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.wicket.util.io; import java.io.IOException; import java.io.OutputStream; import java.io.UnsupportedEncodingException; import java.util.List; /** * This class implements an output stream in which the data is written into a byte array. The buffer * automatically grows as data is written to it. * <p> * The data can be retrieved using <code>toByteArray()</code> and <code>toString()</code>. * <p> * Closing a <tt>ByteArrayOutputStream</tt> has no effect. The methods in this class can be called * after the stream has been closed without generating an <tt>IOException</tt>. * <p> * This is an alternative implementation of the java.io.ByteArrayOutputStream class. The original * implementation only allocates 32 bytes at the beginning. As this class is designed for heavy duty * it starts at 1024 bytes. In contrast to the original it doesn't reallocate the whole memory block * but allocates additional buffers. This way no buffers need to be garbage collected and the * contents don't have to be copied to the new buffer. This class is designed to behave exactly like * the original. The only exception is the deprecated toString(int) method that has been ignored. * * @author <a href="mailto:jeremias@apache.org">Jeremias Maerki</a> * @version $Id$ */ public class ByteArrayOutputStream extends OutputStream { private final List<byte[]> buffers = new java.util.ArrayList<>(); private int count; private byte[] currentBuffer; private int currentBufferIndex; private int filledBufferSum; /** * Creates a new byte array output stream. The buffer capacity is initially 1024 bytes, though * its size increases if necessary. */ public ByteArrayOutputStream() { this(1024); } /** * Creates a new byte array output stream, with a buffer capacity of the specified size, in * bytes. * * @param size * the initial size. * @exception IllegalArgumentException * if size is negative. */ public ByteArrayOutputStream(final int size) { if (size < 0) { throw new IllegalArgumentException("Negative initial size: " + size); } needNewBuffer(size); } /** * Closing a <tt>ByteArrayOutputStream</tt> has no effect. The methods in this class can be * called after the stream has been closed without generating an <tt>IOException</tt>. * * @throws IOException * in case an I/O error occurs */ @Override public void close() throws IOException { // nop } /** * @see java.io.ByteArrayOutputStream#reset() */ public synchronized void reset() { count = 0; filledBufferSum = 0; currentBufferIndex = 0; currentBuffer = getBuffer(currentBufferIndex); } /** * Gets the size. * * @return the size */ public int size() { return count; } /** * Writes to a byte array. * * @return this is a byte array */ public synchronized byte[] toByteArray() { int remaining = count; int pos = 0; byte newbuf[] = new byte[count]; for (int i = 0; i < buffers.size(); i++) { byte[] buf = getBuffer(i); int c = Math.min(buf.length, remaining); System.arraycopy(buf, 0, newbuf, pos, c); pos += c; remaining -= c; if (remaining == 0) { break; } } return newbuf; } /** * @see java.lang.Object#toString() */ @Override public String toString() { return new String(toByteArray()); } /** * This as a string using the provided encoding. * * @param enc * the encoding to use * @return This as a string using the provided encoding * @throws UnsupportedEncodingException */ public String toString(final String enc) throws UnsupportedEncodingException { return new String(toByteArray(), enc); } /** * @see java.io.OutputStream#write(byte[], int, int) */ @Override public synchronized void write(final byte[] b, final int off, final int len) { if ((off < 0) || (off > b.length) || (len < 0) || ((off + len) > b.length) || ((off + len) < 0)) { throw new IndexOutOfBoundsException(); } else if (len == 0) { return; } int newcount = count + len; int remaining = len; int inBufferPos = count - filledBufferSum; while (remaining > 0) { int part = Math.min(remaining, currentBuffer.length - inBufferPos); System.arraycopy(b, off + len - remaining, currentBuffer, inBufferPos, part); remaining -= part; if (remaining > 0) { needNewBuffer(newcount); inBufferPos = 0; } } count = newcount; } /** * Calls the write(byte[]) method. * * @see java.io.OutputStream#write(int) */ @Override public synchronized void write(final int b) { write(new byte[] { (byte) b }, 0, 1); } /** * Write to the given output stream. * * @param out * the output stream to write to * @throws IOException * @see java.io.ByteArrayOutputStream#writeTo(OutputStream) */ public synchronized void writeTo(final OutputStream out) throws IOException { int remaining = count; for (int i = 0; i < buffers.size(); i++) { byte[] buf = getBuffer(i); int c = Math.min(buf.length, remaining); out.write(buf, 0, c); remaining -= c; if (remaining == 0) { break; } } } private byte[] getBuffer(final int index) { return buffers.get(index); } private void needNewBuffer(final int newcount) { if (currentBufferIndex < buffers.size() - 1) { // Recycling old buffer filledBufferSum += currentBuffer.length; currentBufferIndex++; currentBuffer = getBuffer(currentBufferIndex); } else { // Creating new buffer int newBufferSize; if (currentBuffer == null) { newBufferSize = newcount; filledBufferSum = 0; } else { newBufferSize = Math.max(currentBuffer.length << 1, newcount - filledBufferSum); filledBufferSum += currentBuffer.length; } currentBufferIndex++; currentBuffer = new byte[newBufferSize]; buffers.add(currentBuffer); } } }