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authorNorbert Preining <norbert@preining.info>2019-09-02 13:46:59 +0900
committerNorbert Preining <norbert@preining.info>2019-09-02 13:46:59 +0900
commite0c6872cf40896c7be36b11dcc744620f10adf1d (patch)
tree60335e10d2f4354b0674ec22d7b53f0f8abee672 /systems/texlive/tlnet/tlpkg/tlperl/lib/Unicode/Collate.pm
Initial commit
Diffstat (limited to 'systems/texlive/tlnet/tlpkg/tlperl/lib/Unicode/Collate.pm')
-rw-r--r--systems/texlive/tlnet/tlpkg/tlperl/lib/Unicode/Collate.pm2138
1 files changed, 2138 insertions, 0 deletions
diff --git a/systems/texlive/tlnet/tlpkg/tlperl/lib/Unicode/Collate.pm b/systems/texlive/tlnet/tlpkg/tlperl/lib/Unicode/Collate.pm
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index 0000000000..ac1cd03f60
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+++ b/systems/texlive/tlnet/tlpkg/tlperl/lib/Unicode/Collate.pm
@@ -0,0 +1,2138 @@
+package Unicode::Collate;
+
+BEGIN {
+ unless ("A" eq pack('U', 0x41)) {
+ die "Unicode::Collate cannot stringify a Unicode code point\n";
+ }
+ unless (0x41 == unpack('U', 'A')) {
+ die "Unicode::Collate cannot get a Unicode code point\n";
+ }
+}
+
+use 5.006;
+use strict;
+use warnings;
+use Carp;
+use File::Spec;
+
+no warnings 'utf8';
+
+our $VERSION = '1.25';
+our $PACKAGE = __PACKAGE__;
+
+### begin XS only ###
+use XSLoader ();
+XSLoader::load('Unicode::Collate', $VERSION);
+### end XS only ###
+
+my @Path = qw(Unicode Collate);
+my $KeyFile = 'allkeys.txt';
+
+# Perl's boolean
+use constant TRUE => 1;
+use constant FALSE => "";
+use constant NOMATCHPOS => -1;
+
+# A coderef to get combining class imported from Unicode::Normalize
+# (i.e. \&Unicode::Normalize::getCombinClass).
+# This is also used as a HAS_UNICODE_NORMALIZE flag.
+my $CVgetCombinClass;
+
+# Supported Levels
+use constant MinLevel => 1;
+use constant MaxLevel => 4;
+
+# Minimum weights at level 2 and 3, respectively
+use constant Min2Wt => 0x20;
+use constant Min3Wt => 0x02;
+
+# Shifted weight at 4th level
+use constant Shift4Wt => 0xFFFF;
+
+# A boolean for Variable and 16-bit weights at 4 levels of Collation Element
+use constant VCE_TEMPLATE => 'Cn4';
+
+# A sort key: 16-bit weights
+use constant KEY_TEMPLATE => 'n*';
+
+# The tie-breaking: 32-bit weights
+use constant TIE_TEMPLATE => 'N*';
+
+# Level separator in a sort key:
+# i.e. pack(KEY_TEMPLATE, 0)
+use constant LEVEL_SEP => "\0\0";
+
+# As Unicode code point separator for hash keys.
+# A joined code point string (denoted by JCPS below)
+# like "65;768" is used for internal processing
+# instead of Perl's Unicode string like "\x41\x{300}",
+# as the native code point is different from the Unicode code point
+# on EBCDIC platform.
+# This character must not be included in any stringified
+# representation of an integer.
+use constant CODE_SEP => ';';
+ # NOTE: in regex /;/ is used for $jcps!
