https://openjdk.java.net/ 
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 * reserved comment block
 * DO NOT REMOVE OR ALTER!
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/*
 * 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,
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/*
 * $Id: WriterToUTF8Buffered.java,v 1.2.4.1 2005/09/15 08:15:31 suresh_emailid Exp $
 */
package com.sun.org.apache.xml.internal.serializer;

import java.io.IOException;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.io.Writer;



This class writes unicode characters to a byte stream (java.io.OutputStream)
as quickly as possible. It buffers the output in an internal
buffer which must be flushed to the OutputStream when done. This flushing
is done via the close() flush() or flushBuffer() method.
This class is only used internally within Xalan.

@xsl.usageinternal
/**
 * This class writes unicode characters to a byte stream (java.io.OutputStream)
 * as quickly as possible. It buffers the output in an internal
 * buffer which must be flushed to the OutputStream when done. This flushing
 * is done via the close() flush() or flushBuffer() method.
 *
 * This class is only used internally within Xalan.
 *
 * @xsl.usage internal
 */
final class WriterToUTF8Buffered extends Writer implements WriterChain
{

  
number of bytes that the byte buffer can hold.
This is a fixed constant is used rather than m_outputBytes.lenght for performance.

/** number of bytes that the byte buffer can hold.
   * This is a fixed constant is used rather than m_outputBytes.lenght for performance.
   */
  private static final int BYTES_MAX=16*1024;
  
number of characters that the character buffer can hold.
This is 1/3 of the number of bytes because UTF-8 encoding
can expand one unicode character by up to 3 bytes.

/** number of characters that the character buffer can hold.
   * This is 1/3 of the number of bytes because UTF-8 encoding
   * can expand one unicode character by up to 3 bytes.
   */
  private static final int CHARS_MAX=(BYTES_MAX/3);

 // private static final int

  
The byte stream to write to. (sc & sb remove final to compile in JDK 1.1.8) 
/** The byte stream to write to. (sc & sb remove final to compile in JDK 1.1.8) */
  private final OutputStream m_os;

  
The internal buffer where data is stored.
(sc & sb remove final to compile in JDK 1.1.8)

/**
   * The internal buffer where data is stored.
   * (sc & sb remove final to compile in JDK 1.1.8)
   */
  private final byte m_outputBytes[];

  private final char m_inputChars[];

  
The number of valid bytes in the buffer. This value is always
in the range 0 through m_outputBytes.length; elements
m_outputBytes[0] through m_outputBytes[count-1] contain valid
byte data.

/**
   * The number of valid bytes in the buffer. This value is always
   * in the range <tt>0</tt> through <tt>m_outputBytes.length</tt>; elements
   * <tt>m_outputBytes[0]</tt> through <tt>m_outputBytes[count-1]</tt> contain valid
   * byte data.
   */
  private int count;

  
Create an buffered UTF-8 writer.

Params:
  • out –    the underlying output stream.
Throws:
/**
   * Create an buffered UTF-8 writer.
   *
   *
   * @param   out    the underlying output stream.
   *
   * @throws UnsupportedEncodingException
   */
  public WriterToUTF8Buffered(OutputStream out)
          throws UnsupportedEncodingException
  {
      m_os = out;
      // get 3 extra bytes to make buffer overflow checking simpler and faster
      // we won't have to keep checking for a few extra characters
      m_outputBytes = new byte[BYTES_MAX + 3];

      // Big enough to hold the input chars that will be transformed
      // into output bytes in m_ouputBytes.
      m_inputChars = new char[CHARS_MAX + 2];
      count = 0;

//      the old body of this constructor, before the buffersize was changed to a constant
//      this(out, 8*1024);
  }

  /**
   * Create an buffered UTF-8 writer to write data to the
   * specified underlying output stream with the specified buffer
   * size.
   *
   * @param   out    the underlying output stream.
   * @param   size   the buffer size.
   * @exception IllegalArgumentException if size <= 0.
   */
//  public WriterToUTF8Buffered(final OutputStream out, final int size)
//  {
//
//    m_os = out;
//
//    if (size <= 0)
//    {
//      throw new IllegalArgumentException(
//        SerializerMessages.createMessage(SerializerErrorResources.ER_BUFFER_SIZE_LESSTHAN_ZERO, null)); //"Buffer size <= 0");
//    }
//
//    m_outputBytes = new byte[size];
//    count = 0;
//  }

  
Write a single character.  The character to be written is contained in
the 16 low-order bits of the given integer value; the 16 high-order bits
are ignored.

