The available method for ServletInputStream subclasses (tomcat_32 branch)

[Mike Anderson <MM...@novell.com>]

In working with some internal groups, we have some classes that perform file uploads (anyone heard of GroupWise Webaccess?).  One of the things they have done in their servlets that handle this is call the available method on the ServletInputStream so that they can delay the thread for a small amount of time if there isn't anything available to be read from the socket.  This allows the machine and other threads to do other processing, and allows the thread that wants to read the data to gracefully handle a client prematurely shutting down the connection.  This functionality works on other servlet engines (JServ, WebSphere, Novell Servlet Gateway) but doesn't work on Tomcat because the available() method was never implemented in any of the subclasses.  So when availabe() is called, it just resolves down to java.io.InputStream which is documented as returning 0 because subclasses should override this method.  There are 2 ways to fix this:

1.  In BufferedServletInputStream, implement an available() method that returns limit-bytesRead or 0 whichever is greater.  The limit class variable is set to the value of the Content-Length header and bytesRead is the number of bytes read since limit was set.  (See the attached patch).  This is the easy fix but doesn't address the feature of available that says it will return the number of bytes that can be read "without blocking".  Obviously, if there is a large amount of data, a read will most likely block at some point depending on how much is asked for.

2.  Update BufferedServletInputStream to call reqA.available and then update the following files to provide this interface:
  Request.java
  RequestImpl.java
  HttpRequestAdapter.java
  AJP12RequestAdapter.java
  Ajp13RequestAdapter.java
  JNIRequestAdapter.java
Each of these classes would need to provide an appropriate available() method.

I'm willing to figure this out and implement #2 if it is deemed the better approach and only provided #1 because it was a "quick" fix.  I'm also willing to figure this out for the 3.3 tree for either implementation.  I would like to get it into the 3.2.2 branch since that is what most of use here are currently using.

Any response (other than flames:-) appreciated.