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 static org.apache.commons.io.IOUtils.EOF;
020
021import java.io.IOException;
022import java.io.InputStream;
023
024/**
025 * A decorating input stream that counts the number of bytes that have passed
026 * through the stream so far.
027 * <p>
028 * A typical use case would be during debugging, to ensure that data is being
029 * read as expected.
030 * </p>
031 */
032public class CountingInputStream extends ProxyInputStream {
033
034    /** The count of bytes that have passed. */
035    private long count;
036
037    /**
038     * Constructs a new CountingInputStream.
039     *
040     * @param in  the InputStream to delegate to
041     */
042    public CountingInputStream(final InputStream in) {
043        super(in);
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(final int n) {
071        if (n != EOF) {
072            this.count += n;
073        }
074    }
075
076    /**
077     * The number of bytes that have passed through this stream.
078     * <p>
079     * NOTE: From v1.3 this method throws an ArithmeticException if the
080     * count is greater than can be expressed by an {@code int}.
081     * See {@link #getByteCount()} for a method using a {@code long}.
082     *
083     * @return the number of bytes accumulated
084     * @throws ArithmeticException if the byte count is too large
085     */
086    public int getCount() {
087        final long result = getByteCount();
088        if (result > Integer.MAX_VALUE) {
089            throw new ArithmeticException("The byte count " + result + " is too large to be converted to an int");
090        }
091        return (int) result;
092    }
093
094    /**
095     * Set the byte count back to 0.
096     * <p>
097     * NOTE: From v1.3 this method throws an ArithmeticException if the
098     * count is greater than can be expressed by an {@code int}.
099     * See {@link #resetByteCount()} for a method using a {@code long}.
100     *
101     * @return the count previous to resetting
102     * @throws ArithmeticException if the byte count is too large
103     */
104    public int resetCount() {
105        final long result = resetByteCount();
106        if (result > Integer.MAX_VALUE) {
107            throw new ArithmeticException("The byte count " + result + " is too large to be converted to an int");
108        }
109        return (int) result;
110    }
111
112    /**
113     * The number of bytes that have passed through this stream.
114     * <p>
115     * NOTE: This method is an alternative for {@code getCount()}
116     * and was added because that method returns an integer which will
117     * result in incorrect count for files over 2GB.
118     *
119     * @return the number of bytes accumulated
120     * @since 1.3
121     */
122    public synchronized long getByteCount() {
123        return this.count;
124    }
125
126    /**
127     * Set the byte count back to 0.
128     * <p>
129     * NOTE: This method is an alternative for {@code resetCount()}
130     * and was added because that method returns an integer which will
131     * result in incorrect count for files over 2GB.
132     *
133     * @return the count previous to resetting
134     * @since 1.3
135     */
136    public synchronized long resetByteCount() {
137        final long tmp = this.count;
138        this.count = 0;
139        return tmp;
140    }
141
142}