test/jdk/java/io/ByteArrayInputStream/ChunkedTransferTo.java

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/* @test
 * @bug 8316156
 * @summary Ensure ByteArrayInputStream.transferTo does not cause direct memory
 *          to overflow MaxDirectMemorySize
 * @run junit/othervm -XX:MaxDirectMemorySize=5M ChunkedTransferTo
 */

import java.io.ByteArrayInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.channels.Channels;
import java.nio.channels.FileChannel;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Arrays;
import java.util.Random;

import static java.nio.file.StandardCopyOption.REPLACE_EXISTING;
import static java.nio.file.StandardOpenOption.*;

import org.junit.jupiter.api.Test;

public class ChunkedTransferTo {
    // this value must exceed MaxDirectMemorySize
    private static final int SIZE = 10_000_000;

    @Test
    public void byteArrayInputStream() throws IOException {
        byte[] src = new byte[SIZE];
        Random rnd = new Random(System.nanoTime());
        rnd.nextBytes(src);
        try (ByteArrayInputStream bais = new ByteArrayInputStream(src)) {
            Path target = Files.createTempFile("SNA", "FU");
            FileChannel fc = FileChannel.open(target, CREATE, WRITE);
            bais.transferTo(Channels.newOutputStream(fc));
            byte[] dst = new byte[SIZE + 1];
            try (FileInputStream fis = new FileInputStream(target.toFile())) {
                int n = -1;
                if ((n = fis.read(dst)) != SIZE)
                    throw new RuntimeException(n + " != " + SIZE);
            }
            Files.delete(target);
            if (!Arrays.equals(src, 0, SIZE, dst, 0, SIZE))
                throw new RuntimeException("Arrays are not equal");
        } catch (OutOfMemoryError oome) {
            throw new RuntimeException(oome);
        }
    }
}