Java tutorial
/* * 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 471628 2006-11-06 04:06:45Z bayard $ */ 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); } //----------------------------------------------------------------------- /** * Reads a number of bytes into the byte array, keeping count of the * number read. * * @param b the buffer into which the data is read, not null * @return the total number of bytes read into the buffer, -1 if end of stream * @throws IOException if an I/O error occurs * @see java.io.InputStream#read(byte[]) */ public int read(byte[] b) throws IOException { int found = super.read(b); this.count += (found >= 0) ? found : 0; return found; } /** * Reads a number of bytes into the byte array at a specific offset, * keeping count of the number read. * * @param b the buffer into which the data is read, not null * @param off the start offset in the buffer * @param len the maximum number of bytes to read * @return the total number of bytes read into the buffer, -1 if end of stream * @throws IOException if an I/O error occurs * @see java.io.InputStream#read(byte[], int, int) */ public int read(byte[] b, int off, int len) throws IOException { int found = super.read(b, off, len); this.count += (found >= 0) ? found : 0; return found; } /** * Reads the next byte of data adding to the count of bytes received * if a byte is successfully read. * * @return the byte read, -1 if end of stream * @throws IOException if an I/O error occurs * @see java.io.InputStream#read() */ public int read() throws IOException { int found = super.read(); this.count += (found >= 0) ? 1 : 0; return found; } /** * 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) */ public long skip(final long length) throws IOException { final long skip = super.skip(length); this.count += skip; return skip; } //----------------------------------------------------------------------- /** * 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 synchronized 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 synchronized 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; } }