File asString: unable to read file 'projects/opensource/journaledfile/_visible'

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menu                  71 	 1491 	 asString
menu                  219 	 5303 	 name
menu                  252 	 6212 	 parentTable
menu                  131 	 2753 	 allMenus
menu                  389 	 9756 	 displayHeader









journaledfile

a transactional files library





  overview 



A library that supports journaled transactional files. This allows writes to be done to a file without risking file corruption in the event that the process or OS crashes or the power goes out.

How it works:


  
 for each write, it logs the file position, length of 
       write and the data to a log file (file.log) 
  

  
 when JFile_sync() is called:

    

      
 it sets the log header status to "committed"

      
 the log writes are performed on output file
 
      
 the log file is truncated and it's status set to "uncommitted"

    
  

  
 when JFile is opened, if it finds a log file then:

    

       
 if the log status is "committed":

          it assumes the log did not complete it's write so it 

          writes the log to the file again and removes the log and lock

       
 if the log status is "uncommitted":

          it assumes the log is not complete and removes it

    


In this way, the output file is assured to be keep in a consistent 
state (or at least one that corresponds to a sync point).

Also, a read will trigger a sync.

Notes: The log file is byte order dependent.
Also, you never interact with the file pointer directly. 
When you need to position the file pointer, use JFile_setPosition().






  license 


 Revised BSD 








  download 



  JournaledFile.tgz