ByteBuffers.java

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
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 * 2 along with this work; if not, write to the Free Software Foundation,
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/**
 * @test
 * @bug 4844847
 * @summary Test the MessageDigest.update(ByteBuffer) method
 * @author Andreas Sterbenz
 * @key randomness
 */

import java.util.*;
import java.nio.*;

import java.security.*;

public class ByteBuffers {

    public static void main(String[] args) throws Exception {
        Provider p = Security.getProvider("SUN");
        Random random = new Random();
        int n = 10 * 1024;
        byte[] t = new byte[n];
        random.nextBytes(t);

        MessageDigest md = MessageDigest.getInstance("MD5", p);
        byte[] d1 = md.digest(t);

        // test 1: ByteBuffer with an accessible backing array
        ByteBuffer b1 = ByteBuffer.allocate(n + 256);
        b1.position(random.nextInt(256));
        b1.limit(b1.position() + n);
        ByteBuffer b2 = b1.slice();
        b2.put(t);
        b2.clear();
        byte[] d2 = digest(md, b2, random);
        if (Arrays.equals(d1, d2) == false) {
            throw new Exception("Test 1 failed");
        }

        // test 2: direct ByteBuffer
        ByteBuffer b3 = ByteBuffer.allocateDirect(t.length);
        b3.put(t);
        b3.clear();
        byte[] d3 = digest(md, b3, random);
        if (Arrays.equals(d1, d3) == false) {
            throw new Exception("Test 2 failed");
        }

        // test 3: ByteBuffer without an accessible backing array
        b2.clear();
        ByteBuffer b4 = b2.asReadOnlyBuffer();
        byte[] d4 = digest(md, b4, random);
        if (Arrays.equals(d1, d4) == false) {
            throw new Exception("Test 3 failed");
        }
        System.out.println("All tests passed");
    }

    private static byte[] digest(MessageDigest md, ByteBuffer b, Random random) throws Exception {
        int lim = b.limit();
        b.limit(random.nextInt(lim));
        md.update(b);
        if (b.hasRemaining()) {
            throw new Exception("Buffer not consumed");
        }
        b.limit(lim);
        md.update(b);
        if (b.hasRemaining()) {
            throw new Exception("Buffer not consumed");
        }
        return md.digest();
    }
}