 Subclasses that intend to support efficient single-character output
should override this method.

Params:
  • c –  int specifying a character to be written.
Throws:
/**
   * Write a single character.  The character to be written is contained in
   * the 16 low-order bits of the given integer value; the 16 high-order bits
   * are ignored.
   *
   * <p> Subclasses that intend to support efficient single-character output
   * should override this method.
   *
   * @param c  int specifying a character to be written.
   * @exception  IOException  If an I/O error occurs
   */
  public void write(final int c) throws IOException
  {

    /* If we are close to the end of the buffer then flush it.
     * Remember the buffer can hold a few more bytes than BYTES_MAX
     */
    if (count >= BYTES_MAX)
        flushBuffer();

    if (c < 0x80)
    {
       m_outputBytes[count++] = (byte) (c);
    }
    else if (c < 0x800)
    {
      m_outputBytes[count++] = (byte) (0xc0 + (c >> 6));
      m_outputBytes[count++] = (byte) (0x80 + (c & 0x3f));
    }
    else if (c < 0x10000)
    {
      m_outputBytes[count++] = (byte) (0xe0 + (c >> 12));
      m_outputBytes[count++] = (byte) (0x80 + ((c >> 6) & 0x3f));
      m_outputBytes[count++] = (byte) (0x80 + (c & 0x3f));
    }
        else
        {
          m_outputBytes[count++] = (byte) (0xf0 + (c >> 18));
          m_outputBytes[count++] = (byte) (0x80 + ((c >> 12) & 0x3f));
          m_outputBytes[count++] = (byte) (0x80 + ((c >> 6) & 0x3f));
          m_outputBytes[count++] = (byte) (0x80 + (c & 0x3f));
        }

  }


  
Write a portion of an array of characters.

Params:
  • chars –  Array of characters
  • start –   Offset from which to start writing characters
  • length –   Number of characters to write
Throws:
/**
   * Write a portion of an array of characters.
   *
   * @param  chars  Array of characters
   * @param  start   Offset from which to start writing characters
   * @param  length   Number of characters to write
   *
   * @exception  IOException  If an I/O error occurs
   *
   * @throws java.io.IOException
   */
  public void write(final char chars[], final int start, final int length)
          throws java.io.IOException
  {

    // We multiply the length by three since this is the maximum length
    // of the characters that we can put into the buffer.  It is possible
    // for each Unicode character to expand to three bytes.

    int lengthx3 = 3*length;

    if (lengthx3 >= BYTES_MAX - count)
    {
      // The requested length is greater than the unused part of the buffer
      flushBuffer();

      if (lengthx3 > BYTES_MAX)
      {
        /*
         * The requested length exceeds the size of the buffer.
         * Cut the buffer up into chunks, each of which will
         * not cause an overflow to the output buffer m_outputBytes,
         * and make multiple recursive calls.
         * Be careful about integer overflows in multiplication.
         */
        int split = length/CHARS_MAX;
        final int chunks;
        if (length % CHARS_MAX > 0)
            chunks = split + 1;
        else
            chunks = split;
        int end_chunk = start;
        for (int chunk = 1; chunk <= chunks; chunk++)
        {
            int start_chunk = end_chunk;
            end_chunk = start + (int) ((((long) length) * chunk) / chunks);

            // Adjust the end of the chunk if it ends on a high char
            // of a Unicode surrogate pair and low char of the pair
            // is not going to be in the same chunk
            final char c = chars[end_chunk - 1];
            int ic = chars[end_chunk - 1];
            if (c >= 0xD800 && c <= 0xDBFF) {
                // The last Java char that we were going
                // to process is the first of a
                // Java surrogate char pair that
                // represent a Unicode character.

