filesystem-workers.js

/*
Example that utilizes FileSystem API and Web Workers.

Creates a lib.js and worker.js in a temporary file system, then creates a web worker for worker.js that imports lib.js from the local filesystem.

The start of something beautiful?
*/

var fs, liburl, worker = null;

function errorHandler(e) {
  var msg = '';

  switch (e.code) {
    case FileError.QUOTA_EXCEEDED_ERR:
      msg = 'QUOTA_EXCEEDED_ERR';
      break;
    case FileError.NOT_FOUND_ERR:
      msg = 'NOT_FOUND_ERR';
      break;
    case FileError.SECURITY_ERR:
      msg = 'SECURITY_ERR';
      break;
    case FileError.INVALID_MODIFICATION_ERR:
      msg = 'INVALID_MODIFICATION_ERR';
      break;
    case FileError.INVALID_STATE_ERR:
      msg = 'INVALID_STATE_ERR';
      break;
    default:
      msg = 'Unknown Error';
      break;
  };

  console.log('Error: ' + msg);
  console.log(e);
}

function _worker() {
    self.onmessage = function(e) {
        if(e.data.cmd === "init") {
            var liburl = e.data.liburl;
            postMessage("Importing lib from " + liburl);
            importScripts(liburl);
            return;
        }
        postMessage("PONG: " + e.data);
        postMessage("LIB: " + HELLO);
    }
}

// Create a temporary 5mb file system, assign the result to the `fs` var
webkitRequestFileSystem(window.TEMPORARY, 5 * 1024 * 1024, step1, errorHandler);

function step1(f) {
  console.log('FS created.', f);
  fs = f
  fs.root.getFile('lib.js', {create:true}, step2, errorHandler);
}

function step2(e) {
  console.log('lib.js created', e);
  liburl = e.toURL();
  e.createWriter(function(writer) {
    var bb = new WebKitBlobBuilder();
    bb.append('var HELLO="hello, world";');
    writer.write(bb.getBlob('text/javascript'));
    step3();
  }, errorHandler);
}

function step3() {
  console.log('lib.js written');
  // Create our worker script
  fs.root.getFile('worker.js', {create:true}, function(e) {
    e.createWriter(function(writer) {
      var bb = new WebKitBlobBuilder();
      var src = _worker.toString();
      src = src.substring("function _worker() {".length, src.length - 1).trim();
      bb.append(src);
      writer.write(bb.getBlob('text/javascript'));
      step4();
    }, errorHandler);
  }, errorHandler);
}

function step4() {
  console.log('worker.js written');
  // Pull out the worker file and actually create the worker
  fs.root.getFile('worker.js', {}, function(e) {
    worker = new Worker(e.toURL());
    worker.onmessage = function(e) {
      console.log("WORKER: ", e.data, e);
    }
    console.log('posting messages');
    worker.postMessage({ cmd: "init", liburl: liburl });
    worker.postMessage("Alright alright alright");
    console.log('done.');
  }, errorHandler)
}