kafka OrderedBytes 源码

kafka OrderedBytes 代码

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

class OrderedBytes {

    private static final int MIN_KEY_LENGTH = 1;
    /**
     * Returns the upper byte range for a key with a given fixed size maximum suffix
     *
     * Assumes the minimum key length is one byte
     */
    static Bytes upperRange(final Bytes key, final byte[] maxSuffix) {
        final byte[] bytes = key.get();
        final ByteBuffer rangeEnd = ByteBuffer.allocate(bytes.length + maxSuffix.length);
        final int firstTimestampByte = maxSuffix[0] & 0xFF;

        // if firstTimestampByte is 0, we'll put all key bytes into range result because `(bytes[i] & 0xFF) >= firstTimestampByte`
        // will always be true (this is a byte to unsigned int conversion comparison)
        if (firstTimestampByte == 0) {
            return Bytes.wrap(
                rangeEnd
                    .put(bytes)
                    .put(maxSuffix)
                    .array()
            );
        } else {
            int i = 0;
            while (i < bytes.length && (
                i < MIN_KEY_LENGTH // assumes keys are at least one byte long
                || (bytes[i] & 0xFF) >= firstTimestampByte
                )) {
                rangeEnd.put(bytes[i++]);
            }

            rangeEnd.put(maxSuffix);
            rangeEnd.flip();

            final byte[] res = new byte[rangeEnd.remaining()];
            ByteBuffer.wrap(res).put(rangeEnd);
            return Bytes.wrap(res);
        }
    }

    static Bytes lowerRange(final Bytes key, final byte[] minSuffix) {
        final byte[] bytes = key.get();
        final ByteBuffer rangeStart = ByteBuffer.allocate(bytes.length + minSuffix.length);
        // any key in the range would start at least with the given prefix to be
        // in the range, and have at least SUFFIX_SIZE number of trailing zero bytes.

        // unless there is a maximum key length, you can keep appending more zero bytes
        // to keyFrom to create a key that will match the range, yet that would precede
        // KeySchema.toBinaryKey(keyFrom, from, 0) in byte order
        return Bytes.wrap(
            rangeStart
                .put(bytes)
                .put(minSuffix)
                .array()
        );
    }
}

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