Hi, On +2023-01-11 16:34:41 +0100, Simon Tournier wrote: > Hi, > > On Mon, 09 Jan 2023 at 12:16, Ludovic Courtès <l...@gnu.org> wrote: > > Simon Tournier <zimon.touto...@gmail.com> skribis: > > > >> Maybe my question is naive but what is the use case for this (sha256 #f) > >> in the first place? Because maybe it could just error using some > >> ’sanitize’ for the hash record field. > > > > There’s a couple of uses: Chromium, IceCat, and Linux-libre (IIRC). > > > > I don’t like that, but I’m not sure what it would take to change these > > to <computed-file> or something like that. > > Well, from (gnu packages linux) > > --8<---------------cut here---------------start------------->8--- > (origin > (method computed-origin-method) > (file-name (string-append "linux-libre-" version "-guix.tar.xz")) > (sha256 #f) > --8<---------------cut here---------------end--------------->8--- > > and from (gnu packages gnuzilla) > > --8<---------------cut here---------------start------------->8--- > (origin > (method computed-origin-method) > (file-name (string-append "icecat-" %icecat-version ".tar.xz")) > (sha256 #f) > --8<---------------cut here---------------end--------------->8--- > > but not from Chromium, if I read correctly. > > From my understanding, we could have something like, > > (sha256 (no-hash)) > > where ’no-hash’ would return a string, say > "0000000000000000000000000000000000000000000000000000" or whatever else > that would satisfy this hypothetical ’sha256’ sanitizer. > > > Cheers, > simon >
For portability to any hash algorithm that returns a hex string, how about letting them hash a zero-length string (which can never represent a package tarball or other archive), and using the resulting strings as no-hash flags? These strings must be unique for whatever hash algorithm, so a short table could be used to recognize them as no-hash indicators. --8<---------------cut here---------------start------------->8--- $ sha256sum /dev/null e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 /dev/null $ sha256sum <(echo -n '') e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 /dev/fd/63 $ echo -n ''|sha256sum e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 - $ echo -n ""|sha256sum e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 - --8<---------------cut here---------------end--------------->8--- For other hash values on your system, probably the below will show most. Translating from hex to various base32 and other-base alphabets is then trivial, (and open, i.e. permitting new hash representation strings). --8<---------------cut here---------------start------------->8--- $ ls -1d /usr/bin/*sum|while read hasher;do \ echo;echo "$hasher:"; "$hasher" /dev/null;done --8<---------------cut here---------------end--------------->8--- WDYT? -- Regards, Bengt Richter
