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diff --git a/posts/venturing-back-into-c.html b/posts/venturing-back-into-c.html new file mode 100644 index 0000000..16e3047 --- /dev/null +++ b/posts/venturing-back-into-c.html @@ -0,0 +1,153 @@ + +--post-date: 2019-02-17 +--type: blog + <article> + <h1>Venturing back into C</h1> + <p>For the past two weeks or so I have been diving back into C + programming. I've found it to be a very fun and refreshing experience + coming off of a slog of Java 11 updates at work. I've found comfort + in its simplicity and frustrations in my "I can do this without an + IDE" mindset.</p> + <p>I started C programming in College during a 8 AM course of which all I + can remember is that it was at 8 AM. I loved programming in C, dealing + with memory, pointers, no strings, structs, no strings, linking, no + strings. It was a really interesting difference from the web and Java + programming I had done previously. Obviously the lack of the + "string" type made things interesting and initially a challenge + for me back then. In my most recent endevour I found <code class= + 'inline'>char *</code> to be perfectly suitable for every case I came + across. It was usually a separate library that was failing me, not a + fixed char array. This was mostly due to the types of programs I was + writting in college were text adventures where all of what I did was + using strings. And my lack of understanding of what was actually + happening in C was really what was causing all the issues.</p> + <h2>The Project</h2> + <p>I started working on an application I had been meaning to develop + called <a href= + 'https://github.com/s3nd3r5/reminder'><b>reminder.d</b></a>. This daemon + would monitor for reminder notifications I would send via a CLI. It queue + them up based on some time set to send the notification. I ended up + writing both the CLI and the daemon in this past week, both in C.</p> + <h3>The Beginning</h3> + <p>This project started with an outline (as a README) which I think was + the reason this ended up as an actually successful project. I had been + thinking about this for a long time, and had begun using a calendar to + keep track of long term reminders/dates etc. First, I outlined the + architecture "how would I actually do want to send myself + remidners". Since half my day is spent infront of a computer, with a + terminal open or at least two keystrokes away, a CLI would do the trick. + Then how do I actually send myself notifications... writing them down. So + I can use the CLI to write to a file and have a daemon pick up the + changes and notify me once it hits the desired time posted.</p> + <h3>The CLI</h3> + <p>The CLI <b>remindme</b> took in messages and appened them to a file. + This file would be monitored by the daemon later on. Each reminder + consisted of three parts:</p> + <ul> + <li><i>Message</i> - The body of the notification.</li> + <li><i>Time</i> - This is either a datetime or a period for when the + notification should send.</li> + <li><i>Flag</i> - The Flag was set by the CLI when written to the file, + this marks the status of the reminder</li> + </ul>After a notification is written the daemon will pick up the + notification and notify if the time set is now/past. + <h3>The Daemon</h3> + <p>The Daemon <b>reminder-daemon</b> opened and tailed a file at + <i>/usr/local/etc/reminder.d/$USER.list</i>. It would tail the file + monitoring any incoming lines parsing them into reminders. The syntax of + the reminder is <code class='inline'>FLAG EPOCHSEC MESSAGE</code> . + Tokenizing on spaces it was then added to a linked-list sorted by time. + Every second it checks the file for any new lines, adding reminders as + they come in, then check the head of the list. If the reminder at the + head is ready to be notified the daemon pops it off the list and sends + the notification. After a notification is sent successfully the daemon + modifies that line in file updating its <code class='inline'>FLAG</code> + to 'd'. This is so when the daemon starts back up it skips the + reminder. Notifications are sent via <i>libnotify</i>: <code class= + 'inline'>Reminder - $DATETIME</code> with the message body. They are also + set to last until dismissed manually, this way if were to walk away, once + I sat down I'd see the stale reminder waiting.</p> + <h3>Future Plans for Reminder.d</h3> + <p>Having a system to create and send myself notifications is incredibly + useful but having them limit to just the computer I sent them on makes + them a very limited. I have been using them at work for the last few days + and its nice to be able to tell myself to remeber to email a person after + lunch. But I would like to be able to tell myself things later in the + day. I have planned since the beginning to have a remote server I can + sync the reminders through. In addition having an application running on + my phone that also gets and sets reminders.</p> + <p>Remote syncing would change entirely how I deal with reminders in the + file.</p> + <pre> +<code> + struct remnode { + long fileptr; + struct reminder* reminder; + struct remnode* next; + }; + </code></pre> + <p>Is currently the struct I use to keep track of the reminders. + <code class='inline'>fileptr</code> is the line of the file where the + reminder is, so I can <code class='inline'>fseek</code> back to the + location and overwrite its flag. I cannot currently think of a way to + keep the files perfectly identical without introducing countless + edgecases. What I do think might work is providing some form of UUID. + When a remote pull tells the systems daemon that a notification has been + cleared it can mark it by ID. Right now the fileptr is effectively its + ID, but that will not work anymore. A composite key of the daemons own id + (generated at install?) with a new ID of each incoming message would help + ensure uniqueness across ID generations across multiple systems.</p> + <h2>What I've learned</h2> + <p>First off, I probably could've done this in bash. With + <code class='inline'>date notify-send git awk cron</code> and a few other + useful commands I could very easily keep track of file changes and push + notifications at a certain time. But seeing as I scrap together bash + scripts all the time I though C would make things more fun.</p> + <p>Writing manpages was the probably the most fun I had working on the + project. They have a simple elegance to them, similar to C. That being + said you could FEEL the age of the language. Every single decision is + there to make things simple to parse. Even compared to modern markup the + explicit direct nature of the language made it so easy to learn. Every + tag served a specific purpose and each objective I had had a flag to do + it.</p> + <pre><code> +.TH REMINDME 1 +.SH NAME + remindme \- Send yourself reminders at a specific time on one or more devices +.SH SYNOPSIS +.B remindme +[\fB\-t\fR \fITIME\fR] +[\fB\-\-at \fITIME\fR] +[\fB\-i\fR \fIPERIOD\fR] +[\fB\-\-in\fR \fIPERIOD\fR] + </code> + </pre> + <p>Libnotify was insanely easy to work with, from a programming + perspective.</p> + <pre><code> + NotifyNotification *notif = notify_notification_new(title, rem->message, "info"); + notify_notification_set_app_name(notif, APP_NAME); + notify_notification_set_timeout(notif, NOTIFY_EXPIRES_NEVER); + + GError* error = NULL; + gboolean shown = notify_notification_show(notif, &error); + </code> + </pre> + <h2>In closing</h2> + <p>Overall, this was an extremely fun first week of engineering. I look + forward to what I am able to do syncing and sending notifications on + android.</p> + <p>For the zero people reading, grab a beer and outline your project. + Full through. Think about the how, then write it down. Don't worry + about getting in the weeds of how to write a manfile, thats what is fun + about programming. I thought I botched my debian/sid environment + uninstalling and reinstalling a notification daemon. Infact I think its + caused me to take a stance on the whole systemd thing. Either way, start + a private repo (they're free now) write a README and a LICENSE file + and iterate on the README until you realize "oh shit this is + something I can do". Then do it. This project still needs some work, + but for an MVP, its actually done. And now I can dive in the deep end of + trying to actually make it easy to setup on a fresh PC. Or dive into + modern android development and server syncing...</p> + </article> + |