Why twitter can be awesome

If you were born before the 80's (heck maybe before the 90's) you have some idea what twitter is but can't understand what it is for.   Well, I've been thinking about twitter and I have a few ideas.



A tweet (a message on twitter) is a short (140 char max) thought you broadcast to the world.  Now the 'magic' of twitter is this: people can decide to listen to your message, only if they want to.  If you think a tweet is stupid, it is because it isn't written for you, instead of complaining about the tweet, you ignore it '.' This should sounds familiar, it is how broadcast works in ethernet networks, and even how conversations work on public transit.



Since tweets are public, and arguably represent what people are thinking/doing, you can do something you could never do before: see what the world is thinking.  From that starting point, you can join a conversation, or simply learn something interesting.



That said, as I'm looking at twitter, and I'm not finding any conversations I'm interested in joining, or even overhearing. Oh well I'll keep my eye on it.

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Pretty Printing XML on Windows.

It happens to the best of us, we get some ugly XML string with no formatting, and we need to view it, ideally in a formatted fashion. XMLLint is the answer. Ugly XML is the input, nicely formatted XML is the output. Finding a version of XMLLint for windows was a challenge till I found this project: http://code.google.com/p/xmllint. Unfortunately this xmllint requires an xml filename as input, and I wanted a version that takes xml on stdin, and produces pretty xml on stdout(*). Luckily this project had source code available and the pretty printing is trivial, here's the full code listing for 'my version' of XMLLint:



Example Usage(+):









NOTES:

(*) StdIn -> Filter -> StdOut is a common trick for VI folks. the syntax is: :%!

(+) Any guesses why I needed a screen shot for example usage?

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Using Vim and Ctags to edit Powershell

To use vim with a new language you need a few things firstly: indent, syntax and file type plugins. These can be found here .



Next, you need ctags support (this is how vim implements 'goto function'). Ctags doesn't natively support powershell yet, but luckily ctags supports adding languages dynamically. From the command line you can add powershell support to ctags via:

c:\> ctags.exe --langdef=powershell --langmap=powershell:.ps1 --regex-powershell="/^function[\t ]*([a-zA-Z0-9_]+)/\1/d,definition/" --regex-powershell="/^filter[\t ]*([a-zA-Z0-9_]+)/\1/d,definition/" * 

Alternatively you can pass this information into your ctags configuration file. Note that on the command line regexps are in quotes.

C:\> type %USERPROFILE%\ctags.cnf
--langdef=powershell
--langmap=powershell:.ps1
--langmap=powershell:.psm1
--regex-powershell=/^function[\t ]*([a-zA-Z0-9_-]+)/\1/d,definition/
--regex-powershell=/^filter[\t ]*([a-zA-Z0-9_-]+)/\1/d,definition/

Happy PS1Viming.

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The Performance of Everyday Things

I've spent much time fixing code optimizations that added no business value (with often matching performance value). Please do not try to make your code faster unless you need to. The way I handle performance issues on my projects:

1. Define acceptable performance.
2. Write my code as simply as possible.
3. Measure performance: against definition, if performance > acceptable - goto DONE.
4. /*Performance not acceptable*/ Profile; Fix as simply as possible; goto Measure.
5. DONE

To be explicit: I'm comfortable using slower patterns if they are clear and simple. As soon as I've hit my acceptable performance bar - I'm done.

With that out of the way, let me discuss a performance riddle I hit this week. I was wandering through some powershell code that processed slews of objects (over 200K of 'em):

$interestingObjects = @()
foreach ($object in $inputObjects) 
{
    if ($object.IsInteresting) 
    {
        $interestingObjects += $objects
    }
}

$interestingObjects

I'm a real fan of succinct code so I replaced the code with the following and it was much faster:

$inputObjects| where {$_.IsInteresting}

I prefer the succinct version of the code, but why is this one liner so much faster? The answer lies in the type of $interestingObjects:

PS C:\Users\igord> $interestingObjects.GetType()

IsPublic IsSerial Name                                     BaseType
-------- -------- ----                                     --------
True     True     Object[]                                 System.Array

$interestingObjects is an array, so when we add an item, we could end up doing an expensive operation - for example:

$Array + $item :=
     $newArray = new Object[$array.Length+1]
     $array.CopyTo(newArray,0)   # O(N) copy - nasty for large datasets.
     $newArray[$array.Length] = item
     return $newArray

BTW - in .NET List is implemented via an ArrayList. ArrayList is an Array with the helpful property that Add is mostly O(1):

• If Count already equals Capacity, the capacity of the list is doubled by automatically reallocating the internal array and copying the existing elements to the new array before the new element is added.



