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Dailyprogammer Challenge #199 - Bank Numbers Pt 1

I have attempted another dailyprogammer challenge on reddit.

This time, the challenge is to take a number in and print a 'banner' representing that number, like this:

Input: 47262

Output:
    _  _  _  _
|_|  | _||_  _|
  |  ||_ |_||_

Here is my solution:

using System;

public class BigDigits
{
    static string[,] bannerTemplates = new string[,]{
        { " _ ", "| |", "|_|" },
        { "   ", "  |", "  |" },
        { " _ ", " _|", "|_ " },
        { " _ ", " _|", " _|" },
        { "   ", "|_|", "  |" },
        { " _ ", "|_ ", " _|" },
        { " _ ", "|_ ", "|_|" },
        { " _ ", "  |", "  |" },
        { " _ ", "|_|", "|_|" },
        { " _ ", "|_|", " _|" }
    };

    static void Main(string[] args)
    {
        if (args.Length == 0)
        {
            Console.WriteLine("This program converts a number to a banner.");
            Console.WriteLine("\nUse it like this: ");
            Console.WriteLine("    bigintbanners.exe <number>");
            Console.WriteLine("\n<number>: The number you want to convert.");
            return;
        }

        char[] intChars = args[0].ToCharArray();
        string[] resultLines = new string[3];
        int currentDigit = 0;

        int i = 0;

        for(i = 0; i < intChars.Length; i++)
        {
            currentDigit = int.Parse(intChars[i].ToString());
            for (int j = 0; j < 3; j++)
            {
                resultLines[j] += bannerTemplates[currentDigit,j];
            }
        }

        for(i = 0; i < resultLines.Length; i++)
        {
            Console.WriteLine(resultLines[i]);
        }
    }
}

I find the dailyprogrammer challenges to be a great way to practice a language that you are learning.

32 bit binary, SHA1: 0fc2483dacf151b162e22b3f9b4c5c64e6fe5bdf

Reddit post link

Ask below if you need a different binary (e.g. 64 bit, ARM, etc)

Stardust Update: Email Notifications

Welcome to another blog update.

Yesterday I added email notifications to the blog comments. You may have noticed that there is an extra optional field for you to put your email address in when commenting. If you do so, anybody who replies to your comment will trigger an email notification which will go to the email address that you specified.

Currently the only method I have for you to unsubscribe from these emails is to email emails at starbeamrainbowlabs dot com, and I will process your request manually. Make sure that you include a copy of the email that you don't want anymore, since it contains information about the comment that you posted that I will have to edit. In the future I hope to have an automated system that you will be able to use.

If you notice any issues with this, please leave a comment below.

The other thing that I added is email notifications for myself. Now, every time somebody comments on my blog I will receive an email notification telling me about it. This is mainly because I forgot to check for new comments - you should receive a reply to your comment much faster now :)

Finding Favicons with PHP

There hasn't been a post here for a little while because I have been ill. I am back now though :)

While writing more Bloworm, I needed a function that would automatically detect the url of the favicon that is associated with a given url. I wrote a quick function to do this a while ago - and have been improving it little by little.

I now have it at a point where it finds the correct url 99% of the time, so I thought that I would share it with you.

/*
 * @summary Given a url, this function will attempt to find it's correspending favicon.
 *
 * @returns The url of the corresponding favicon.
 */
function auto_find_favicon_url($url)
{
    if(!validate_url($url))
        senderror(new api_error(400, 520, "The url you specified for the favicon was invalid."));

    // todo protect against downloading large files
    // todo send HEAD request instead of GET request
    try {
        $headers = get_headers($url, true);
    } catch (Exception $e) {
        senderror(new api_error(502, 710, "Failed to fetch the headers from url: $url"));
    }
    $headers = array_change_key_case($headers);

    $urlparts = [];
    preg_match("/^([a-z]+)\:(?:\/\/)?([^\/?#]+)(.*)/i", $url, $urlparts);

    $content_type = $headers["content-type"];
    if(!is_string($content_type)) // account for arrays of content types
        $content_type = $content_type[0];

    $faviconurl = "images/favicon-default.png";
    if(strpos($content_type, "text/html") !== false)
    {
        try {
            $html = file_get_contents($url);
        } catch (Exception $e) {
            senderror(new api_error(502, 711, "Failed to fetch url: $url"));
        }
        $matches = [];
        if(preg_match("/rel=\"shortcut(?: icon)?\" (?:href=[\'\"]([^\'\"]+)[\'\"])/i", $html, $matches) === 1)
        {
            $faviconurl = $matches[1];
            // make sure that the favicon url is absolute
            if(preg_match("/^[a-z]+\:(?:\/\/)?/i", $faviconurl) === 0)
            {
                // the url is not absolute, make it absolute
                $basepath = dirname($urlparts[3]);

