fast-dtoa.h   [plain text]

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#ifndef DOUBLE_CONVERSION_FAST_DTOA_H_
#define DOUBLE_CONVERSION_FAST_DTOA_H_

#include "utils.h"

namespace WTF {

namespace double_conversion {
    
    enum FastDtoaMode {
        // Computes the shortest representation of the given input. The returned
        // result will be the most accurate number of this length. Longer
        // representations might be more accurate.
        FAST_DTOA_SHORTEST,
        // Computes a representation where the precision (number of digits) is
        // given as input. The precision is independent of the decimal point.
        FAST_DTOA_PRECISION
    };
    
    // FastDtoa will produce at most kFastDtoaMaximalLength digits. This does not
    // include the terminating '\0' character.
    static const int kFastDtoaMaximalLength = 17;
    
    // Provides a decimal representation of v.
    // The result should be interpreted as buffer * 10^(point - length).
    //
    // Precondition:
    //   * v must be a strictly positive finite double.
    //
    // Returns true if it succeeds, otherwise the result can not be trusted.
    // There will be *length digits inside the buffer followed by a null terminator.
    // If the function returns true and mode equals
    //   - FAST_DTOA_SHORTEST, then
    //     the parameter requested_digits is ignored.
    //     The result satisfies
    //         v == (double) (buffer * 10^(point - length)).
    //     The digits in the buffer are the shortest representation possible. E.g.
    //     if 0.099999999999 and 0.1 represent the same double then "1" is returned
    //     with point = 0.
    //     The last digit will be closest to the actual v. That is, even if several
    //     digits might correctly yield 'v' when read again, the buffer will contain
    //     the one closest to v.
    //   - FAST_DTOA_PRECISION, then
    //     the buffer contains requested_digits digits.
    //     the difference v - (buffer * 10^(point-length)) is closest to zero for
    //     all possible representations of requested_digits digits.
    //     If there are two values that are equally close, then FastDtoa returns
    //     false.
    // For both modes the buffer must be large enough to hold the result.
    bool FastDtoa(double d,
                  FastDtoaMode mode,
                  int requested_digits,
                  BufferReference<char> buffer,
                  int* length,
                  int* decimal_point);
    
}  // namespace double_conversion

} // namespace WTF

#endif  // DOUBLE_CONVERSION_FAST_DTOA_H_