org.apache.poi.ss.util.MutableFPNumber Maven / Gradle / Ivy
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package org.apache.poi.ss.util;
import java.math.BigInteger;
final class MutableFPNumber {
// TODO - what about values between (1014-0.5) and (1014-0.05) ?
/**
* The minimum value in 'Base-10 normalised form'.
* When {@link #_binaryExponent} == 46 this is the the minimum {@link #_frac} value
* (1014-0.05) * 2^17
*
* Values between (1014-0.05) and 1014 will be represented as '1'
* followed by 14 zeros.
* Values less than (1014-0.05) will get shifted by one more power of 10
*
* This frac value rounds to '1' followed by fourteen zeros with an incremented decimal exponent
*/
private static final BigInteger BI_MIN_BASE = new BigInteger("0B5E620F47FFFE666", 16);
/**
* For 'Base-10 normalised form'
* The maximum {@link #_frac} value when {@link #_binaryExponent} == 49
* (10^15-0.5) * 2^14
*/
private static final BigInteger BI_MAX_BASE = new BigInteger("0E35FA9319FFFE000", 16);
/**
* Width of a long
*/
private static final int C_64 = 64;
/**
* Minimum precision after discarding whole 32-bit words from the significand
*/
private static final int MIN_PRECISION = 72;
private BigInteger _significand;
private int _binaryExponent;
public MutableFPNumber(BigInteger frac, int binaryExponent) {
_significand = frac;
_binaryExponent = binaryExponent;
}
public MutableFPNumber copy() {
return new MutableFPNumber(_significand, _binaryExponent);
}
public void normalise64bit() {
int oldBitLen = _significand.bitLength();
int sc = oldBitLen - C_64;
if (sc == 0) {
return;
}
if (sc < 0) {
throw new IllegalStateException("Not enough precision");
}
_binaryExponent += sc;
if (sc > 32) {
int highShift = (sc-1) & 0xFFFFE0;
_significand = _significand.shiftRight(highShift);
sc -= highShift;
oldBitLen -= highShift;
}
if (sc < 1) {
throw new IllegalStateException();
}
_significand = Rounder.round(_significand, sc);
if (_significand.bitLength() > oldBitLen) {
sc++;
_binaryExponent++;
}
_significand = _significand.shiftRight(sc);
}
public int get64BitNormalisedExponent() {
return _binaryExponent + _significand.bitLength() - C_64;
}
public boolean isBelowMaxRep() {
int sc = _significand.bitLength() - C_64;
return _significand.compareTo(BI_MAX_BASE.shiftLeft(sc)) < 0;
}
public boolean isAboveMinRep() {
int sc = _significand.bitLength() - C_64;
return _significand.compareTo(BI_MIN_BASE.shiftLeft(sc)) > 0;
}
public NormalisedDecimal createNormalisedDecimal(int pow10) {
// missingUnderBits is (0..3)
int missingUnderBits = _binaryExponent-39;
int fracPart = (_significand.intValue() << missingUnderBits) & 0xFFFF80;
long wholePart = _significand.shiftRight(C_64-_binaryExponent-1).longValue();
return new NormalisedDecimal(wholePart, fracPart, pow10);
}
public void multiplyByPowerOfTen(int pow10) {
TenPower tp = TenPower.getInstance(Math.abs(pow10));
if (pow10 < 0) {
mulShift(tp._divisor, tp._divisorShift);
} else {
mulShift(tp._multiplicand, tp._multiplierShift);
}
}
private void mulShift(BigInteger multiplicand, int multiplierShift) {
_significand = _significand.multiply(multiplicand);
_binaryExponent += multiplierShift;
// check for too much precision
int sc = (_significand.bitLength() - MIN_PRECISION) & 0xFFFFFFE0;
// mask makes multiples of 32 which optimises BigInteger.shiftRight
if (sc > 0) {
// no need to round because we have at least 8 bits of extra precision
_significand = _significand.shiftRight(sc);
_binaryExponent += sc;
}
}
private static final class Rounder {
private static final BigInteger[] HALF_BITS;
static {
BigInteger[] bis = new BigInteger[33];
long acc=1;
for (int i = 1; i < bis.length; i++) {
bis[i] = BigInteger.valueOf(acc);
acc <<=1;
}
HALF_BITS = bis;
}
/**
* @param nBits number of bits to shift right
*/
public static BigInteger round(BigInteger bi, int nBits) {
if (nBits < 1) {
return bi;
}
return bi.add(HALF_BITS[nBits]);
}
}
/**
* Holds values for quick multiplication and division by 10
*/
private static final class TenPower {
private static final BigInteger FIVE = new BigInteger("5");
private static final TenPower[] _cache = new TenPower[350];
public final BigInteger _multiplicand;
public final BigInteger _divisor;
public final int _divisorShift;
public final int _multiplierShift;
private TenPower(int index) {
BigInteger fivePowIndex = FIVE.pow(index);
int bitsDueToFiveFactors = fivePowIndex.bitLength();
int px = 80 + bitsDueToFiveFactors;
BigInteger fx = BigInteger.ONE.shiftLeft(px).divide(fivePowIndex);
int adj = fx.bitLength() - 80;
_divisor = fx.shiftRight(adj);
bitsDueToFiveFactors -= adj;
_divisorShift = -(bitsDueToFiveFactors+index+80);
int sc = fivePowIndex.bitLength() - 68;
if (sc > 0) {
_multiplierShift = index + sc;
_multiplicand = fivePowIndex.shiftRight(sc);
} else {
_multiplierShift = index;
_multiplicand = fivePowIndex;
}
}
static TenPower getInstance(int index) {
TenPower result = _cache[index];
if (result == null) {
result = new TenPower(index);
_cache[index] = result;
}
return result;
}
}
public ExpandedDouble createExpandedDouble() {
return new ExpandedDouble(_significand, _binaryExponent);
}
}