                // the path should not include the basepath if the favicon url begins with a slash
                if(substr($faviconurl, 0, 1) === "/")
                {
                    $faviconurl = "$urlparts[1]://$urlparts[2]$faviconurl";
                }
                else
                {
                    $faviconurl = "$urlparts[1]://$urlparts[2]$basepath/$faviconurl";
                }
            }
        }
    }

    if($faviconurl == "images/favicon-default.png")
    {
        // we have not found the url of the favicon yet, parse the url
        // todo guard against invalid urls

        $faviconurl = "$urlparts[1]://$urlparts[2]/favicon.ico";
        $faviconurl = follow_redirects($faviconurl);
        $favheaders = get_headers($faviconurl, true);
        $favheaders = array_change_key_case($favheaders);

        if(preg_match("/2\d{3}/i", $favheaders[0]) === 0)
            return $faviconurl;
    }

    return $faviconurl;
}

This code is pulled directly from the Bloworm source code - so you will need to edit it slightly to suit your needs. It is not perfect, and will probably will be updated from time to time.

Cool Resources: Subtle Patterns

An example of a pattern from subtlepatterns.com.

I have a different sort of post for you today: A post about pair of websites that I have found that are really quite useful. Quite often when I am creating a website or webpage for some reason or other (today I needed one for bloworm), I keep finding that it always looks a bit plain. These websites that I have found today help to partially solve that problem. They are full of simple tileable textures that look great as backgrounds in many different contexts.

The first is called subtlepatterns.com. It contains a bunch of free to use textures that go well in the background of something without standing out.

The second is called transparenttextures.com. It is similar to the website above - but the textures it provides are transparent so that you can overlay them on top of something else. These are good when you have a colour in mind, but want to add a little something to it to make it look a little less plain.

Dailyprogrammer challenge #197 - Validating ISBN Numbers

Hello again!

I now have a reddit account. You can find it here: https://www.reddit.com/user/starbeamrainbowlabs

I have attempted the latest Daily Programmer challenge.

This time I have written it in javascript. The challenge was to validate an ISBN-10 number. To validate an ISBN-10 number, you add 10 times the first number to 9 times the second number to 8 times the third number and so on. This total should leave no remainder when divided by 11. In addition, the letter X stands for a value of 10.

Here is my solution:

function validate_isbn(isbn) {
    var i = 10,
        tot = isbn.replace(/-/g, "").split("").reduce(function (total, char) {
            if (char.toLowerCase() == "x")
                total += i * 10;
            else
                total += i * parseInt(char);
            i--;
            return total;
        }, 0);

    if (tot % 11 === 0)
        return true;
    else
        return false;
}

I minified it by hand too:

function validate_isbn(a){var i = 10;if(a.replace(/-/g,"").split("").reduce(function(b, c){if(c.toLowerCase()=="x")b+=i*10;else b+=i* parseInt(c);i--;return b;},0)%11==0)return true;else return false;}

I should probably attempt the next challenge in C♯ so that I keep practising it.

The daily programmer challenge can be found here: Daily Programmer Challenge #197 - ISBN Validator

Sorting Algorithms 3 / 5: Insertion Sort

Hello again!

This is the 3rd of 5 sorting algorithms that I will be implementing and posting about.

Today I have a reverse insertion sorter for you.

An (reverse) insertion sort takes number one from the end of the array, and shuffles it along to the right until it is in the right place. Then it picks the next number along and does the same, until the whole array is sorted.

/// <summary>
/// Performs an insertion sort in the array.
/// </summary>
/// <param name="array">A reference to the array to sort.</param>
static void insertion_sort(ref int[] array)
{
    for (int i = array.Length - 2; i >= 0; i--)
    {
        int shp = i;
        //                                                      |
        //make sure that we don't fall off the end of the array V
        while(shp < array.Length - 1 && array[shp] > array[shp + 1]) 
        {
            swap_places(ref array, shp, shp + 1);
            shp++;
        }

        Console.Write("i: {0} ", i);
        print_array(ref array);
    }
}

Here is some example output:

