Circular Char Buffer : Buffering « File Input Output « Java






Circular Char Buffer

    

/*
 * Circular Character Buffer
 * Copyright (C) 2002 Stephen Ostermiller
 * http://ostermiller.org/contact.pl?regarding=Java+Utilities
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * See COPYING.TXT for details.
 */

import java.io.*;

/**
 * Implements the Circular Buffer producer/consumer model for characters.
 * More information about this class is available from <a target="_top" href=
 * "http://ostermiller.org/utils/CircularCharBuffer.html">ostermiller.org</a>.
 * <p>
 * Using this class is a simpler alternative to using a PipedReader
 * and a PipedWriter. PipedReaders and PipedWriters don't support the
 * mark operation, don't allow you to control buffer sizes that they use,
 * and have a more complicated API that requires instantiating two
 * classes and connecting them.
 * <p>
 * This class is thread safe.
 *
 * @see CircularByteBuffer
 * @see CircularObjectBuffer
 *
 * @author Stephen Ostermiller http://ostermiller.org/contact.pl?regarding=Java+Utilities
 * @since ostermillerutils 1.00.00
 */
public class CircularCharBuffer {

  /**
   * The default size for a circular character buffer.
   *
   * @since ostermillerutils 1.00.00
   */
  private final static int DEFAULT_SIZE = 1024;

  /**
   * A buffer that will grow as things are added.
   *
   * @since ostermillerutils 1.00.00
   */
  public final static int INFINITE_SIZE = -1;

  /**
   * The circular buffer.
   * <p>
   * The actual capacity of the buffer is one less than the actual length
   * of the buffer so that an empty and a full buffer can be
   * distinguished.  An empty buffer will have the markPostion and the
   * writePosition equal to each other.  A full buffer will have
   * the writePosition one less than the markPostion.
   * <p>
   * There are three important indexes into the buffer:
   * The readPosition, the writePosition, and the markPosition.
   * If the Reader has never been marked, the readPosition and
   * the markPosition should always be the same.  The characters
   * available to be read go from the readPosition to the writePosition,
   * wrapping around the end of the buffer.  The space available for writing
   * goes from the write position to one less than the markPosition,
   * wrapping around the end of the buffer.  The characters that have
   * been saved to support a reset() of the Reader go from markPosition
   * to readPosition, wrapping around the end of the buffer.
   *
   * @since ostermillerutils 1.00.00
   */
  protected char[] buffer;
  /**
   * Index of the first character available to be read.
   *
   * @since ostermillerutils 1.00.00
   */
  protected volatile int readPosition = 0;
  /**
   * Index of the first character available to be written.
   *
   * @since ostermillerutils 1.00.00
   */
  protected volatile int writePosition = 0;
  /**
   * Index of the first saved character. (To support stream marking.)
   *
   * @since ostermillerutils 1.00.00
   */
  protected volatile int markPosition = 0;
  /**
   * Number of characters that have to be saved
   * to support mark() and reset() on the Reader.
   *
   * @since ostermillerutils 1.00.00
   */
  protected volatile int markSize = 0;
  /**
   * If this buffer is infinite (should resize itself when full)
   *
   * @since ostermillerutils 1.00.00
   */
  protected volatile boolean infinite = false;
  /**
   * True if a write to a full buffer should block until the buffer
   * has room, false if the write method should throw an IOException
   *
   * @since ostermillerutils 1.00.00
   */
  protected boolean blockingWrite = true;
  /**
   * The Reader that can empty this buffer.
   *
   * @since ostermillerutils 1.00.00
   */
  protected Reader reader = new CircularCharBufferReader();
  /**
   * true if the close() method has been called on the Reader
   *
   * @since ostermillerutils 1.00.00
   */
  protected boolean readerClosed = false;
  /**
   * The Writer that can fill this buffer.
   *
   * @since ostermillerutils 1.00.00
   */
  protected Writer writer = new CircularCharBufferWriter();
  /**
   * true if the close() method has been called on the writer
   *
   * @since ostermillerutils 1.00.00
   */
  protected boolean writerClosed = false;

  /**
   * Make this buffer ready for reuse.  The contents of the buffer
   * will be cleared and the streams associated with this buffer
   * will be reopened if they had been closed.
   *
   * @since ostermillerutils 1.00.00
   */
  public void clear(){
    synchronized (this){
      readPosition = 0;
      writePosition = 0;
      markPosition = 0;
      readerClosed = false;
      writerClosed = false;
    }
  }

