111111111111.0) -> "1.1111111111111111e+21"
230   //
231   // Note: the conversion may round the output if the returned string
232   // is accurate enough to uniquely identify the input-number.
233   // For example the most precise representation of the double 9e59 equals
234   // "899999999999999918767229449717619953810131273674690656206848", but
235   // the converter will return the shorter (but still correct) "9e59".
236   //
237   // Returns true if the conversion succeeds. The conversion always succeeds
238   // except when the input value is special and no infinity_symbol or
239   // nan_symbol has been given to the constructor.
240   //
241   // The length of the longest result is the maximum of the length of the
242   // following string representations (each with possible examples):
243   // - NaN and negative infinity: "NaN", "-Infinity", "-inf".
244   // - -10^(decimal_in_shortest_high - 1):
245   //      "-100000000000000000000", "-1000000000000000.0"
246   // - the longest string in range [0; -10^decimal_in_shortest_low]. Generally,
247   //   this string is 3 + kBase10MaximalLength - decimal_in_shortest_low.
248   //   (Sign, '0', decimal point, padding zeroes for decimal_in_shortest_low,
249   //   and the significant digits).
250   //      "-0.0000033333333333333333", "-0.0012345678901234567"
251   // - the longest exponential representation. (A negative number with
252   //   kBase10MaximalLength significant digits).
253   //      "-1.7976931348623157e+308", "-1.7976931348623157E308"
254   // In addition, the buffer must be able to hold the trailing '\0' character.
255   bool ToShortest(double value, StringBuilder* result_builder) const {
256     return ToShortestIeeeNumber(value, result_builder, SHORTEST);
257   }
258 
259   // Same as ToShortest, but for single-precision floats.
260   bool ToShortestSingle(float value, StringBuilder* result_builder) const {
261     return ToShortestIeeeNumber(value, result_builder, SHORTEST_SINGLE);
262   }
263 
264 
265   // Computes a decimal representation with a fixed number of digits after the
266   // decimal point. The last emitted digit is rounded.
267   //
268   // Examples:
269   //   ToFixed(3.12, 1) -> "3.1"
270   //   ToFixed(3.1415, 3) -> "3.142"
271   //   ToFixed(1234.56789, 4) -> "1234.5679"
272   //   ToFixed(1.23, 5) -> "1.23000"
273   //   ToFixed(0.1, 4) -> "0.1000"
274   //   ToFixed(1e30, 2) -> "1000000000000000019884624838656.00"
275   //   ToFixed(0.1, 30) -> "0.100000000000000005551115123126"
276   //   ToFixed(0.1, 17) -> "0.10000000000000001"
277   //
278   // If requested_digits equals 0, then the tail of the result depends on
279   // the EMIT_TRAILING_DECIMAL_POINT and EMIT_TRAILING_ZERO_AFTER_POINT.
280   // Examples, for requested_digits == 0,
281   //   let EMIT_TRAILING_DECIMAL_POINT and EMIT_TRAILING_ZERO_AFTER_POINT be
282   //    - false and false: then 123.45 -> 123
283   //                             0.678 -> 1
284   //    - true and false: then 123.45 -> 123.
285   //                            0.678 -> 1.
286   //    - true and true: then 123.45 -> 123.0
287   //                           0.678 -> 1.0
288   //
289   // Returns true if the conversion succeeds. The conversion always succeeds
290   // except for the following cases:
291   //   - the input value is special and no infinity_symbol or nan_symbol has
292   //     been provided to the constructor,
293   //   - 'value' > 10^kMaxFixedDigitsBeforePoint, or
294   //   - 'requested_digits' > kMaxFixedDigitsAfterPoint.
295   // The last two conditions imply that the result for non-special values never
296   // contains more than
297   //  1 + kMaxFixedDigitsBeforePoint + 1 + kMaxFixedDigitsAfterPoint characters
298   // (one additional character for the sign, and one for the decimal point).
299   // In addition, the buffer must be able to hold the trailing '\0' character.
300   bool ToFixed(double value,
301                int requested_digits,
302                StringBuilder* result_builder) const;
303 
304   // Computes a representation in exponential format with requested_digits
305   // after the decimal point. The last emitted digit is rounded.
306   // If requested_digits equals -1, then the shortest exponential representation
307   // is computed.
308   //
309   // Examples with EMIT_POSITIVE_EXPONENT_SIGN deactivated, and
310   //               exponent_character set to 'e'.
