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From-SVN: r102074

libjava/classpath/java/io/PipedInputStream.java

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+/* PipedInputStream.java -- Read portion of piped streams.
+   Copyright (C) 1998, 1999, 2000, 2001, 2003, 2005  Free Software Foundation, Inc.
+
+This file is part of GNU Classpath.
+
+GNU Classpath 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, or (at your option)
+any later version.
+ 
+GNU Classpath 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.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library.  Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module.  An independent module is a module which is not derived from
+or based on this library.  If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so.  If you do not wish to do so, delete this
+exception statement from your version. */
+
+package java.io;
+
+// NOTE: This implementation is very similar to that of PipedReader.  If you 
+// fix a bug in here, chances are you should make a similar change to the 
+// PipedReader code.
+
+/**
+  * An input stream that reads its bytes from an output stream
+  * to which it is connected. 
+  * <p>
+  * Data is read and written to an internal buffer.  It is highly recommended
+  * that the <code>PipedInputStream</code> and connected 
+  * <code>PipedOutputStream</code>
+  * be part of different threads.  If they are not, the read and write 
+  * operations could deadlock their thread.
+  *
+  * @specnote The JDK implementation appears to have some undocumented 
+  *           functionality where it keeps track of what thread is writing
+  *           to pipe and throws an IOException if that thread susequently
+  *           dies. This behaviour seems dubious and unreliable - we don't
+  *           implement it.
+  *
+  * @author Aaron M. Renn (arenn@urbanophile.com)
+  */
+public class PipedInputStream extends InputStream
+{
+  /** PipedOutputStream to which this is connected. Null only if this 
+    * InputStream hasn't been connected yet. */
+  PipedOutputStream source;
+
+  /** Set to true if close() has been called on this InputStream. */
+  boolean closed;
+
+
+  /**
+   * The size of the internal buffer used for input/output.
+   */
+  /* The "Constant Field Values" Javadoc of the Sun J2SE 1.4
+   * specifies 1024.
+   */
+  protected static final int PIPE_SIZE = 1024;
+
+
+  /**
+    * This is the internal circular buffer used for storing bytes written
+    * to the pipe and from which bytes are read by this stream
+    */
+  protected byte[] buffer = new byte[PIPE_SIZE];
+
+  /**
+    * The index into buffer where the next byte from the connected
+    * <code>PipedOutputStream</code> will be written. If this variable is 
+    * equal to <code>out</code>, then the buffer is full. If set to < 0,
+    * the buffer is empty.
+    */
+  protected int in = -1;
+
+  /**
+    * This index into the buffer where bytes will be read from.
+    */
+  protected int out = 0;
+
+  /** Buffer used to implement single-argument read/receive */
+  private byte[] read_buf = new byte[1];
+
+  /**
+    * Creates a new <code>PipedInputStream</code> that is not connected to a 
+    * <code>PipedOutputStream</code>.  It must be connected before bytes can 
+    * be read from this stream.
+    */
+  public PipedInputStream()
+  {
+  }
+
+  /**
+    * This constructor creates a new <code>PipedInputStream</code> and connects
+    * it to the passed in <code>PipedOutputStream</code>. The stream is then 
+    * ready for reading.
+    *
+    * @param source The <code>PipedOutputStream</code> to connect this 
+    * stream to
+    *
+    * @exception IOException If <code>source</code> is already connected.
+    */
+  public PipedInputStream(PipedOutputStream source) throws IOException
+  {
+    connect(source);
+  }
+
+  /**
+    * This method connects this stream to the passed in 
+    * <code>PipedOutputStream</code>.
+    * This stream is then ready for reading.  If this stream is already
+    * connected or has been previously closed, then an exception is thrown
+    *
+    * @param src The <code>PipedOutputStream</code> to connect this stream to
+    *
+    * @exception IOException If this PipedInputStream or <code>source</code> 
+    *                        has been connected already.
+    */
+  public void connect(PipedOutputStream source) throws IOException
+  {
+    // The JDK (1.3) does not appear to check for a previously closed 
+    // connection here.
+    
+    if (this.source != null || source.sink != null)
+      throw new IOException ("Already connected");
+    
+    source.sink = this;
+    this.source = source;
+  }
+  
+  /**
+  * This method receives a byte of input from the source PipedOutputStream.
+  * If the internal circular buffer is full, this method blocks.
+  *
+  * @param val The byte to write to this stream
+  *
+  * @exception IOException if error occurs
+  * @specnote Weird. This method must be some sort of accident.
+  */
+  protected synchronized void receive(int val) throws IOException
+  {
+    read_buf[0] = (byte) (val & 0xff);
+    receive (read_buf, 0, 1);
+  }
+
+  /**
+    * This method is used by the connected <code>PipedOutputStream</code> to
+    * write bytes into the buffer.
+    *
+    * @param buf The array containing bytes to write to this stream
+    * @param offset The offset into the array to start writing from
+    * @param len The number of bytes to write.
+    *
+    * @exception IOException If an error occurs
+    * @specnote This code should be in PipedOutputStream.write, but we
+    *           put it here in order to support that bizarre recieve(int)
+    *           method.
+    */  
+  synchronized void receive(byte[] buf, int offset, int len)
+    throws IOException
+  {
+    if (closed)
+      throw new IOException ("Pipe closed");
+
+    int bufpos = offset;
+    int copylen;
+    
+    while (len > 0)
+      {
+        try
+	  {
+	    while (in == out)
+	      {
+		// The pipe is full. Wake up any readers and wait for them.
