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)

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