decimal128.py 文件源码

def _decimal_to_128(value):
    """Converts a decimal.Decimal to BID (high bits, low bits).

    :Parameters:
      - `value`: An instance of decimal.Decimal
    """
    with decimal.localcontext(_DEC128_CTX) as ctx:
        value = ctx.create_decimal(value)

    if value.is_infinite():
        return _NINF if value.is_signed() else _PINF

    sign, digits, exponent = value.as_tuple()

    if value.is_nan():
        if digits:
            raise ValueError("NaN with debug payload is not supported")
        if value.is_snan():
            return _NSNAN if value.is_signed() else _PSNAN
        return _NNAN if value.is_signed() else _PNAN

    significand = int("".join([str(digit) for digit in digits]))
    bit_length = _bit_length(significand)

    high = 0
    low = 0
    for i in range(min(64, bit_length)):
        if significand & (1 << i):
            low |= 1 << i

    for i in range(64, bit_length):
        if significand & (1 << i):
            high |= 1 << (i - 64)

    biased_exponent = exponent + _EXPONENT_BIAS

    if high >> 49 == 1:
        high = high & 0x7fffffffffff
        high |= _EXPONENT_MASK
        high |= (biased_exponent & 0x3fff) << 47
    else:
        high |= biased_exponent << 49

    if sign:
        high |= _SIGN

    return high, low