content: /*
   * 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.trogdor.workload;
  
  import com.fasterxml.jackson.annotation.JsonCreator;
  import com.fasterxml.jackson.annotation.JsonProperty;
  
  import java.util.Random;
  
  /**
   * A PayloadGenerator which generates a uniform random payload.
   *
   * This generator generates pseudo-random payloads that can be reproduced from run to run.
   * The guarantees are the same as those of java.util.Random.
   *
   * This payload generator also has the option to append padding bytes at the end of the payload.
   * The padding bytes are always the same, no matter what the position is.  This is useful when
   * simulating a partly-compressible stream of user data.
   */
  public class UniformRandomPayloadGenerator implements PayloadGenerator {
      private final int size;
      private final long seed;
      private final int padding;
      private final Random random = new Random();
      private final byte[] padBytes;
      private final byte[] randomBytes;
  
      @JsonCreator
      public UniformRandomPayloadGenerator(@JsonProperty("size") int size,
                                           @JsonProperty("seed") long seed,
                                           @JsonProperty("padding") int padding) {
          this.size = size;
          this.seed = seed;
          this.padding = padding;
          if (padding < 0 || padding > size) {
              throw new RuntimeException("Invalid value " + padding + " for " +
                  "padding: the number of padding bytes must not be smaller than " +
                  "0 or greater than the total payload size.");
          }
          this.padBytes = new byte[padding];
          random.setSeed(seed);
          random.nextBytes(padBytes);
          this.randomBytes = new byte[size - padding];
      }
  
      @JsonProperty
      public int size() {
          return size;
      }
  
      @JsonProperty
      public long seed() {
          return seed;
      }
  
      @JsonProperty
      public int padding() {
          return padding;
      }
  
      @Override
      public synchronized byte[] generate(long position) {
          byte[] result = new byte[size];
          if (randomBytes.length > 0) {
              random.setSeed(seed + position);
              random.nextBytes(randomBytes);
              System.arraycopy(randomBytes, 0, result, 0, Math.min(randomBytes.length, result.length));
          }
          if (padBytes.length > 0) {
              System.arraycopy(padBytes, 0, result, randomBytes.length, result.length - randomBytes.length);
          }
          return result;
      }
  }
  