/*
This file is part of jpcsp.

Jpcsp is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

Jpcsp is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Jpcsp.  If not, see <http://www.gnu.org/licenses/>.
 */
package jpcsp.Allegrex.compiler.nativeCode;

import java.math.BigInteger;

/**
 * Unsigned long integer (64-bit) arithmetic.
 * 
 * @author gid15
 *
 */
public class ULongInteger extends AbstractNativeCodeSequence {
	public static void mult() {
		long a = getLong(getGprA0(), getGprA1());
		long b = getLong(getGprA2(), getGprA3());

		long result = a * b;

		setGprV0V1(result);
	}

	public static void div() {
		long a = getLong(getGprA0(), getGprA1());
		long b = getLong(getGprA2(), getGprA3());

		long result;
		if (a >= 0 && b >= 0) {
			// If both operands are positive, we can use normal "long" arithmetic
			result = a / b;
		} else {
			// If one of the operands is negative, we have to use BigInteger arithmetic.
			// Only BigInteger handles correctly value above 0x80000000000

			// Input bytes for BigInteger are assumed to be in big-endian byte-order.
			final byte[] bytesA = new byte[8];
			final byte[] bytesB = new byte[8];
			for (int i = 7; i >= 0; i--) {
				bytesA[i] = (byte) a;
				bytesB[i] = (byte) b;
				a >>= 8;
				b >>= 8;
			}

			// Create positive BigInteger values, the signum is always 1 for positive values.
			BigInteger bigA = new BigInteger(1, bytesA);
			BigInteger bigB = new BigInteger(1, bytesB);

			// Compute the division
			BigInteger bigResult = bigA.divide(bigB);

			// and convert the result to a long value.
			result = bigResult.longValue();
		}

		setGprV0V1(result);
	}
}