IOUtil.java

/*
 * SPDX-License-Identifier: Apache-2.0
 * See LICENSE file for details.
 *
 * Copyright 2025-2026 Hazendaz
 * Copyright 2011-2025 Acegi Technology Pty Limited.
 */
package au.com.acegi.xmlformat;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.util.zip.CRC32;
import java.util.zip.CheckedInputStream;
import java.util.zip.Checksum;

/**
 * Utility methods for dealing with I/O resources.
 */
final class IOUtil {

    private IOUtil() {
    }

    /**
     * Returns a CRC32 of the provided input stream.
     *
     * @param in
     *            to CRC32
     *
     * @return the CRC32 value
     *
     * @throws IOException
     *             if unable to read the input stream
     */
    @SuppressWarnings("PMD.EmptyWhileStmt")
    static long hash(final InputStream in) throws IOException {
        final Checksum cksum = new CRC32();
        final CheckedInputStream is = new CheckedInputStream(in, cksum);
        final byte[] buff = new byte[4_096];
        while (is.read(buff) >= 0) {
            // CheckInputStream will update its internal checksum
        }
        return is.getChecksum().getValue();
    }

    /**
     * Returns a CRC32 of the given file.
     *
     * @param file
     *            to CRC32
     *
     * @return the CRC32 value
     *
     * @throws IOException
     *             if unable to read the file
     */
    static long hash(final File file) throws IOException {
        try (InputStream fis = Files.newInputStream(file.toPath())) {
            return hash(fis);
        }
    }

}