Geekality » Snippet

JavaScript: Uppercase first letter in a string

Torleif — Wed, 30 Jun 2010 13:21:07 +0000

In PHP there is a very handy function called ucfirst which

Returns a string with the first character of str capitalized, if that character is alphabetic.

Needed that in JavaScript, but discovered there was no such thing.

Luckily I quickly found a function over at StackOverflow that I adjusted slightly and added to the string class:

String.prototype.ucfirst = function()
{
return this.charAt(0).toUpperCase() + this.substr(1);
}

Can be used like so:

alert('some text'.ucfirst())
// Alerts: Some text

Alternative method

In some cases it might be good to handle this in CSS instead though. For example to uppercase the first letter in all list items, you can do this:

li:first-letter
{
text-transform: uppercase;
}

Weeee Ok, back to work…

PHP: How to easily provide JSON and JSONP

Torleif — Sun, 27 Jun 2010 18:03:28 +0000

Have some server-side data that you would like to grab through an AJAX call? For example by using the jQuery.ajax method?

A really easy way of doing this is by using the JSON format.

JSON

It is hyper simple. All you need to do is to set the content-type to application/json and encode your data using the json_encode function.

header('content-type: application/json; charset=utf-8');

$data = array(1, 2, 3, 4, 5, 6, 7, 8, 9);

echo json_encode($data);

You can test it out for example in the FireBug console by running this line:

$.ajax({url: 'data.php'})
// Response: [1,2,3,4,5,6,7,8,9]

You should see the request being done in the console and also in the Net tab. If it didn’t work, you might be subject to the following:

Due to browser security restrictions, most “Ajax” requests are subject to the same origin policy; the request can not successfully retrieve data from a different domain, subdomain, or protocol.

A nice and simple solution to that problem is JSONP.

JSONP

As stated on Wikipedia,

JSONP or “JSON with padding” is a complement to the base JSON data format, a usage pattern that allows a page to request and more meaningfully use JSON from a server other than the primary server.

I’m not sure I get everything about JSONP, but I have used it and I know that it works It’s almost just as easy as plain JSON actually, and all that’s needed is to wrap the JSON encoded data in a callback function provided as a GET parameter.

header('content-type: application/json; charset=utf-8');

$data = array(1, 2, 3, 4, 5, 6, 7, 8, 9);

echo $_GET['callback']. '('.json_encode($data).')';

You can test it by running

$.ajax({url: 'data.php', dataType:'jsonp'})
// Response: jsonp1277656587731([1,2,3,4,5,6,7,8,9])

This time you won’t see the call in the FireBug console though, but only in the Net tab. That’s because the data is loaded in a script tag instead of through an actual AJAX call. Thankfully jQuery handles all of that though, so you don’t have to worry about it at all. You’ll get the same JSON data in your response handler, ready to be used however you want to

What if you’d like to have both options?

JSON and JSONP

Providing both is easy as cake. Just check if the callback parameter is set or not:

header('content-type: application/json; charset=utf-8');

$data = array(1, 2, 3, 4, 5, 6, 7, 8, 9);
$json = json_encode($data);

echo isset($_GET['callback'])
? "{$_GET['callback']}($json)"
: $json;

That’s all! Please comment if you have any feedback

PHP: Generating transparent PNG fillers

Torleif — Sun, 13 Jun 2010 13:45:38 +0000

So, I was fooling around the other day with an HTML table and wanted to make the odd rows slightly darker. Figured I could use for example an 80% transparent black PNG to do that (or could have just assigned a darker color, but where’s the fun in that?). Either way, ended up making a little something that I thought I could share just for the fun of it. I learned a few things, so maybe someone else can too

So, here’s how to make a small transparent PNG filler image on-the-fly using PHP

I called the script fill.php, and the first line looks like this:

header('Content-type: image/png');

This starts the php script and sets the content-type to image/png which means the web browser will that we are an image and not an html file which usually is the default.

Next up we get the parameters from the user:

$p = $_GET + array
(
'r' => 0,
'g' => 0,
'b' => 0,
'a' => 0,
);

Here I create an array with default values and merge it with the $_GET array so that values from the user will override the default values. This means we are sure we have all the values we need and that the user only have to specify the ones he want to.

