private static int Math_Frexp(ILuaState lua)
{
double d = lua.L_CheckNumber(1);
// Translate the double into sign, exponent and mantissa.
long bits = BitConverter.DoubleToInt64Bits(d);
// Note that the shift is sign-extended, hence the test against -1 not 1
bool negative = (bits < 0);
int exponent = (int)((bits >> 52) & 0x7ffL);
long mantissa = bits & 0xfffffffffffffL;
// Subnormal numbers; exponent is effectively one higher,
// but there's no extra normalisation bit in the mantissa
if (exponent == 0)
{
exponent++;
}
// Normal numbers; leave exponent as it is but add extra
// bit to the front of the mantissa
else
{
mantissa = mantissa | (1L << 52);
}
// Bias the exponent. It's actually biased by 1023, but we're
// treating the mantissa as m.0 rather than 0.m, so we need
// to subtract another 52 from it.
exponent -= 1075;
if (mantissa == 0)
{
lua.PushNumber(0.0);
lua.PushNumber(0.0);
return(2);
}
/* Normalize */
while ((mantissa & 1) == 0)
{ /* i.e., Mantissa is even */
mantissa >>= 1;
exponent++;
}
double m = (double)mantissa;
double e = (double)exponent;
while (m >= 1)
{
m /= 2.0;
e += 1.0;
}
if (negative)
{
m = -m;
}
lua.PushNumber(m);
lua.PushNumber(e);
return(2);
}
/// <summary>
///
/// </summary>
/// <param name="num"></param>
public void Add(double num)
{
long numBits = BitConverter.DoubleToInt64Bits(num);
if (isFirst)
{
commonBits = numBits;
commonSignExp = SignExpBits(commonBits);
isFirst = false;
return;
}
long numSignExp = SignExpBits(numBits);
if (numSignExp != commonSignExp)
{
commonBits = 0;
return;
}
commonMantissaBitsCount = NumCommonMostSigMantissaBits(commonBits, numBits);
commonBits = ZeroLowerBits(commonBits, 64 - (12 + commonMantissaBitsCount));
}