  /**
   * Retrieve a Writer that can be used to fill
   * this buffer.
   * <p>
   * Write methods may throw a BufferOverflowException if
   * the buffer is not large enough.  A large enough buffer
   * size must be chosen so that this does not happen or
   * the caller must be prepared to catch the exception and
   * try again once part of the buffer has been consumed.
   *
   *
   * @return the producer for this buffer.
   *
   * @since ostermillerutils 1.00.00
   */
  public Writer getWriter(){
    return writer;
  }

  /**
   * Retrieve a Reader that can be used to empty
   * this buffer.
   * <p>
   * This Reader supports marks at the expense
   * of the buffer size.
   *
   * @return the consumer for this buffer.
   *
   * @since ostermillerutils 1.00.00
   */
  public Reader getReader(){
    return reader;
  }

  /**
   * Get number of characters that are available to be read.
   * <p>
   * Note that the number of characters available plus
   * the number of characters free may not add up to the
   * capacity of this buffer, as the buffer may reserve some
   * space for other purposes.
   *
   * @return the size in characters of this buffer
   *
   * @since ostermillerutils 1.00.00
   */
  public int getAvailable(){
    synchronized (this){
      return available();
    }
  }

  /**
   * Get the number of characters this buffer has free for
   * writing.
   * <p>
   * Note that the number of characters available plus
   * the number of characters free may not add up to the
   * capacity of this buffer, as the buffer may reserve some
   * space for other purposes.
   *
   * @return the available space in characters of this buffer
   *
   * @since ostermillerutils 1.00.00
   */
  public int getSpaceLeft(){
    synchronized (this){
      return spaceLeft();
    }
  }

  /**
   * Get the capacity of this buffer.
   * <p>
   * Note that the number of characters available plus
   * the number of characters free may not add up to the
   * capacity of this buffer, as the buffer may reserve some
   * space for other purposes.
   *
   * @return the size in characters of this buffer
   *
   * @since ostermillerutils 1.00.00
   */
  public int getSize(){
    synchronized (this){
      return buffer.length;
    }
  }

  /**
   * double the size of the buffer
   *
   * @since ostermillerutils 1.00.00
   */
  private void resize(){
    char[] newBuffer = new char[buffer.length * 2];
    int marked = marked();
    int available = available();
    if (markPosition <= writePosition){
      // any space between the mark and
      // the first write needs to be saved.
      // In this case it is all in one piece.
      int length = writePosition - markPosition;
      System.arraycopy(buffer, markPosition, newBuffer, 0, length);
    } else {
      int length1 = buffer.length - markPosition;
      System.arraycopy(buffer, markPosition, newBuffer, 0, length1);
      int length2 = writePosition;
      System.arraycopy(buffer, 0, newBuffer, length1, length2);
    }
    buffer = newBuffer;
    markPosition = 0;
    readPosition = marked;
    writePosition = marked + available;
  }

  /**
   * Space available in the buffer which can be written.
   *
   * @since ostermillerutils 1.00.00
   */
  private int spaceLeft(){
    if (writePosition < markPosition){
      // any space between the first write and
      // the mark except one character is available.
      // In this case it is all in one piece.
      return (markPosition - writePosition - 1);
    }
    // space at the beginning and end.
    return ((buffer.length - 1) - (writePosition - markPosition));
  }

  /**
   * Characters available for reading.
   *
   * @since ostermillerutils 1.00.00
   */
  private int available(){
    if (readPosition <= writePosition){
      // any space between the first read and
      // the first write is available.  In this case i
      // is all in one piece.
      return (writePosition - readPosition);
    }
    // space at the beginning and end.
    return (buffer.length - (readPosition - writePosition));
  }

  /**
   * Characters saved for supporting marks.
   *
   * @since ostermillerutils 1.00.00
   */
  private int marked(){
    if (markPosition <= readPosition){
      // any space between the markPosition and
      // the first write is marked.  In this case i
      // is all in one piece.
      return (readPosition - markPosition);
    }
    // space at the beginning and end.
    return (buffer.length - (markPosition - readPosition));
  }

  /**
   * If we have passed the markSize reset the
   * mark so that the space can be used.
   *
   * @since ostermillerutils 1.00.00
   */
  private void ensureMark(){
    if (marked() >= markSize){
      markPosition = readPosition;
      markSize = 0;
    }
  }