+
+# boolean values of variable weights
+use constant NON_VAR => 0; # Non-Variable character
+use constant VAR => 1; # Variable character
+
+# specific code points
+use constant Hangul_SIni => 0xAC00;
+use constant Hangul_SFin => 0xD7A3;
+
+# Logical_Order_Exception in PropList.txt
+my $DefaultRearrange = [ 0x0E40..0x0E44, 0x0EC0..0x0EC4 ];
+
+# for highestFFFF and minimalFFFE
+my $HighestVCE = pack(VCE_TEMPLATE, 0, 0xFFFE, 0x20, 0x5, 0xFFFF);
+my $minimalVCE = pack(VCE_TEMPLATE, 0, 1, 0x20, 0x5, 0xFFFE);
+
+sub UCA_Version { '34' }
+
+sub Base_Unicode_Version { '9.0.0' }
+
+######
+
+sub pack_U {
+ return pack('U*', @_);
+}
+
+sub unpack_U {
+ return unpack('U*', shift(@_).pack('U*'));
+}
+
+######
+
+my (%VariableOK);
+@VariableOK{ qw/
+ blanked non-ignorable shifted shift-trimmed
+ / } = (); # keys lowercased
+
+our @ChangeOK = qw/
+ alternate backwards level normalization rearrange
+ katakana_before_hiragana upper_before_lower ignore_level2
+ overrideCJK overrideHangul overrideOut preprocess UCA_Version
+ hangul_terminator variable identical highestFFFF minimalFFFE
+ long_contraction
+ /;
+
+our @ChangeNG = qw/
+ entry mapping table maxlength contraction
+ ignoreChar ignoreName undefChar undefName rewrite
+ versionTable alternateTable backwardsTable forwardsTable
+ rearrangeTable variableTable
+ derivCode normCode rearrangeHash backwardsFlag
+ suppress suppressHash
+ __useXS /; ### XS only
+# The hash key 'ignored' was deleted at v 0.21.
+# The hash key 'isShift' was deleted at v 0.23.
+# The hash key 'combining' was deleted at v 0.24.
+# The hash key 'entries' was deleted at v 0.30.
+# The hash key 'L3_ignorable' was deleted at v 0.40.
+
+sub version {
+ my $self = shift;
+ return $self->{versionTable} || 'unknown';
+}
+
+my (%ChangeOK, %ChangeNG);
+@ChangeOK{ @ChangeOK } = ();
+@ChangeNG{ @ChangeNG } = ();
+
+sub change {
+ my $self = shift;
+ my %hash = @_;
+ my %old;
+ if (exists $hash{alternate}) {
+ if (exists $hash{variable}) {
+ delete $hash{alternate};
+ } else {
+ $hash{variable} = $hash{alternate};
+ }
+ }
+ foreach my $k (keys %hash) {
+ if (exists $ChangeOK{$k}) {
+ $old{$k} = $self->{$k};
+ $self->{$k} = $hash{$k};
+ } elsif (exists $ChangeNG{$k}) {
+ croak "change of $k via change() is not allowed!";
+ }
+ # else => ignored
+ }
+ $self->checkCollator();
+ return wantarray ? %old : $self;
+}
+
+sub _checkLevel {
+ my $level = shift;
+ my $key = shift; # 'level' or 'backwards'
+ MinLevel <= $level or croak sprintf
+ "Illegal level %d (in value for key '%s') lower than %d.",
+ $level, $key, MinLevel;
+ $level <= MaxLevel or croak sprintf
+ "Unsupported level %d (in value for key '%s') higher than %d.",
+ $level, $key, MaxLevel;
+}
+
+my %DerivCode = (
+ 8 => \&_derivCE_8,
+ 9 => \&_derivCE_9,
+ 11 => \&_derivCE_9, # 11 == 9
+ 14 => \&_derivCE_14,
+ 16 => \&_derivCE_14, # 16 == 14
+ 18 => \&_derivCE_18,
+ 20 => \&_derivCE_20,
+ 22 => \&_derivCE_22,
+ 24 => \&_derivCE_24,
+ 26 => \&_derivCE_24, # 26 == 24
+ 28 => \&_derivCE_24, # 28 == 24
+ 30 => \&_derivCE_24, # 30 == 24
+ 32 => \&_derivCE_32,
+ 34 => \&_derivCE_34,
+ 36 => \&_derivCE_36,
+);
+
+sub checkCollator {
+ my $self = shift;
+ _checkLevel($self->{level}, 'level');
+
+ $self->{derivCode} = $DerivCode{ $self->{UCA_Version} }
+ or croak "Illegal UCA version (passed $self->{UCA_Version}).";
+
+ $self->{variable} ||= $self->{alternate} || $self->{variableTable} ||
+ $self->{alternateTable} || 'shifted';
+ $self->{variable} = $self->{alternate} = lc($self->{variable});
+ exists $VariableOK{ $self->{variable} }
+ or croak "$PACKAGE unknown variable parameter name: $self->{variable}";
+
+ if (! defined $self->{backwards}) {
+ $self->{backwardsFlag} = 0;
+ } elsif (! ref $self->{backwards}) {
+ _checkLevel($self->{backwards}, 'backwards');
+ $self->{backwardsFlag} = 1 << $self->{backwards};
+ } else {
+ my %level;
+ $self->{backwardsFlag} = 0;
+ for my $b (@{ $self->{backwards} }) {
+ _checkLevel($b, 'backwards');
+ $level{$b} = 1;
+ }
+ for my $v (sort keys %level) {
+ $self->{backwardsFlag} += 1 << $v;
+ }
+ }
+
+ defined $self->{rearrange} or $self->{rearrange} = [];
+ ref $self->{rearrange}
+ or croak "$PACKAGE: list for rearrangement must be store in ARRAYREF";
+
+ # keys of $self->{rearrangeHash} are $self->{rearrange}.
