Hi! > Maybe with adding compression it could make a replacement for > doublespace? (running it through the network redirector obviously)
Nope, doublespace compresses the actual data on your disk, not the space which is free anyway ;-). I think it would be nice to have a driver for one of those free / open compressed embedded filesystems for DOS. Some ad-hoc suggestions for a new filesystem: Keep a normal FAT and boot sector and stuff, but wrap all the access to the data clusters. For each data cluster, keep some pointer to where it ACTUALLY starts (granularity: cluster, sector or byte) and allow the clusters to be compressed. You would need some offline "make compressed version of this filesystem" tool and you would not be able to write to the filesystem later. To get a relatively simple implementation, you can assume that each cluster is separately compressed, for example with LZSS. Then you only look at one cluster at a time for uncompressing. Max amount of extra metadata: 32 bits per cluster. Note that you do not store the size of the compressed cluster nor any "this cluster is not compressed flag" - you can easily derive those from the difference between this and next cluster start. To reduce the space taken by the extra metadata, you can use a more "granular" offset for the actual data location, and you can compress the offset array by only storing the size of each compressed cluster instead of its offset. To avoid too much speed loss, you could still keep the offset of every Nth cluster in some array in RAM to reduce the needed "counting". You can even store the size of each compressed cluster in a "granular" way, eg by saying that each compressed cluster has to start at a sector boundary and thereby is a multiple of a sector size in compressed size (ignore trailing garbage). That way, you can get by with for example 1 byte of extra metadata per cluster. Actually the whole "special tables for compressed filesystem" stuff could be stored at the space taken by the second FAT :-). Then a compressed filesystem can not take more space than the uncompressed version even in the worst case of "all filled with uncompressible files". Just some inspiration for the compressed FAT FS dreamers :-D. Eric ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Freedos-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freedos-devel
