CODEWITHSUNDEEP
c#regexperformanceurl
Adam Paquette
Adam Paquette

Reputation: 1393

C# Regex optimisation

I'm trying to parse URLs from a file. My regex is working for 80% of the time but I need to modify it for exceptions. It's starting to get complicated and I would like to know how could I write a nice and clean regex for this input file to get host in one group and the URI part in a second.

Ex : http://stackoverflow.com/index.php where stackoverflow.com is the host and /index.php is the URI.

Input file : 

//cdn.sstatic.net/stackoverflow/img/favicon.ico
//cdn.sstatic.net/stackoverflow/img/apple-touch-icon.png
/opensearch.xml
/
#
http://www.stackoverflow.com
http://www.stackoverflow.com/
http://stackoverflow.com/
http://careers.stackoverflow.com
aaa#aaa.com
aaa.com#aaa
aaa#aaa
#aaa
#
fakedomain/index.php
fakedomain.com/index.php
fakedomain.com/
/fakedomain.com/
/index.html/
index.html

Regex : 

(?:.*?//)?(.*?)(/.*|$)

Result : 

1 : //cdn.sstatic.net/stackoverflow/img/favicon.ico has 2 groups:
    cdn.sstatic.net
    /stackoverflow/img/favicon.ico

2 : //cdn.sstatic.net/stackoverflow/img/apple-touch-icon.png has 2 groups:
    cdn.sstatic.net
    /stackoverflow/img/apple-touch-icon.png

3 : /opensearch.xml has 2 groups:
    /opensearch.xml

4 : / has 2 groups:

    /

5 : http://www.stackoverflow.com has 2 groups:
    http:
    //www.stackoverflow.com

6 : http://www.stackoverflow.com/ has 2 groups:
    www.stackoverflow.com
    /

7 : http://stackoverflow.com/ has 2 groups:
    stackoverflow.com
    /

8 : http://careers.stackoverflow.com has 2 groups:
    http:
    //careers.stackoverflow.com

7 : fakedomain/index.php has 2 groups:
    fakedomain
    /index.php

8 : fakedomain.com/index.php has 2 groups:
    fakedomain.com
    /index.php

9 : fakedomain.com/ has 2 groups:
    fakedomain.com
    /

10 : /fakedomain.com/ has 2 groups:

     /fakedomain.com/

11 : /index.html/ has 2 groups:

     /index.html/

12 : index.html has 2 groups:
     index.html

13 :  has 2 groups:

C# regex tester : http://derekslager.com/blog/posts/2007/09/a-better-dotnet-regular-expression-tester.ashx

So how could I remove links with .ico or .png and adding some other fixes and also getting a nice and clean regex?

Upvotes: 2

Views: 103

Answers (1)

John Spong
John Spong

Reputation: 1381

Regular expressions are a very flexible tool, but for any sort of standardized format, there is almost always a standard parser that does the job faster and better.

Use System.Uri (http://msdn.microsoft.com/en-us/library/system.uri.aspx) which will handle all of the corner cases for you.

Upvotes: 7

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