  /**
   * Create a new buffer with a default capacity.
   * Writing to a full buffer will block until space
   * is available rather than throw an exception.
   *
   * @since ostermillerutils 1.00.00
   */
  public CircularCharBuffer(){
    this (DEFAULT_SIZE, true);
  }

  /**
   * Create a new buffer with given capacity.
   * Writing to a full buffer will block until space
   * is available rather than throw an exception.
   * <p>
   * Note that the buffer may reserve some characters for
   * special purposes and capacity number of characters may
   * not be able to be written to the buffer.
   * <p>
   * Note that if the buffer is of INFINITE_SIZE it will
   * neither block or throw exceptions, but rather grow
   * without bound.
   *
   * @param size desired capacity of the buffer in characters or CircularCharBuffer.INFINITE_SIZE
   *
   * @since ostermillerutils 1.00.00
   */
  public CircularCharBuffer(int size){
    this (size, true);
  }

  /**
   * Create a new buffer with a default capacity and
   * given blocking behavior.
   *
   * @param blockingWrite true writing to a full buffer should block
   *        until space is available, false if an exception should
   *        be thrown instead.
   *
   * @since ostermillerutils 1.00.00
   */
  public CircularCharBuffer(boolean blockingWrite){
    this (DEFAULT_SIZE, blockingWrite);
  }

  /**
   * Create a new buffer with the given capacity and
   * blocking behavior.
   * <p>
   * Note that the buffer may reserve some characters for
   * special purposes and capacity number of characters may
   * not be able to be written to the buffer.
   * <p>
   * Note that if the buffer is of CircularCharBuffer.INFINITE_SIZE it will
   * neither block or throw exceptions, but rather grow
   * without bound.
   *
   * @param size desired capacity of the buffer in characters or CircularCharBuffer.INFINITE_SIZE
   * @param blockingWrite true writing to a full buffer should block
   *        until space is available, false if an exception should
   *        be thrown instead.
   *
   * @since ostermillerutils 1.00.00
   */
  public CircularCharBuffer(int size, boolean blockingWrite){
    if (size == INFINITE_SIZE){
      buffer = new char[DEFAULT_SIZE];
      infinite = true;
    } else {
      buffer = new char[size];
      infinite = false;
    }
    this.blockingWrite = blockingWrite;
  }

  /**
   * Class for reading from a circular character buffer.
   *
   * @since ostermillerutils 1.00.00
   */
  protected class CircularCharBufferReader extends Reader {

    /**
     * Close the stream. Once a stream has been closed, further read(), ready(),
     * mark(), or reset() invocations will throw an IOException. Closing a
     * previously-closed stream, however, has no effect.
     *
     * @throws IOException never.
     *
     * @since ostermillerutils 1.00.00
     */
    @Override public void close() throws IOException {
      synchronized (CircularCharBuffer.this){
        readerClosed = true;
      }
    }

    /**
     * Mark the present position in the stream. Subsequent calls to reset() will
     * attempt to reposition the stream to this point.
     * <p>
     * The readAheadLimit must be less than the size of circular buffer.
     *
     * @param readAheadLimit Limit on the number of characters that may be read while
     *    still preserving the mark. After reading this many characters, attempting to
     *    reset the stream will fail.
     * @throws IOException if the stream is closed, or the buffer size is greater
     * than or equal to the readAheadLimit.
     *
     * @since ostermillerutils 1.00.00
     */
    @Override public void mark(int readAheadLimit) throws IOException {
      synchronized (CircularCharBuffer.this){
        if (readerClosed) throw new IOException("Reader has been closed; cannot mark a closed Reader.");
        if (buffer.length - 1 <= readAheadLimit) throw new IOException("Cannot mark stream, readAheadLimit bigger than buffer size.");
        markSize = readAheadLimit;
        markPosition = readPosition;
      }
    }

    /**
     * Tell whether this stream supports the mark() operation.
     *
     * @return true, mark is supported.
     *
     * @since ostermillerutils 1.00.00
     */
    @Override public boolean markSupported() {
      return true;
    }

