On 06/08/2024 04:55, Wilhelm Spiegl via Freedos-devel wrote:
I just stumbled over this old bug report referring to xcopy:
https://sourceforge.net/p/freedos/bugs/346/
It is still active. means: It can happen that only some files will be
copied, others not.
A comment in that thread links to a repo on GitHub, FDOS/xcopy. It has a
"version 1.5" last updated 3 years ago. From an examination of the code,
the bug is probably still present.
The two checks are in the form "if (number_of_bytes_to_add >
free_diskspace) { complain(); clean_up(); exit(39); }".
Part of me would be tempted to do "ceiling division" in both cases and
operate in terms of clusters, while another part of me is aware that
doing an unsigned 32-bit saturating multiply would probably be "good
enough".
... now that I think of it, converting the sizes from bytes to clusters
via ceiling division would actually be the best solution here.
That is: (WARNING: This is untested, might not even compile, and would
need to have its math checked possibly via exhaustive search)
getdfree(dest_drive, &disktable);
[unsigned long] bpc = (unsigned long) disktable.df_sclus *
disktable.df_bsec; /* bytes per cluster, 2^10 x 2^16 = 2^26 < 2^32 so
this step should be OK */
[unsigned long] free_clusters = (unsigned long) disktable.df_avail;
and the easy case (the "else" block used when a file does not already
exist):
if ((src_statbuf.st_size + (cpb - 1UL)) / cpb > free_clusters) { ... }
and the hard case (the "if" block used when a file already exists):
if ( (src_statbuf.st_size > dest_statbuf.st_size) &&
((src_statbuf.st_size + (bpc - 1UL)) / bpc - (dest_statbuf.st_size +
(bpc - 1UL)) / bpc) > free_clusters) ) { ... }
I claim no copyright on these code snippets, but they will end up under
GPLv2-only due to the Xcopy project licence.
Regards,
Ben R
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