+ $self->{rearrangeHash} = undef;
+
+ if (@{ $self->{rearrange} }) {
+ @{ $self->{rearrangeHash} }{ @{ $self->{rearrange} } } = ();
+ }
+
+ $self->{normCode} = undef;
+
+ if (defined $self->{normalization}) {
+ eval { require Unicode::Normalize };
+ $@ and croak "Unicode::Normalize is required to normalize strings";
+
+ $CVgetCombinClass ||= \&Unicode::Normalize::getCombinClass;
+
+ if ($self->{normalization} =~ /^(?:NF)D\z/) { # tweak for default
+ $self->{normCode} = \&Unicode::Normalize::NFD;
+ }
+ elsif ($self->{normalization} ne 'prenormalized') {
+ my $norm = $self->{normalization};
+ $self->{normCode} = sub {
+ Unicode::Normalize::normalize($norm, shift);
+ };
+ eval { $self->{normCode}->("") }; # try
+ $@ and croak "$PACKAGE unknown normalization form name: $norm";
+ }
+ }
+ return;
+}
+
+sub new
+{
+ my $class = shift;
+ my $self = bless { @_ }, $class;
+
+### begin XS only ###
+ if (! exists $self->{table} && !defined $self->{rewrite} &&
+ !defined $self->{undefName} && !defined $self->{ignoreName} &&
+ !defined $self->{undefChar} && !defined $self->{ignoreChar}) {
+ $self->{__useXS} = \&_fetch_simple;
+ } else {
+ $self->{__useXS} = undef;
+ }
+### end XS only ###
+
+ # keys of $self->{suppressHash} are $self->{suppress}.
+ if ($self->{suppress} && @{ $self->{suppress} }) {
+ @{ $self->{suppressHash} }{ @{ $self->{suppress} } } = ();
+ } # before read_table()
+
+ # If undef is passed explicitly, no file is read.
+ $self->{table} = $KeyFile if ! exists $self->{table};
+ $self->read_table() if defined $self->{table};
+
+ if ($self->{entry}) {
+ while ($self->{entry} =~ /([^\n]+)/g) {
+ $self->parseEntry($1, TRUE);
+ }
+ }
+
+ # only in new(), not in change()
+ $self->{level} ||= MaxLevel;
+ $self->{UCA_Version} ||= UCA_Version();
+
+ $self->{overrideHangul} = FALSE
+ if ! exists $self->{overrideHangul};
+ $self->{overrideCJK} = FALSE
+ if ! exists $self->{overrideCJK};
+ $self->{normalization} = 'NFD'
+ if ! exists $self->{normalization};
+ $self->{rearrange} = $self->{rearrangeTable} ||
+ ($self->{UCA_Version} <= 11 ? $DefaultRearrange : [])
+ if ! exists $self->{rearrange};
+ $self->{backwards} = $self->{backwardsTable}
+ if ! exists $self->{backwards};
+ exists $self->{long_contraction} or $self->{long_contraction}
+ = 22 <= $self->{UCA_Version} && $self->{UCA_Version} <= 24;
+
+ # checkCollator() will be called in change()
+ $self->checkCollator();
+
+ return $self;
+}
+
+sub parseAtmark {
+ my $self = shift;
+ my $line = shift; # after s/^\s*\@//
+
+ if ($line =~ /^version\s*(\S*)/) {
+ $self->{versionTable} ||= $1;
+ }
+ elsif ($line =~ /^variable\s+(\S*)/) { # since UTS #10-9
+ $self->{variableTable} ||= $1;
+ }
+ elsif ($line =~ /^alternate\s+(\S*)/) { # till UTS #10-8
+ $self->{alternateTable} ||= $1;
+ }
+ elsif ($line =~ /^backwards\s+(\S*)/) {
