third_party/WebKit/Source/wtf/dtoa/fast-dtoa.h

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  27
  28 #ifndef DOUBLE_CONVERSION_FAST_DTOA_H_
  29 #define DOUBLE_CONVERSION_FAST_DTOA_H_
  30
  31 #include "utils.h"
  32
  33 namespace WTF {
  34
  35 namespace double_conversion {
  36
  37     enum FastDtoaMode {
  38         // Computes the shortest representation of the given input. The returned
  39         // result will be the most accurate number of this length. Longer
  40         // representations might be more accurate.
  41         FAST_DTOA_SHORTEST,
  42         // Computes a representation where the precision (number of digits) is
  43         // given as input. The precision is independent of the decimal point.
  44         FAST_DTOA_PRECISION
  45     };
  46
  47     // FastDtoa will produce at most kFastDtoaMaximalLength digits. This does not
  48     // include the terminating '\0' character.
  49     static const int kFastDtoaMaximalLength = 17;
  50
  51     // Provides a decimal representation of v.
  52     // The result should be interpreted as buffer * 10^(point - length).
  53     //
  54     // Precondition:
  55     //   * v must be a strictly positive finite double.
  56     //
  57     // Returns true if it succeeds, otherwise the result can not be trusted.
  58     // There will be *length digits inside the buffer followed by a null terminator.
  59     // If the function returns true and mode equals
  60     //   - FAST_DTOA_SHORTEST, then
  61     //     the parameter requested_digits is ignored.
  62     //     The result satisfies
  63     //         v == (double) (buffer * 10^(point - length)).
  64     //     The digits in the buffer are the shortest representation possible. E.g.
  65     //     if 0.099999999999 and 0.1 represent the same double then "1" is returned
  66     //     with point = 0.
  67     //     The last digit will be closest to the actual v. That is, even if several
  68     //     digits might correctly yield 'v' when read again, the buffer will contain
  69     //     the one closest to v.
  70     //   - FAST_DTOA_PRECISION, then
  71     //     the buffer contains requested_digits digits.
  72     //     the difference v - (buffer * 10^(point-length)) is closest to zero for
  73     //     all possible representations of requested_digits digits.
  74     //     If there are two values that are equally close, then FastDtoa returns
  75     //     false.
  76     // For both modes the buffer must be large enough to hold the result.
  77     bool FastDtoa(double d,
  78                   FastDtoaMode mode,
  79                   int requested_digits,
  80                   Vector<char> buffer,
  81                   int* length,
  82                   int* decimal_point);
  83
  84 }  // namespace double_conversion
  85
  86 } // namespace WTF
  87
  88 #endif  // DOUBLE_CONVERSION_FAST_DTOA_H_