+		notifyAll();
+		wait();
+		// The pipe could have been closed while we were waiting.
+	        if (closed)
+		  throw new IOException ("Pipe closed");
+	      }
+	  }
+	catch (InterruptedException ix)
+	  {
+            throw new InterruptedIOException ();
+	  }
+
+	if (in < 0) // The pipe is empty.
+	  in = 0;
+	
+	// Figure out how many bytes from buf can be copied without 
+	// overrunning out or going past the length of the buffer.
+	if (in < out)
+	  copylen = Math.min (len, out - in);
+	else
+	  copylen = Math.min (len, buffer.length - in);
+
+	// Copy bytes until the pipe is filled, wrapping if necessary.
+	System.arraycopy(buf, bufpos, buffer, in, copylen);
+	len -= copylen;
+	bufpos += copylen;
+	in += copylen;
+	if (in == buffer.length)
+	  in = 0;
+      }
+    // Notify readers that new data is in the pipe.
+    notifyAll();
+  }
+  
+  /**
+    * This method reads one byte from the stream.
+    * -1 is returned to indicated that no bytes can be read
+    * because the end of the stream was reached.  If the stream is already
+    * closed, a -1 will again be returned to indicate the end of the stream.
+    * 
+    * <p>This method will block if no byte is available to be read.</p>
+    *
+    * @return the value of the read byte value, or -1 of the end of the stream
+    * was reached
+    * 
+    * @throws IOException if an error occured
+    */
+  public int read() throws IOException
+  {
+    // Method operates by calling the multibyte overloaded read method
+    // Note that read_buf is an internal instance variable.  I allocate it
+    // there to avoid constant reallocation overhead for applications that
+    // call this method in a loop at the cost of some unneeded overhead
+    // if this method is never called.
+
+    int r = read(read_buf, 0, 1);
+    return r != -1 ? (read_buf[0] & 0xff) : -1;
+  }
+  
+  /**
+    * This method reads bytes from the stream into a caller supplied buffer.
+    * It starts storing bytes at position <code>offset</code> into the 
+    * buffer and
+    * reads a maximum of <code>len</code> bytes.  Note that this method 
+    * can actually
+    * read fewer than <code>len</code> bytes.  The actual number of bytes 
+    * read is
+    * returned.  A -1 is returned to indicated that no bytes can be read
+    * because the end of the stream was reached - ie close() was called on the
+    * connected PipedOutputStream.
+    * <p>
+    * This method will block if no bytes are available to be read.
+    *
+    * @param buf The buffer into which bytes will be stored
+    * @param offset The index into the buffer at which to start writing.
+    * @param len The maximum number of bytes to read.
+    *
+    * @exception IOException If <code>close()</code> was called on this Piped
+    *                        InputStream.
+    */  
+  public synchronized int read(byte[] buf, int offset, int len)
+    throws IOException
+  {
+    if (source == null)
+      throw new IOException ("Not connected");
+    if (closed)
+      throw new IOException ("Pipe closed");
+
+    // If the buffer is empty, wait until there is something in the pipe 
+    // to read.
+    try
+      {
+	while (in < 0)
+	  {
+	    if (source.closed)
+	      return -1;
+	    wait();
+	  }
+      }
+    catch (InterruptedException ix)
+      {
+        throw new InterruptedIOException();
+      }
+    
+    int total = 0;
+    int copylen;
+    
+    while (true)
+      {
+	// Figure out how many bytes from the pipe can be copied without 
+	// overrunning in or going past the length of buf.
+	if (out < in)
+	  copylen = Math.min (len, in - out);
+	else
+	  copylen = Math.min (len, buffer.length - out);
+
+        System.arraycopy (buffer, out, buf, offset, copylen);
+	offset += copylen;
+	len -= copylen;
+	out += copylen;
+	total += copylen;
+	
+	if (out == buffer.length)
+	  out = 0;
+	
+	if (out == in)
+	  {
+	    // Pipe is now empty.
+	    in = -1;
+	    out = 0;
+	  }
+
+        // If output buffer is filled or the pipe is empty, we're done.
+	if (len == 0 || in == -1)
+	  {
+	    // Notify any waiting outputstream that there is now space
+	    // to write.
+	    notifyAll();
+	    return total;
+	  }
+      }
+  }
+  
+  /**
+    * This method returns the number of bytes that can be read from this stream
+    * before blocking could occur.  This is the number of bytes that are
+    * currently unread in the internal circular buffer.  Note that once this
+    * many additional bytes are read, the stream may block on a subsequent
+    * read, but it not guaranteed to block.
+    *
+    * @return The number of bytes that can be read before blocking might occur
+    *
+    * @exception IOException If an error occurs
+    */  
+  public synchronized int available() throws IOException
+  {
+    // The JDK 1.3 implementation does not appear to check for the closed or 
+    // unconnected stream conditions here.
+    
+    if (in < 0)
+      return 0;
+    else if (out < in)
+      return in - out;
+    else
+      return (buffer.length - out) + in;
+  }
+  
+  /**
+  * This methods closes the stream so that no more data can be read
+  * from it.
+  *
+  * @exception IOException If an error occurs
+  */
+  public synchronized void close() throws IOException
+  {
+    closed = true;
+    // Wake any thread which may be in receive() waiting to write data.
+    notifyAll();
+  }
+}
+