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Commons IO example source code file (ByteArrayOutputStream.java)

This example Commons IO source code file (ByteArrayOutputStream.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Commons IO tags/keywords

bytearrayinputstream, bytearrayoutputstream, bytearrayoutputstream, closedinputstream, empty_byte_array, indexoutofboundsexception, inputstream, io, ioexception, ioexception, list, override, override, string, string, util

The Commons IO ByteArrayOutputStream.java source code

/*
 * 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.output;
 
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.SequenceInputStream;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import org.apache.commons.io.input.ClosedInputStream;

/**
 * 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() and
 * <code>toString().
 * <p>
 * Closing a <tt>ByteArrayOutputStream has no effect. The methods in
 * this class can be called after the stream has been closed without
 * generating an <tt>IOException.
 * <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
 * @author Holger Hoffstatte
 * @version $Id: ByteArrayOutputStream.java 1021884 2010-10-12 18:49:16Z ggregory $
 */
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 final List<byte[]> 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(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);
        }
        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(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(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;
        }
    }

    /**
     * Write a byte to byte array.
     * @param b the byte to write
     */
    @Override
    public synchronized void write(int b) {
        int inBufferPos = count - filledBufferSum;
        if (inBufferPos == currentBuffer.length) {
            needNewBuffer(count + 1);
            inBufferPos = 0;
        }
        currentBuffer[inBufferPos] = (byte) b;
        count++;
    }

    /**
     * Writes the entire contents of the specified input stream to this
     * byte stream. Bytes from the input stream are read directly into the
     * internal buffers of this streams.
     *
     * @param in the input stream to read from
     * @return total number of bytes read from the input stream
     *         (and written to this stream)
     * @throws IOException if an I/O error occurs while reading the input stream
     * @since Commons IO 1.4
     */
    public synchronized int write(InputStream in) throws IOException {
        int readCount = 0;
        int inBufferPos = count - filledBufferSum;
        int n = in.read(currentBuffer, inBufferPos, currentBuffer.length - inBufferPos);
        while (n != -1) {
            readCount += n;
            inBufferPos += n;
            count += n;
            if (inBufferPos == currentBuffer.length) {
                needNewBuffer(currentBuffer.length);
                inBufferPos = 0;
            }
            n = in.read(currentBuffer, inBufferPos, currentBuffer.length - inBufferPos);
        }
        return readCount;
    }

    /**
     * Return the current size of the byte array.
     * @return the current size of the byte array
     */
    public synchronized int size() {
        return count;
    }

    /**
     * Closing a <tt>ByteArrayOutputStream has no effect. The methods in
     * this class can be called after the stream has been closed without
     * generating an <tt>IOException.
     *
     * @throws IOException never (this method should not declare this exception
     * but it has to now due to backwards compatability)
     */
    @Override
    public void close() throws IOException {
        //nop
    }

    /**
     * @see java.io.ByteArrayOutputStream#reset()
     */
    public synchronized void reset() {
        count = 0;
        filledBufferSum = 0;
        currentBufferIndex = 0;
        currentBuffer = buffers.get(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 (byte[] buf : buffers) {
            int c = Math.min(buf.length, remaining);
            out.write(buf, 0, c);
            remaining -= c;
            if (remaining == 0) {
                break;
            }
        }
    }

    /**
     * Fetches entire contents of an <code>InputStream and represent
     * same data as result InputStream.
     * <p>
     * This method is useful where,
     * <ul>
     * <li>Source InputStream is slow.
     * <li>It has network resources associated, so we cannot keep it open for
     * long time.</li>
     * <li>It has network timeout associated.
     * </ul>
     * It can be used in favor of {@link #toByteArray()}, since it
     * avoids unnecessary allocation and copy of byte[].<br>
     * This method buffers the input internally, so there is no need to use a
     * <code>BufferedInputStream.
     * 
     * @param input Stream to be fully buffered.
     * @return A fully buffered stream.
     * @throws IOException if an I/O error occurs
     * @since Commons IO 2.0
     */
    public static InputStream toBufferedInputStream(InputStream input)
            throws IOException {
        ByteArrayOutputStream output = new ByteArrayOutputStream();
        output.write(input);
        return output.toBufferedInputStream();
    }

    /**
     * Gets the current contents of this byte stream as a Input Stream. The
     * returned stream is backed by buffers of <code>this stream,
     * avoiding memory allocation and copy, thus saving space and time.<br>
     * 
     * @return the current contents of this output stream.
     * @see java.io.ByteArrayOutputStream#toByteArray()
     * @see #reset()
     * @since Commons IO 2.0
     */
    private InputStream toBufferedInputStream() {
        int remaining = count;
        if (remaining == 0) {
            return new ClosedInputStream();
        }
        List<ByteArrayInputStream> list = new ArrayList(buffers.size());
        for (byte[] buf : buffers) {
            int c = Math.min(buf.length, remaining);
            list.add(new ByteArrayInputStream(buf, 0, c));
            remaining -= c;
            if (remaining == 0) {
                break;
            }
        }
        return new SequenceInputStream(Collections.enumeration(list));
    }

    /**
     * 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 (byte[] buf : buffers) {
            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.
     * @return the contents of the byte array as a String
     * @see java.io.ByteArrayOutputStream#toString()
     */
    @Override
    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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