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.beam.sdk.util;
  
  import java.io.ByteArrayInputStream;
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.lang.ref.SoftReference;
  import org.apache.beam.sdk.annotations.Internal;
  
  /** Utility functions for stream operations. */
  @Internal
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public class StreamUtils {
  
    private StreamUtils() {}
  
    private static final int BUF_SIZE = 8192;
  
    private static ThreadLocal<SoftReference<byte[]>> threadLocalBuffer = new ThreadLocal<>();
  
    /** Efficient converting stream to bytes. */
    public static byte[] getBytesWithoutClosing(InputStream stream) throws IOException {
      if (stream instanceof ExposedByteArrayInputStream) {
        // Fast path for the exposed version.
        return ((ExposedByteArrayInputStream) stream).readAll();
      } else if (stream instanceof ByteArrayInputStream) {
        // Fast path for ByteArrayInputStream.
        byte[] ret = new byte[stream.available()];
        stream.read(ret);
        return ret;
      }
      // Falls back to normal stream copying.
      SoftReference<byte[]> refBuffer = threadLocalBuffer.get();
      byte[] buffer = refBuffer == null ? null : refBuffer.get();
      if (buffer == null) {
        buffer = new byte[BUF_SIZE];
        threadLocalBuffer.set(new SoftReference<>(buffer));
      }
      ByteArrayOutputStream outStream = new ByteArrayOutputStream();
      while (true) {
        int r = stream.read(buffer);
        if (r == -1) {
          break;
        }
        outStream.write(buffer, 0, r);
      }
      return outStream.toByteArray();
    }
  }
  