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jBasics is a collection of useful utility classes for Java. This includes helper for XML, mathematic functions, restful web services helper, pattern oriented programming interfaces and more. Currently Java7 and up is supported. Version 1.0 will required at leaset Java8.
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/*
 * Copyright (c) 2009-2015
 * 	IT-Consulting Stephan Schloepke (http://www.schloepke.de/)
 * 	klemm software consulting Mirko Klemm (http://www.klemm-scs.com/)
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package org.jbasics.math.obsolete;

import java.util.Arrays;

public class LittleEndianLongStore implements DataStorage {
	private static final long[] ZERO = new long[0];
	private static final byte[] ZERO_BYTES = new byte[]{0};
	private long[] magnitude;

	public LittleEndianLongStore() {
		this(ZERO);
	}

	public LittleEndianLongStore(long[] magnitude) {
		this.magnitude = magnitude;
	}

	public LittleEndianLongStore(int value) {
		this(new long[]{value});
	}

	public LittleEndianLongStore(long value) {
		this(new long[]{value});
	}

	public LittleEndianLongStore(byte[] input) {
		if (input == null || input.length == 0) {
			this.magnitude = ZERO;
		} else {
			long[] result = new long[(input.length + 7) / 8];
			int j = input.length;
			for (int i = 0; i < result.length; i++) {
				if (j > 7) {
					result[i] = (input[--j] & 0xffL) | (input[--j] & 0xffL) << 8 | (input[--j] & 0xffL) << 16 | (input[--j] & 0xffL) << 24 | (input[--j] & 0xffL) << 32 | (input[--j] & 0xffL) << 40 | (input[--j] & 0xffL) << 48 | (input[--j] & 0xffL) << 56;
				} else if (j == 7) {
					result[i] = (input[--j] & 0xffL) | (input[--j] & 0xffL) << 8 | (input[--j] & 0xffL) << 16 | (input[--j] & 0xffL) << 24 | (input[--j] & 0xffL) << 32 | (input[--j] & 0xffL) << 40 | (input[--j] & 0xffL) << 48;
				} else if (j == 6) {
					result[i] = (input[--j] & 0xffL) | (input[--j] & 0xffL) << 8 | (input[--j] & 0xffL) << 16 | (input[--j] & 0xffL) << 24 | (input[--j] & 0xffL) << 32 | (input[--j] & 0xffL) << 40;
				} else if (j == 5) {
					result[i] = (input[--j] & 0xffL) | (input[--j] & 0xffL) << 8 | (input[--j] & 0xffL) << 16 | (input[--j] & 0xffL) << 24 | (input[--j] & 0xffL) << 32;
				} else if (j == 4) {
					result[i] = (input[--j] & 0xffL) | (input[--j] & 0xffL) << 8 | (input[--j] & 0xffL) << 16 | (input[--j] & 0xffL) << 24;
				} else if (j == 3) {
					result[i] = (input[--j] & 0xffL) | (input[--j] & 0xffL) << 8 | (input[--j] & 0xffL) << 16;
				} else if (j == 2) {
					result[i] = (input[--j] & 0xffL) | (input[--j] & 0xffL) << 8;
				} else if (j == 1) {
					result[i] = (input[--j] & 0xffL);
				}
			}
			this.magnitude = result;
		}
	}

	public LittleEndianLongStore add(LittleEndianLongStore summand) {
		long[] x = this.magnitude;
		long[] y = summand.magnitude;
		if (x.length < y.length) {
			x = y;
			y = this.magnitude;
		}
		long[] result = new long[x.length];
		// from now we know x is the longer and y the shorter. so lets iterate over y and add
		boolean carry = false;
		int i;
		long xi, sum;
		for (i = 0; i < y.length; i++) {
			xi = x[i];
			if (carry) {
				carry = ((sum = result[i] = (xi + y[i]) + 1) >>> 1) < (xi >>> 1) || ((sum >>> 1) == (xi >>> 1) && (((sum | xi) & 0x1) != 0));
			} else {
				sum = result[i] = (xi + y[i]);
				carry = (sum >>> 1) < (xi >>> 1) || ((sum >>> 1) == (xi >>> 1) && ((xi & 0x1) != 0));
			}
		}
		// we have a carry from the iteration before. so we need to actually iterate any further
		// with x
		while (i < x.length && carry) {
			carry = (result[i] = x[i] + 1) == 0;
			i++;
		}

		int xl = x.length;
		while (i < xl) {
			result[i] = x[i++];
		}

		if (carry) {
			// now we have the problem that a sum is still arround from the iteration before. So
			// we need to advance the array and add one element
			long[] t = new long[result.length + 1];
			System.arraycopy(result, 0, t, 0, result.length);
			t[result.length] = 1;
			return new LittleEndianLongStore(t);
		}
		return new LittleEndianLongStore(result);
	}

	public LittleEndianLongStore subtract(LittleEndianLongStore subtraction) {
		// TODO Auto-generated method stub
		return null;
	}