The r, g and b values should be a number between 0 and 255 and the alpha value should be between 0 and 127. So, next up we need to make sure that that is the case so we don’t use some other bogus we might have gotten:

array_walk($p, function (&$item, $key)
{
$item = min(max(0, $item), $key == 'a' ? 127 : 255);
});

This goes through each parameter and makes sure it is a number between 0 and 255 (or 127 for the alpha).

Since we have what we need now, we can start with creating our image:

$img = @imagecreatetruecolor(15, 15)
or die('Cannot Initialize new GD image stream');

We also need to set a flag that we want to use full alpha channel information (as opposed to single-color transparency) in this image:

imagesavealpha($img, true);

We are now ready to fill our image with the color we are asked for:

$color = imagecolorallocatealpha($img,
$p['r'],
$p['g'],
$p['b'],
$p['a']);
imagefill($img, 0, 0, $color);

And finally output the result and destroy the image resource we have been working with:

imagepng($img, null, 9);
imagedestroy($img);

And that’s actually all there is to it!

The complete code looks like this:

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header('Content-type: image/png');

// Replace default parameters with user input
$p = $_GET + array
(
'r' => 0,
'g' => 0,
'b' => 0,
'a' => 0,
);

// Make sure they are within limits
// (colors: 0-255, alpha: 0-127)
array_walk($p, function (&$val, $key)
{
$val = min(max(0, $val), $key == 'a' ? 127 : 255);
});

// Create image
$img = @imagecreatetruecolor(15, 15)
or die('Cannot Initialize new GD image stream');

// Use full alpha channel information
imagesavealpha($img, true);

// Fill image
$color = imagecolorallocatealpha($img,
$p['r'],
$p['g'],
$p['b'],
$p['a']);
imagefill($img, 0, 0, $color);

// Output result
imagepng($img, null, 9);
imagedestroy($img);

If you want to check out a working demo version of this, you can test out my little testing tool I created while having fun with this at tools.geekality.net/filling-factory

Let me know what you think! And as usual, please let me know if you see something that is wrong or could be improved or anything like that

C#: How to send emails

Torleif — Sun, 16 May 2010 00:21:02 +0000

Sending a basic email message in a C# application is quite easy thanks to a class called SmptClient.

We simply need an address to send to, an address to send from, the message we want to send and the client:

That was pretty simple, wasn’t it? But what if we need to authenticate with our server? And what if we want to send our message in a more secure manner?

Authentication

You will quite often find that an SMTP server requires you to authenticate yourself before it will let you do anything. This is however very simple to do. All we need, is to provide our credentials to the client:

var client = new SmtpClient("smtp.example.com")
{
Credentials = new NetworkCredential
{
UserName = "me@example.com",
Password = "password",
},
};

Now, when you try to send your message like before, it should be sent without problems But what if you want to send your email securely?

Using SSL to encrypt the connection

To send emails through an encrypted connection, all you have to do is to set the EnableSSL property of the SmtpClient to true:

var client = new SmtpClient("smtp.example.com")
{
EnableSSL = true,
Credentials = new NetworkCredential
{
UserName = "me@example.com",
Password = "password",
},
};

When you now try to send your email, it will use the Secure Socket Layer to encrypt the connection. Like me, you might run into a problem though; an AuthenticationException with the following message: The remote certificate is invalid according to the validation procedure.

Imperfect certificates

After reading about how these certificates work and some more digging around I found out that the certificate of the SMTP server I use is considered invalid for two reasons: Firstly it was not issued by a trusted Certification Authority (like VeriSign or Thawte), but by my host (Dreamhost) themselves. And finally there is a mismatch between the domain I’m connecting to (smtp.example.com) and the domain the certificate was issued to (mail.dreamhost.com).

Manual certificate validation

SSL has two purposes: security and authentication. And the security will actually work fine and all the traffic will be encrypted even if the authentication fails. In other words, as long as we can look at the certificate ourselves and be sure that we thrust it, we can go ahead and continue with our work.

