[Coco] Megaread problems

[Dave Philipsen]

On 3/27/2017 5:25 PM, Bill Pierce via Coco wrote:
> Dave, Ded allows "@" due to the fact it only reads 256 bytes at a time. Again, a definite byte count, therefore "@" is just used to tell ded to start at the raw beginning of the device instead of a file location, which is actually handled in 256 byte sectors after the file is located anyway.
> Ded ALWAYS reads just 256 bytes (1 sector) at a time regardless of whether it's a file or raw device.
> Giving ded a filename is just a way of saying "start at sector xxxx and follow this sector pattern...".
> Giving ded "@" just tells it "Start on sector 0 and read the sectors contiguously".
> Using "@" on a file (ded /dd/cmds/dir@) gets the same results as it does without the "@". It will stop on the end of the file.

Yes, but my point is that ded knows how large the device is.  For 
instance, I have a ramdisk that is 8MB ($8000 sectors from 
$0000-$7FFF).  If I ask ded to search to sector number $8000 it will not 
even try try to go there because it knows it's beyond the range of the 
device.  Ded understands how to find the size of the device when it is 
opened as 'ded /dd@' and even though it only reads 256 bytes at a time 
it *will stop* at the end of the device.

>
> Instead of adding "@" to copy, a better solution is "diskcopy" or "dsave", or even "backup" (when source and destination are of the same type & size), all of which will copy an entire disk.
> Then again, the ability to use "copy /dd /d1" would be handy....
> "One utility to bind them, one utility to rule them all!"
> :-)

I agree that diskcopy, dsave, and backup have their places. However, I 
was speaking of the ability to backup up a device as an image file which 
copy could do if it were made smart enough to understand when the 'from' 
file is actually a device.


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> Bill Pierce
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