On Tue, Aug 6, 2024, 4:48 AM Ben Russell via Freedos-devel < freedos-devel@lists.sourceforge.net> wrote:
> 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 > I will try and update xcopy on GitHub with your suggestions and post an updated release. Jeremy
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