    /**
     * Read a single character.
     * This method will block until a character is available, an I/O error occurs,
     * or the end of the stream is reached.
     *
     * @return The character read, as an integer in the range 0 to 65535 (0x00-0xffff),
     *     or -1 if the end of the stream has been reached
     * @throws IOException if the stream is closed.
     *
     * @since ostermillerutils 1.00.00
     */
    @Override public int read() throws IOException {
      while (true){
        synchronized (CircularCharBuffer.this){
          if (readerClosed) throw new IOException("Reader has been closed; cannot read from a closed Reader.");
          int available = available();
          if (available > 0){
            int result = buffer[readPosition] & 0xffff;
            readPosition++;
            if (readPosition == buffer.length){
              readPosition = 0;
            }
            ensureMark();
            return result;
          } else if (writerClosed){
            return -1;
          }
        }
        try {
          Thread.sleep(100);
        } catch(Exception x){
          throw new IOException("Blocking read operation interrupted.");
        }
      }
    }

    /**
     * Read characters into an array.
     * This method will block until some input is available,
     * an I/O error occurs, or the end of the stream is reached.
     *
     * @param cbuf Destination buffer.
     * @return The number of characters read, or -1 if the end of
     *   the stream has been reached
     * @throws IOException if the stream is closed.
     *
     * @since ostermillerutils 1.00.00
     */
    @Override public int read(char[] cbuf) throws IOException {
      return read(cbuf, 0, cbuf.length);
    }

    /**
     * Read characters into a portion of an array.
     * This method will block until some input is available,
     * an I/O error occurs, or the end of the stream is reached.
     *
     * @param cbuf Destination buffer.
     * @param off Offset at which to start storing characters.
     * @param len Maximum number of characters to read.
     * @return The number of characters read, or -1 if the end of
     *   the stream has been reached
     * @throws IOException if the stream is closed.
     *
     * @since ostermillerutils 1.00.00
     */
    @Override public int read(char[] cbuf, int off, int len) throws IOException {
      while (true){
        synchronized (CircularCharBuffer.this){
          if (readerClosed) throw new IOException("Reader has been closed; cannot read from a closed Reader.");
          int available = available();
          if (available > 0){
            int length = Math.min(len, available);
            int firstLen = Math.min(length, buffer.length - readPosition);
            int secondLen = length - firstLen;
            System.arraycopy(buffer, readPosition, cbuf, off, firstLen);
            if (secondLen > 0){
              System.arraycopy(buffer, 0, cbuf, off+firstLen,  secondLen);
              readPosition = secondLen;
            } else {
              readPosition += length;
            }
            if (readPosition == buffer.length) {
              readPosition = 0;
            }
            ensureMark();
            return length;
          } else if (writerClosed){
            return -1;
          }
        }
        try {
          Thread.sleep(100);
        } catch(Exception x){
          throw new IOException("Blocking read operation interrupted.");
        }
      }
    }

    /**
     * Tell whether this stream is ready to be read.
     *
     * @return True if the next read() is guaranteed not to block for input,
     *    false otherwise. Note that returning false does not guarantee that
     *    the next read will block.
     * @throws IOException if the stream is closed.
     *
     * @since ostermillerutils 1.00.00
     */
    @Override public boolean ready() throws IOException {
      synchronized (CircularCharBuffer.this){
        if (readerClosed) throw new IOException("Reader has been closed, it is not ready.");
        return (available() > 0);
      }
    }

    /**
     * Reset the stream.
     * If the stream has been marked, then attempt to reposition i
     * at the mark. If the stream has not been marked, or more characters
     * than the readAheadLimit have been read, this method has no effect.
     *
     * @throws IOException if the stream is closed.
     *
     * @since ostermillerutils 1.00.00
     */
    @Override public void reset() throws IOException {
      synchronized (CircularCharBuffer.this){
        if (readerClosed) throw new IOException("Reader has been closed; cannot reset a closed Reader.");
        readPosition = markPosition;
      }
    }

    /**
     * Skip characters.
     * This method will block until some characters are available,
     * an I/O error occurs, or the end of the stream is reached.
     *
     * @param n The number of characters to skip
     * @return The number of characters actually skipped
     * @throws IllegalArgumentException if n is negative.
     * @throws IOException if the stream is closed.
     *
     * @since ostermillerutils 1.00.00
     */
    @Override public long skip(long n) throws IOException, IllegalArgumentException {
      while (true){
        synchronized (CircularCharBuffer.this){
          if (readerClosed) throw new IOException("Reader has been closed; cannot skip characters on a closed Reader.");
          int available = available();
          if (available > 0){
            int length = Math.min((int)n, available);
            int firstLen = Math.min(length, buffer.length - readPosition);
            int secondLen = length - firstLen;
            if (secondLen > 0){
              readPosition = secondLen;
            } else {
              readPosition += length;
            }
            if (readPosition == buffer.length) {
              readPosition = 0;
            }
            ensureMark();
            return length;
          } else if (writerClosed){
            return 0;
          }
        }
        try {
          Thread.sleep(100);
        } catch(Exception x){
          throw new IOException("Blocking read operation interrupted.");
        }
      }
    }
  }