• If Count is less than Capacity, this method is an O(1) operation. If the capacity needs to be increased to accommodate the new element, this method becomes an O(n) operation, where n is Count.

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Do your certificate management in Powershell

I do a lot of security work, and that means lots of time poking at certificates. Tooling for certificates was never something I was happy with until I stumbled upon powershell. Let me give you a demo:

PS C:\> cd cert:

PS cert:\> cd .\LocalMachine\My
PS cert:\LocalMachine\My> dir

    Directory: Microsoft.PowerShell.Security\Certificate::LocalMachine\My


Thumbprint                                Subject
----------                                -------
4EE3FDE4FFF422935CAA0CA2783EF2CA601D6DE5  CN=NonSecretGlobalEncryptKey
272BDAC53C26CC5A8067FE6076D2F74797F69AF7  CN=igordm1, OU=Workstations, OU=Machines, DC=redmond, DC=corp, DC=microsof...


PS cert:\LocalMachine\My> cd\
PS cert:> cd .\CurrentUser\Root
PS cert:\CurrentUser\Root> dir | where {$_.Subject -like "*Veri*"}


    Directory: Microsoft.PowerShell.Security\Certificate::CurrentUser\Root


Thumbprint                                Subject
----------                                -------
18F7C1FCC3090203FD5BAA2F861A754976C8DD25  OU="NO LIABILITY ACCEPTED, (c)97 VeriSign, Inc.", OU=VeriSign Time Stampin...
85371CA6E550143DCE2803471BDE3A09E8F8770F  OU=VeriSign Trust Network, OU="(c) 1998 VeriSign, Inc. - For authorized us...
742C3192E607E424EB4549542BE1BBC53E6174E2  OU=Class 3 Public Primary Certification Authority, O="VeriSign, Inc.", C=US
4F65566336DB6598581D584A596C87934D5F2AB4  OU=Class 3 Public Primary Certification Authority, O="VeriSign, Inc.", C=US
4EB6D578499B1CCF5F581EAD56BE3D9B6744A5E5  CN=VeriSign Class 3 Public Primary Certification Authority - G5, OU="(c) 2...
24A40A1F573643A67F0A4B0749F6A22BF28ABB6B  OU=VeriSign Commercial Software Publishers CA, O="VeriSign, Inc.", L=Internet


PS cert:\CurrentUser\Root> $cert = gi 24A40A1F573643A67F0A4B0749F6A22BF28ABB6B

PS cert:\CurrentUser\Root> $cert.ToString()
[Subject]
  OU=VeriSign Commercial Software Publishers CA, O="VeriSign, Inc.", L=Internet

[Issuer]
  OU=VeriSign Commercial Software Publishers CA, O="VeriSign, Inc.", L=Internet

[Serial Number]
  03C78F37DB9228DF3CBB1AAD82FA6710

[Not Before]
  4/8/1996 5:00:00 PM

[Not After]
  1/7/2004 3:59:59 PM

[Thumbprint]
  24A40A1F573643A67F0A4B0749F6A22BF28ABB6B

PS cert:\CurrentUser\Root>

Does the output of $cert.ToString() look familiar? It's actually the ToString() on X509Certificate2. This means as well as having a great certificate store browser, you also get to access the CLR certificate classes interactively - Yeehaw!

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Need another monitor? Try a USB Video Card.

I use 3 monitors at work and it is awesome. My laptop only drives two monitors so for the 3rd monitor I picked up a USB video card,  the  EVGA 100-US-UV16A1 . This thing works (*). The device installs drivers automatically and works like a charm on Windows 7. It only supports upto 1600x1200.  Also, I don't play games so I can't tell you how well that works, but for reading email and viewing OneNote  I can't tell this is a USB video card.



