Re: [libvirt] [PATCH v2 3/5] Extend nwfilter schema to accept comment attributes

Eric Blake <eblake(a)redhat.com&gt; wrote on 09/28/2010 03:26:48 PM: > [image removed] > > Re: [libvirt] [PATCH v2 3/5] Extend nwfilter schema to accept > comment attributes > > Eric Blake > > to: > > Stefan Berger > > 09/28/2010 03:27 PM > > Cc: > > libvir-list > > On 09/28/2010 04:28 AM, Stefan Berger wrote: > >> okay. It also leaves out 8-bit bytes - could that be a problem for i18n > > > >> where people want comments with native-language accented characters? > >> That is, are we being too strict here? Maybe a better pattern would be > >> to reject specific non-printing ASCII bytes we want to avoid, assuing > >> you can use escape sequences like [^\001]? > > > > Looking at > > > > http://www.asciitable.com/ > > > > I should probably include 0x20-0x7E and 128-175, 224-238 - maybe even > > more? So the regex then becomes > > > > [&#x20;-&#x7E;&#128;-&#175;&#224;-&#238;]{0,256} > > True ASCII is strictly 7-bit; any locale where isprint() returns true on > 8-bit bytes is a superset single-byte encoding, such as ISO-8859-1, or > 'extended ascii' from the URL you posted above. But I'm also thinking > about multi-byte encodings, like UTF-8, where we cannot a priori write a > regex that will accept all valid Unicode printable characters, in part > because you have to look at more than one byte at a time to determine if > you have a printable character. Which goes back to my suggestion of an > inverse charset - rejecting bytes that are known to be non-printable > ASCII, and letting everything else whether or not it is is a printable > byte sequence in the current locale. So what about this idea: exclude > control characters except for tab, and let space and everything after > through (I don't know if it needs to be adjusted to also reject &#x00): > > [^&#x01;-&#x08&#x0A-&#x1F]{0,256} Fine by me. We may just give the impression of accepting unicode while the code does not handle it.