Club Amiga de Montreal - CAM/CAM_CD_1.iso/files/345.lha/trackutil/tfile.doc

Text File | 1990-01-28 | 5.6 KB | 130 lines

                      TFILE -- reserves tracks on a disk

             (C) Copyright Eddy Carroll 1990. Freely distributable.


INTRODUCTION

    There are occasionally times when you want highspeed access to floppy
    disks, and don't want the overhead associated with going through
    AmigaDos. One example might be a program to play sound samples
    directly from disk (reading in a track's worth of data at a time).
    Another example is copying a "minidisk" into RAD: during bootup (see
    the documentation for TCOPY for more information on this).

    This is fine in theory, but if you go and start using disk tracks for
    your own data, sooner or later you're going to overwrite some AmigaDOS
    information (or AmigaDOS will overwrite your tracks). What you really
    need is a way to tell AmigaDOS not to use the tracks that you are
    using.

    This is in fact exactly what TFILE does (what a coincidence :-)
    It creates a dummy file on a disk that looks to AmigaDOS as if it
    contains all the blocks associated with a range of tracks. You can
    then happily intermix your private data and standard AmigaDOS files
    without any danger of one corrupting the other. For example, if you
    have a game that wants direct access to your hard drive, you could
    reserve a few cylinders for it to use without having to do a complete
    reformat and partition. Similarly for something like AMax.


USAGE

    The command template for Tfile looks like this:

        tfile <pathname> <start> <end>

    <pathname> is the full AmigaDOS pathname of the file you want to
    create which will reserve the tracks. You must specify a disk device
    (such as DF0:) rather than a volume name. You may like to stick the
    file out of the way in the Devs directory or some such place, called
    something like TracksX-Y.

    <start> and <end> specify the range of tracks to be reserved. When
    you run Tfile, these tracks must not be in use by AmigaDOS or Tfile
    will complain. Hence, it's a good idea to run Tfile shortly after you
    have just formatted a disk, and only then copy over any AmigaDOS files
    you want to use (AmigaDOS will arrange them nicely around your reserved
    tracks). Obviously, <start> must be less than <end>, and neither can
    exceed the number of tracks available on the disk. Tracks are numbered
    from 0 upwards, so the 80 tracks on DF0: are numbered 0 to 79.

    AmigaDOS usually reserves a few blocks at the start of a disk for
    private information. The bootblock on floppy disks is a good example
    of this. If the track range you specify includes these reserved blocks,
    Tfile will print a warning message. You can safely ignore this -- it is
    just there to remind you that you need to be careful writing to the
    tracks you specified so as not to overwrite important information.

    To make things clearer, a quick example might be useful. Lets suppose
    you want to reserve the last 10 tracks on a floppy disk for some
    reason (tracks 70 to 79). Just put the disk in DF0: and say

        tfile df0:Tracks70-79 70 79

    and after a few moments of disk access, you will find yourself with
    a new file which is 107848 bytes in size, and a correspondingly
    smaller amount of room on the disk.


ADDITIONAL NOTES

    Tfile will work with both the old filing system and fast filing system.
    On the OFS, if you try to display the dummy file, you will see a brief
    message telling you that it isn't a real file, and describing which
    tracks it reserves. You will not be able to access anything other
    than the message, and it's not a good idea to try and fool AmigaDOS
    into letting you.

    On the FFS, you will see the same message, but shortly after that will
    come the actual raw track data itself. This is due to the different
    ways the OFS and FFS store the data blocks of a file. If you have a
    file editor such as NewZap, you can even edit the disk blocks directly;
    with the exception of the initial "message" block, the blocks are
    arranged in sequence from the start to end track.

    You can have several different portions of the disk reserved if you
    like (you might want to reserve almost all of the disk except for a
    little bit in the middle for the AmigaDOS root block).

    When you are finished using the tracks, you can release the blocks
    back to AmigaDOS by deleting the dummy file.

    You may occasionally have trouble finding free room on a disk. David
    Gay has written a nice pair of programs which display disk fragmentation
    and free blocks. These can be found on Fish Disk 278
    under the collective title `frag'.


FUTURE ADDITIONS

    One thing I would like to add is the ability to read in a list of
    block numbers from a file and reserve those blocks listed, rather
    than being restricted to complete tracks. You could then use Tfile
    to map out bad blocks on hard drives, in conjunction with some
    program that would actually find such blocks for you. As it is,
    you could use Tfile to map out bad tracks on AmigaDOS floppies,
    but given the cost of blank disks these days and the chances of
    a disk with one bad track developing others, it's not really
    a sensible gamble.

    To add block lists would not be too difficult given the current
    implementation; the only thing needed is time. Unfortunately, I don't
    have very much of that at the moment, so don't expect them any time soon.


RELEASE HISTORY

    V1.0
        First release, January 1990. No known bugs, as yet.


AUTHOR

    Please direct any praise, criticism, general suggestions or
    large sums of money to:

    Eddy Carroll
    [e-mail] (Trinity College, Dublin, Ireland)