bignum-dtoa.h   [plain text]

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#ifndef DOUBLE_CONVERSION_BIGNUM_DTOA_H_
#define DOUBLE_CONVERSION_BIGNUM_DTOA_H_

#include "utils.h"

namespace WTF {

namespace double_conversion {
    
    enum BignumDtoaMode {
        // Return the shortest correct representation.
        // For example the output of 0.299999999999999988897 is (the less accurate but
        // correct) 0.3.
        BIGNUM_DTOA_SHORTEST,
        // Return a fixed number of digits after the decimal point.
        // For instance fixed(0.1, 4) becomes 0.1000
        // If the input number is big, the output will be big.
        BIGNUM_DTOA_FIXED,
        // Return a fixed number of digits, no matter what the exponent is.
        BIGNUM_DTOA_PRECISION
    };
    
    // Converts the given double 'v' to ascii.
    // The result should be interpreted as buffer * 10^(point-length).
    // The buffer will be null-terminated.
    //
    // The input v must be > 0 and different from NaN, and Infinity.
    //
    // The output depends on the given mode:
    //  - SHORTEST: produce the least amount of digits for which the internal
    //   identity requirement is still satisfied. If the digits are printed
    //   (together with the correct exponent) then reading this number will give
    //   'v' again. The buffer will choose the representation that is closest to
    //   'v'. If there are two at the same distance, than the number is round up.
    //   In this mode the 'requested_digits' parameter is ignored.
    //  - FIXED: produces digits necessary to print a given number with
    //   'requested_digits' digits after the decimal point. The produced digits
    //   might be too short in which case the caller has to fill the gaps with '0's.
    //   Example: toFixed(0.001, 5) is allowed to return buffer="1", point=-2.
    //   Halfway cases are rounded up. The call toFixed(0.15, 2) thus returns
    //     buffer="2", point=0.
    //   Note: the length of the returned buffer has no meaning wrt the significance
    //   of its digits. That is, just because it contains '0's does not mean that
    //   any other digit would not satisfy the internal identity requirement.
    //  - PRECISION: produces 'requested_digits' where the first digit is not '0'.
    //   Even though the length of produced digits usually equals
    //   'requested_digits', the function is allowed to return fewer digits, in
    //   which case the caller has to fill the missing digits with '0's.
    //   Halfway cases are again rounded up.
    // 'BignumDtoa' expects the given buffer to be big enough to hold all digits
    // and a terminating null-character.
    void BignumDtoa(double v, BignumDtoaMode mode, int requested_digits,
                    BufferReference<char> buffer, int* length, int* point);
    
}  // namespace double_conversion

} // namespace WTF

#endif  // DOUBLE_CONVERSION_BIGNUM_DTOA_H_