code: /*
   * 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.commons.io.input;
  
  import java.io.IOException;
  import java.io.InputStream;
  
  /**
   * A decorating input stream that counts the number of bytes that have passed
   * through the stream so far.
   * <p>
   * A typical use case would be during debugging, to ensure that data is being
   * read as expected.
   *
   * @author Marcelo Liberato
   * @version $Id: CountingInputStream.java 1004079 2010-10-04 01:11:27Z niallp $
   */
  public class CountingInputStream extends ProxyInputStream {
  
      /** The count of bytes that have passed. */
      private long count;
  
      /**
       * Constructs a new CountingInputStream.
       *
       * @param in  the InputStream to delegate to
       */
      public CountingInputStream(InputStream in) {
          super(in);
      }
  
      //-----------------------------------------------------------------------
  
      /**
       * Skips the stream over the specified number of bytes, adding the skipped
       * amount to the count.
       *
       * @param length  the number of bytes to skip
       * @return the actual number of bytes skipped
       * @throws IOException if an I/O error occurs
       * @see java.io.InputStream#skip(long)
       */
      @Override
      public synchronized long skip(final long length) throws IOException {
          final long skip = super.skip(length);
          this.count += skip;
          return skip;
      }
  
      /**
       * Adds the number of read bytes to the count.
       *
       * @param n number of bytes read, or -1 if no more bytes are available
       * @since Commons IO 2.0
       */
      @Override
      protected synchronized void afterRead(int n) {
          if (n != -1) {
              this.count += n;
          }
      }
  
      //-----------------------------------------------------------------------
      /**
       * The number of bytes that have passed through this stream.
       * <p>
       * NOTE: From v1.3 this method throws an ArithmeticException if the
       * count is greater than can be expressed by an <code>int</code>.
       * See {@link #getByteCount()} for a method using a <code>long</code>.
       *
       * @return the number of bytes accumulated
       * @throws ArithmeticException if the byte count is too large
       */
      public int getCount() {
          long result = getByteCount();
          if (result > Integer.MAX_VALUE) {
              throw new ArithmeticException("The byte count " + result + " is too large to be converted to an int");
          }
          return (int) result;
      }
  
      /** 
       * Set the byte count back to 0. 
       * <p>
       * NOTE: From v1.3 this method throws an ArithmeticException if the
       * count is greater than can be expressed by an <code>int</code>.
       * See {@link #resetByteCount()} for a method using a <code>long</code>.
       *
       * @return the count previous to resetting
       * @throws ArithmeticException if the byte count is too large
       */
      public int resetCount() {
          long result = resetByteCount();
          if (result > Integer.MAX_VALUE) {
              throw new ArithmeticException("The byte count " + result + " is too large to be converted to an int");
          }
          return (int) result;
      }
  
      /**
       * The number of bytes that have passed through this stream.
       * <p>
       * NOTE: This method is an alternative for <code>getCount()</code>
       * and was added because that method returns an integer which will
       * result in incorrect count for files over 2GB.
       *
       * @return the number of bytes accumulated
       * @since Commons IO 1.3
       */
      public synchronized long getByteCount() {
          return this.count;
      }
  
      /** 
       * Set the byte count back to 0. 
       * <p>
       * NOTE: This method is an alternative for <code>resetCount()</code>
       * and was added because that method returns an integer which will
       * result in incorrect count for files over 2GB.
       *
       * @return the count previous to resetting
       * @since Commons IO 1.3
       */
      public synchronized long resetByteCount() {
          long tmp = this.count;
          this.count = 0;
          return tmp;
      }
  
  }
  