output.log

tim@touchsmart:~/Code$ nvm use v0.11.2-generators
Now using node v0.11.2-generators
tim@touchsmart:~/Code$ node --harmony testgen.js 
<Buffer 76 61 72 20 66 73 20 3d 20 72 65 71 75 69 72 65 28 27 66 73 27 29 3b 0a 66 75 6e 63 74 69 6f 6e 20 72 65 61 64 46 69 6c 65 28 70 61 74 68 2c 20 65 6e 63 ...>
Sleeping for 2000ms...
Done

testgen.js

var fs = require('fs');
function readFile(path, encoding) {
  return function (callback) {
    fs.readFile(path, encoding, callback);
  };
}

function sleep(ms) {
  return function (callback) {
    setTimeout(callback, ms);
  };
}

function run(makeGenerator) {
  return function () {
    var generator = makeGenerator.apply(this, arguments);
    var continuable, sync, value;

    next();
    function next() {
      while (!(continuable = generator.send(value)).done) {
        continuable = continuable.value;
        sync = undefined;
        continuable(callback);
        if (sync === undefined) {
          sync = false;
          break;
        }
      }
    }
    function callback(err, val) {
      if (err) return generator.throw(err);
      value = val;
      if (sync === undefined) {
        sync = true;
      }
      else {
        next();
      }
    }
  }
}


run(function* () {
  console.log(yield readFile(__filename));
  console.log("Sleeping for 2000ms...");
  yield sleep(2000);
  console.log("Done");
})();