311   //   ToExponential(3.12, 1) -> "3.1e0"
312   //   ToExponential(5.0, 3) -> "5.000e0"
313   //   ToExponential(0.001, 2) -> "1.00e-3"
314   //   ToExponential(3.1415, -1) -> "3.1415e0"
315   //   ToExponential(3.1415, 4) -> "3.1415e0"
316   //   ToExponential(3.1415, 3) -> "3.142e0"
317   //   ToExponential(123456789000000, 3) -> "1.235e14"
318   //   ToExponential(1000000000000000019884624838656.0, -1) -> "1e30"
319   //   ToExponential(1000000000000000019884624838656.0, 32) ->
320   //                     "1.00000000000000001988462483865600e30"
321   //   ToExponential(1234, 0) -> "1e3"
322   //
323   // Returns true if the conversion succeeds. The conversion always succeeds
324   // except for the following cases:
325   //   - the input value is special and no infinity_symbol or nan_symbol has
326   //     been provided to the constructor,
327   //   - 'requested_digits' > kMaxExponentialDigits.
328   //
329   // The last condition implies that the result never contains more than
330   // kMaxExponentialDigits + 8 characters (the sign, the digit before the
331   // decimal point, the decimal point, the exponent character, the
332   // exponent's sign, and at most 3 exponent digits).
333   // In addition, the buffer must be able to hold the trailing '\0' character.
334   bool ToExponential(double value,
335                      int requested_digits,
336                      StringBuilder* result_builder) const;
337 
338 
339   // Computes 'precision' leading digits of the given 'value' and returns them
340   // either in exponential or decimal format, depending on
341   // max_{leading|trailing}_padding_zeroes_in_precision_mode (given to the
342   // constructor).
343   // The last computed digit is rounded.
344   //
345   // Example with max_leading_padding_zeroes_in_precision_mode = 6.
346   //   ToPrecision(0.0000012345, 2) -> "0.0000012"
347   //   ToPrecision(0.00000012345, 2) -> "1.2e-7"
348   // Similarly the converter may add up to
349   // max_trailing_padding_zeroes_in_precision_mode in precision mode to avoid
350   // returning an exponential representation. A zero added by the
351   // EMIT_TRAILING_ZERO_AFTER_POINT flag is counted for this limit.
352   // Examples for max_trailing_padding_zeroes_in_precision_mode = 1:
353   //   ToPrecision(230.0, 2) -> "230"
354   //   ToPrecision(230.0, 2) -> "230."  with EMIT_TRAILING_DECIMAL_POINT.
355   //   ToPrecision(230.0, 2) -> "2.3e2" with EMIT_TRAILING_ZERO_AFTER_POINT.
356   // Examples for max_trailing_padding_zeroes_in_precision_mode = 3, and no
357   //    EMIT_TRAILING_ZERO_AFTER_POINT:
358   //   ToPrecision(123450.0, 6) -> "123450"
359   //   ToPrecision(123450.0, 5) -> "123450"
360   //   ToPrecision(123450.0, 4) -> "123500"
361   //   ToPrecision(123450.0, 3) -> "123000"
362   //   ToPrecision(123450.0, 2) -> "1.2e5"
363   //
364   // Returns true if the conversion succeeds. The conversion always succeeds
365   // except for the following cases:
366   //   - the input value is special and no infinity_symbol or nan_symbol has
367   //     been provided to the constructor,
368   //   - precision < kMinPericisionDigits
369   //   - precision > kMaxPrecisionDigits
370   //
371   // The last condition implies that the result never contains more than
372   // kMaxPrecisionDigits + 7 characters (the sign, the decimal point, the
373   // exponent character, the exponent's sign, and at most 3 exponent digits).
374   // In addition, the buffer must be able to hold the trailing '\0' character.
375   bool ToPrecision(double value,
376                    int precision,
377                    StringBuilder* result_builder) const;
378 #endif // not needed for ICU
379 
380   enum DtoaMode {
381     // Produce the shortest correct representation.
382     // For example the output of 0.299999999999999988897 is (the less accurate
383     // but correct) 0.3.
384     SHORTEST,
385     // Same as SHORTEST, but for single-precision floats.
386     SHORTEST_SINGLE,
387     // Produce a fixed number of digits after the decimal point.
388     // For instance fixed(0.1, 4) becomes 0.1000
389     // If the input number is big, the output will be big.
390     FIXED,
391     // Fixed number of digits (independent of the decimal point).
392     PRECISION
393   };
394 
395   // Converts the given double 'v' to digit characters. 'v' must not be NaN,
396   // +Infinity, or -Infinity. In SHORTEST_SINGLE-mode this restriction also
397   // applies to 'v' after it has been casted to a single-precision float. That
398   // is, in this mode static_cast<float>(v) must not be NaN, +Infinity or
399   // -Infinity.
