src/main/java/org/apache/cassandra/sidecar/utils/XXHash32DigestVerifier.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.cassandra.sidecar.utils;

import io.vertx.core.Future;
import io.vertx.core.MultiMap;
import io.vertx.core.Promise;
import io.vertx.core.file.AsyncFile;
import io.vertx.core.file.FileSystem;
import net.jpountz.xxhash.StreamingXXHash32;
import net.jpountz.xxhash.XXHashFactory;
import org.apache.cassandra.sidecar.common.data.XXHash32Digest;
import org.jetbrains.annotations.VisibleForTesting;

import static org.apache.cassandra.sidecar.common.http.SidecarHttpHeaderNames.CONTENT_XXHASH32;
import static org.apache.cassandra.sidecar.common.http.SidecarHttpHeaderNames.CONTENT_XXHASH32_SEED;

/**
 * Implementation of {@link DigestVerifier} to calculate the digest and match the calculated digest
 * with the expected digest.
 */
public class XXHash32DigestVerifier extends AsyncFileDigestVerifier<XXHash32Digest>
{
    protected XXHash32DigestVerifier(FileSystem fs, XXHash32Digest digest)
    {
        super(fs, digest);
    }

    public static XXHash32DigestVerifier create(FileSystem fs, MultiMap headers)
    {
        XXHash32Digest digest = new XXHash32Digest(headers.get(CONTENT_XXHASH32), headers.get(CONTENT_XXHASH32_SEED));
        return new XXHash32DigestVerifier(fs, digest);
    }

    @Override
    @VisibleForTesting
    protected Future<String> calculateDigest(AsyncFile file)
    {
        Promise<String> result = Promise.promise();
        Future<String> future = result.future();

        // might have shared hashers with ThreadLocal
        XXHashFactory factory = XXHashFactory.safeInstance();

        int seed = maybeGetSeedOrDefault();
        StreamingXXHash32 hasher = factory.newStreamingHash32(seed);

        future.onComplete(ignored -> hasher.close());

        readFile(file, result, buf -> {
                     byte[] bytes = buf.getBytes();
                     hasher.update(bytes, 0, bytes.length);
                 },
                 _v -> result.complete(Long.toHexString(hasher.getValue())));

        return future;
    }

    protected int maybeGetSeedOrDefault()
    {
        String seedHex = digest.seedHex();
        if (seedHex != null)
        {
            return (int) Long.parseLong(seedHex, 16);
        }
        return 0x9747b28c; // random seed for initializing
    }
}