iotdb-core/tsfile/src/main/java/org/apache/iotdb/tsfile/utils/PublicBAOS.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.iotdb.tsfile.utils;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.util.Arrays;

/**
 * A subclass extending <code>ByteArrayOutputStream</code>. It's used to return the byte array
 * directly. Note that the size of byte array is large than actual size of valid contents, thus it's
 * used cooperating with <code>size()</code> or <code>capacity = size</code> This class extends
 * ByteArrayOutputStream and intentionally remove the 'synchronized' keyword in write methods for
 * better performance. (Not thread safe)
 */
public class PublicBAOS extends ByteArrayOutputStream {
  private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;

  public PublicBAOS() {
    super();
  }

  public PublicBAOS(int size) {
    super(size);
  }

  private void ensureCapacity(int minCapacity) {
    // overflow-conscious code
    if (minCapacity - buf.length > 0) {
      grow(minCapacity);
    }
  }

  private void grow(int minCapacity) {
    // overflow-conscious code
    int oldCapacity = buf.length;
    int newCapacity = oldCapacity << 1;
    if (newCapacity - minCapacity < 0) {
      newCapacity = minCapacity;
    }
    if (newCapacity - MAX_ARRAY_SIZE > 0) {
      newCapacity = hugeCapacity(minCapacity);
    }
    buf = Arrays.copyOf(buf, newCapacity);
  }

  private static int hugeCapacity(int minCapacity) {
    if (minCapacity < 0) {
      // overflow
      throw new OutOfMemoryError();
    }
    return (minCapacity > MAX_ARRAY_SIZE) ? Integer.MAX_VALUE : MAX_ARRAY_SIZE;
  }

  @Override
  public void write(int b) {
    ensureCapacity(count + 1);
    buf[count] = (byte) b;
    count += 1;
  }

  @Override
  public void write(byte b[], int off, int len) {
    if ((off < 0) || (off > b.length) || (len < 0) || ((off + len) - b.length > 0)) {
      throw new IndexOutOfBoundsException();
    }
    ensureCapacity(count + len);
    System.arraycopy(b, off, buf, count, len);
    count += len;
  }

  @Override
  public byte[] toByteArray() {
    return Arrays.copyOf(buf, count);
  }

  @Override
  public String toString() {
    return new String(buf, 0, count);
  }

  @Override
  public String toString(String charsetName) throws UnsupportedEncodingException {
    return new String(buf, 0, count, charsetName);
  }

  /**
   * get current all bytes data
   *
   * @return all bytes data
   */
  public byte[] getBuf() {

    return this.buf;
  }

  /**
   * It's not a thread-safe method. Override the super class's implementation. Remove the
   * synchronized key word, to save the synchronization overhead.
   *
   * <p>Writes the complete contents of this byte array output stream to the specified output stream
   * argument, as if by calling the output stream's write method using <code>
   * out.write(buf, 0, count)</code>.
   *
   * @param out the output stream to which to write the data.
   * @exception IOException if an I/O error occurs.
   */
  @Override
  @SuppressWarnings("squid:S3551")
  public void writeTo(OutputStream out) throws IOException {
    out.write(buf, 0, count);
  }

  /**
   * It's not a thread-safe method. Override the super class's implementation. Remove the
   * synchronized key word, to save the synchronization overhead.
   *
   * <p>Resets the <code>count</code> field of this byte array output stream to zero, so that all
   * currently accumulated output in the output stream is discarded. The output stream can be used
   * again, reusing the already allocated buffer space.
   */
  @Override
  @SuppressWarnings("squid:S3551")
  public void reset() {
    count = 0;
  }

  /**
   * The synchronized keyword in this function is intentionally removed. For details, see
   * https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=173085039
   */
  @Override
  @SuppressWarnings("squid:S3551")
  public int size() {
    return count;
  }

  public void truncate(int size) {
    count = size;
  }
}