Author

Colin is a data analyst, currently working in Whitehorse, Yukon.

Showing blog posts written by: Colin Luoma

More threading possibilities in bittyhttp

bittyhttp is a C library that I've been working on that aims to make building web services in C as easy as possible. Check out my last post for a better description and to see some examples.

One use-case that I see for bittyhttp is adding HTTP functionality to existing C applications. For example, if there is a long-running process somewhere on a server, it would be easy to expose some of its configuration over a web interface using bittyhttp. So to target this use-case there are a few changes to bittyhttp to make this particular situation easier.

Users can now start the server in its own thread. For example:

int
main(int argc, char **argv)
{
    bhttp_server *server = bhttp_server_new();
    /* setup server, add handlers, etc. */
    bhttp_server_start(server, 1);
   
    /* continue with normal application execution */

    bhttp_server_stop(server);
    bhttp_server_free(server);
    return 0;
}

This starts bittyhttp in a separate thread and returns immediately. So one could insert this at the appropriate place in an application to easily spin off an HTTP server. Then, when needed, a simple call to bhttp_server_stop and bhttp_server_free will shut down the server and free resources.

In this mode it is also possible to register new callback handlers while the server is running, adding even more flexibility. Overall, this is a small update but I think it makes it much easier to use and incorporate into other applications.

In other developments, I've also been experimenting with some sort of Lua interface to allow writing callbacks in Lua. I've actually used this in another project of mine but I'm not particularly happy with the implementation. So it's still squarely in the experimental category.

bittyhttp is distributed under GPLv3. However, if you're interested in incorporating it into your project, and need another license, feel free to reach out.

Thanks for reading!


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bittyhttp - A Threaded Library for Building REST Services in C

bittyhttp is a new library that I've been working on that aims to make building web services in C as easy as possible. Microservices and HTTP APIs are very common these days and bittyhttp offers the ability to implement these in C without much hassle. It takes care of running the server so all the user needs to do is implement their callbacks.

When using bittyhttp, the user registers handlers to URLs with a callback function pointer. If an HTTP request is received that matches the handler URL, the callback is executed. Inside the callback, information about the HTTP request is exposed and allows the user to decide how they would like to handle the request. If no handler is found, bittyhttp defaults to acting like a standard webserver.

Check out the full project on GitHub.

A Quick Example

For instance, we can register a simple handler like this:

bhttp_add_simple_handler(server,
                            BHTTP_GET | BHTTP_POST,  // http methods
                            "/helloworld",           // pattern to match
                            helloworld_handler);     // callback function

And then implement whatever logic we need in the callback like this:

int helloworld_handler(bhttp_request *req, bhttp_response *res)
{
    /* business logic */
    bstr bs;
    bstr_init(&bs);
    bstr_append_printf(&bs, "<html><p>Hello, world! from URL: %s</p><p>%s</p><p>%s</p></html>",
                      bstr_cstring(&req->uri),
                      bstr_cstring(&req->uri_path),
                      bstr_cstring(&req->uri_query));
    bhttp_res_set_body_text(res, bstr_cstring(&bs));
    bstr_free_contents(&bs);
    
    /* add custom headers and response code */
    bhttp_res_add_header(res, "content-type", "text/html");
    res->response_code = BHTTP_200_OK;
    return 0;
}

Because bittyhttp uses a separate thread to handle each request, some care needs to be taken in the callbacks to prevent race conditions. Changing data that is not allocated inside of a callback will often require the use of mutexes or similar data structures. A database connection pool, for example, would need to be properly managed.

Use Cases

I see bittyhttp having 2 primary use cases. The first being to implement often-used API endpoints in C, for performance reasons. Perhaps authentication endpoints get hit a lot and you want to speed these up.

The second is adding HTTP support to an existing C application. Maybe you have an existing long-running application on a server somewhere and you want to expose some of its configurations via HTTP. In that case, bittyhttp would be an excellent option.

bittyhttp is GPLv3 licensed, and available on GitHub, but I would be open to relicensing it for specific cases. If you are interested in using it in your application, feel free to get in contact with me at [email protected].

squid poll

As a fun, little proof-of-concept, I created a site called squid poll. It's basically a Straw Poll clone that uses bittyhttp as its API backend. Feel free to visit the site to create your own poll, or fill out the one below:


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Building a Video Baby Monitor with a Raspberry Pi and Wt

How it looks on the Raspberry Pi LCD touchscreen.

There are a lot of baby monitors out there on the market. But none of the ones with video really seemed like a good fit for us. Most either work over wifi, in which case who knows where else that video is going, or talk directly to a monitoring device, which then means keeping track of and charging another thing. I thought I could do a little better.

The task seemed straightforward enough: somehow get pictures from a camera pointed at the baby, onto my local Raspberry Pi server, where they could then be viewed by anybody with a web browser on the LAN. This way, everything stays local to our home network and we could use our smartphones to check in on the little sleeper.

I tackled the receive image and show it on a webpage side of the project first. For this I used the Wt C++ toolkit. Wt is kind of like Qt but for the web. It makes designing layouts and interfaces like building any other GUI app. It's also possible to create REST endpoints using Wt. This meant I was able have the ability to receive an image and have the viewing interface in the same application. This simplified things a lot since all the business logic could be placed in a single executable.

One cool side-effect of working with pictures is that it makes creating timelapses, like the one below, extremely easy. Watching a full night timelapse can then be pretty entertaining to see exactly how the little one ends up in such weird positions. Sometimes, the baby is most definitely not how you left it.

Timelapse shot using a few frames.

