public static FastIntegerFixed[] DigitLengthBoundsFixed <THelper>(
IRadixMathHelper <THelper> helper,
FastIntegerFixed fei)
{
int radix = helper.GetRadix();
FastIntegerFixed fastpath = FastPathDigitLength(fei, radix);
if (fastpath != null)
{
return(new FastIntegerFixed[] { fastpath, fastpath });
}
if (radix == 10)
{
EInteger[] fi = DecimalDigitLengthBoundsAsEI(fei.ToEInteger());
return(new FastIntegerFixed[] {
FastIntegerFixed.FromBig(fi[0]),
FastIntegerFixed.FromBig(fi[1]),
});
}
else
{
FastInteger fi = helper.GetDigitLength(fei.ToEInteger());
FastIntegerFixed fif = FastIntegerFixed.FromFastInteger(fi);
return(new FastIntegerFixed[] { fif, fif });
}
}
public static FastIntegerFixed DigitLengthFixed <THelper>(
IRadixMathHelper <THelper> helper,
FastIntegerFixed fei)
{
FastIntegerFixed fastpath = FastPathDigitLength(fei, helper.GetRadix());
if (fastpath != null)
{
return(fastpath);
}
FastInteger fi = helper.GetDigitLength(fei.ToEInteger());
FastIntegerFixed fif = FastIntegerFixed.FromFastInteger(fi);
return(fif);
}
private static FastIntegerFixed FastPathDigitLength(
FastIntegerFixed fei,
int radix)
{
if (fei.CanFitInInt32())
{
int ifei = fei.ToInt32();
if (ifei != Int32.MinValue)
{
if (radix == 2)
{
return(FastIntegerFixed.FromInt32((int)BitLength(Math.Abs(ifei))));
}
else if (radix == 10)
{
return(FastIntegerFixed.FromInt32(
(int)DecimalDigitLength(Math.Abs(ifei))));
}
}
}
else
{
if (radix == 2)
{
long i64 = fei.ToEInteger().GetUnsignedBitLengthAsInt64();
if (i64 != Int64.MaxValue)
{
return(FastIntegerFixed.FromInt64(i64));
}
}
else if (radix == 10)
{
EInteger ei = fei.ToEInteger();
long i64 = ei.GetUnsignedBitLengthAsInt64();
if (i64 < 33)
{
// Can easily be calculated without estimation
return(FastIntegerFixed.FromInt32(
(int)ei.GetDigitCountAsInt64()));
}
else if (i64 <= 2135)
{
var bitlen = (int)i64;
// Approximation of ln(2)/ln(10)
int minDigits = 1 + (((bitlen - 1) * 631305) >> 21);
int maxDigits = 1 + ((bitlen * 631305) >> 21);
if (minDigits == maxDigits)
{
return(FastIntegerFixed.FromInt32(minDigits));
}
}
else if (i64 <= 6432162)
{
var bitlen = (int)i64;
// Approximation of ln(2)/ln(10)
int minDigits = 1 + (int)(((long)(bitlen - 1) * 661971961083L) >>
41);
int maxDigits = 1 + (int)(((long)bitlen * 661971961083L) >> 41);
if (minDigits == maxDigits)
{
return(FastIntegerFixed.FromInt32(minDigits));
}
}
}
}
return(null);
}
