On 9/15/22 16:32, enh wrote: > On Thu, Sep 15, 2022 at 1:45 PM Rob Landley <r...@landley.net > <mailto:r...@landley.net>> wrote: > > On 9/15/22 07:30, Yi-yo Chiang via Toybox wrote: > > grep is slow when the number of patterns is large. > ... > > xxd -p -c 0 -l 40 /dev/urandom > > Huh, WHY does that produce two lines of output? > > $ xxd -p -c 0 -l 40 /dev/urandom > 1fcf13e1b4844ba209fb9958bde26a13577c577744f1b1290240d03f4f8e > 644fd0687c39b1aa8a68 > > Behavior is consistent between toybox xxd and debian's, but Elliott sent > in the > xxd implementation and I don't use it much, so... Feeding in -c 40 and -c > 80 > make no difference? > > i think that's actually a bug caused by this: > > // Plain style is 30 bytes/line, no grouping. > > if (FLAG(p)) TT.c = TT.g = 30; > > should presumably be > > // Plain style is 30 bytes/line, no grouping. > if (FLAG(p)) { > if (!TT.c) TT.c = 30; > if (!TT.g) TT.g = 30; > } > > ?
Except we didn't set -g so it would still be set to 30, which is going to stick spaces into the output. And xxd_main() starts with if (!TT.c) TT.c = blah so it would never be zero at that point unless we reorder the code, and then once THAT'S fixed -c 0 is still !TT.c and if I switch that to if (FLAG(c)) to allow c = 0 through (which the range in the optstr is allowing) it's used to cap the length in readall() meaning the first read becomes EOF so no output gets produced. > certainly "real" xxd works for me on macos and debian, both of which have the > same version of xxd: > > ~$ xxd --version > xxd 2022-01-14 by Juergen Weigert et al. > ~$ xxd -p -c 0 -l 40 /dev/urandom > ac160632955aa9d938e60d3533cbcf0febb4decdd12f130e415913ff1fe6e2abcaf7c4a8e980de7a See, this is extra weird: nothing set -g so it should default to 2. Somehow it knows to set itself to... I'm guessing 0. Did -p -c 0 get special cased, or did -p change its default to avoid any breaks even without the -c 0? (Sounds like the latter is more likely, but I tried "yum install xxd" on my fedora 36 VM and yum doesn't know what an xxd is. > ah, but on another box with 2021-10-22 it's broken. so it looks like "real" > xxd > had the same bug and fixed it recently? Eh, seems more like a design decision than a bug. Before -p was wordwrapping the hexdump output and now it isn't. I dunno if it always isn't, or just with -c 0? We didn't set -g and it has a nonzero default value (1, 2, or 4 depending on barometric pressure)... I also note that the man page says -g 0 switches off grouping, but does NOT say that -c 0 switches off columns? In the V1.10 version I have installed, -c 0 seems to be a NOP: $ sha1sum < /dev/null | xxd -c 0 00000000: 6461 3339 6133 6565 3565 3662 3462 3064 da39a3ee5e6b4b0d 00000010: 3332 3535 6266 6566 3935 3630 3138 3930 3255bfef95601890 00000020: 6166 6438 3037 3039 2020 2d0a afd80709 -. Once again: easy to change the behavior, hard to tell what the changed behavior should be. Easiest is to have -p force -g to 0 and -c to huge (stomping whatever else got set in both). I could also teach -c that 0 means infinite (well, sizeof(toybuf) implementation limit which is still bigger than the 256 directly settable limit that I have no idea why it's there) if that's actually a thing...? (Grumble grumble no standard and the reference implementation has version skew...) Rob _______________________________________________ Toybox mailing list Toybox@lists.landley.net http://lists.landley.net/listinfo.cgi/toybox-landley.net