  /**
   * Class for writing to a circular character buffer.
   * If the buffer is full, the writes will either block
   * until there is some space available or throw an IOException
   * based on the CircularCharBuffer's preference.
   *
   * @since ostermillerutils 1.00.00
   */
  protected class CircularCharBufferWriter extends Writer {

    /**
     * Close the stream, flushing it first.
     * This will cause the reader associated with this circular buffer
     * to read its last characters once it empties the buffer.
     * 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 IOException never.
     *
     * @since ostermillerutils 1.00.00
     */
    @Override public void close() throws IOException {
      synchronized (CircularCharBuffer.this){
        if (!writerClosed){
          flush();
        }
        writerClosed = true;
      }
    }

    /**
     * Flush the stream.
     *
     * @throws IOException if the stream is closed.
     *
     * @since ostermillerutils 1.00.00
     */
    @Override public void flush() throws IOException {
      if (writerClosed) throw new IOException("Writer has been closed; cannot flush a closed Writer.");
      if (readerClosed) throw new IOException("Buffer closed by Reader; cannot flush.");
      // this method needs to do nothing
    }

    /**
     * Write an array of characters.
     * If the buffer allows blocking writes, this method will block until
     * all the data has been written rather than throw an IOException.
     *
     * @param cbuf Array of characters to be written
     * @throws BufferOverflowException if buffer does not allow blocking writes
     *   and the buffer is full.  If the exception is thrown, no data
     *   will have been written since the buffer was set to be non-blocking.
     * @throws IOException if the stream is closed, or the write is interrupted.
     *
     * @since ostermillerutils 1.00.00
     */
    @Override public void write(char[] cbuf) throws IOException {
      write(cbuf, 0, cbuf.length);
    }

    /**
     * Write a portion of an array of characters.
     * If the buffer allows blocking writes, this method will block until
     * all the data has been written rather than throw an IOException.
     *
     * @param cbuf Array of characters
     * @param off Offset from which to start writing characters
     * @param len - Number of characters to write
     * @throws BufferOverflowException if buffer does not allow blocking writes
     *   and the buffer is full.  If the exception is thrown, no data
     *   will have been written since the buffer was set to be non-blocking.
     * @throws IOException if the stream is closed, or the write is interrupted.
     *
     * @since ostermillerutils 1.00.00
     */
    @Override public void write(char[] cbuf, int off, int len) throws IOException {
      while (len > 0){
        synchronized (CircularCharBuffer.this){
          if (writerClosed) throw new IOException("Writer has been closed; cannot write to a closed Writer.");
          if (readerClosed) throw new IOException("Buffer closed by Reader; cannot write to a closed buffer.");
          int spaceLeft = spaceLeft();
          while (infinite && spaceLeft < len){
            resize();
            spaceLeft = spaceLeft();
          }
          if (!blockingWrite && spaceLeft < len) throw new Exception("CircularCharBuffer is full; cannot write " + len + " characters");
          int realLen = Math.min(len, spaceLeft);
          int firstLen = Math.min(realLen, buffer.length - writePosition);
          int secondLen = Math.min(realLen - firstLen, buffer.length - markPosition - 1);
          int written = firstLen + secondLen;
          if (firstLen > 0){
            System.arraycopy(cbuf, off, buffer, writePosition, firstLen);
          }
          if (secondLen > 0){
            System.arraycopy(cbuf, off+firstLen, buffer, 0, secondLen);
            writePosition = secondLen;
          } else {
            writePosition += written;
          }
          if (writePosition == buffer.length) {
            writePosition = 0;
          }
          off += written;
          len -= written;
        }
        if (len > 0){
          try {
            Thread.sleep(100);
          } catch(Exception x){
            throw new IOException("Waiting for available space in buffer interrupted.");
          }
        }
      }
    }