+ push @{ $self->{backwardsTable} }, $1;
+ }
+ elsif ($line =~ /^forwards\s+(\S*)/) { # perhaps no use
+ push @{ $self->{forwardsTable} }, $1;
+ }
+ elsif ($line =~ /^rearrange\s+(.*)/) { # (\S*) is NG
+ push @{ $self->{rearrangeTable} }, _getHexArray($1);
+ }
+}
+
+sub read_table {
+ my $self = shift;
+
+### begin XS only ###
+ if ($self->{__useXS}) {
+ my @rest = _fetch_rest(); # complex matter need to parse
+ for my $line (@rest) {
+ next if $line =~ /^\s*#/;
+
+ if ($line =~ s/^\s*\@//) {
+ $self->parseAtmark($line);
+ } else {
+ $self->parseEntry($line);
+ }
+ }
+ return;
+ }
+### end XS only ###
+
+ my($f, $fh);
+ foreach my $d (@INC) {
+ $f = File::Spec->catfile($d, @Path, $self->{table});
+ last if open($fh, $f);
+ $f = undef;
+ }
+ if (!defined $f) {
+ $f = File::Spec->catfile(@Path, $self->{table});
+ croak("$PACKAGE: Can't locate $f in \@INC (\@INC contains: @INC)");
+ }
+
+ while (my $line = <$fh>) {
+ next if $line =~ /^\s*#/;
+
+ if ($line =~ s/^\s*\@//) {
+ $self->parseAtmark($line);
+ } else {
+ $self->parseEntry($line);
+ }
+ }
+ close $fh;
+}
+
+
+##
+## get $line, parse it, and write an entry in $self
+##
+sub parseEntry
+{
+ my $self = shift;
+ my $line = shift;
+ my $tailoring = shift;
+ my($name, $entry, @uv, @key);
+
+ if (defined $self->{rewrite}) {
+ $line = $self->{rewrite}->($line);
+ }
+
+ return if $line !~ /^\s*[0-9A-Fa-f]/;
+
+ # removes comment and gets name
+ $name = $1
+ if $line =~ s/[#%]\s*(.*)//;
+ return if defined $self->{undefName} && $name =~ /$self->{undefName}/;
+
+ # gets element
+ my($e, $k) = split /;/, $line;
+ croak "Wrong Entry: <charList> must be separated by ';' from <collElement>"
+ if ! $k;
+
+ @uv = _getHexArray($e);
+ return if !@uv;
+ return if @uv > 1 && $self->{suppressHash} && !$tailoring &&
+ exists $self->{suppressHash}{$uv[0]};
+ $entry = join(CODE_SEP, @uv); # in JCPS
+
+ if (defined $self->{undefChar} || defined $self->{ignoreChar}) {
+ my $ele = pack_U(@uv);
+
+ # regarded as if it were not stored in the table
+ return
+ if defined $self->{undefChar} && $ele =~ /$self->{undefChar}/;
+
+ # replaced as completely ignorable
+ $k = '[.0000.0000.0000.0000]'
+ if defined $self->{ignoreChar} && $ele =~ /$self->{ignoreChar}/;
+ }
+
+ # replaced as completely ignorable
+ $k = '[.0000.0000.0000.0000]'
+ if defined $self->{ignoreName} && $name =~ /$self->{ignoreName}/;
+
+ my $is_L3_ignorable = TRUE;
+
+ foreach my $arr ($k =~ /\[([^\[\]]+)\]/g) { # SPACEs allowed
+ my $var = $arr =~ /\*/; # exactly /^\*/ but be lenient.
+ my @wt = _getHexArray($arr);
+ push @key, pack(VCE_TEMPLATE, $var, @wt);
+ $is_L3_ignorable = FALSE
+ if $wt[0] || $wt[1] || $wt[2];
+ # Conformance Test for 3.1.1 and 4.0.0 shows Level 3 ignorable
+ # is completely ignorable.
+ # For expansion, an entry $is_L3_ignorable
+ # if and only if "all" CEs are [.0000.0000.0000].