400   //
401   // The result should be interpreted as buffer * 10^(point-length).
402   //
403   // The digits are written to the buffer in the platform's charset, which is
404   // often UTF-8 (with ASCII-range digits) but may be another charset, such
405   // as EBCDIC.
406   //
407   // The output depends on the given mode:
408   //  - SHORTEST: produce the least amount of digits for which the internal
409   //   identity requirement is still satisfied. If the digits are printed
410   //   (together with the correct exponent) then reading this number will give
411   //   'v' again. The buffer will choose the representation that is closest to
412   //   'v'. If there are two at the same distance, than the one farther away
413   //   from 0 is chosen (halfway cases - ending with 5 - are rounded up).
414   //   In this mode the 'requested_digits' parameter is ignored.
415   //  - SHORTEST_SINGLE: same as SHORTEST but with single-precision.
416   //  - FIXED: produces digits necessary to print a given number with
417   //   'requested_digits' digits after the decimal point. The produced digits
418   //   might be too short in which case the caller has to fill the remainder
419   //   with '0's.
420   //   Example: toFixed(0.001, 5) is allowed to return buffer="1", point=-2.
421   //   Halfway cases are rounded towards +/-Infinity (away from 0). The call
422   //   toFixed(0.15, 2) thus returns buffer="2", point=0.
423   //   The returned buffer may contain digits that would be truncated from the
424   //   shortest representation of the input.
425   //  - PRECISION: produces 'requested_digits' where the first digit is not '0'.
426   //   Even though the length of produced digits usually equals
427   //   'requested_digits', the function is allowed to return fewer digits, in
428   //   which case the caller has to fill the missing digits with '0's.
429   //   Halfway cases are again rounded away from 0.
430   // DoubleToAscii expects the given buffer to be big enough to hold all
431   // digits and a terminating null-character. In SHORTEST-mode it expects a
432   // buffer of at least kBase10MaximalLength + 1. In all other modes the
433   // requested_digits parameter and the padding-zeroes limit the size of the
434   // output. Don't forget the decimal point, the exponent character and the
435   // terminating null-character when computing the maximal output size.
436   // The given length is only used in debug mode to ensure the buffer is big
437   // enough.
438   // ICU PATCH: Export this as U_I18N_API for unit tests.
439   static void U_I18N_API DoubleToAscii(double v,
440                             DtoaMode mode,
441                             int requested_digits,
442                             char* buffer,
443                             int buffer_length,
444                             bool* sign,
445                             int* length,
446                             int* point);
447 
448 #if 0 // not needed for ICU
449  private:
450   // Implementation for ToShortest and ToShortestSingle.
451   bool ToShortestIeeeNumber(double value,
452                             StringBuilder* result_builder,
453                             DtoaMode mode) const;
454 
455   // If the value is a special value (NaN or Infinity) constructs the
456   // corresponding string using the configured infinity/nan-symbol.
457   // If either of them is nullptr or the value is not special then the
458   // function returns false.
459   bool HandleSpecialValues(double value, StringBuilder* result_builder) const;
460   // Constructs an exponential representation (i.e. 1.234e56).
461   // The given exponent assumes a decimal point after the first decimal digit.
462   void CreateExponentialRepresentation(const char* decimal_digits,
463                                        int length,
464                                        int exponent,
465                                        StringBuilder* result_builder) const;
466   // Creates a decimal representation (i.e 1234.5678).
467   void CreateDecimalRepresentation(const char* decimal_digits,
468                                    int length,
469                                    int decimal_point,
470                                    int digits_after_point,
471                                    StringBuilder* result_builder) const;
472 
473   const int flags_;
474   const char* const infinity_symbol_;
475   const char* const nan_symbol_;
476   const char exponent_character_;
477   const int decimal_in_shortest_low_;
478   const int decimal_in_shortest_high_;
479   const int max_leading_padding_zeroes_in_precision_mode_;
480   const int max_trailing_padding_zeroes_in_precision_mode_;
481   const int min_exponent_width_;
482 #endif // not needed for ICU
483 
484   DOUBLE_CONVERSION_DISALLOW_IMPLICIT_CONSTRUCTORS(DoubleToStringConverter);
485 };
486 
487 }  // namespace double_conversion
488 
489 // ICU PATCH: Close ICU namespace
490 U_NAMESPACE_END
491 
492 #endif  // DOUBLE_CONVERSION_DOUBLE_TO_STRING_H_
493 #endif // ICU PATCH: close #if !UCONFIG_NO_FORMATTING
494