    /**
     * 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.
     * If the buffer allows blocking writes, this method will block until
     * all the data has been written rather than throw an IOException.
     *
     * @param c number of characters to be written
     * @throws BufferOverflowException if buffer does not allow blocking writes
     *   and the buffer is full.
     * @throws IOException if the stream is closed, or the write is interrupted.
     *
     * @since ostermillerutils 1.00.00
     */
    @Override public void write(int c) throws IOException {
      boolean written = false;
      while (!written){
        synchronized (CircularCharBuffer.this){
          if (writerClosed) throw new IOException("Writer has been closed; cannot write to a closed Writer.");
          if (readerClosed) throw new IOException("Buffer closed by Reader; cannot write to a closed buffer.");
          int spaceLeft = spaceLeft();
          while (infinite && spaceLeft < 1){
            resize();
            spaceLeft = spaceLeft();
          }
          if (!blockingWrite && spaceLeft < 1) throw new Exception("CircularCharBuffer is full; cannot write 1 character");
          if (spaceLeft > 0){
            buffer[writePosition] = (char)(c & 0xffff);
            writePosition++;
            if (writePosition == buffer.length) {
              writePosition = 0;
            }
            written = true;
          }
        }
        if (!written){
          try {
            Thread.sleep(100);
          } catch(Exception x){
            throw new IOException("Waiting for available space in buffer interrupted.");
          }
        }
      }
    }

    /**
     * Write a string.
     * If the buffer allows blocking writes, this method will block until
     * all the data has been written rather than throw an IOException.
     *
     * @param str String to be written
     * @throws BufferOverflowException if buffer does not allow blocking writes
     *   and the buffer is full.  If the exception is thrown, no data
     *   will have been written since the buffer was set to be non-blocking.
     * @throws IOException if the stream is closed, or the write is interrupted.
     *
     * @since ostermillerutils 1.00.00
     */
    @Override public void write(String str) throws IOException {
      write(str, 0, str.length());
    }

    /**
     * Write a portion of a string.
     * If the buffer allows blocking writes, this method will block until
     * all the data has been written rather than throw an IOException.
     *
     * @param str A String
     * @param off Offset from which to start writing characters
     * @param len Number of characters to write
     * @throws BufferOverflowException if buffer does not allow blocking writes
     *   and the buffer is full.  If the exception is thrown, no data
     *   will have been written since the buffer was set to be non-blocking.
     * @throws IOException if the stream is closed, or the write is interrupted.
     *
     * @since ostermillerutils 1.00.00
     */
    @Override public void write(String str, int off, int len) throws IOException {
      while (len > 0){
        synchronized (CircularCharBuffer.this){
          if (writerClosed) throw new IOException("Writer has been closed; cannot write to a closed Writer.");
          if (readerClosed) throw new IOException("Buffer closed by Reader; cannot write to a closed buffer.");
          int spaceLeft = spaceLeft();
          while (infinite && spaceLeft < len){
            resize();
            spaceLeft = spaceLeft();
          }
          if (!blockingWrite && spaceLeft < len) throw new Exception("CircularCharBuffer is full; cannot write " + len + " characters");
          int realLen = Math.min(len, spaceLeft);
          int firstLen = Math.min(realLen, buffer.length - writePosition);
          int secondLen = Math.min(realLen - firstLen, buffer.length - markPosition - 1);
          int written = firstLen + secondLen;
          for (int i=0; i<firstLen; i++){
            buffer[writePosition + i] = str.charAt(off+i);
          }
          if (secondLen > 0){
            for (int i=0; i<secondLen; i++){
              buffer[i] = str.charAt(off+firstLen+i);
            }
            writePosition = secondLen;
          } else {
            writePosition += written;
          }
          if (writePosition == buffer.length) {
            writePosition = 0;
          }
          off += written;
          len -= written;
        }
        if (len > 0){
          try {
            Thread.sleep(100);
          } catch(Exception x){
            throw new IOException("Waiting for available space in buffer interrupted.");
          }
        }
      }
    }
  }
}

   
    
    
    
  








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3.Using BuffersUsing Buffers
4.Output BufferingOutput Buffering
5.Getting different representations from a ByteBufferGetting different representations from a ByteBuffer
6.Manipulating ints in a ByteBuffer with an IntBufferManipulating ints in a ByteBuffer with an IntBuffer
7.Circular Byte Buffer
8.Circular Char Buffer from http://ostermiller.org
9.Buffered copying
10.Byte Buffer
11.Char Buffer
12.Caching InputStream
13.Caching OutputStream
14.ByteBuffer FloatBuffer demo