Re: Overlap between StreamReader and FileReader

On Fri, May 17, 2013 at 6:15 PM, Anne van Kesteren <annevk@annevk.nl> wrote:

> The main problem is that Stream per Streams API is not what you expect
>  from an IO stream, but it's more what Blob should've been (Blob
> without synchronous size). What we want I think is a real IO stream.
> If we also need Blob without synchronous size is less clear to me.


Forgetting File API completely, for example, ... how about simple socket
like interface?

// Downloading big data

var remaining;
var type = null;
var payload = '';
function processData(data) {
  var offset = 0;
  while (offset < data.length) {
    if (!type) {
      var type = data.substr(offset, 1);
      remaining = payloadSize(type);
    } else if (remaining > 0) {
      var consume = Math.min(remaining, data.length - offset);
      payload += data.substr(offset, consume);
      offset += consume;
    } else if (remaining == 0) {
      if (type == FOO) {
        foo(payload);
      } else if (type == BAR) {
        bar(payload);
      }
      type = null;
    }
  }
}

var client = new XMLHttpRequest();
client.onreadystatechange = function() {
  if (this.readyState == this.LOADING) {
    var responseStream = this.response;
    responseStream.setBufferSize(1024);
    responseStream.ondata = function(evt) {
      processData(evt.data);
      // Consumed data will be invalidated and memory used for the data
will be released.
    };
    responseStream.onclose = function() {
      // Reached end of response body
      ...
    };
    responseStream.start();
    // Now responseStream starts forwarding events happen on XHR to its
callbacks.
  }
};
client.open("GET", "/foobar");
client.responseType = "stream";
client.send();

// Uploading big data

var client = new XMLHttpRequest();
client.open("POST", "/foobar");

var requestStream = new WriteStream(1024);

var producer = new Producer();
producer.ondata = function(evt.data) {
  requestStream.send(evt.data);
};
producer.onclose = function() {
  requestStream.close();
};

client.send(requestStream);