+ }
+
+ # mapping: be an array ref or not exists (any false value is disallowed)
+ $self->{mapping}{$entry} = $is_L3_ignorable ? [] : \@key;
+
+ # maxlength: be more than 1 or not exists (any false value is disallowed)
+ if (@uv > 1) {
+ if (!$self->{maxlength}{$uv[0]} || $self->{maxlength}{$uv[0]} < @uv) {
+ $self->{maxlength}{$uv[0]} = @uv;
+ }
+ }
+
+ # contraction: be 1 or not exists (any false value is disallowed)
+ while (@uv > 2) {
+ pop @uv;
+ my $fake_entry = join(CODE_SEP, @uv); # in JCPS
+ $self->{contraction}{$fake_entry} = 1;
+ }
+}
+
+
+sub viewSortKey
+{
+ my $self = shift;
+ my $str = shift;
+ $self->visualizeSortKey($self->getSortKey($str));
+}
+
+
+sub process
+{
+ my $self = shift;
+ my $str = shift;
+ my $prep = $self->{preprocess};
+ my $norm = $self->{normCode};
+
+ $str = &$prep($str) if ref $prep;
+ $str = &$norm($str) if ref $norm;
+ return $str;
+}
+
+##
+## arrayref of JCPS = splitEnt(string to be collated)
+## arrayref of arrayref[JCPS, ini_pos, fin_pos] = splitEnt(string, TRUE)
+##
+sub splitEnt
+{
+ my $self = shift;
+ my $str = shift;
+ my $wLen = shift; # with Length
+
+ my $map = $self->{mapping};
+ my $max = $self->{maxlength};
+ my $reH = $self->{rearrangeHash};
+ my $vers = $self->{UCA_Version};
+ my $ver9 = $vers >= 9 && $vers <= 11;
+ my $long = $self->{long_contraction};
+ my $uXS = $self->{__useXS}; ### XS only
+
+ my @buf;
+
+ # get array of Unicode code point of string.
+ my @src = unpack_U($str);
+
+ # rearrangement:
+ # Character positions are not kept if rearranged,
+ # then neglected if $wLen is true.
+ if ($reH && ! $wLen) {
+ for (my $i = 0; $i < @src; $i++) {
+ if (exists $reH->{ $src[$i] } && $i + 1 < @src) {
+ ($src[$i], $src[$i+1]) = ($src[$i+1], $src[$i]);
+ $i++;
+ }
+ }
+ }
+
+ # remove a code point marked as a completely ignorable.
+ for (my $i = 0; $i < @src; $i++) {
+ if ($vers <= 20 && _isIllegal($src[$i])) {
+ $src[$i] = undef;
+ } elsif ($ver9) {
+ $src[$i] = undef if exists $map->{ $src[$i] }
+ ? @{ $map->{ $src[$i] } } == 0
+ : $uXS && _ignorable_simple($src[$i]); ### XS only
+ }
+ }
+
+ for (my $i = 0; $i < @src; $i++) {
+ my $jcps = $src[$i];
+
+ # skip removed code point
+ if (! defined $jcps) {
+ if ($wLen && @buf) {
+ $buf[-1][2] = $i + 1;
+ }
+ next;
+ }
+
+ my $i_orig = $i;
+
+ # find contraction
+ if (exists $max->{$jcps}) {
+ my $temp_jcps = $jcps;
+ my $jcpsLen = 1;
+ my $maxLen = $max->{$jcps};
+
+ for (my $p = $i + 1; $jcpsLen < $maxLen && $p < @src; $p++) {
+ next if ! defined $src[$p];
+ $temp_jcps .= CODE_SEP . $src[$p];
+ $jcpsLen++;
+ if (exists $map->{$temp_jcps}) {
+ $jcps = $temp_jcps;
+ $i = $p;
+ }
+ }
+
+ # discontiguous contraction with Combining Char (cf. UTS#10, S2.1).
+ # This process requires Unicode::Normalize.
+ # If "normalization" is undef, here should be skipped *always*
+ # (in spite of bool value of $CVgetCombinClass),
+ # since canonical ordering cannot be expected.
+ # Blocked combining character should not be contracted.
+
+ # $self->{normCode} is false in the case of "prenormalized".