To check the certificate ourselves we can provide a RemoteCertificateValidationCallback delegate to a class called the ServicePointManager.

ServicePointManager.ServerCertificateValidationCallback
= OurCertificateValidation;

But how can we decide if we should trust the certificate or not? Well, I have found three ways that works nicely. Well, actually just two since the first way is to just cover your eyes and let anything pass.

Pretend validation

The following implementation is a way to simply say that I don’t care:

static bool OurCertificateValidation(object s, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
{
return true;
}

This is of course not very good… we should at least make some effort and check if the certificate is the one we should be getting. We can for example…

Check the certificate fingerprint

Certificates have something called a fingerprint and if we know the fingerprint of the certificate we should get, then we can compare it with the fingerprint of the one we actually got.

static bool OurCertificateValidation(object s, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
{
return certificate.GetCertHashString()
== "6B8C79AB966D70277BA86E6F820859A2B5B8CCC0"; // SHA-1 fingerprint
}

If you don’t think this is enough, you can for example…

Check the whole certificate

If you can export the certificate to a file somehow, you can then later compare the certificate you get with the one you have stored and make sure they are equal.

static bool OurCertificateValidation(object s, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
{
var actualCertificate = X509Certificate.CreateFromCertFile("example.cert");
return certificate.Equals(actualCertificate);
}

I got a hold of the certificate file by sticking the following snippet inside my validation delegate, ran my code once, and then changed it back to normal again:

static bool OurCertificateValidation(object s, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
{
using (var file = File.Create("example.cert"))
{
var cert = certificate.Export(X509ContentType.Cert);
file.Write(cert, 0, cert.Length);
}
return false;
}

I also successfully exported it from Opera, which I use as an email client, by going to Preferences, Security, Manage Certificates, Approved and then export the one I want. This of course assumes you have have previously approved the certificate for use with Opera.

Wrap-up

That’s all for now! Found it kind of fun to get this working and thought I could share it in case someone else struggles with this. Please comment and let me know if I have misunderstood something or done a big blunder or something like that! I mostly just know that my code is working, so if you know more about how these security issues work and you know something you think i should know as well: Please share! I’d like to learn

Here is my final complete code:

using System;
using System.Net.Mail;
using System.Net;
using System.Security.Authentication;
using System.Security.Cryptography.X509Certificates;
using System.IO;
using System.Net.Security;

namespace Geekality.SecureEmail
{
class Program
{
static bool OurCertificateValidation(object s, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
{
var actualCertificate = X509Certificate.CreateFromCertFile("example.com.cert");

return certificate.Equals(actualCertificate);
}

static void Main(string[] args)
{
// Register our own certificate validation
ServicePointManager.ServerCertificateValidationCallback = OurCertificateValidation;

// Message
var from = new MailAddress("me@example.com", "Me");
var to = new MailAddress("you@example.com", "Myself");

var message = new MailMessage(from, to)
{
Subject = "Greetings!",
Body = "How are you doing today?",
};

// Create client
var client = new SmtpClient("smtp.example.com")
{
EnableSsl = true,
Credentials = new NetworkCredential
{
UserName = "me@example.com",
Password = "password",
},
};

// Try to send
using (client)
{
try
{
client.Send(message);
Console.WriteLine("Message sent!");
}
catch (AuthenticationException e)
{
Console.WriteLine(e.Message);
}
catch (SmtpException e)
{
Console.WriteLine(e.Message);
}
}

Console.ReadKey(true);
}
}
}

How to check for duplicates

Torleif — Tue, 19 Jan 2010 16:57:09 +0000

Say you have an IEnumerable of some sort and you want to check if it contains any duplicates. How do you do that?

Terrible solution

I needed to do this a while ago and the first solution that hit me wasn’t exactly good. Linq has method called Distinct, which returns the distinct items in a sequence (weeds out duplicates). Using that to check if duplicates exists you can do something like this:

var hasDuplicates =
subjects.Count() != subjects.Distinct().Count();

This is of course a really bad solution. So don’t use it!

Good solution

The much better solution is to use a HashSet.

