Re: java/3426: java.io.InputStreamReader, infinite loop

[Tom Tromey <tromey at redhat dot com>]

The following reply was made to PR libgcj/3426; it has been noted by GNATS.

From: Tom Tromey <tromey@redhat.com>
To: david-b@pacbell.net
Cc: gcc-gnats@gcc.gnu.org
Subject: Re: java/3426: java.io.InputStreamReader, infinite loop
Date: 29 Jun 2001 18:20:47 -0600

 Hi David.  Could you try this untested patch and see if it helps this
 problem?
 
 If it doesn't work for you I will try to reproduce the failure myself
 and then I'll debug it for real.  I'll also do that if you can't test
 it.  (However, if I do have to do that it will have to be a lower
 priority...)
 
 2001-06-29  Tom Tromey  <tromey@redhat.com>
 
 	Fix for PR libgcj/3426:
 	* java/io/BufferedInputStream.java (refill): Now package-private.
 	* java/io/InputStreamReader.java (ready): Simplified.
 	(refill): New method.
 	(read): Use it.
 
 Tom
 
 Index: java/io/BufferedInputStream.java
 ===================================================================
 RCS file: /cvs/gcc/gcc/libjava/java/io/BufferedInputStream.java,v
 retrieving revision 1.3
 diff -u -r1.3 BufferedInputStream.java
 --- BufferedInputStream.java	2000/03/07 19:55:26	1.3
 +++ BufferedInputStream.java	2001/06/29 23:56:54
 @@ -1,4 +1,4 @@
 -/* Copyright (C) 1998, 1999  Free Software Foundation
 +/* Copyright (C) 1998, 1999, 2001  Free Software Foundation
  
     This file is part of libgcj.
  
 @@ -131,7 +131,7 @@
      return origN - n;
    }
  
 -  private boolean refill() throws IOException
 +  boolean refill() throws IOException
    {
      if (markpos < 0)
        count = pos = 0;
 Index: java/io/InputStreamReader.java
 ===================================================================
 RCS file: /cvs/gcc/gcc/libjava/java/io/InputStreamReader.java,v
 retrieving revision 1.8
 diff -u -r1.8 InputStreamReader.java
 --- InputStreamReader.java	2001/02/09 01:54:38	1.8
 +++ InputStreamReader.java	2001/06/29 23:56:54
 @@ -44,6 +44,11 @@
  
    private InputStreamReader(InputStream in, BytesToUnicode decoder)
    {
 +    // FIXME: someone could pass in a BufferedInputStream whose buffer
 +    // is smaller than the longest encoded character for this
 +    // encoding.  We will probably go into an infinite loop in this
 +    // case.  We probably ought to just have our own byte buffering
 +    // here.
      this.in = in instanceof BufferedInputStream
                ? (BufferedInputStream) in
                : new BufferedInputStream(in);
 @@ -76,28 +81,11 @@
  
  	if (wpos < wcount)
  	  return true;
 -	if (work == null)
 -	  {
 -	    work = new char[100];
 -	    wpos = 0;
 -	    wcount = 0;
 -	  }
 -	for (;;)
 -	  {
 -	    if (in.available() <= 0)
 -	      return false;
 -	    in.mark(1);
 -	    int b = in.read();
 -	    if (b < 0)
 -	      return true;
 -	    in.reset();
 -	    converter.setInput(in.buf, in.pos, in.count);
 -	    wpos = 0;
 -	    wcount = converter.read(work, 0, work.length);
 -	    in.skip(converter.inpos - in.pos);
 -	    if (wcount > 0)
 -	      return true;
 -	  }
 +
 +	// According to the spec, an InputStreamReader is ready if its
 +	// input buffer is not empty (above), or if bytes are
 +	// available on the underlying byte stream.
 +	return in.available () > 0;
        }
    }
  
 @@ -108,33 +96,23 @@
  	if (in == null)
  	  throw new IOException("Stream closed");
  
 +	if (length == 0)
 +	  return 0;
 +
  	int wavail = wcount - wpos;
 -	if (wavail > 0)
 -	  {
 -	    if (length > wavail)
 -	      length = wavail;
 -	    System.arraycopy(work, wpos, buf, offset, length);
 -	    wpos += length;
 -	    return length;
 -	  }
 -	else
 +	if (wavail <= 0)
  	  {
 -	    if (length == 0)
 -	      return 0;
 -	    for (;;)
 -	      {
 -		in.mark(1);
 -		int b = in.read();
 -		if (b < 0)
 -		  return -1;
 -		in.reset();
 -		converter.setInput(in.buf, in.pos, in.count);
 -		int count = converter.read (buf, offset, length);
 -		in.skip(converter.inpos - in.pos);
 -		if (count > 0)
 -		  return count;
 -	      }
 +	    // Nothing waiting, so refill our buffer.
 +	    if (! refill ())
 +	      return -1;
 +	    wavail = wcount - wpos;
  	  }
 +
 +	if (length > wavail)
 +	  length = wavail;
 +	System.arraycopy(work, wpos, buf, offset, length);
 +	wpos += length;
 +	return length;
        }
    }
  
 @@ -146,24 +124,39 @@
  	  throw new IOException("Stream closed");
  
  	int wavail = wcount - wpos;
 -	if (wavail > 0)
 -	  return work[wpos++];
 -	if (work == null)
 +	if (wavail <= 0)
  	  {
 -	    work = new char[100];
 -	    wpos = 0;
 -	    wcount = 0;
 +	    // Nothing waiting, so refill our buffer.
 +	    if (! refill ())
 +	      return -1;
  	  }
 -	else if (wavail == 0)
 +
 +	return work[wpos++];
 +      }
 +  }
 +
 +  // Read more bytes and convert them into the WORK buffer.
 +  // Return false on EOF.
 +  private boolean refill () throws IOException
 +  {
 +    wcount = wpos = 0;
 +    for (;;)
 +      {
 +	// We have knowledge of the internals of BufferedInputStream
 +	// here.  Eww.
 +	in.mark (0);
 +	boolean r = ! in.refill ();
 +	in.reset ();
 +	if (! r)
 +	  return false;
 +	converter.setInput(in.buf, in.pos, in.count);
 +	int count = converter.read (work, wpos, work.length - wpos);
 +	in.skip(converter.inpos - in.pos);
 +	if (count > 0)
  	  {
 -	    wpos = 0;
 -	    wcount = 0;
 +	    wcount += count;
 +	    return true;
  	  }
 -	int count = read(work, wpos, work.length-wpos);
 -	if (count <= 0)
 -	  return -1;
 -	wcount = wpos + count;
 -	return work[wpos++];
        }
    }
  }