org.apache.tomcat.util.http.fileupload.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.tomcat.util.http.fileupload;
import java.io.IOException;
import java.io.OutputStream;
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.
*
* The data can be retrieved using toByteArray() and
* toString().
*
* Closing a {@code ByteArrayOutputStream} has no effect. The methods in
* this class can be called after the stream has been closed without
* generating an {@code IOException}.
*
* This is an alternative implementation of the {@link 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.
*/
public class ByteArrayOutputStream extends OutputStream {
static final int DEFAULT_SIZE = 1024;
/** 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 final List buffers = new ArrayList<>();
/** 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(DEFAULT_SIZE);
}
/**
* 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(final int size) {
if (size < 0) {
throw new IllegalArgumentException(
"Negative initial size: " + size);
}
synchronized (this) {
needNewBuffer(size);
}
}
/**
* 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(final int newcount) {
if (currentBufferIndex < buffers.size() - 1) {
//Recycling old buffer
filledBufferSum += currentBuffer.length;
currentBufferIndex++;
currentBuffer = buffers.get(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);
}
}
/**
* Write the bytes to byte array.
* @param b the bytes to write
* @param off The start offset
* @param len The number of bytes to write
*/
@Override
public 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;
}
synchronized (this) {
final int newcount = count + len;
int remaining = len;
int inBufferPos = count - filledBufferSum;
while (remaining > 0) {
final 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;
}
}
/**
* Write a byte to byte array.
* @param b the byte to write
*/
@Override
public synchronized void write(final int b) {
int inBufferPos = count - filledBufferSum;
if (inBufferPos == currentBuffer.length) {
needNewBuffer(count + 1);
inBufferPos = 0;
}
currentBuffer[inBufferPos] = (byte) b;
count++;
}
/**
* Closing a {@code ByteArrayOutputStream} has no effect. The methods in
* this class can be called after the stream has been closed without
* generating an {@code IOException}.
*
* @throws IOException never (this method should not declare this exception
* but it has to now due to backwards compatibility)
*/
@Override
public void close() throws IOException {
//nop
}
/**
* 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(final OutputStream out) throws IOException {
int remaining = count;
for (final byte[] buf : buffers) {
final int c = Math.min(buf.length, remaining);
out.write(buf, 0, c);
remaining -= c;
if (remaining == 0) {
break;
}
}
}
/**
* Gets the current 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;
}
final byte newbuf[] = new byte[remaining];
int pos = 0;
for (final byte[] buf : buffers) {
final int c = Math.min(buf.length, remaining);
System.arraycopy(buf, 0, newbuf, pos, c);
pos += c;
remaining -= c;
if (remaining == 0) {
break;
}
}
return newbuf;
}
}