[ 17, 10, 83, 67, 8, 50, 46, 63, 2, 41, 95, 92, 96, 69, 97, 67, 14, 53, 1, 38, 47, 63, 68, 91, 93 ]
i: 23 [ 17, 10, 83, 67, 8, 50, 46, 63, 2, 41, 95, 92, 96, 69, 97, 67, 14, 53, 1, 38, 47, 63, 68, 91, 93 ]
i: 22 [ 17, 10, 83, 67, 8, 50, 46, 63, 2, 41, 95, 92, 96, 69, 97, 67, 14, 53, 1, 38, 47, 63, 68, 91, 93 ]
i: 21 [ 17, 10, 83, 67, 8, 50, 46, 63, 2, 41, 95, 92, 96, 69, 97, 67, 14, 53, 1, 38, 47, 63, 68, 91, 93 ]
i: 20 [ 17, 10, 83, 67, 8, 50, 46, 63, 2, 41, 95, 92, 96, 69, 97, 67, 14, 53, 1, 38, 47, 63, 68, 91, 93 ]
i: 19 [ 17, 10, 83, 67, 8, 50, 46, 63, 2, 41, 95, 92, 96, 69, 97, 67, 14, 53, 1, 38, 47, 63, 68, 91, 93 ]
i: 18 [ 17, 10, 83, 67, 8, 50, 46, 63, 2, 41, 95, 92, 96, 69, 97, 67, 14, 53, 1, 38, 47, 63, 68, 91, 93 ]
i: 17 [ 17, 10, 83, 67, 8, 50, 46, 63, 2, 41, 95, 92, 96, 69, 97, 67, 14, 1, 38, 47, 53, 63, 68, 91, 93 ]
i: 16 [ 17, 10, 83, 67, 8, 50, 46, 63, 2, 41, 95, 92, 96, 69, 97, 67, 1, 14, 38, 47, 53, 63, 68, 91, 93 ]
i: 15 [ 17, 10, 83, 67, 8, 50, 46, 63, 2, 41, 95, 92, 96, 69, 97, 1, 14, 38, 47, 53, 63, 67, 68, 91, 93 ]
i: 14 [ 17, 10, 83, 67, 8, 50, 46, 63, 2, 41, 95, 92, 96, 69, 1, 14, 38, 47, 53, 63, 67, 68, 91, 93, 97 ]
i: 13 [ 17, 10, 83, 67, 8, 50, 46, 63, 2, 41, 95, 92, 96, 1, 14, 38, 47, 53, 63, 67, 68, 69, 91, 93, 97 ]
i: 12 [ 17, 10, 83, 67, 8, 50, 46, 63, 2, 41, 95, 92, 1, 14, 38, 47, 53, 63, 67, 68, 69, 91, 93, 96, 97 ]
i: 11 [ 17, 10, 83, 67, 8, 50, 46, 63, 2, 41, 95, 1, 14, 38, 47, 53, 63, 67, 68, 69, 91, 92, 93, 96, 97 ]
i: 10 [ 17, 10, 83, 67, 8, 50, 46, 63, 2, 41, 1, 14, 38, 47, 53, 63, 67, 68, 69, 91, 92, 93, 95, 96, 97 ]
i: 9 [ 17, 10, 83, 67, 8, 50, 46, 63, 2, 1, 14, 38, 41, 47, 53, 63, 67, 68, 69, 91, 92, 93, 95, 96, 97 ]
i: 8 [ 17, 10, 83, 67, 8, 50, 46, 63, 1, 2, 14, 38, 41, 47, 53, 63, 67, 68, 69, 91, 92, 93, 95, 96, 97 ]
i: 7 [ 17, 10, 83, 67, 8, 50, 46, 1, 2, 14, 38, 41, 47, 53, 63, 63, 67, 68, 69, 91, 92, 93, 95, 96, 97 ]
i: 6 [ 17, 10, 83, 67, 8, 50, 1, 2, 14, 38, 41, 46, 47, 53, 63, 63, 67, 68, 69, 91, 92, 93, 95, 96, 97 ]
i: 5 [ 17, 10, 83, 67, 8, 1, 2, 14, 38, 41, 46, 47, 50, 53, 63, 63, 67, 68, 69, 91, 92, 93, 95, 96, 97 ]
i: 4 [ 17, 10, 83, 67, 1, 2, 8, 14, 38, 41, 46, 47, 50, 53, 63, 63, 67, 68, 69, 91, 92, 93, 95, 96, 97 ]
i: 3 [ 17, 10, 83, 1, 2, 8, 14, 38, 41, 46, 47, 50, 53, 63, 63, 67, 67, 68, 69, 91, 92, 93, 95, 96, 97 ]
i: 2 [ 17, 10, 1, 2, 8, 14, 38, 41, 46, 47, 50, 53, 63, 63, 67, 67, 68, 69, 83, 91, 92, 93, 95, 96, 97 ]
i: 1 [ 17, 1, 2, 8, 10, 14, 38, 41, 46, 47, 50, 53, 63, 63, 67, 67, 68, 69, 83, 91, 92, 93, 95, 96, 97 ]
i: 0 [ 1, 2, 8, 10, 14, 17, 38, 41, 46, 47, 50, 53, 63, 63, 67, 67, 68, 69, 83, 91, 92, 93, 95, 96, 97 ]

Full source code (pastebin)

Binary (MD5: 01b2d774c70ce46d8e0641da948bc25e, SHA1: 537ee665162887f629200d8839b108a3e4098d38)

Recording animated gifs on Linux with Silentcast

Using Silentcast

A few months ago I was asked how I created animated gifs on Linux, and I said that I use silentcast. I also said that I'd write a blog post on it. I've been very busy since then, but now I have found some time when I remembered to post about it and am not exhausted.

