icuSources/i18n/double-conversion-fast-dtoa.h

   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 2010 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 //
  11 //     * Redistributions of source code must retain the above copyright
  12 //       notice, this list of conditions and the following disclaimer.
  13 //     * Redistributions in binary form must reproduce the above
  14 //       copyright notice, this list of conditions and the following
  15 //       disclaimer in the documentation and/or other materials provided
  16 //       with the distribution.
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  18 //       contributors may be used to endorse or promote products derived
  19 //       from this software without specific prior written permission.
  20 //
  21 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  22 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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  31 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  32
  33 // ICU PATCH: ifdef around UCONFIG_NO_FORMATTING
  34 #include "unicode/utypes.h"
  35 #if !UCONFIG_NO_FORMATTING
  36
  37 #ifndef DOUBLE_CONVERSION_FAST_DTOA_H_
  38 #define DOUBLE_CONVERSION_FAST_DTOA_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 enum FastDtoaMode {
  50   // Computes the shortest representation of the given input. The returned
  51   // result will be the most accurate number of this length. Longer
  52   // representations might be more accurate.
  53   FAST_DTOA_SHORTEST,
  54   // Same as FAST_DTOA_SHORTEST but for single-precision floats.
  55   FAST_DTOA_SHORTEST_SINGLE,
  56   // Computes a representation where the precision (number of digits) is
  57   // given as input. The precision is independent of the decimal point.
  58   FAST_DTOA_PRECISION
  59 };
  60
  61 // FastDtoa will produce at most kFastDtoaMaximalLength digits. This does not
  62 // include the terminating '\0' character.
  63 static const int kFastDtoaMaximalLength = 17;
  64 // Same for single-precision numbers.
  65 static const int kFastDtoaMaximalSingleLength = 9;
  66
  67 // Provides a decimal representation of v.
  68 // The result should be interpreted as buffer * 10^(point - length).
  69 //
  70 // Precondition:
  71 //   * v must be a strictly positive finite double.
  72 //
  73 // Returns true if it succeeds, otherwise the result can not be trusted.
  74 // There will be *length digits inside the buffer followed by a null terminator.
  75 // If the function returns true and mode equals
  76 //   - FAST_DTOA_SHORTEST, then
  77 //     the parameter requested_digits is ignored.
  78 //     The result satisfies
  79 //         v == (double) (buffer * 10^(point - length)).
  80 //     The digits in the buffer are the shortest representation possible. E.g.
  81 //     if 0.099999999999 and 0.1 represent the same double then "1" is returned
  82 //     with point = 0.
  83 //     The last digit will be closest to the actual v. That is, even if several
  84 //     digits might correctly yield 'v' when read again, the buffer will contain
  85 //     the one closest to v.
  86 //   - FAST_DTOA_PRECISION, then
  87 //     the buffer contains requested_digits digits.
  88 //     the difference v - (buffer * 10^(point-length)) is closest to zero for
  89 //     all possible representations of requested_digits digits.
  90 //     If there are two values that are equally close, then FastDtoa returns
  91 //     false.
  92 // For both modes the buffer must be large enough to hold the result.
  93 bool FastDtoa(double d,
  94               FastDtoaMode mode,
  95               int requested_digits,
  96               Vector<char> buffer,
  97               int* length,
  98               int* decimal_point);
  99
 100 }  // namespace double_conversion
 101
 102 // ICU PATCH: Close ICU namespace
 103 U_NAMESPACE_END
 104
 105 #endif  // DOUBLE_CONVERSION_FAST_DTOA_H_
 106 #endif // ICU PATCH: close #if !UCONFIG_NO_FORMATTING