(*) If you're not impressed this thing works, you should be. A back of the envelope bandwidth analysis:



Required Bandwidth:



= 1600pixels x 1200pixels x 24 bits per pixel x 30 frames/second

= 1.38 Gbps



Actual USB 2.0 bandwidth:

= 480Mbps

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Using TShark

Today I realized this blog lost its google analytics (GA) tracking. Ooops, I accidentally erased the javascript that talks to Google Analytics in my blog template. I fixed the template on my blog, and wanted to verify my browser was sending data to GA. It takes the GA UI a while to show you data is coming in, so I decided to use tshark to see if my tracker code is working.

Tshark is the command line version of Wireshark, an Ethernet level packet sniffer. Lets see what HTTP GETs occur when I connect to one of my posts:

C:\Program Files\Wireshark>tshark.exe | findstr GET
Capturing on Microsoft
1) 67.936320 192.168.1.100 -> 64.233.169.191 HTTP GET  /2009/07/finding-clr-exceptions-with-visual.html HTTP/1.1 
2) 68.211983 192.168.1.100 -> 64.233.169.191 HTTP GET /dyn-css/authorization.css?targetBlogID=7821316&zx=defa99ec-5585-4463-a42d-a32bf4868482 HTTP/1.1
3) 68.393167 192.168.1.100 -> 64.233.169.139 HTTP GET  /__utm.gif?utmwv=4.5.8&utmn=1895005015&utmhn=ig2600.blogspot.com&utmcs=UTF-8&utmsr=1600x1200&utmsc=32-bit&ut
mul=en-us&utmje=1&utmfl=10.0%20r32&utmdt=Igor%27s%20Computer%20Blog%3A%20Finding%20CLR%20exceptions%20without%20visual%20studio&utmhid=396081822&utmr=0&utmp=%2F
2009%2F07%2Ffinding-clr-exceptions-with-visual.html&utmac=UA-6806517-1&utmcc=__utma%3D91978370.809539203.1241314101.1255744665.1255763228.10%3B%2B__utmz%3D91978
370.1255744665.9.3.utmcsr%3Dblogger.com%7Cutmccn%3D(referral)%7Cutmcmd%3Dreferral%7Cutmcct%3D%2Fhtml%3B HTTP/1.1 
4) 68.393325 192.168.1.100 -> 64.233.169.191 HTTP GET /navbar.g?targetBlogID=7821316&blogName=Igor%27s+Computer+Blog&publishMode=PUBLISH_MODE_BLOGSPOT&navbarType=
BLUE&layoutType=LAYOUTS&searchRoot=http%3A%2F%2Fig2600.blogspot.com%2Fsearch&blogLocale=en_US&homepageUrl=http%3A%2F%2Fig2600.blogspot.com%2F&targetPostID=61412
67244510925043 HTTP/1.1
5) 68.517559 192.168.1.100 -> 64.233.169.191 HTTP GET /2009/07/finding-clr-exceptions-with-visual.html?action=backlinks&widgetId=Blog1&widgetType=Blog&responseTyp
e=js&postID=6141267244510925043 HTTP/1.1
6) 68.601057 192.168.1.100 -> 64.233.169.118 HTTP GET /gadgets/ifr?url=http%3A%2F%2Fwww.google.com%2Ffriendconnect%2Fgadgets%2Fmembers.xml&container=peoplesense&p
arent=http%3A%2F%2Fig2600.blogspot.com%2F&mid=0&view=profile&libs=opensocial-0.8%3Askins%3Adynamic-height%3Agoogle.blog&v=0.463.3〈=en&country=US&communityId
=02722510552710003866&caller=http%3A%2F%2Fig2600.blogspot.com%2F2009%2F07%2Ffinding-clr-exceptions-with-visual.html HTTP/1.1
7) 68.807944 192.168.1.100 -> 64.233.169.118 HTTP GET /gadgets/deps.js HTTP/1.1

What is that __utm.gif we GET in frame 3? How strange that it includes my screen resolution. A quick bing search finds this is indeed the connection to GA. So, my tracking code is good, and you should go learn how to use tshark.

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