The HashSet class provides high performance set operations. A set is a collection that contains no duplicate elements, and whose elements are in no particular order.

In addition to the fact that it cannot contain duplicate items, it also has a very nice add-method which returns false if the item is already in the set.

To check for duplicates using a hash set we can start out by assuming there is no duplicates and then add items to the hash set until we either run out of items, or we try to add an item that already exists. In the first case our assumption was right and in the second it turned out to be wrong.

var set = new HashSet<T>();

var hasDuplicates = false;

foreach (var s in subjects)
if (!set.Add(s))
{
hasDuplicates = true;
break;
}

Good and handy solution

Since we don’t want to type in that stuff over and over again we want this snippet in a nice extension method. Code snippet coming up

using System.Collections.Generic;

namespace Geekality.Snippets
{
public static class EnumerableExtensions
{
public static bool HasDuplicates<T>(this IEnumerable<T> subjects)
{
return HasDuplicates(subjects, EqualityComparer<T>.Default);
}

public static bool HasDuplicates<T>(this IEnumerable<T> subjects, IEqualityComparer<T> comparer)
{
if(subjects == null)
throw new ArgumentNullException("subjects");

if(comparer == null)
throw new ArgumentNullException("comparer");

var set = new HashSet<T>(comparer);

foreach (var s in subjects)
if (!set.Add(s))
return true;

return false;
}
}
}

Simple and handy. You use it for example like this:

if(subjects.HasDuplicates())
{
// Do something
}

Hope it can help someone, somewhere, below and/or over the rainbow

Let me know what you think. I’m always open for improvements and feedback

Generics and checking for null

Torleif — Fri, 13 Nov 2009 16:19:15 +0000

When writing C#, in Visual Studio, using generics… have you ever tried checking for null? I have always found that a bit of a hassle.

Say we have this method which returns the subject if it is not null, and the result of a createNew() function if it is null.

public static T NewIfNull<T>(this T subject, Func<T> createNew)
{
if (subject == null)
return createNew();
return subject;
}

Not claiming this is a very useful method, but it was the simplest thing I could come up with Anyways, in Visual Studio you will now probably have a blue (is blue here at least) squiggly line under the equality operator. It states you are doing a Possible compare of value type with ‘null’, which of course is reasonable and correct. We could just ignore it and move on… but we don’t really like squiggly lines, do we? I sure don’t… so lets get rid of it.

Faulty solution

ReSharper suggests that I use default(T) instead of null, like this:

public static T NewIfNull<T>(T subject, Func<T> createNew)
{
if (subject == default(T))
return createNew();
return subject;
}

Now, this won’t do at all. First of all, we don’t really want to check for default(T), we want to check for null. And second of all, we now have a long red squiggly line under the whole equality statement! It says that it Cannot apply operator ‘==’ to operands of type ‘T’ and ‘T’. That messages doesn’t really make much sense to me, to be honest, but I trust that it is true. Either way, we have to get rid of it.

Good solution

ReferenceEquals to the rescue! We can use that method, instead of the equality operator, and compare with null like we intended!

public static T NewIfNull<T>(T subject, Func<T> createNew)
{
if (ReferenceEquals(subject, null))
return createNew();
return subject;
}

That is kind of ugly though… And it is so much longer to type. And, most importantly, it kind of makes the code a bit unreadable… At least if you have a bunch of things you have to check for null, like I did today.

But fear not! Today I came up with a tiny, but brilliant extension method which makes things a lot better:

public static bool IsNull<T>(this T subject)
{
return ReferenceEquals(subject, null);
}

public static T NewIfNull<T>(T subject, Func<T> createNew)
{
if (subject.IsNull())
return createNew();
return subject;
}

Doesn’t that just look a lot cleaner? I think so

And yes, I know this isn’t really a big issue. And I realize you have probably all come up with something similar already. Yes, I am slow But hey, I figured it might be worth sharing this anyways, just in case you hadn’t thought about it before. I sure hadn’t! And I really do think that tiny snippet of code made a huge difference in code readability. And we all want that, don’t we? Yes, yes we do…