What is Tristanable?

Tristan B. Kildaire



Seeing that I just updated the project homepage for Tristanable I thought I should give you a summary of that page to give those a taste of what Tristanable really is.

What problems does it solve?

Human example

Say now you made a request to a server with a tag 1 and expect a reply with that same tag 1. Now, for a moment, think about what would happen in a tagless system. You would be expecting a reply, say now the weather report for your area, but what if the server has another thread that writes an instant messenger notification to the server’s socket before the weather message is sent? Now you will inetrpret those bytes as if they were a weather message.

Tristanable provides a way for you to receive the “IM notification first” but block and dequeue (when it arrives in the queue) for the “weather report”. Irresepctoive of wether (no pun intended) the weather report arrives before the “IM notification” or after.

Code example

If we wanted to implement the following we would do the following. One note is that instead of waiting on messages of a specific “type” (or rather tag), tristanable provides not just a one-message lengthb uffer per tag but infact a full queue per tag, meaning any received message with tag 1 will be enqueued and not dropped after the first message of type 1 is buffered.

import tristanable.manager;
import tristanable.queue;
import tristanable.queueitem;

/* Create a manager to manage the socket for us */
Manager manager = new Manager(socket);

/* Create a Queue for all "weather messages" */
Queue weatherQueue = new Queue(1);

/* Create a Queue for all "IM notifications" */
Queue instantNotification = new Queue(2);

/* Tell the manager to look out for tagged messages `1` and `2` */

/* Now we can block on this queue and return with its head */
QueueItem message = weatherQueue.dequeue();

Surely, there must be some sort of encoding mechanism too? The messages afterall need to be encoded. No problem!, we have that sorted:

import tristanable.encoding;

/* Let's send it with tag 1 and data "Hello" */
ulong tag = 1;
byte[] data = cast(byte[])"Hello";

/* When sending a message */
DataMessage tristanEncoded = new DataMessage(tag, data);

/* Then send it */

And let tristanable handle it! We even handle the message lengths and everything using another great project bformat.


[4 bytes (size-2, little endian)][8 bytes - tag][(2-size) bytes - data]

Using tristanable in your D project

You can easily add the library (source-based) to your project by running the following command in your project’s root:

dub add tristanable

Closing remarks

The project itself has been done for a while but I have been adding some nicer touches here and there as I use it in other projects - however nothing that will bloat it, rather features that just make sense. I will never add something like signal hooks etc. to the library as that isn’t the point of it. In that sense it isn’t aimed at being an event-loop system, but rather just a queue-filtering mechanism as described.