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/*
 * Licensed to Elastic Search and Shay Banon under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. Elastic Search 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.elasticsearch.common.io;

import org.elasticsearch.common.thread.ThreadLocals;

import java.io.IOException;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.util.Arrays;

/**
 * Similar to {@link java.io.ByteArrayOutputStream} just not synced.
 *
 * @author kimchy (Shay Banon)
 */
public class FastByteArrayOutputStream extends OutputStream {

    /**
     * A thread local based cache of {@link FastByteArrayOutputStream}.
     */
    public static class Cached {

        private static final ThreadLocal> cache = new ThreadLocal>() {
            @Override protected ThreadLocals.CleanableValue initialValue() {
                return new ThreadLocals.CleanableValue(new FastByteArrayOutputStream());
            }
        };

        /**
         * Returns the cached thread local byte stream, with its internal stream cleared.
         */
        public static FastByteArrayOutputStream cached() {
            FastByteArrayOutputStream os = cache.get().get();
            os.reset();
            return os;
        }
    }

    /**
     * The buffer where data is stored.
     */
    protected byte buf[];

    /**
     * The number of valid bytes in the buffer.
     */
    protected int count;

    /**
     * Creates a new byte array output stream. The buffer capacity is
     * initially 32 bytes, though its size increases if necessary.
     */
    public FastByteArrayOutputStream() {
        this(32);
    }

    /**
     * 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 FastByteArrayOutputStream(int size) {
        if (size < 0) {
            throw new IllegalArgumentException("Negative initial size: "
                    + size);
        }
        buf = new byte[size];
    }

    /**
     * Writes the specified byte to this byte array output stream.
     *
     * @param b the byte to be written.
     */
    public void write(int b) {
        int newcount = count + 1;
        if (newcount > buf.length) {
            buf = Arrays.copyOf(buf, Math.max(buf.length << 1, newcount));
        }
        buf[count] = (byte) b;
        count = newcount;
    }

    /**
     * Writes len bytes from the specified byte array
     * starting at offset off to this byte array output stream.
     *
     * NO checks for bounds, parameters must be ok!
     *
     * @param b   the data.
     * @param off the start offset in the data.
     * @param len the number of bytes to write.
     */
    public void write(byte b[], int off, int len) {
        if (len == 0) {
            return;
        }
        int newcount = count + len;
        if (newcount > buf.length) {
            buf = Arrays.copyOf(buf, Math.max(buf.length << 1, newcount));
        }
        System.arraycopy(b, off, buf, count, len);
        count = newcount;
    }

    /**
     * Writes the complete contents of this byte array output stream to
     * the specified output stream argument, as if by calling the output
     * stream's write method using out.write(buf, 0, count).
     *
     * @param out the output stream to which to write the data.
     * @throws IOException if an I/O error occurs.
     */
    public void writeTo(OutputStream out) throws IOException {
        out.write(buf, 0, count);
    }

    /**
     * Resets the count field of this byte array output
     * stream to zero, so that all currently accumulated output in the
     * output stream is discarded. The output stream can be used again,
     * reusing the already allocated buffer space.
     *
     * @see java.io.ByteArrayInputStream#count
     */
    public void reset() {
        count = 0;
    }

    /**
     * Creates a newly allocated byte array. Its size is the current
     * size of this output stream and the valid contents of the buffer
     * have been copied into it.
     *
     * @return the current contents of this output stream, as a byte array.
     * @see java.io.ByteArrayOutputStream#size()
     */
    public byte copiedByteArray()[] {
        return Arrays.copyOf(buf, count);
    }

    /**
     * Returns the underlying byte array. Note, use {@link #size()} in order to know
     * the length of it.
     */
    public byte[] unsafeByteArray() {
        return buf;
    }

    /**
     * Returns the current size of the buffer.
     *
     * @return the value of the count field, which is the number
     *         of valid bytes in this output stream.
     * @see java.io.ByteArrayOutputStream#count
     */
    public int size() {
        return count;
    }

    /**
     * Seeks back to the given position. Size will become the seeked location.
     */
    public void seek(int position) {
        this.count = position;
    }

    /**
     * Converts the buffer's contents into a string decoding bytes using the
     * platform's default character set. The length of the new String
     * is a function of the character set, and hence may not be equal to the
     * size of the buffer.
     * 
     * 
 This method always replaces malformed-input and unmappable-character
     * sequences with the default replacement string for the platform's
     * default character set. The {@linkplain java.nio.charset.CharsetDecoder}
     * class should be used when more control over the decoding process is
     * required.
     *
     * @return String decoded from the buffer's contents.
     * @since JDK1.1
     */
    public String toString() {
        return new String(buf, 0, count);
    }

    /**
     * Converts the buffer's contents into a string by decoding the bytes using
     * the specified {@link java.nio.charset.Charset charsetName}. The length of
     * the new String is a function of the charset, and hence may not be
     * equal to the length of the byte array.
     * 

     *  This method always replaces malformed-input and unmappable-character
     * sequences with this charset's default replacement string. The {@link
     * java.nio.charset.CharsetDecoder} class should be used when more control
     * over the decoding process is required.
     *
     * @param charsetName the name of a supported
     *                    {@linkplain java.nio.charset.Charset charset}
     * @return String decoded from the buffer's contents.
     * @throws java.io.UnsupportedEncodingException
     *          If the named charset is not supported
     * @since JDK1.1
     */
    public String toString(String charsetName)
            throws UnsupportedEncodingException {
        return new String(buf, 0, count, charsetName);
    }

    /**
     * Closing a ByteArrayOutputStream has no effect. The methods in
     * this class can be called after the stream has been closed without
     * generating an IOException.
     * 

     */
    public void close() throws IOException {
    }
}