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/*

 * @test

 * @bug 8200698

 * @summary Tests that exceptions are thrown for ops which would overflow

 * @run testng/othervm -Xmx4g LargeValueExceptions

 */

import java.math.BigInteger;

import static java.math.BigInteger.ONE;

import org.testng.annotations.Test;

//

// The intent of this test is to probe the boundaries between overflow and

// non-overflow, principally for multiplication and squaring, specifically

// the largest values which should not overflow and the smallest values which

// should. The transition values used are not necessarily at the exact

// boundaries but should be "close." Quite a few different values were used

// experimentally before settling on the ones in this test. For multiplication

// and squaring all cases are exercised: definite overflow and non-overflow

// which can be detected "up front," and "indefinite" overflow, i.e., overflow

// which cannot be detected up front so further calculations are required.

//

// Testing negative values is unnecessary. For both multiplication and squaring

// the paths lead to the Toom-Cook algorithm where the signum is used only to

// determine the sign of the result and not in the intermediate calculations.

// This is also true for exponentiation.

//

// @Test annotations with optional element "enabled" set to "false" should

// succeed when "enabled" is set to "true" but they take too to run in the

// course of the typical regression test execution scenario.

//

public class LargeValueExceptions {

    // BigInteger.MAX_MAG_LENGTH

    private static final int MAX_INTS = 1 << 26;

    // Number of bits corresponding to MAX_INTS

    private static final long MAX_BITS = (0xffffffffL & MAX_INTS) << 5L;

    // Half BigInteger.MAX_MAG_LENGTH

    private static final int MAX_INTS_HALF = MAX_INTS / 2;

    // --- squaring ---

    // Largest no overflow determined by examining data lengths alone.

    @Test(enabled=false)

    public void squareNoOverflow() {

        BigInteger x = ONE.shiftLeft(16*MAX_INTS - 1).subtract(ONE);

        BigInteger y = x.multiply(x);

    }

    // Smallest no overflow determined by extra calculations.

    @Test(enabled=false)

    public void squareIndefiniteOverflowSuccess() {

        BigInteger x = ONE.shiftLeft(16*MAX_INTS - 1);

        BigInteger y = x.multiply(x);

    }

    // Largest overflow detected by extra calculations.

    @Test(expectedExceptions=ArithmeticException.class,enabled=false)

    public void squareIndefiniteOverflowFailure() {

        BigInteger x = ONE.shiftLeft(16*MAX_INTS).subtract(ONE);

        BigInteger y = x.multiply(x);

    }

    // Smallest overflow detected by examining data lengths alone.

    @Test(expectedExceptions=ArithmeticException.class)

    public void squareDefiniteOverflow() {

        BigInteger x = ONE.shiftLeft(16*MAX_INTS);

        BigInteger y = x.multiply(x);

    }

    // --- multiplication ---

    // Largest no overflow determined by examining data lengths alone.

    @Test(enabled=false)

    public void multiplyNoOverflow() {

        final int halfMaxBits = MAX_INTS_HALF << 5;

        BigInteger x = ONE.shiftLeft(halfMaxBits).subtract(ONE);

        BigInteger y = ONE.shiftLeft(halfMaxBits - 1).subtract(ONE);

        BigInteger z = x.multiply(y);

    }

    // Smallest no overflow determined by extra calculations.

    @Test(enabled=false)

    public void multiplyIndefiniteOverflowSuccess() {

        BigInteger x = ONE.shiftLeft((int)(MAX_BITS/2) - 1);

        long m = MAX_BITS - x.bitLength();

        BigInteger y = ONE.shiftLeft((int)(MAX_BITS/2) - 1);

        long n = MAX_BITS - y.bitLength();

        if (m + n != MAX_BITS) {

            throw new RuntimeException("Unexpected leading zero sum");

        }

        BigInteger z = x.multiply(y);

    }

    // Largest overflow detected by extra calculations.

    @Test(expectedExceptions=ArithmeticException.class,enabled=false)

    public void multiplyIndefiniteOverflowFailure() {

        BigInteger x = ONE.shiftLeft((int)(MAX_BITS/2)).subtract(ONE);

        long m = MAX_BITS - x.bitLength();

        BigInteger y = ONE.shiftLeft((int)(MAX_BITS/2)).subtract(ONE);

        long n = MAX_BITS - y.bitLength();

        if (m + n != MAX_BITS) {

            throw new RuntimeException("Unexpected leading zero sum");

        }

        BigInteger z = x.multiply(y);

    }

    // Smallest overflow detected by examining data lengths alone.

    @Test(expectedExceptions=ArithmeticException.class)

    public void multiplyDefiniteOverflow() {

        // multiply by 4 as MAX_INTS_HALF refers to ints

        byte[] xmag = new byte[4*MAX_INTS_HALF];

        xmag[0] = (byte)0xff;

        BigInteger x = new BigInteger(1, xmag);

        byte[] ymag = new byte[4*MAX_INTS_HALF + 1];

        ymag[0] = (byte)0xff;

        BigInteger y = new BigInteger(1, ymag);

        BigInteger z = x.multiply(y);

    }

    // --- exponentiation ---

    @Test(expectedExceptions=ArithmeticException.class)

    public void powOverflow() {

        BigInteger.TEN.pow(Integer.MAX_VALUE);

    }

    @Test(expectedExceptions=ArithmeticException.class)

    public void powOverflow1() {

        int shift = 20;

        int exponent = 1 << shift;

        BigInteger x = ONE.shiftLeft((int)(MAX_BITS / exponent));

        BigInteger y = x.pow(exponent);

    }

    @Test(expectedExceptions=ArithmeticException.class)

    public void powOverflow2() {

        int shift = 20;

        int exponent = 1 << shift;

        BigInteger x = ONE.shiftLeft((int)(MAX_BITS / exponent)).add(ONE);

        BigInteger y = x.pow(exponent);

    }

    @Test(expectedExceptions=ArithmeticException.class,enabled=false)

    public void powOverflow3() {

        int shift = 20;

        int exponent = 1 << shift;

        BigInteger x = ONE.shiftLeft((int)(MAX_BITS / exponent)).subtract(ONE);

        BigInteger y = x.pow(exponent);

    }

    @Test(enabled=false)

    public void powOverflow4() {

        int shift = 20;

        int exponent = 1 << shift;

        BigInteger x = ONE.shiftLeft((int)(MAX_BITS / exponent - 1)).add(ONE);

        BigInteger y = x.pow(exponent);

    }

}