/*

  * 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.nio.charset.Charset;

 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()</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 {@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.

  *

  * @version $Id: ByteArrayOutputStream.java 1471767 2013-04-24 23:24:19Z sebb $

  */

 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<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;

     /** Flag to indicate if the buffers can be reused after reset */

     private boolean reuseBuffers = true;

     /**

      * 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(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++;

     }

     /**

      * 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 1.4

      */

     public synchronized int write(final 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</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 compatibility)

      */

     @Override

     public void close() throws IOException {

         //nop

     }

     /**

      * @see java.io.ByteArrayOutputStream#reset()

      */

     public synchronized void reset() {

         count = 0;

         filledBufferSum = 0;

         currentBufferIndex = 0;

         if (reuseBuffers) {

             currentBuffer = buffers.get(currentBufferIndex);

         } else {

             //Throw away old buffers

             currentBuffer = null;

             int size = buffers.get(0).length;

             buffers.clear();

             needNewBuffer(size);

             reuseBuffers = true;

         }

     }

     /**

      * 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;

             }

         }

     }

     /**

      * Fetches entire contents of an <code>InputStream</code> and represent

      * same data as result InputStream.

      * <p>

      * This method is useful where,

      * <ul>

      * <li>Source InputStream is slow.</li>

      * <li>It has network resources associated, so we cannot keep it open for

      * long time.</li>

      * <li>It has network timeout associated.</li>

      * </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</code>.

      *

      * @param input Stream to be fully buffered.

      * @return A fully buffered stream.

      * @throws IOException if an I/O error occurs

      * @since 2.0

      */

     public static InputStream toBufferedInputStream(final InputStream input)

             throws IOException {

         // It does not matter if a ByteArrayOutputStream is not closed as close() is a no-op

         @SuppressWarnings("resource")

         final ByteArrayOutputStream output = new ByteArrayOutputStream();

         output.write(input);

         return output.toInputStream();

     }

     /**

      * Gets the current contents of this byte stream as a Input Stream. The

      * returned stream is backed by buffers of <code>this</code> 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 2.5

      */

     public synchronized InputStream toInputStream() {

         int remaining = count;

         if (remaining == 0) {

             return new ClosedInputStream();

         }

         final List<ByteArrayInputStream> list = new ArrayList<ByteArrayInputStream>(buffers.size());

         for (final byte[] buf : buffers) {

             final int c = Math.min(buf.length, remaining);

             list.add(new ByteArrayInputStream(buf, 0, c));

             remaining -= c;

             if (remaining == 0) {

                 break;

             }

         }

         reuseBuffers = false;

         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;

         }

         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;

     }

     /**

      * Gets the curent contents of this byte stream as a string

      * using the platform default charset.

      * @return the contents of the byte array as a String

      * @see java.io.ByteArrayOutputStream#toString()

      * @deprecated 2.5 use {@link #toString(String)} instead

      */

     @Override

     @Deprecated

     public String toString() {

         // make explicit the use of the default charset

         return new String(toByteArray(), Charset.defaultCharset());

     }

     /**

      * 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(final String enc) throws UnsupportedEncodingException {

         return new String(toByteArray(), enc);

     }

     /**

      * Gets the curent contents of this byte stream as a string

      * using the specified encoding.

      *

      * @param charset  the character encoding

      * @return the string converted from the byte array

      * @see java.io.ByteArrayOutputStream#toString(String)

      * @since 2.5

      */

     public String toString(final Charset charset) {

         return new String(toByteArray(), charset);

     }

 }