btrue@emdeng.Dayton.NCR.COM (Barry.True) (07/10/89)
Does anyone know of a data compression/decompression algorithm that can be used to compress an eleven byte MS-DOS file mask (i.e., filename/ext.) so that two of the bytes can be freed up for use? Sources would be helpful.
btrue@emdeng.Dayton.NCR.COM (Barry.True) (07/10/89)
Does anyone know of a data compression/decompression algorithm that we can use to compress an eleven-byte MS-DOS file mase (i.e., filename/ext.) so that two of the bytes can be freed up for use? Sources would be helpful. Please respond via E-Mail.
Bob.Stout@p6.f506.n106.z1.fidonet.org (Bob Stout) (07/13/89)
In an article of <10 Jul 89 14:19:28 GMT>, Barry.True writes: >Does anyone know of a data compression/decompression algorithm that can be >used to compress an eleven byte MS-DOS file mask (i.e., filename/ext.) so >that two of the bytes can be freed up for use? The fact that MS-DOS file names are always upper case and may only consist of alphanumeric characters plus 15 additional characters (total of 51 characters out of 256 possible codes) might suggest something. Even assuming 64 valid characters would compress 11 bytes into 8.25 bytes, thereby freeing up the two bytes you need.
richard@pantor.UUCP (Richard Sargent) (07/14/89)
> From: Bob.Stout@p6.f506.n106.z1.fidonet.org (Bob Stout) > Message-ID: <16942.24BD4537@urchin.fidonet.org> > Date: 13 Jul 89 07:18:57 GMT [ stuff deleted ] > The fact that MS-DOS file names are always upper case and may only consist of > alphanumeric characters plus 15 additional characters (total of 51 characters > out of 256 possible codes) might suggest something. Really? Try the following at your DOS prompt: c> edlin test<ALT-1-2-8>.dat ... c> dir .dat I think you'll be surprised. All codes from 128 through 255 are acceptable to DOS (actually, I only sampled the range, including boundary conditions, so maybe ALT-1-6-0 won't work, but it is unlikely). No codes between 0 and 31 seem to be acceptable. My testing was done under Compaq DOS 3.31. Richard Sargent Internet: richard@pantor.UUCP Systems Analyst UUCP: uunet!pantor!richard
tneff@bfmny0.UUCP (Tom Neff) (07/16/89)
One should not confuse the set of filenames MS-DOS will create and access (via its INT 21H system calls) with the subset thereof that the default shell COMMAND.COM is prepared to parse from your command line. Using MS-DOS calls you can create a file using almost any characters except '.' and NUL - the former delimits the name/extension boundary and the latter denotes end of string. (DOS 2.0+ routines assumed here.) Several vendors take advantage of this to put strange filenames in their directories, to keep Joe Dumb User from fooling with them or to avoid innocent name space collisions. COMMAND.COM, on the other hand, when it parses your ASCII command line to extract things like filenames, has far stricter rules. This isn't really comp.lang.c but what the heck. -- "My God, Thiokol, when do you \\ Tom Neff want me to launch -- next April?" \\ uunet!bfmny0!tneff
Bob.Stout@p6.f506.n106.z1.fidonet.org (Bob Stout) (07/17/89)
In an article of <14 Jul 89 14:05:55 GMT>, (Richard Sargent) writes: >> From: Bob.Stout@p6.f506.n106.z1.fidonet.org (Bob Stout) >> The fact that MS-DOS file names are always upper case and may only consist >> of alphanumeric characters plus 15 additional characters (total of 51 >> characters out of 256 possible codes) might suggest something. > >Really? Try the following at your DOS prompt: > >c> edlin test<ALT-1-2-8>.dat >... >c> dir .dat > >I think you'll be surprised. All codes from 128 through 255 are acceptable OK, you got me - DOS internally couldn't care less, but the docs for most versions of DOS will tell you that only A-Z, 0-9, and most special characters other than '*', '?', '.', and ' ' are legal. If you follow the rules (i.e. guaranteed to work for all versions of DOS including those yet to come) laid down my Microsoft and IBM, 64 characters should suffice.
diamond@csl.sony.JUNET (Norman Diamond) (07/20/89)
In an article of <14 Jul 89 14:05:55 GMT>, (Richard Sargent) writes: >>I think you'll be surprised. All codes from 128 through 255 are acceptable [to MS-DOS]. In article <17193.24C32414@urchin.fidonet.org> Bob.Stout@p6.f506.n106.z1.fidonet.org (Bob Stout) writes: >OK, you got me - DOS internally couldn't care less, but the docs for most >versions of DOS will tell you that only A-Z, 0-9, and most special characters >other than '*', '?', '.', and ' ' are legal. If you follow the rules (i.e. >guaranteed to work for all versions of DOS including those yet to come) laid >down my Microsoft and IBM, 64 characters should suffice. Some versions of MS-DOS are sold to the other 80% of the industrialized world. So some versions of MS-DOS permit some of those other characters to be used. The rules are not guaranteed and it is not a good idea to "know" that 64 characters suffice. -- -- Norman Diamond, Sony Computer Science Lab (diamond%csl.sony.jp@relay.cs.net) The above opinions are inherited by your machine's init process (pid 1), after being disowned and orphaned. However, if you see this at Waterloo or Anterior, then their administrators must have approved of these opinions.
spierk@turing.cs.rpi.edu (Kevin Spier) (08/16/90)
I am looking for a book which describes a variety of compression schemes and algorithms along with sample C implementations. Please e-mail your suggestions to me and will post a summary if there is interest. Kevin L. Spier spierk@turing.cs.rpi.edu Kevin L. Spier spierk@turing.cs.rpi.edu