On Fri, Dec 14, 2007 at 08:34:13AM +0100, Jim Meyering wrote:
You're right that we shouldn't use isalnum here. However, we shouldn't use inequality comparisons, either. While 0 <= c <= 9 is guaranteed to be ok for the digits, the a..z and A..Z ranges need not be contiguous, i.e., with EBCDIC:
http://www.natural-innovations.com/computing/asciiebcdic.html
so how about this instead?
int is_alphanum (char c) { switch (c) { /* generated by LC_ALL=C perl -e \ "print map {qq(case '\$_': )}('a'..'z', 'A'..'Z', '0'..'9')"|fmt case 'a': case 'b': case 'c': case 'd': case 'e': case 'f': case 'g': case 'h': case 'i': case 'j': case 'k': case 'l': case 'm': case 'n': case 'o': case 'p': case 'q': case 'r': case 's': case 't': case 'u': case 'v': case 'w': case 'x': case 'y': case 'z': case 'A': case 'B': case 'C': case 'D': case 'E': case 'F': case 'G': case 'H': case 'I': case 'J': case 'K': case 'L': case 'M': case 'N': case 'O': case 'P': case 'Q': case 'R': case 'S': case 'T': case 'U': case 'V': case 'W': case 'X': case 'Y': case 'Z': case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9':
This makes it unreadable, really no.
Of course, systems for which this can make a difference (z/OS, S390) may not be libvirt portability targets, but better safe than sorry.
I do that kind range comparison in libxml2. This raised a problem only once ever on an Unisys mainframe, they upgraded the compiler and got an ascii option which allowed to fix it without patching libxml2. Maintainance wise, I really prefer we keep the status quo. Daniel -- Red Hat Virtualization group http://redhat.com/virtualization/ Daniel Veillard | virtualization library http://libvirt.org/ veillard@redhat.com | libxml GNOME XML XSLT toolkit http://xmlsoft.org/ http://veillard.com/ | Rpmfind RPM search engine http://rpmfind.net/