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import java.lang.invoke.MethodHandle;

import java.lang.invoke.MethodHandles;

import java.lang.invoke.MethodType;

import java.lang.reflect.Constructor;

import java.lang.reflect.Field;

import java.lang.reflect.Method;

import java.math.BigInteger;

import java.util.Arrays;

import java.util.Random;

/**

 * @test

 * @bug 8130150

 * @library /testlibrary

 * @summary Verify that the Montgomery multiply intrinsic works and correctly checks its arguments.

 */

public class MontgomeryMultiplyTest {

    static final MethodHandles.Lookup lookup = MethodHandles.lookup();

    static final MethodHandle montgomeryMultiplyHandle, montgomerySquareHandle;

    static final MethodHandle bigIntegerConstructorHandle;

    static final Field bigIntegerMagField;

    static {

       // Use reflection to gain access to the methods we want to test.

        try {

            Method m = BigInteger.class.getDeclaredMethod("montgomeryMultiply",

                /*a*/int[].class, /*b*/int[].class, /*n*/int[].class, /*len*/int.class,

                /*inv*/long.class, /*product*/int[].class);

            m.setAccessible(true);

            montgomeryMultiplyHandle = lookup.unreflect(m);

            m = BigInteger.class.getDeclaredMethod("montgomerySquare",

                /*a*/int[].class, /*n*/int[].class, /*len*/int.class,

                /*inv*/long.class, /*product*/int[].class);

            m.setAccessible(true);

            montgomerySquareHandle = lookup.unreflect(m);

            Constructor c

                = BigInteger.class.getDeclaredConstructor(int.class, int[].class);

            c.setAccessible(true);

            bigIntegerConstructorHandle = lookup.unreflectConstructor(c);

            bigIntegerMagField = BigInteger.class.getDeclaredField("mag");

            bigIntegerMagField.setAccessible(true);

        } catch (Throwable ex) {

            throw new RuntimeException(ex);

        }

    }

    // Invoke either BigInteger.montgomeryMultiply or BigInteger.montgomerySquare.

    int[] montgomeryMultiply(int[] a, int[] b, int[] n, int len, long inv,

                             int[] product) throws Throwable {

        int[] result =

            (a == b) ? (int[]) montgomerySquareHandle.invokeExact(a, n, len, inv, product)

                     : (int[]) montgomeryMultiplyHandle.invokeExact(a, b, n, len, inv, product);

        return Arrays.copyOf(result, len);

    }

    // Invoke the private constructor BigInteger(int[]).

    BigInteger newBigInteger(int[] val) throws Throwable {

        return (BigInteger) bigIntegerConstructorHandle.invokeExact(1, val);

    }

    // Get the private field BigInteger.mag

    int[] mag(BigInteger n) {

        try {

            return (int[]) bigIntegerMagField.get(n);

        } catch (Exception ex) {

            throw new RuntimeException(ex);

        }

    }

    // Montgomery multiplication

    // Calculate a * b * r^-1 mod n)

    //

    // R is a power of the word size

    // N' = R^-1 mod N

    //

    // T := ab

    // m := (T mod R)N' mod R [so 0 <= m < R]

    // t := (T + mN)/R

    // if t >= N then return t - N else return t

    //

    BigInteger montgomeryMultiply(BigInteger a, BigInteger b, BigInteger N,

            int len, BigInteger n_prime)

            throws Throwable {

        BigInteger T = a.multiply(b);

        BigInteger R = BigInteger.ONE.shiftLeft(len*32);

        BigInteger mask = R.subtract(BigInteger.ONE);

        BigInteger m = (T.and(mask)).multiply(n_prime);

        m = m.and(mask); // i.e. m.mod(R)

        T = T.add(m.multiply(N));

        T = T.shiftRight(len*32); // i.e. T.divide(R)

        if (T.compareTo(N) > 0) {

            T = T.subtract(N);

        }

        return T;

    }

    // Call the Montgomery multiply intrinsic.

    BigInteger montgomeryMultiply(int[] a_words, int[] b_words, int[] n_words,

            int len, BigInteger inv)

            throws Throwable {

        BigInteger t = montgomeryMultiply(

                newBigInteger(a_words),

                newBigInteger(b_words),

                newBigInteger(n_words),

                len, inv);

        return t;

    }

    // Check that the Montgomery multiply intrinsic returns the same

    // result as the longhand calculation.

    void check(int[] a_words, int[] b_words, int[] n_words, int len, BigInteger inv)

            throws Throwable {

        BigInteger n = newBigInteger(n_words);

        BigInteger slow = montgomeryMultiply(a_words, b_words, n_words, len, inv);

        BigInteger fast

            = newBigInteger(montgomeryMultiply

                            (a_words, b_words, n_words, len, inv.longValue(), null));

        // The intrinsic may not return the same value as the longhand

        // calculation but they must have the same residue mod N.

        if (!slow.mod(n).equals(fast.mod(n))) {

            throw new RuntimeException();

        }

    }

    Random rnd = new Random(0);

    // Return a random value of length <= bits in an array of even length

    int[] random_val(int bits) {

        int len = (bits+63)/64;  // i.e. length in longs

        int[] val = new int[len*2];

        for (int i = 0; i < val.length; i++)

            val[i] = rnd.nextInt();

        int leadingZeros = 64 - (bits & 64);

        if (leadingZeros >= 32) {

            val[0] = 0;

            val[1] &= ~(-1l << (leadingZeros & 31));

        } else {

            val[0] &= ~(-1l << leadingZeros);

