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Common functionality for HBase

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/*
 * 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.hadoop.hbase.io.compress;

import org.apache.yetus.audience.InterfaceAudience;

@InterfaceAudience.Private
public final class CompressionUtil {

  private CompressionUtil() {
  }

  /**
   * Round up to the next power of two, unless the value would become negative (ints are signed), in
   * which case just return Integer.MAX_VALUE.
   */
  public static int roundInt2(int v) {
    v = Integer.highestOneBit(v) << 1;
    if (v < 0) {
      return Integer.MAX_VALUE;
    }
    return v;
  }

  /**
   * Most compression algorithms can be presented with pathological input that causes an expansion
   * rather than a compression. Hadoop's compression API requires that we calculate additional
   * buffer space required for the worst case. There is a formula developed for gzip that applies as
   * a ballpark to all LZ variants. It should be good enough for now and has been tested as such
   * with a range of different inputs.
   */
  public static int compressionOverhead(int bufferSize) {
    // Given an input buffer of 'buffersize' bytes we presume a worst case expansion of
    // 32 bytes (block header) and addition 1/6th of the input size.
    return (bufferSize / 6) + 32;
  }
}