                if (end_chunk < start + length) {
                    // Avoid spanning by including the low
                    // char in the current chunk of chars.
                    end_chunk++;
                } else {
                    /* This is the last char of the last chunk,
                     * and it is the high char of a high/low pair with
                     * no low char provided.
                     * TODO: error message needed.
                     * The char array incorrectly ends in a high char
                     * of a high/low surrogate pair, but there is
                     * no corresponding low as the high is the last char
                     */
                    end_chunk--;
                }
            }


            int len_chunk = (end_chunk - start_chunk);
            this.write(chars,start_chunk, len_chunk);
        }
        return;
      }
    }



    final int n = length+start;
    final byte[] buf_loc = m_outputBytes; // local reference for faster access
    int count_loc = count;      // local integer for faster access
    int i = start;
    {
        /* This block could be omitted and the code would produce
         * the same result. But this block exists to give the JIT
         * a better chance of optimizing a tight and common loop which
         * occurs when writing out ASCII characters.
         */
        char c;
        for(; i < n && (c = chars[i])< 0x80 ; i++ )
            buf_loc[count_loc++] = (byte)c;
    }
    for (; i < n; i++)
    {

      final char c = chars[i];

      if (c < 0x80)
        buf_loc[count_loc++] = (byte) (c);
      else if (c < 0x800)
      {
        buf_loc[count_loc++] = (byte) (0xc0 + (c >> 6));
        buf_loc[count_loc++] = (byte) (0x80 + (c & 0x3f));
      }
      /**
        * The following else if condition is added to support XML 1.1 Characters for
        * UTF-8:   [1111 0uuu] [10uu zzzz] [10yy yyyy] [10xx xxxx]*
        * Unicode: [1101 10ww] [wwzz zzyy] (high surrogate)
        *          [1101 11yy] [yyxx xxxx] (low surrogate)
        *          * uuuuu = wwww + 1
        */
      else if (c >= 0xD800 && c <= 0xDBFF)
      {
          char high, low;
          high = c;
          i++;
          low = chars[i];

          buf_loc[count_loc++] = (byte) (0xF0 | (((high + 0x40) >> 8) & 0xf0));
          buf_loc[count_loc++] = (byte) (0x80 | (((high + 0x40) >> 2) & 0x3f));
          buf_loc[count_loc++] = (byte) (0x80 | ((low >> 6) & 0x0f) + ((high << 4) & 0x30));
          buf_loc[count_loc++] = (byte) (0x80 | (low & 0x3f));
      }
      else
      {
        buf_loc[count_loc++] = (byte) (0xe0 + (c >> 12));
        buf_loc[count_loc++] = (byte) (0x80 + ((c >> 6) & 0x3f));
        buf_loc[count_loc++] = (byte) (0x80 + (c & 0x3f));
      }
    }
    // Store the local integer back into the instance variable
    count = count_loc;

  }

  
Write a string.

Params:
  • s –  String to be written
Throws:
/**
   * Write a string.
   *
   * @param  s  String to be written
   *
   * @exception  IOException  If an I/O error occurs
   */
  public void write(final String s) throws IOException
  {

    // We multiply the length by three since this is the maximum length
    // of the characters that we can put into the buffer.  It is possible
    // for each Unicode character to expand to three bytes.
    final int length = s.length();
    int lengthx3 = 3*length;

    if (lengthx3 >= BYTES_MAX - count)
    {
      // The requested length is greater than the unused part of the buffer
      flushBuffer();

      if (lengthx3 > BYTES_MAX)
      {
        /*
         * The requested length exceeds the size of the buffer,
         * so break it up in chunks that don't exceed the buffer size.
         */
         final int start = 0;
         int split = length/CHARS_MAX;
         final int chunks;
         if (length % CHARS_MAX > 0)
             chunks = split + 1;
         else
             chunks = split;
         int end_chunk = 0;
         for (int chunk = 1; chunk <= chunks; chunk++)
         {
             int start_chunk = end_chunk;
             end_chunk = start + (int) ((((long) length) * chunk) / chunks);
             s.getChars(start_chunk,end_chunk, m_inputChars,0);
             int len_chunk = (end_chunk - start_chunk);

             // Adjust the end of the chunk if it ends on a high char
             // of a Unicode surrogate pair and low char of the pair
             // is not going to be in the same chunk
             final char c = m_inputChars[len_chunk - 1];
             if (c >= 0xD800 && c <= 0xDBFF) {
                 // Exclude char in this chunk,
                 // to avoid spanning a Unicode character
                 // that is in two Java chars as a high/low surrogate
                 end_chunk--;
                 len_chunk--;
                 if (chunk == chunks) {
                     /* TODO: error message needed.
                      * The String incorrectly ends in a high char
                      * of a high/low surrogate pair, but there is
                      * no corresponding low as the high is the last char
                      * Recover by ignoring this last char.
                      */
                 }
             }

