Circular File

When I wrote my first article on CodeGuru, Expandable, Data Type-Neutral Buffer Class, I realized that there are lot of people seeking the code for a circular file. Hence, I developed my own circular file implementation, and want to share this. Its interface is very simple. Everything basically revolves around the Addline(CString) method which you use to add a line at a time to the current file.


  • //Create New File with Name "default Log" with 100 Lines
  • //Create File with Name strFile Name But 100 lines
    CCirFile(char * strFileName); 
  • //You can specify file Name and File Size
    CCirFile(char * ,int ); 


  • //All file initialization here
    int InitFile(); 
  • //You should call this function to add new line at start of file
    int AddLine( CString );  


  • It's not a true circular file implementation. It adds each new line to the beginning of the file, and moves the remaining lines, truncating the last line
  • It's slow and performance could be dramatically increased via the use of multiple threads.


Download demo project - 28 Kb


  • Interesting, but what limitations :(

    Posted by Legacy on 07/09/2002 12:00am

    Originally posted by: C�dric

    Your implementation is interesting and even more because you're cool guy  who shares it.

    As you said, the 'AddLine()' is slow and doesn't produce a real circular file. So an easy way to improve it erasing this two limitations is to use the next ZwXxx Routines of the MSDN Library :

    - ZwCreateFile()
    - ZwWriteFile() and ByteOffset args
    - ZwQueryInformationFile() and FILE_STANDARD_INFORMATION
    - ZwClose()

    Indeed, you can limit the size of the file thanks to an if_then_else instruction and the ZwQueryInformationFile Routine. Then, the args ByteOffset allow to write from a selected byte in the file. So you can simply implement a real circular file.

    Thanks, bye. ;o)

Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • The open source cloud computing project OpenStack has come a long way since NASA and Rackspace launched it in 2010. Backed by leading technology infrastructure providers including Cisco, Dell, EMC, HP, IBM, Intel, and VMware, OpenStack underpins significant workloads at an increasingly diverse set of organizations, including BWM, CERN, Comcast, eBay, and Wal-Mart. For CIOs engaged in broader programs to win, serve, and retain customers -- and refocus business technology (BT) spend -- a planned and pragmatic …

  • Featuring Art Schoeller, VP and Principal Analyst, at Forrester Research Live Event Date: November 9, 2016 @ 10 AM PT / 1 PM ET Being "proactive" with your customers is not enough to survive in the market today. The truth is, organizations that understand how to engage customers on their preferred channels will create contextual, and relevant experiences for customers. Plus, they will see the financial impact of nurturing long-term customer loyalty. Join our guest speaker Art Schoeller, VP and Principal …

Most Popular Programming Stories

More for Developers

RSS Feeds

Thanks for your registration, follow us on our social networks to keep up-to-date