org.apache.wicket.util.io.ByteArrayOutputStream Maven / Gradle / Ivy
/*
* 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.
*
* The data can be retrieved using toByteArray() and toString().
*
* Closing a ByteArrayOutputStream has no effect. The methods in this class can be called
* after the stream has been closed without generating an IOException.
*
* 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 Jeremias Maerki
* @version $Id$
*/
public class ByteArrayOutputStream extends OutputStream
{
private final List 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 ByteArrayOutputStream has no effect. The methods in this class can be
* called after the stream has been closed without generating an IOException.
*
* @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);
}
}
}