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package org.bouncycastle.math.ec;
import java.math.BigInteger;
/**
* Class representing a simple version of a big decimal. A
* SimpleBigDecimal is basically a
* {@link java.math.BigInteger BigInteger} with a few digits on the right of
* the decimal point. The number of (binary) digits on the right of the decimal
* point is called the scale of the SimpleBigDecimal.
* Unlike in {@link java.math.BigDecimal BigDecimal}, the scale is not adjusted
* automatically, but must be set manually. All SimpleBigDecimals
* taking part in the same arithmetic operation must have equal scale. The
* result of a multiplication of two SimpleBigDecimals returns a
* SimpleBigDecimal with double scale.
*/
class SimpleBigDecimal
//extends Number // not in J2ME - add compatibility class?
{
private static final long serialVersionUID = 1L;
private final BigInteger bigInt;
private final int scale;
/**
* Returns a SimpleBigDecimal representing the same numerical
* value as value.
* @param value The value of the SimpleBigDecimal to be
* created.
* @param scale The scale of the SimpleBigDecimal to be
* created.
* @return The such created SimpleBigDecimal.
*/
public static SimpleBigDecimal getInstance(BigInteger value, int scale)
{
return new SimpleBigDecimal(value.shiftLeft(scale), scale);
}
/**
* Constructor for SimpleBigDecimal. The value of the
* constructed SimpleBigDecimal equals bigInt /
* 2scale.
* @param bigInt The bigInt value parameter.
* @param scale The scale of the constructed SimpleBigDecimal.
*/
public SimpleBigDecimal(BigInteger bigInt, int scale)
{
if (scale < 0)
{
throw new IllegalArgumentException("scale may not be negative");
}
this.bigInt = bigInt;
this.scale = scale;
}
private void checkScale(SimpleBigDecimal b)
{
if (scale != b.scale)
{
throw new IllegalArgumentException("Only SimpleBigDecimal of " +
"same scale allowed in arithmetic operations");
}
}
public SimpleBigDecimal adjustScale(int newScale)
{
if (newScale < 0)
{
throw new IllegalArgumentException("scale may not be negative");
}
if (newScale == scale)
{
return this;
}
return new SimpleBigDecimal(bigInt.shiftLeft(newScale - scale),
newScale);
}
public SimpleBigDecimal add(SimpleBigDecimal b)
{
checkScale(b);
return new SimpleBigDecimal(bigInt.add(b.bigInt), scale);
}
public SimpleBigDecimal add(BigInteger b)
{
return new SimpleBigDecimal(bigInt.add(b.shiftLeft(scale)), scale);
}
public SimpleBigDecimal negate()
{
return new SimpleBigDecimal(bigInt.negate(), scale);
}
public SimpleBigDecimal subtract(SimpleBigDecimal b)
{
return add(b.negate());
}
public SimpleBigDecimal subtract(BigInteger b)
{
return new SimpleBigDecimal(bigInt.subtract(b.shiftLeft(scale)),
scale);
}
public SimpleBigDecimal multiply(SimpleBigDecimal b)
{
checkScale(b);
return new SimpleBigDecimal(bigInt.multiply(b.bigInt), scale + scale);
}
public SimpleBigDecimal multiply(BigInteger b)
{
return new SimpleBigDecimal(bigInt.multiply(b), scale);
}
public SimpleBigDecimal divide(SimpleBigDecimal b)
{
checkScale(b);
BigInteger dividend = bigInt.shiftLeft(scale);
return new SimpleBigDecimal(dividend.divide(b.bigInt), scale);
}
public SimpleBigDecimal divide(BigInteger b)
{
return new SimpleBigDecimal(bigInt.divide(b), scale);
}
public SimpleBigDecimal shiftLeft(int n)
{
return new SimpleBigDecimal(bigInt.shiftLeft(n), scale);
}
public int compareTo(SimpleBigDecimal val)
{
checkScale(val);
return bigInt.compareTo(val.bigInt);
}
public int compareTo(BigInteger val)
{
return bigInt.compareTo(val.shiftLeft(scale));
}
public BigInteger floor()
{
return bigInt.shiftRight(scale);
}
public BigInteger round()
{
SimpleBigDecimal oneHalf = new SimpleBigDecimal(ECConstants.ONE, 1);
return add(oneHalf.adjustScale(scale)).floor();
}
public int intValue()
{
return floor().intValue();
}
public long longValue()
{
return floor().longValue();
}
/* NON-J2ME compliant.
public double doubleValue()
{
return Double.valueOf(toString()).doubleValue();
}
public float floatValue()
{
return Float.valueOf(toString()).floatValue();
}
*/
public int getScale()
{
return scale;
}
public String toString()
{
if (scale == 0)
{
return bigInt.toString();
}
BigInteger floorBigInt = floor();
BigInteger fract = bigInt.subtract(floorBigInt.shiftLeft(scale));
if (bigInt.signum() == -1)
{
fract = ECConstants.ONE.shiftLeft(scale).subtract(fract);
}
if ((floorBigInt.signum() == -1) && (!(fract.equals(ECConstants.ZERO))))
{
floorBigInt = floorBigInt.add(ECConstants.ONE);
}
String leftOfPoint = floorBigInt.toString();
char[] fractCharArr = new char[scale];
String fractStr = fract.toString(2);
int fractLen = fractStr.length();
int zeroes = scale - fractLen;
for (int i = 0; i < zeroes; i++)
{
fractCharArr[i] = '0';
}
for (int j = 0; j < fractLen; j++)
{
fractCharArr[zeroes + j] = fractStr.charAt(j);
}
String rightOfPoint = new String(fractCharArr);
StringBuffer sb = new StringBuffer(leftOfPoint);
sb.append(".");
sb.append(rightOfPoint);
return sb.toString();
}
public boolean equals(Object o)
{
if (this == o)
{
return true;
}
if (!(o instanceof SimpleBigDecimal))
{
return false;
}
SimpleBigDecimal other = (SimpleBigDecimal)o;
return ((bigInt.equals(other.bigInt)) && (scale == other.scale));
}
public int hashCode()
{
return bigInt.hashCode() ^ scale;
}
}