        }

        return val;

    }

    void testOneLength(int lenInBits, int lenInInts) throws Throwable {

        BigInteger mod = new BigInteger(lenInBits, 2, rnd);

        BigInteger r = BigInteger.ONE.shiftLeft(lenInInts * 32);

        BigInteger n_prime = mod.modInverse(r).negate();

        // Make n.length even, padding with a zero if necessary

        int[] n = mag(mod);

        if (n.length < lenInInts) {

            int[] x = new int[lenInInts];

            System.arraycopy(n, 0, x, lenInInts-n.length, n.length);

            n = x;

        }

        for (int i = 0; i < 10000; i++) {

            // multiply

            check(random_val(lenInBits), random_val(lenInBits), n, lenInInts, n_prime);

            // square

            int[] tmp = random_val(lenInBits);

            check(tmp, tmp, n, lenInInts, n_prime);

        }

    }

    // Test the Montgomery multiply intrinsic with a bunch of random

    // values of varying lengths.  Do this for long enough that the

    // caller of the intrinsic is C2-compiled.

    void testResultValues() throws Throwable {

        // Test a couple of interesting edge cases.

        testOneLength(1024, 32);

        testOneLength(1025, 34);

        for (int j = 10; j > 0; j--) {

            // Construct a random prime whose length in words is even

            int lenInBits = rnd.nextInt(2048) + 64;

            int lenInInts = (lenInBits + 63)/64*2;

            testOneLength(lenInBits, lenInInts);

        }

    }

    // Range checks

    void testOneMontgomeryMultiplyCheck(int[] a, int[] b, int[] n, int len, long inv,

                                        int[] product, Class klass) {

        try {

            montgomeryMultiply(a, b, n, len, inv, product);

        } catch (Throwable ex) {

            if (klass.isAssignableFrom(ex.getClass()))

                return;

            throw new RuntimeException(klass + " expected, " + ex + " was thrown");

        }

        throw new RuntimeException(klass + " expected, was not thrown");

    }

    void testOneMontgomeryMultiplyCheck(int[] a, int[] b, BigInteger n, int len, BigInteger inv,

            Class klass) {

        testOneMontgomeryMultiplyCheck(a, b, mag(n), len, inv.longValue(), null, klass);

    }

    void testOneMontgomeryMultiplyCheck(int[] a, int[] b, BigInteger n, int len, BigInteger inv,

            int[] product, Class klass) {

        testOneMontgomeryMultiplyCheck(a, b, mag(n), len, inv.longValue(), product, klass);

    }

    void testMontgomeryMultiplyChecks() {

        int[] blah = random_val(40);

        int[] small = random_val(39);

        BigInteger mod = new BigInteger(40*32 , 2, rnd);

        BigInteger r = BigInteger.ONE.shiftLeft(40*32);

        BigInteger n_prime = mod.modInverse(r).negate();

        // Length out of range: square

        testOneMontgomeryMultiplyCheck(blah, blah, mod, 41, n_prime, IllegalArgumentException.class);

        testOneMontgomeryMultiplyCheck(blah, blah, mod, 0, n_prime, IllegalArgumentException.class);

        testOneMontgomeryMultiplyCheck(blah, blah, mod, -1, n_prime, IllegalArgumentException.class);

        // As above, but for multiply

        testOneMontgomeryMultiplyCheck(blah, blah.clone(), mod, 41, n_prime, IllegalArgumentException.class);

        testOneMontgomeryMultiplyCheck(blah, blah.clone(), mod, 0, n_prime, IllegalArgumentException.class);

        testOneMontgomeryMultiplyCheck(blah, blah.clone(), mod, 0, n_prime, IllegalArgumentException.class);

        // Length odd

        testOneMontgomeryMultiplyCheck(small, small, mod, 39, n_prime, IllegalArgumentException.class);

        testOneMontgomeryMultiplyCheck(small, small, mod, 0, n_prime, IllegalArgumentException.class);

        testOneMontgomeryMultiplyCheck(small, small, mod, -1, n_prime, IllegalArgumentException.class);

        // As above, but for multiply

        testOneMontgomeryMultiplyCheck(small, small.clone(), mod, 39, n_prime, IllegalArgumentException.class);

        testOneMontgomeryMultiplyCheck(small, small.clone(), mod, 0, n_prime, IllegalArgumentException.class);

        testOneMontgomeryMultiplyCheck(small, small.clone(), mod, -1, n_prime, IllegalArgumentException.class);

        // array too small

        testOneMontgomeryMultiplyCheck(blah, blah, mod, 40, n_prime, small, IllegalArgumentException.class);

        testOneMontgomeryMultiplyCheck(blah, blah.clone(), mod, 40, n_prime, small, IllegalArgumentException.class);

        testOneMontgomeryMultiplyCheck(small, blah, mod, 40, n_prime, blah, IllegalArgumentException.class);

        testOneMontgomeryMultiplyCheck(blah, small, mod, 40, n_prime, blah, IllegalArgumentException.class);

        testOneMontgomeryMultiplyCheck(blah, blah, mod, 40, n_prime, small, IllegalArgumentException.class);

        testOneMontgomeryMultiplyCheck(small, small, mod, 40, n_prime, blah, IllegalArgumentException.class);

    }

    public static void main(String args[]) {

        try {

            new MontgomeryMultiplyTest().testMontgomeryMultiplyChecks();

            new MontgomeryMultiplyTest().testResultValues();

        } catch (Throwable ex) {

            throw new RuntimeException(ex);

        }

     }

}