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High performance arbitrary precision arithmetic library

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package org.apfloat.internal;

import org.apfloat.ApfloatContext;
import org.apfloat.ApfloatRuntimeException;
import org.apfloat.spi.ConvolutionStrategy;
import org.apfloat.spi.DataStorageBuilder;
import org.apfloat.spi.DataStorage;
import org.apfloat.spi.ArrayAccess;

/**
 * Short convolution strategy.
 * Performs a simple multiplication when the size of one operand is 1.
 *
 * @version 1.1
 * @author Mikko Tommila
 */

public class LongShortConvolutionStrategy
    extends LongBaseMath
    implements ConvolutionStrategy
{
    // Implementation notes:
    // - Assumes that the operands have been already truncated to match resultSize (the resultSize argument is ignored)
    // - This class shouldn't be converted to a single class using generics because the performance impact is noticeable

    /**
     * Creates a convolution strategy using the specified radix.
     *
     * @param radix The radix that will be used.
     */

    public LongShortConvolutionStrategy(int radix)
    {
        super(radix);
    }

    public DataStorage convolute(DataStorage x, DataStorage y, long resultSize)
        throws ApfloatRuntimeException
    {
        DataStorage shortStorage, longStorage, resultStorage;

        if (x.getSize() > 1)
        {
            shortStorage = y;
            longStorage = x;
        }
        else
        {
            shortStorage = x;
            longStorage = y;
        }

        assert (shortStorage.getSize() == 1);

        long size = longStorage.getSize() + 1;

        ArrayAccess arrayAccess = shortStorage.getArray(DataStorage.READ, 0, 1);
        long factor = arrayAccess.getLongData()[arrayAccess.getOffset()];
        arrayAccess.close();

        ApfloatContext ctx = ApfloatContext.getContext();
        DataStorageBuilder dataStorageBuilder = ctx.getBuilderFactory().getDataStorageBuilder();
        resultStorage = dataStorageBuilder.createDataStorage(size * 8);
        resultStorage.setSize(size);

        DataStorage.Iterator src = longStorage.iterator(DataStorage.READ, size - 1, 0),
                             dst = resultStorage.iterator(DataStorage.WRITE, size, 0);

        long carry = baseMultiplyAdd(src, null, factor, 0, dst, size - 1);
        dst.setLong(carry);
        dst.close();

        return resultStorage;
    }

    private static final long serialVersionUID = 1971685561366493327L;
}