             this.write(m_inputChars,0, len_chunk);
         }
         return;
      }
    }


    s.getChars(0, length , m_inputChars, 0);
    final char[] chars = m_inputChars;
    final int n = length;
    final byte[] buf_loc = m_outputBytes; // local reference for faster access
    int count_loc = count;      // local integer for faster access
    int i = 0;
    {
        /* This block could be omitted and the code would produce
         * the same result. But this block exists to give the JIT
         * a better chance of optimizing a tight and common loop which
         * occurs when writing out ASCII characters.
         */
        char c;
        for(; i < n && (c = chars[i])< 0x80 ; i++ )
            buf_loc[count_loc++] = (byte)c;
    }
    for (; i < n; i++)
    {

      final char c = chars[i];

      if (c < 0x80)
        buf_loc[count_loc++] = (byte) (c);
      else if (c < 0x800)
      {
        buf_loc[count_loc++] = (byte) (0xc0 + (c >> 6));
        buf_loc[count_loc++] = (byte) (0x80 + (c & 0x3f));
      }
    /**
      * The following else if condition is added to support XML 1.1 Characters for
      * UTF-8:   [1111 0uuu] [10uu zzzz] [10yy yyyy] [10xx xxxx]*
      * Unicode: [1101 10ww] [wwzz zzyy] (high surrogate)
      *          [1101 11yy] [yyxx xxxx] (low surrogate)
      *          * uuuuu = wwww + 1
      */
    else if (c >= 0xD800 && c <= 0xDBFF)
    {
        char high, low;
        high = c;
        i++;
        low = chars[i];

        buf_loc[count_loc++] = (byte) (0xF0 | (((high + 0x40) >> 8) & 0xf0));
        buf_loc[count_loc++] = (byte) (0x80 | (((high + 0x40) >> 2) & 0x3f));
        buf_loc[count_loc++] = (byte) (0x80 | ((low >> 6) & 0x0f) + ((high << 4) & 0x30));
        buf_loc[count_loc++] = (byte) (0x80 | (low & 0x3f));
    }
      else
      {
        buf_loc[count_loc++] = (byte) (0xe0 + (c >> 12));
        buf_loc[count_loc++] = (byte) (0x80 + ((c >> 6) & 0x3f));
        buf_loc[count_loc++] = (byte) (0x80 + (c & 0x3f));
      }
    }
    // Store the local integer back into the instance variable
    count = count_loc;

  }

  
Flush the internal buffer

Throws:
  • IOException – 
/**
   * Flush the internal buffer
   *
   * @throws IOException
   */
  public void flushBuffer() throws IOException
  {

    if (count > 0)
    {
      m_os.write(m_outputBytes, 0, count);

      count = 0;
    }
  }

  
Flush the stream.  If the stream has saved any characters from the
various write() methods in a buffer, write them immediately to their
intended destination.  Then, if that destination is another character or
byte stream, flush it.  Thus one flush() invocation will flush all the
buffers in a chain of Writers and OutputStreams.

Throws:
/**
   * Flush the stream.  If the stream has saved any characters from the
   * various write() methods in a buffer, write them immediately to their
   * intended destination.  Then, if that destination is another character or
   * byte stream, flush it.  Thus one flush() invocation will flush all the
   * buffers in a chain of Writers and OutputStreams.
   *
   * @exception  IOException  If an I/O error occurs
   *
   * @throws java.io.IOException
   */
  public void flush() throws java.io.IOException
  {
    flushBuffer();
    m_os.flush();
  }

  
Close the stream, flushing it first.  Once a stream has been closed,
further write() or flush() invocations will cause an IOException to be
thrown.  Closing a previously-closed stream, however, has no effect.

Throws:
/**
   * Close the stream, flushing it first.  Once a stream has been closed,
   * further write() or flush() invocations will cause an IOException to be
   * thrown.  Closing a previously-closed stream, however, has no effect.
   *
   * @exception  IOException  If an I/O error occurs
   *
   * @throws java.io.IOException
   */
  public void close() throws java.io.IOException
  {
    flushBuffer();
    m_os.close();
  }

  
Get the output stream where the events will be serialized to.

Returns:reference to the result stream, or null of only a writer was
set.
/**
   * Get the output stream where the events will be serialized to.
   *
   * @return reference to the result stream, or null of only a writer was
   * set.
   */
  public OutputStream getOutputStream()
  {
    return m_os;
  }

  public Writer getWriter()
  {
    // Only one of getWriter() or getOutputStream() can return null
    // This type of writer wraps an OutputStream, not a Writer.
    return null;
  }
}