implements an output stream in which the data is written into a byte array. The buffer automatically grows as data is written to it.
/*
* 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 jacky.lanlan.song.extension.struts.util;
import java.io.IOException;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
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>
* @author Holger Hoffstatte
* @version $Id: ByteArrayOutputStream.java 491007 2006-12-29 13:50:34Z
* scolebourne $
*/
public class ByteArrayOutputStream extends OutputStream {
/** A singleton empty byte array. */
private static final byte[] EMPTY_BYTE_ARRAY = new byte[0];
/** The list of buffers, which grows and never reduces. */
private List<byte[]> buffers = new ArrayList<byte[]>();
/** The index of the current buffer. */
private int currentBufferIndex;
/** The total count of bytes in all the filled buffers. */
private int filledBufferSum;
/** The current buffer. */
private byte[] currentBuffer;
/** The total count of bytes written. */
private int count;
/**
* 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
* @throws IllegalArgumentException
* if size is negative
*/
public ByteArrayOutputStream(int size) {
if (size < 0) { throw new IllegalArgumentException(
"Negative initial size: " + size); }
needNewBuffer(size);
}
/**
* Return the appropriate <code>byte[]</code> buffer specified by index.
*
* @param index
* the index of the buffer required
* @return the buffer
*/
private byte[] getBuffer(int index) {
return buffers.get(index);
}
/**
* Makes a new buffer available either by allocating a new one or re-cycling
* an existing one.
*
* @param newcount
* the size of the buffer if one is created
*/
private void needNewBuffer(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);
}
}
/**
* @see java.io.OutputStream#write(byte[], int, int)
*/
public void write(byte[] b, int off, 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; }
synchronized (this) {
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;
}
}
/**
* @see java.io.OutputStream#write(int)
*/
public synchronized void write(int b) {
int inBufferPos = count - filledBufferSum;
if (inBufferPos == currentBuffer.length) {
needNewBuffer(count + 1);
inBufferPos = 0;
}
currentBuffer[inBufferPos] = (byte) b;
count++;
}
/**
* @see java.io.ByteArrayOutputStream#size()
*/
public synchronized int size() {
return count;
}
/**
* 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
* never (this method should not declare this exception but it has
* to now due to backwards compatability)
*/
public void close() throws IOException {
// nop
}
/**
* @see java.io.ByteArrayOutputStream#reset()
*/
public synchronized void reset() {
count = 0;
filledBufferSum = 0;
currentBufferIndex = 0;
currentBuffer = getBuffer(currentBufferIndex);
}
/**
* Writes the entire contents of this byte stream to the specified output
* stream.
*
* @param out
* the output stream to write to
* @throws IOException
* if an I/O error occurs, such as if the stream is closed
* @see java.io.ByteArrayOutputStream#writeTo(OutputStream)
*/
public synchronized void writeTo(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;
}
}
}
/**
* Gets the curent contents of this byte stream as a byte array. The result is
* independent of this stream.
*
* @return the current contents of this output stream, as a byte array
* @see java.io.ByteArrayOutputStream#toByteArray()
*/
public synchronized byte[] toByteArray() {
int remaining = count;
if (remaining == 0) { return EMPTY_BYTE_ARRAY; }
byte newbuf[] = new byte[remaining];
int pos = 0;
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;
}
/**
* Gets the curent contents of this byte stream as a string.
*
* @see java.io.ByteArrayOutputStream#toString()
*/
public String toString() {
return new String(toByteArray());
}
/**
* Gets the curent contents of this byte stream as a string using the
* specified encoding.
*
* @param enc
* the name of the character encoding
* @return the string converted from the byte array
* @throws UnsupportedEncodingException
* if the encoding is not supported
* @see java.io.ByteArrayOutputStream#toString(String)
*/
public String toString(String enc) throws UnsupportedEncodingException {
return new String(toByteArray(), enc);
}
}
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