libjava/java/io/PipedReader.java

// PipedReader.java - Piped character stream.

/* Copyright (C) 1998, 1999  Cygnus Solutions

   This file is part of libgcj.

This software is copyrighted work licensed under the terms of the
Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
details.  */

package java.io;

/**
 * @author Tom Tromey <tromey@cygnus.com>
 * @date September 25, 1998 
 */

/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
 * "The Java Language Specification", ISBN 0-201-63451-1
 * Status:  Complete to 1.1.
 */

public class PipedReader extends Reader
{
  public void close () throws IOException
  {
    closed = true;
  }

  public void connect (PipedWriter src) throws IOException
  {
    if (closed)
      throw new IOException ("already closed");
    if (writer != null)
      {
	if (writer == src)
	  return;
	throw new IOException ("already connected");
      }
    try
      {
	writer = src;
	writer.connect(this);
      }
    catch (IOException e)
      {
	writer = null;
	throw e;
      }
  }

  public PipedReader ()
  {
    super ();
    writer = null;
    closed = false;
    in = -1;
    out = 0;
    pipeBuffer = new char[1024];
  }

  public PipedReader (PipedWriter src) throws IOException
  {
    super ();
    closed = false;
    in = -1;
    out = 0;
    pipeBuffer = new char[1024];
    connect (src);
  }

  public int read (char buf[], int offset, int count) throws IOException
  {
    if (closed)
      throw new IOException ("closed");
    if (count < 0)
      throw new ArrayIndexOutOfBoundsException ();
    int toCopy = count;
    synchronized (lock)
      {
	while (toCopy > 0)
	  {
	    // Wait for data in the pipe.  If the writer is closed and
	    // no data has been copied into the output buffer, return
	    // the magic EOF number.
	    while (in == -1)
	      {
		if (writer.isClosed())
		  {
		    if (toCopy < count)
		      return count - toCopy;
		    return -1;
		  }

		// Note that JCL doesn't say this is the right thing
		// to do.  Still, it feels right, and we must deal
		// with an interrupt somehow.
		try
		  {
		    lock.wait();
		  }
		catch (InterruptedException e)
		  {
		    InterruptedIOException io
		      = new InterruptedIOException (e.getMessage());
		    io.bytesTransferred = count - toCopy;
		    throw io;
		  }
	      }
	    // Now copy some data from pipe into user buffer.
	    int len;
	    if (in < out)
	      len = pipeBuffer.length - out;
	    else
	      len = in - out;
	    len = len > toCopy ? toCopy : len;
	    System.arraycopy(pipeBuffer, out, buf, offset, len);
	    out += len;
	    if (out == pipeBuffer.length)
	      out = 0;
	    toCopy -= len;
	    offset += len;
	    // If we've read all the data, then reset so that we know
	    // there is nothing left to be read.
	    if (in == out)
	      in = -1;
	    // Tell anybody waiting for space in the buffer.
	    lock.notifyAll();
	  }
      }
    return count;
  }

  void receive (char buf[], int offset, int count) throws IOException
  {
    if (count < 0)
      throw new ArrayIndexOutOfBoundsException ();
    int original = count;
    synchronized (lock)
      {
	while (count > 0)
	  {
	    // Wait until there is some space in the buffer.
	    while (in == out)
	      {
		try
		  {
		    lock.wait();
		  }
		catch (InterruptedException e)
		  {
		    // Turn interrupts into IO interrupts.
		    InterruptedIOException io
		      = new InterruptedIOException (e.getMessage());
		    io.bytesTransferred = original - count;
		    throw io;
		  }
	      }

	    // Compute destination in the pipe.
	    int base, len;
	    if (in == -1)
	      {
		base = 0;
		len = pipeBuffer.length;
	      }
	    else if (in < out)
	      {
		base = in;
		len = out - in;
	      }
	    else
	      {
		base = in;
		len = pipeBuffer.length - in;
	      }
	    int copyLen = len > count ? count : len;
	    // Copy data and update local state.
	    System.arraycopy(buf, offset, pipeBuffer, base, copyLen);
	    in = base + copyLen;
	    if (in == pipeBuffer.length)
	      in = 0;
	    count -= copyLen;
	    offset += copyLen;
	    // Tell anybody waiting for data.
	    lock.notifyAll();
	  }
      }
  }


  boolean isClosed ()
  {
    return closed;
  }

  // The associated writer.
  private PipedWriter writer;
  // True if this reader has been closed.
  boolean closed;

  // Index of next character to overwrite when receive() is called.
  // If -1, then that means the buffer is empty.
  private int in;
  // Index of next character to return from read().
  private int out;

  // The pipe buffer itself.
  private char[] pipeBuffer;
}