kafka SegmentedCacheFunction 源码

kafka SegmentedCacheFunction 代码

文件路径：/streams/src/main/java/org/apache/kafka/streams/state/internals/SegmentedCacheFunction.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.kafka.streams.state.internals;

import org.apache.kafka.common.utils.Bytes;
import org.apache.kafka.streams.state.internals.SegmentedBytesStore.KeySchema;

import java.nio.ByteBuffer;

class SegmentedCacheFunction implements CacheFunction {

    private static final int SEGMENT_ID_BYTES = 8;

    private final KeySchema keySchema;
    private final long segmentInterval;

    SegmentedCacheFunction(final KeySchema keySchema, final long segmentInterval) {
        this.keySchema = keySchema;
        this.segmentInterval = segmentInterval;
    }

    @Override
    public Bytes key(final Bytes cacheKey) {
        return Bytes.wrap(bytesFromCacheKey(cacheKey));
    }

    @Override
    public Bytes cacheKey(final Bytes key) {
        return cacheKey(key, segmentId(key));
    }

    Bytes cacheKey(final Bytes key, final long segmentId) {
        final byte[] keyBytes = key.get();
        final ByteBuffer buf = ByteBuffer.allocate(SEGMENT_ID_BYTES + keyBytes.length);
        buf.putLong(segmentId).put(keyBytes);
        return Bytes.wrap(buf.array());
    }

    static byte[] bytesFromCacheKey(final Bytes cacheKey) {
        final byte[] binaryKey = new byte[cacheKey.get().length - SEGMENT_ID_BYTES];
        System.arraycopy(cacheKey.get(), SEGMENT_ID_BYTES, binaryKey, 0, binaryKey.length);
        return binaryKey;
    }

    public long segmentId(final Bytes key) {
        return segmentId(keySchema.segmentTimestamp(key));
    }

    long segmentId(final long timestamp) {
        return timestamp / segmentInterval;
    }

    long getSegmentInterval() {
        return segmentInterval;
    }

    int compareSegmentedKeys(final Bytes cacheKey, final Bytes storeKey) {
        final long storeSegmentId = segmentId(storeKey);
        final long cacheSegmentId = ByteBuffer.wrap(cacheKey.get()).getLong();

        final int segmentCompare = Long.compare(cacheSegmentId, storeSegmentId);
        if (segmentCompare == 0) {
            final byte[] cacheKeyBytes = cacheKey.get();
            final byte[] storeKeyBytes = storeKey.get();
            return Bytes.BYTES_LEXICO_COMPARATOR.compare(
                cacheKeyBytes, SEGMENT_ID_BYTES, cacheKeyBytes.length - SEGMENT_ID_BYTES,
                storeKeyBytes, 0, storeKeyBytes.length
            );
        } else {
            return segmentCompare;
        }
    }
}

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