001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 * 
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 * 
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.io.input;
018
019import java.io.IOException;
020import java.io.InputStream;
021
022/**
023 * A decorating input stream that counts the number of bytes that have passed
024 * through the stream so far.
025 * <p>
026 * A typical use case would be during debugging, to ensure that data is being
027 * read as expected.
028 *
029 * @version $Id: CountingInputStream.java 1304052 2012-03-22 20:55:29Z ggregory $
030 */
031public class CountingInputStream extends ProxyInputStream {
032
033    /** The count of bytes that have passed. */
034    private long count;
035
036    /**
037     * Constructs a new CountingInputStream.
038     *
039     * @param in  the InputStream to delegate to
040     */
041    public CountingInputStream(InputStream in) {
042        super(in);
043    }
044
045    //-----------------------------------------------------------------------
046
047    /**
048     * Skips the stream over the specified number of bytes, adding the skipped
049     * amount to the count.
050     *
051     * @param length  the number of bytes to skip
052     * @return the actual number of bytes skipped
053     * @throws IOException if an I/O error occurs
054     * @see java.io.InputStream#skip(long)
055     */
056    @Override
057    public synchronized long skip(final long length) throws IOException {
058        final long skip = super.skip(length);
059        this.count += skip;
060        return skip;
061    }
062
063    /**
064     * Adds the number of read bytes to the count.
065     *
066     * @param n number of bytes read, or -1 if no more bytes are available
067     * @since 2.0
068     */
069    @Override
070    protected synchronized void afterRead(int n) {
071        if (n != -1) {
072            this.count += n;
073        }
074    }
075
076    //-----------------------------------------------------------------------
077    /**
078     * The number of bytes that have passed through this stream.
079     * <p>
080     * NOTE: From v1.3 this method throws an ArithmeticException if the
081     * count is greater than can be expressed by an <code>int</code>.
082     * See {@link #getByteCount()} for a method using a <code>long</code>.
083     *
084     * @return the number of bytes accumulated
085     * @throws ArithmeticException if the byte count is too large
086     */
087    public int getCount() {
088        long result = getByteCount();
089        if (result > Integer.MAX_VALUE) {
090            throw new ArithmeticException("The byte count " + result + " is too large to be converted to an int");
091        }
092        return (int) result;
093    }
094
095    /** 
096     * Set the byte count back to 0. 
097     * <p>
098     * NOTE: From v1.3 this method throws an ArithmeticException if the
099     * count is greater than can be expressed by an <code>int</code>.
100     * See {@link #resetByteCount()} for a method using a <code>long</code>.
101     *
102     * @return the count previous to resetting
103     * @throws ArithmeticException if the byte count is too large
104     */
105    public int resetCount() {
106        long result = resetByteCount();
107        if (result > Integer.MAX_VALUE) {
108            throw new ArithmeticException("The byte count " + result + " is too large to be converted to an int");
109        }
110        return (int) result;
111    }
112
113    /**
114     * The number of bytes that have passed through this stream.
115     * <p>
116     * NOTE: This method is an alternative for <code>getCount()</code>
117     * and was added because that method returns an integer which will
118     * result in incorrect count for files over 2GB.
119     *
120     * @return the number of bytes accumulated
121     * @since 1.3
122     */
123    public synchronized long getByteCount() {
124        return this.count;
125    }
126
127    /** 
128     * Set the byte count back to 0. 
129     * <p>
130     * NOTE: This method is an alternative for <code>resetCount()</code>
131     * and was added because that method returns an integer which will
132     * result in incorrect count for files over 2GB.
133     *
134     * @return the count previous to resetting
135     * @since 1.3
136     */
137    public synchronized long resetByteCount() {
138        long tmp = this.count;
139        this.count = 0;
140        return tmp;
141    }
142
143}