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

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  27
  28 #ifndef DOUBLE_CONVERSION_BIGNUM_DTOA_H_
  29 #define DOUBLE_CONVERSION_BIGNUM_DTOA_H_
  30
  31 #include "utils.h"
  32
  33 namespace WTF {
  34
  35 namespace double_conversion {
  36
  37     enum BignumDtoaMode {
  38         // Return the shortest correct representation.
  39         // For example the output of 0.299999999999999988897 is (the less accurate but
  40         // correct) 0.3.
  41         BIGNUM_DTOA_SHORTEST,
  42         // Return a fixed number of digits after the decimal point.
  43         // For instance fixed(0.1, 4) becomes 0.1000
  44         // If the input number is big, the output will be big.
  45         BIGNUM_DTOA_FIXED,
  46         // Return a fixed number of digits, no matter what the exponent is.
  47         BIGNUM_DTOA_PRECISION
  48     };
  49
  50     // Converts the given double 'v' to ascii.
  51     // The result should be interpreted as buffer * 10^(point-length).
  52     // The buffer will be null-terminated.
  53     //
  54     // The input v must be > 0 and different from NaN, and Infinity.
  55     //
  56     // The output depends on the given mode:
  57     //  - SHORTEST: produce the least amount of digits for which the internal
  58     //   identity requirement is still satisfied. If the digits are printed
  59     //   (together with the correct exponent) then reading this number will give
  60     //   'v' again. The buffer will choose the representation that is closest to
  61     //   'v'. If there are two at the same distance, than the number is round up.
  62     //   In this mode the 'requested_digits' parameter is ignored.
  63     //  - FIXED: produces digits necessary to print a given number with
  64     //   'requested_digits' digits after the decimal point. The produced digits
  65     //   might be too short in which case the caller has to fill the gaps with '0's.
  66     //   Example: toFixed(0.001, 5) is allowed to return buffer="1", point=-2.
  67     //   Halfway cases are rounded up. The call toFixed(0.15, 2) thus returns
  68     //     buffer="2", point=0.
  69     //   Note: the length of the returned buffer has no meaning wrt the significance
  70     //   of its digits. That is, just because it contains '0's does not mean that
  71     //   any other digit would not satisfy the internal identity requirement.
  72     //  - PRECISION: produces 'requested_digits' where the first digit is not '0'.
  73     //   Even though the length of produced digits usually equals
  74     //   'requested_digits', the function is allowed to return fewer digits, in
  75     //   which case the caller has to fill the missing digits with '0's.
  76     //   Halfway cases are again rounded up.
  77     // 'BignumDtoa' expects the given buffer to be big enough to hold all digits
  78     // and a terminating null-character.
  79     void BignumDtoa(double v, BignumDtoaMode mode, int requested_digits,
  80                     Vector<char> buffer, int* length, int* point);
  81
  82 }  // namespace double_conversion
  83
  84 } // namespace WTF
  85
  86 #endif  // DOUBLE_CONVERSION_BIGNUM_DTOA_H_