pfloat.py 文件源码

def getf(self):
        """convert the stored floating-point number into a python native float"""
        exponentbias = (2**self.components[1])/2 - 1
        res = bitmap.new( self.__getvalue__(), sum(self.components) )

        # extract components
        res,sign = bitmap.shift(res, self.components[0])
        res,exponent = bitmap.shift(res, self.components[1])
        res,mantissa = bitmap.shift(res, self.components[2])

        if exponent > 0 and exponent < (2**self.components[2]-1):
            # convert to float
            s = -1 if sign else +1
            e = exponent - exponentbias
            m = 1.0 + (float(mantissa) / 2**self.components[2])

            # done
            return math.ldexp( math.copysign(m,s), e)

        # FIXME: this should return NaN or something
        Log.warn('float_t.getf : {:s} : Invalid exponent value : {:d}'.format(self.instance(), exponent))
        return 0.0