Idle Hacking

It was a pretty quiet release, but after many months we’ve release 1.2. It runs on top of XULRunner, the Firefox based runtime environment. We choose to use the XULRunner 1.8 tree instead of the 1.8.0 tree, so that we could make use of some of the new features like nsISAXMLReader.

New features in the product include it’s ability to manage multiple insurance plans per record. Meaning we support splitting a doctors bill between multiple insurance comapies – something our competitors don’t handle. Also, we reduced the footprint to only 6.9 megs from 8.04 megs. The download is free with registration.  UPDATE:  SimoHealth was acquired by revolution health in 2005.  RevolutionHealth was acquired by waterfront media – SimoHealth was decomissioned between 2006 and 2007.  If you would like to get the source drop me a line, it’s pretty dated at this point.

Software Health, Javascript, XPCOM, XULRunner

My first pass was to use nsIIOService to create an nsIChannel. This worked and gave me time to focus on getting my parser methods correct.

function runRestoreFromChannel( urlSpec, progress )
{
 var ioService = CC["@mozilla.org/network/io-service;1"].getService(CI.nsIIOService);
 var reader = CC["@mozilla.org/saxparser/xmlreader;1"].createInstance(CI.nsISAXXMLReader);
 var channel = ioService.newChannel( urlSpec,null,null );

 channel.notificationCallbacks = progress;
 reader.contentHandler = new RestoreParser( broker, progress );

 reader.parseAsync( null );
 channel.contentType = "text/xml";
 //channel.loadFlags = CI.nsIRequest.LOAD_BACKGROUND;
 channel.asyncOpen( reader, null );
}

This solution has one major flaw. The nsIFileInputStream that’s created reads in very large chunks from the filesystem for performance. The problem is during my parse I do some fairly intensive I/O operations as I read my data in. But since, almost all the data is read in by the nsIInputStream, it means my GUI is locked up while I’m processing the data. To get around this I thought about writing my own nsIStreamListener and controlling how the data is passed to my nsISAXXMLReader. The problem there is I’d either have to buffer all the data or still be stuck in a loop on the main thread blocking the UI. Ideally, I’d be able to run the parser in a background thread at full speed. As a simple workaround I can use nsIInputStreamPump. It works almost identically to using the nsIChannel, except I can specify how much data to read at a time (i.e. the chunk size). There was one minor little problem that can be worked around using a custom nsIStreamListener around the nsISAXXMLReader.

Here’s the code for setting up the parser:

var reader = CC["@mozilla.org/saxparser/xmlreader;1"].createInstance(CI.nsISAXXMLReader);
var filestream = CC["@mozilla.org/network/file-input-stream;1"].createInstance(CI.nsIFileInputStream);
var pump = CC["@mozilla.org/network/input-stream-pump;1"].createInstance(CI.nsIInputStreamPump);
var ioService = CC["@mozilla.org/network/io-service;1"].getService(CI.nsIIOService);
var channel = ioService.newChannel( urlSpec,null,null );
var uri = ioService.newURI( urlSpec, null, null );

filestream.init(file, 0x01, 0444, 0);

reader.contentHandler = new RestoreParser( broker, progress );

reader.parseAsync( null );

pump.init( filestream, -1, -1, StreamChunkSize, 1, false );
reader.baseURI = uri;
pump.asyncRead( new StreamListener( reader, progress, channel ), null );

Here’s the code for wrapping the nsIStreamListener:

function StreamListener( reader, progress, channel )
{
 this.reader = reader;
 this.progress = progress;
 this.channel = channel;
}
StreamListener.prototype = {
 reader:null,
 onStartRequest: function( request,context ){
   dump( "starting\n" );
   // XXX: passing channel here to work around bug in nsParser.cpp
   this.reader.onStartRequest( this.channel, context );
 },
 onDataAvailable: function( request, context, input, offset, count ){
   dump( "offset: " + offset + ", count: " + count + "\n" );
   // XXX: passing channel here to work around bug in nsParser.cpp
   this.reader.onDataAvailable( this.channel, context, input, offset, count );
   this.progress.onProgress( request, context, offset, offset + count );
 },
 onStopRequest: function( request, context, status ){
   // XXX: passing channel here to work around bug in nsParser.cpp
   this.reader.onStopRequest( this.channel, context, status );
 }
};

Software Javascript, XML, XPCOM, XUL

I did a search today through simohealth code and found that we use Components.interfaces and Components.classes a lot. Our use currently accounts for 9K in simo.jar. I calculated that by replacing all occurrences with CI and CC could reduce the size by 8.41K!

Software Javascript, XPCOM

For those interested I put together a Mac Build. I was in the middle of refactoring the playlist when I got side tracked with work and metro stop, so the current state of xulmusic is certainly not pretty… Anyway, I think this still serves as a pretty good example. So, here’s a link to the binary for Mac OSX for those interested. xullicious.com/XULMusic.app.tar.bz2 11M

Software C++, Javascript, Mac OSX, XPCOM, XULRunner