package regcharclass_multi_char_folds; use 5.015; use strict; use warnings; use Unicode::UCD "prop_invmap"; # This returns an array of strings of the form # "\x{foo}\x{bar}\x{baz}" # of the sequences of code points that are multi-character folds in the # current Unicode version. If the parameter is 1, all such folds are # returned. If the parameters is 0, only the ones containing exclusively # Latin1 characters are returned. In the latter case all combinations of # Latin1 characters that can fold to the base one are returned. Thus for # 'ss', it would return in addition, 'Ss', 'sS', and 'SS'. This is because # this code is designed to help regcomp.c, and EXACTFish regnodes. For # non-UTF-8 patterns, the strings are not folded, so we need to check for the # upper and lower case versions. For UTF-8 patterns, the strings are folded, # except in EXACTFL nodes) so we only need to worry about the fold version. # All folded-to characters in non-UTF-8 (Latin1) are members of fold-pairs, # at least within Latin1, 'k', and 'K', for example. So there aren't # complications with dealing with unfolded input. That's not true of UTF-8 # patterns, where things can get tricky. Thus for EXACTFL nodes where things # aren't all folded, code has to be written specially to handle this, instead # of the macros here being extended to try to handle it. # # There are no non-ASCII Latin1 multi-char folds currently, and none likely to # be ever added. Thus the output is the same as if it were just asking for # ASCII characters, not full Latin1. Hence, it is suitable for generating # things that match EXACTFA. It does check for and croak if there ever were # to be an upper Latin1 range multi-character fold. # # This is designed for input to regen/regcharlass.pl. sub gen_combinations ($;) { # Generate all combinations for the first parameter which is an array of # arrays. my ($fold_ref, $string, $i) = @_; $string = "" unless $string; $i = 0 unless $i; my @ret; # Look at each element in this level's array. foreach my $j (0 .. @{$fold_ref->[$i]} - 1) { # Append its representation to what we have currently my $new_string = sprintf "$string\\x{%X}", $fold_ref->[$i][$j]; if ($i >= @$fold_ref - 1) { # Final level: just return it push @ret, "\"$new_string\""; } else { # Generate the combinations for the next level with this one's push @ret, &gen_combinations($fold_ref, $new_string, $i + 1); } } return @ret; } sub multi_char_folds ($) { my $all_folds = shift; # The single parameter is true if wants all # multi-char folds; false if just the ones that # are all ascii my ($cp_ref, $folds_ref, $format) = prop_invmap("Case_Folding"); die "Could not find inversion map for Case_Folding" unless defined $format; die "Incorrect format '$format' for Case_Folding inversion map" unless $format eq 'al'; my @folds; for my $i (0 .. @$folds_ref - 1) { next unless ref $folds_ref->[$i]; # Skip single-char folds # The code in regcomp.c currently assumes that no multi-char fold # folds to the upper Latin1 range. It's not a big deal to add; we # just have to forbid such a fold in EXACTFL nodes, like we do already # for ascii chars in EXACTFA (and EXACTFL) nodes. But I (khw) doubt # that there will ever be such a fold created by Unicode, so the code # isn't there to occupy space and time; instead there is this check. die sprintf("regcomp.c can't cope with a latin1 multi-char fold (found in the fold of 0x%X", $cp_ref->[$i]) if grep { $_ < 256 && chr($_) !~ /[[:ascii:]]/ } @{$folds_ref->[$i]}; # Create a line that looks like "\x{foo}\x{bar}\x{baz}" of the code # points that make up the fold. my $fold = join "", map { sprintf "\\x{%X}", $_ } @{$folds_ref->[$i]}; $fold = "\"$fold\""; # Skip if something else already has this fold next if grep { $_ eq $fold } @folds; if ($all_folds) { push @folds, $fold } # Skip if wants only all-ascii folds, and there is a non-ascii elsif (! grep { chr($_) =~ /[^[:ascii:]]/ } @{$folds_ref->[$i]}) { # If the fold is to a cased letter, replace the entry with an # array which also includes its upper case. my $this_fold_ref = $folds_ref->[$i]; for my $j (0 .. @$this_fold_ref - 1) { my $this_ord = $this_fold_ref->[$j]; if (chr($this_ord) =~ /\p{Cased}/) { my $uc = ord(uc(chr($this_ord))); undef $this_fold_ref->[$j]; @{$this_fold_ref->[$j]} = ( $this_ord, $uc); } } # Then generate all combinations of upper/lower case of the fold. push @folds, gen_combinations($this_fold_ref); } } # \x17F is the small LONG S, which folds to 's'. Both Capital and small # LATIN SHARP S fold to 'ss'. Therefore, they should also match two 17F's # in a row under regex /i matching. But under /iaa regex matching, all # three folds to 's' are prohibited, but the sharp S's should still match # two 17F's. This prohibition causes our regular regex algorithm that # would ordinarily allow this match to fail. This is the only instance in # all Unicode of this kind of issue. By adding a special case here, we # can use the regular algorithm (with some other changes elsewhere as # well). # # It would be possible to re-write the above code to automatically detect # and handle this case, and any others that might eventually get added to # the Unicode standard, but I (khw) don't think it's worth it. I believe # that it's extremely unlikely that more folds to ASCII characters are # going to be added, and if I'm wrong, fold_grind.t has the intelligence # to detect them, and test that they work, at which point another special # case could be added here if necessary. # # No combinations of this with 's' need be added, as any of these # containing 's' are prohibted under /iaa. push @folds, '"\x{17F}\x{17F}"' if $all_folds; return @folds; } 1