	public LittleEndianLongStore multiply(LittleEndianLongStore factor) {
		// TODO Auto-generated method stub
		return null;
	}

	public byte[] toByteArray() {
		if (this.magnitude == null || this.magnitude.length == 0) {
			return ZERO_BYTES;
		}
		int bytes = (this.magnitude.length - 1) * 8;
		long temp = this.magnitude[this.magnitude.length - 1];
		if (temp < 0) {
			bytes += 9;
		} else if (temp >= 0x0100000000000000L) {
			bytes += 8;
		} else if (temp >= 0x0001000000000000L) {
			bytes += 7;
		} else if (temp >= 0x0000010000000000L) {
			bytes += 6;
		} else if (temp >= 0x0000000100000000L) {
			bytes += 5;
		} else if (temp >= 0x0000000001000000L) {
			bytes += 4;
		} else if (temp >= 0x0000000000010000L) {
			bytes += 3;
		} else if (temp >= 0x0000000000000100L) {
			bytes += 2;
		} else if (temp > 0) {
			bytes += 1;
		}
		byte[] result = new byte[bytes];
		for (int i = 0; i < this.magnitude.length; i++) {
			long x = this.magnitude[i];
			if (bytes > 7) {
				result[--bytes] = (byte) ((x & 0x00000000000000ffL));
				result[--bytes] = (byte) ((x & 0x000000000000ff00L) >>> 8);
				result[--bytes] = (byte) ((x & 0x0000000000ff0000L) >>> 16);
				result[--bytes] = (byte) ((x & 0x00000000ff000000L) >>> 24);
				result[--bytes] = (byte) ((x & 0x000000ff00000000L) >>> 32);
				result[--bytes] = (byte) ((x & 0x0000ff0000000000L) >>> 40);
				result[--bytes] = (byte) ((x & 0x00ff000000000000L) >>> 48);
				result[--bytes] = (byte) (x >>> 56);
			} else if (bytes == 7) {
				result[--bytes] = (byte) ((x & 0x00000000000000ffL));
				result[--bytes] = (byte) ((x & 0x000000000000ff00L) >>> 8);
				result[--bytes] = (byte) ((x & 0x0000000000ff0000L) >>> 16);
				result[--bytes] = (byte) ((x & 0x00000000ff000000L) >>> 24);
				result[--bytes] = (byte) ((x & 0x000000ff00000000L) >>> 32);
				result[--bytes] = (byte) ((x & 0x0000ff0000000000L) >>> 40);
				result[--bytes] = (byte) ((x & 0x00ff000000000000L) >>> 48);
			} else if (bytes == 6) {
				result[--bytes] = (byte) ((x & 0x00000000000000ffL));
				result[--bytes] = (byte) ((x & 0x000000000000ff00L) >>> 8);
				result[--bytes] = (byte) ((x & 0x0000000000ff0000L) >>> 16);
				result[--bytes] = (byte) ((x & 0x00000000ff000000L) >>> 24);
				result[--bytes] = (byte) ((x & 0x000000ff00000000L) >>> 32);
				result[--bytes] = (byte) ((x & 0x0000ff0000000000L) >>> 40);
			} else if (bytes == 5) {
				result[--bytes] = (byte) ((x & 0x00000000000000ffL));
				result[--bytes] = (byte) ((x & 0x000000000000ff00L) >>> 8);
				result[--bytes] = (byte) ((x & 0x0000000000ff0000L) >>> 16);
				result[--bytes] = (byte) ((x & 0x00000000ff000000L) >>> 24);
				result[--bytes] = (byte) ((x & 0x000000ff00000000L) >>> 32);
			} else if (bytes == 4) {
				result[--bytes] = (byte) ((x & 0x00000000000000ffL));
				result[--bytes] = (byte) ((x & 0x000000000000ff00L) >>> 8);
				result[--bytes] = (byte) ((x & 0x0000000000ff0000L) >>> 16);
				result[--bytes] = (byte) ((x & 0x00000000ff000000L) >>> 24);
			} else if (bytes == 3) {
				result[--bytes] = (byte) ((x & 0x00000000000000ffL));
				result[--bytes] = (byte) ((x & 0x000000000000ff00L) >>> 8);
				result[--bytes] = (byte) ((x & 0x0000000000ff0000L) >>> 16);
			} else if (bytes == 2) {
				result[--bytes] = (byte) ((x & 0x00000000000000ffL));
				result[--bytes] = (byte) ((x & 0x000000000000ff00L) >>> 8);
			} else if (bytes == 1) {
				result[--bytes] = (byte) ((x & 0x00000000000000ffL));
			}
		}
		return result;
	}

	public boolean isZero() {
		return this.magnitude == null || this.magnitude.length == 0 || zeroscan(this.magnitude);
	}

	private boolean zeroscan(long[] in) {
		for (long x : in) {
			if (x != 0) {
				return false;
			}
		}
		return true;
	}

	@Override
	public int hashCode() {
		return 31 + Arrays.hashCode(this.magnitude);
	}
}