/*
    * Copyright (C) 2007 The Guava Authors
    *
    * Licensed 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 com.google.common.io;
  
  import com.google.common.annotations.Beta;
  
  import java.io.FilterInputStream;
  import java.io.IOException;
  import java.io.InputStream;
  
  import javax.annotation.Nullable;
  
  /**
   * An {@link InputStream} that counts the number of bytes read.
   *
   * @author Chris Nokleberg
   * @since 1.0
   */
  @Beta
  public final class CountingInputStream extends FilterInputStream {
  
    private long count;
    private long mark = -1;
  
    /**
     * Wraps another input stream, counting the number of bytes read.
     *
     * @param in the input stream to be wrapped
     */
    public CountingInputStream(@Nullable InputStream in) {
      super(in);
    }
  
    /** Returns the number of bytes read. */
    public long getCount() {
      return count;
    }
  
    @Override public int read() throws IOException {
      int result = in.read();
      if (result != -1) {
        count++;
      }
      return result;
    }
  
    @Override public int read(byte[] b, int off, int len) throws IOException {
      int result = in.read(b, off, len);
      if (result != -1) {
        count += result;
      }
      return result;
    }
  
    @Override public long skip(long n) throws IOException {
      long result = in.skip(n);
      count += result;
      return result;
    }
  
    @Override public synchronized void mark(int readlimit) {
      in.mark(readlimit);
      mark = count;
      // it's okay to mark even if mark isn't supported, as reset won't work
    }
  
    @Override public synchronized void reset() throws IOException {
      if (!in.markSupported()) {
        throw new IOException("Mark not supported");
      }
      if (mark == -1) {
        throw new IOException("Mark not set");
      }
  
      in.reset();
      count = mark;
    }
  }