Silentcast is a very versatile screen recording application that outputs either a set of png images, an animated gif, or 2 different types of video. It uses png files to store frames, so it isn't suitable for recording at a high fps or for very long, but it is still brilliant for recording short clips for your blog or to accopany a bug report.

Silentcast's dialogs stay in front of everything else that you have open, so you don't need to worry about loosing the window somewhere along the line. It integrates nicely with the Unity desktop (I haven't tried others yet), which makes it feel more intuitive and makes it easer to use. It also allows you to modify the intermediate png files before the final product is stitched together, too, allowing for precise edits to make the resulting gif loop perfectly.

It is written in bash, which makes it perfectly suited for usage on both Mac and Linux system , but I don't think that Windows is supported as of the time of posting. The other issue is that it took me a little while to work out how to record a custom area - this is done by the "Transparent Window Interior" option under "Area to be recorded". I also find it to be a little bit unpoliished around the edges (the icon especially needs some work), but overall it is an excellent piece of software that makes recording an animated gif on Linux a breeze - it's streets ahead of any other competing projects.

The animated gif above was taken and modified from Silentcast's GitHub project page.

Algorithms 2 / 5: Reverse Selection Sort

It has been a while since I have implemented a sorting algorithm - I should probably have implemented these a little bit earlier than I have done :)

Today I bring you the C sharp version of the selection sort I posted earlier. To mix it up a bit htough this implementation is in reverse.

  1. Find the largest number in the sequence
  2. If it is larger than the number at the end of the array, swap them
  3. Find the next largest number
  4. If it is larger than the next number along from the end of the array, swap them
  5. Repeat steps 3 and 4 until all the numbers have been sorted.

Here is the code:

/// <summary>
/// Performs a selection sort on an array of ints.
/// </summary>
/// <param name="array">The array to sort.</param>
static void selection_sort(ref int[] array)
{
    int limit = array.Length - 1;
    while(limit > 0)
    {
        //find the index with the maximum value
        int max_index = 0; //set the max to the first element in the array
        //don't search the first element in the array, we have already done that on the line above
        for(int i = limit - 1; i > 0; i--)
        {
            if(array[i] > array[max_index])
                max_index = i;
        }
        if(array[max_index] > array[limit])
        {
            //we have found an index with a high value than the current limit
            swap_places(ref array, max_index, limit);
        }

        limit--;
    }
}

Full Source Code (pastebin) Link to binary (MD5: ef5e0f15c9bc181d36b193160e3f8ad9 SHA1: ad49eb97675ca6ec9cc9dfebb63fbe03cfa27534)

Next up: Insertion sorting.

Twitter Account

I now have a twitter account!

You can find it here.

It will be mostly automated, once I rewrite the blog posting system. Until then I will post manually.

I plan to have the blog automatically tweet about new blog posts, but I will have to build some kind of system that will be able to tell the difference between new and updated posts first, since I make usually make several corrections to each my blog posts once I have posted them.

Following Redirects in PHP

Recently I have found that PHP sometimes doesn't follow redirects (e.g. the get_headers() function). So I wrote this quick function to follow a url's redirects to a certain depth:

/*
 * @summary Follows a chain of redirects and returns that last url in the sequence.
 * 
 * @param $url - The url to start at.
 * @param $maxdepth - The maximum depth to which to travel following redirects.
 * 
 * @returns The url at the end of the redirect chain.
 */
function follow_redirects($url, $maxdepth = 10, $depth = 0)
{
    //return the current url if we have hit the maximum depth
    if($depth >= $maxdepth)
        return $url;

    //download the headers from the url and make all the keys lowercase
    $headers = get_headers($url, true);
    $headers = array_change_key_case($headers);
    //we have a redirect if the `location` header is set
    if(isset($headers["location"]))
    {
        return follow_redirects($headers["location"], $maxdepth, $depth + 1);
    }
    else
    {
        return $url;
    }
}

For example, you could do this:

follow_redirects("https://example.com/some/path", 5);

That would follow the redirects, starting at https://example.com/some/path, to a maximum depth of 5 urls.

When I learn networking in C♯ (and if it doesn't follow redirects), I will rewrite this function in C♯ for you.

Art by Mythdael