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package sun.security.util.math;

import java.math.BigInteger;

Default implementations of methods for IntegerModuloP. 
See Also:
IntegerModuloP/**
 * Default implementations of methods for {@code IntegerModuloP}.
 *
 * @see IntegerModuloP
 */
public abstract class AbstractElement implements IntegerModuloP {

    @Override
    public byte[] addModPowerTwo(IntegerModuloP b, int len) {
        byte[] result = new byte[len];
        addModPowerTwo(b, result);
        return result;
    }

    @Override
    public byte[] asByteArray(int len) {
        byte[] result = new byte[len];
        asByteArray(result);
        return result;
    }

    @Override
    public ImmutableIntegerModuloP multiplicativeInverse() {
        return pow(getField().getSize().subtract(BigInteger.valueOf(2)));
    }

    @Override
    public ImmutableIntegerModuloP subtract(IntegerModuloP b) {
        return add(b.additiveInverse());
    }

    @Override
    public ImmutableIntegerModuloP square() {
        return multiply(this);
    }

    @Override
    public ImmutableIntegerModuloP pow(BigInteger b) {
        //Public implementation is square and multiply
        MutableIntegerModuloP y = getField().get1().mutable();
        MutableIntegerModuloP x = mutable();
        int bitLength = b.bitLength();
        for (int bit = 0; bit < bitLength; bit++) {
            if (b.testBit(bit)) {
                // odd
                y.setProduct(x);
            }
            x.setSquare();
        }
        return y.fixed();
    }
}