ResettableStringWriter.java

/*
 * JMeter Report Server
 * Copyright (C) 2010 eXcentia
 * dev@sonar.codehaus.org
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 3 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02
 */

package es.excentia.jmeter.report.server.testresults;

import java.io.IOException;
import java.io.Writer;

/**
 * A Writer that buffers the data in memory as a string. The buffer can be reset
 * at any time and the contents of the buffer will be returned.
 */
public class ResettableStringWriter extends Writer {

  /**
   * The internal buffer used to store the data written to this stream.
   */
  private StringBuilder mBuffer = new StringBuilder();

  /**
   * The maximum bytes this writer will buffer.
   */
  private int mMaxBytes = 1024;

  /**
   * Constructs the writer which will hold a fixed maximum of bytes. If more
   * bytes are written, an exception will be raised.
   * 
   * @param maxBytes
   *          the maximum number of bytes this writer will buffer
   */
  public ResettableStringWriter(int maxBytes) {
    mMaxBytes = maxBytes;
  }

  @Override
  public void close() throws IOException {
    // no op
  }

  @Override
  public void flush() throws IOException {
    // no op
  }

  @Override
  public void write(char[] cbuf, int off, int len) throws IOException {
    mBuffer.append(cbuf, off, len);

    if (mBuffer.length() > mMaxBytes) {
      throw new IOException("Memory buffer overflow");
    }
  }

  /**
   * Resets the stream to a length of zero. Any data written to the stream since
   * the last call to reset will be returned.
   * 
   * @return the contents of the stream buffer
   */
  public String reset() {
    String data = mBuffer.toString();
    mBuffer.setLength(0);
    return data;
  }
}