Method to virtualize large files in a sandbox

Abstract

There is provided a method and system with an improved bitmap access control method of file virtualization for large files in sandbox. The process divides a large file to pieces clusters by fixed byte counts, building a mapping relationship between logical view of sandboxed file and physical shadow file on disk. Thus, there is no need to copy an entire file when a file is modified and waste the user's disk storage.

What is claimed is: 
     
         1 . A method to provide an improved bitmap access control method of file virtualization for a large file in sandbox comprising:
 dividing a large file to pieces clusters by fixed byte counts; and   building a mapping relationship between logical view of a sandboxed file and a physical shadow file on disk.   
     
     
         2 . The method according to  claim 1 , where the large file is modified comprising:
 Dividing the large file into clusters;   Allocating a bitmap containing filesize/clustersize bits;   Running a process in a sandbox which reads a cluster from original large file if the bit is zero; and   Running a process in a sandbox which reads a cluster from shadow file if the bit is one.   
     
     
         3 . The method according to  claim 1 , where callback routine is written comprising:
 Writing a virtual file by the sandbox process;   Calculating modified clusters and marking corresponding bits to 1 in bitmap; and   Treating all clusters beyond bitmap's size as 1.   
     
     
         4 . A method according to  claim 1 , where consistent baseline view of file in sandbox is provided comprising:
 Monitoring modifications to original from outside processes;   Defining the modified cluster bit as 1 in bitmap;   Modifying the original file directly without extra process;   Defining the modified cluster bit as 0 in bitmap; and   Copying original data to the shadow file and setting corresponding bit as 1.