The second piece, the camera, is built from a Raspberry Pi Zero W with an infrared camera and a couple of IR LEDs, all mounted to a mini-tripod. All the camera does is take pictures every few seconds and send them to the local server, running the Wt application, via an HTTP POST request. Because all the important logic is in the Wt application, the camera unit itself remains relatively dumb. This is important so that the camera can be unplugged or moved without affecting the viewer application. No need to worry about pulling the power cord whenever.

Any web browser on the local network can access the viewing page. In practice this usually means a smartphone, but also sometimes another browser window set to 'always on top' when on a PC. The viewer shows the most recent picture it received and the timestamp that it was taken. The timestamp is important so it is easy to tell if something has stopped working. The viewer will also push the newest image over websockets to the browser and update itself without having to do any page reloads.

Overall, this turned out to be one of my more useful household projects. Both my wife and I have been using it to keep an eye on the little one while napping or in the evenings during bedtime.

Check out the full code on GitHub if you're interesting in the specifics.

I should also note, that this isn't - and shouldn't be - used as the main source of monitoring a child or baby. Our apartment is rather small so we are always in earshot. This is not a safety device! It's simply to check in on how the little one is sleeping.


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Rewriting LaserChess in the Godot Engine


Download link a the bottom of this post

About 8 years ago now, I created a computer version of the board game Khet, an Egyptian-themed, chess-like game involving mirrors and lasers. I changed it to a space theme and gave it the creative title of LaserChess.

I wrote LaserChess in the now ancient SDL 1.2 and targeted the GPH Caanoo open source handheld. SDL has sinced moved on, and this made trying to recompile it on a modern Linux installation a bit of pain. So I took this as a fun excuse to dive a little bit into the Godot Engine. Godot is an open source 2D/3D game engine and editor.

With Godot's editor and scripting language, it was pretty easy to get a quick prototype of the basic gameplay functionality up and running. Implementing the game's logic in GDScript was also surprisingly easy. LaserChess being a turn-based board game with strict rules certainly helped make things a bit simpler. Most of my time was actually spent on the user experience, trying to make buttons and menus look fancy (I hope somewhat successfully).

LaserChess also features an AI opponent, built from scratch in C, using well established techniques from chess AI engines. Godot has a feature that it calls GDNative which allows you to compile C code for integration into a Godot application. So using GDNative, I was able to re-use my old AI code to include in the Godot version of LaserChess. Despite the AI missing many optimizations, it still poses quite a challenge and I have yet to beat it on higher difficulties.

In the end, I was really impressed at what Godot was able to do with relative ease. Getting a functional prototype running was so quick I can see it being a great tool to evaluate gameplay ideas without having to start something from scratch. GDNative is also a pretty attractive feature by letting you interface with so much other code; you're not restricted to staying within Godot's scripting language.

If you're interested in the game itself, give it a try on Windows or Linux.


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Historical Linux Statistics from Steam's Hardware & Software Survey

Steam is a popular gaming storefront and platform on Window, macOS, and Linux. Every month they publish their Hardware & Software Survey with overall summary statistics of their users. The data can also be segregated by operating system.

I wanted to see how the share of Linux has changed over time on Steam. Unfortunately, the survey data is only ever available for the previous month. So I wrote a small R script (GitHub link) to scrape historic survey results from the internet archive's Wayback Machine and current data directly from Valve. A few months were missing from the Wayback Machine, which was a bummer, but enough data was available to get a feel for how the metrics have changed over time.

Steam Survey Linux User Percentage for this month

Linux User Percentage

The drop in Linux user share in late 2017 to early 2018 was due to a combination of factors. First was a counting error in the survey that Valve admitted to and later fixed. The error resulted in over-inflated user numbers from net cafes. Additionally, this time period was the peak player count for the hugely successful title PlayerUnknown's Battlegrounds. PUBG brought a lot of new players to the Steam platform from regions where net cafes are a popular way to play games. Both of these factors combined to substantially deflate the Linux user share on Steam.

Because of overall growth of Steam however, a drop in Linux share does not necessarily mean an absolute drop in Linux players. In Steam 2019 Year in Review, they mention and monthly active user count of almost 95 million. That equates to about 850k monthly Linux players during 2019.

Steam Survey Linux User Percentage

Linux User Percentage by OS Language

Restricting to reported OS language shows some interesting results with regards to the Linux share on Steam. The percentage of Linux users, of those with an English language OS, is around twice that of the general population. It's unclear whether this difference is due more English speakers preferring Linux, or more Linux users preferring English. But it's a surprising difference non-the-less.

Steam Survey Linux User Percentage by OS Language

Processor Preference of Linux Users

Since the release of AMDs Ryzen CPU line in early 2017, more and more Linux users have been foregoing Intel processors in favour of AMD. However, Intel still has a clear market lead.

Steam Survey Linux User Processor Vendor Usage

GPU Vendor Preference of Linux Users

AMD is taking up ground in the GPU space among Linux users on Steam. The results of AMDs open source initiative began to bear fruit in 2017/18 as game performance approached some of Nvidia's offerings.

Despite a closed-source video driver, Nvidia still remains the main choice among Linux users.

Steam Survey Linux User GPU Vendor Usage

Most Popular Linux Distros

Steam (unfortunately) does not report many different Linux distributions, preferring to group most in the 'Other' category.

Ubuntu remains the most popular Linux distribution on Steam and many Linux games specifically target Ubuntu as a supported OS. This has the effect of generally being the smoothest experience for new users.

Outside of Ubuntu, there is a great variety of Linux distributions, many of which will also have no issues running games on Steam.

Steam Survey Linux Top Distros

In addition to the snapshot of data above, I've setup a page on my Linux gaming blog with the same charts that are updated automatically, with an R script, whenever new data becomes available.


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