+ if ($self->{normalization}) {
+ my $cont = $self->{contraction};
+ my $preCC = 0;
+ my $preCC_uc = 0;
+ my $jcps_uc = $jcps;
+ my(@out, @out_uc);
+
+ for (my $p = $i + 1; $p < @src; $p++) {
+ next if ! defined $src[$p];
+ my $curCC = $CVgetCombinClass->($src[$p]);
+ last unless $curCC;
+ my $tail = CODE_SEP . $src[$p];
+
+ if ($preCC != $curCC && exists $map->{$jcps.$tail}) {
+ $jcps .= $tail;
+ push @out, $p;
+ } else {
+ $preCC = $curCC;
+ }
+
+ next if !$long;
+
+ if ($preCC_uc != $curCC &&
+ (exists $map->{$jcps_uc.$tail} ||
+ exists $cont->{$jcps_uc.$tail})) {
+ $jcps_uc .= $tail;
+ push @out_uc, $p;
+ } else {
+ $preCC_uc = $curCC;
+ }
+ }
+
+ if (@out_uc && exists $map->{$jcps_uc}) {
+ $jcps = $jcps_uc;
+ $src[$_] = undef for @out_uc;
+ } else {
+ $src[$_] = undef for @out;
+ }
+ }
+ }
+
+ # skip completely ignorable
+ if (exists $map->{$jcps} ? @{ $map->{$jcps} } == 0 :
+ $uXS && $jcps !~ /;/ && _ignorable_simple($jcps)) { ### XS only
+ if ($wLen && @buf) {
+ $buf[-1][2] = $i + 1;
+ }
+ next;
+ }
+
+ push @buf, $wLen ? [$jcps, $i_orig, $i + 1] : $jcps;
+ }
+ return \@buf;
+}
+
+##
+## VCE = _pack_override(input, codepoint, derivCode)
+##
+sub _pack_override ($$$) {
+ my $r = shift;
+ my $u = shift;
+ my $der = shift;
+
+ if (ref $r) {
+ return pack(VCE_TEMPLATE, NON_VAR, @$r);
+ } elsif (defined $r) {
+ return pack(VCE_TEMPLATE, NON_VAR, $r, Min2Wt, Min3Wt, $u);
+ } else {
+ $u = 0xFFFD if 0x10FFFF < $u;
+ return $der->($u);
+ }
+}
+
+##
+## list of VCE = getWt(JCPS)
+##
+sub getWt
+{
+ my $self = shift;
+ my $u = shift;
+ my $map = $self->{mapping};
+ my $der = $self->{derivCode};
+ my $out = $self->{overrideOut};
+ my $uXS = $self->{__useXS}; ### XS only
+
+ return if !defined $u;
+ return $self->varCE($HighestVCE) if $u eq 0xFFFF && $self->{highestFFFF};
+ return $self->varCE($minimalVCE) if $u eq 0xFFFE && $self->{minimalFFFE};
+ $u = 0xFFFD if $u !~ /;/ && 0x10FFFF < $u && !$out;
+
+ my @ce;
+ if (exists $map->{$u}) {
+ @ce = @{ $map->{$u} }; # $u may be a contraction
+### begin XS only ###
+ } elsif ($uXS && _exists_simple($u)) {
+ @ce = _fetch_simple($u);
+### end XS only ###
+ } elsif (Hangul_SIni <= $u && $u <= Hangul_SFin) {
+ my $hang = $self->{overrideHangul};
+ if ($hang) {
+ @ce = map _pack_override($_, $u, $der), $hang->($u);
+ } elsif (!defined $hang) {
+ @ce = $der->($u);
+ } else {
+ my $max = $self->{maxlength};
+ my @decH = _decompHangul($u);
+
+ if (@decH == 2) {
+ my $contract = join(CODE_SEP, @decH);
+ @decH = ($contract) if exists $map->{$contract};
+ } else { # must be <@decH == 3>
+ if (exists $max->{$decH[0]}) {
+ my $contract = join(CODE_SEP, @decH);
+ if (exists $map->{$contract}) {
+ @decH = ($contract);
+ } else {
+ $contract = join(CODE_SEP, @decH[0,1]);
+ exists $map->{$contract} and @decH = ($contract, $decH[2]);
+ }
+ # even if V's ignorable, LT contraction is not supported.
+ # If such a situation were required, NFD should be used.
+ }
+ if (@decH == 3 && exists $max->{$decH[1]}) {
+ my $contract = join(CODE_SEP, @decH[1,2]);
+ exists $map->{$contract} and @decH = ($decH[0], $contract);
+ }
+ }
+
+ @ce = map({
+ exists $map->{$_} ? @{ $map->{$_} } :
+ $uXS && _exists_simple($_) ? _fetch_simple($_) : ### XS only
+ $der->($_);
+ } @decH);
+ }
+ } elsif ($out && 0x10FFFF < $u) {
+ @ce = map _pack_override($_, $u, $der), $out->($u);
+ } else {
+ my $cjk = $self->{overrideCJK};
+ my $vers = $self->{UCA_Version};
+ if ($cjk && _isUIdeo($u, $vers)) {
+ @ce = map _pack_override($_, $u, $der), $cjk->($u);
+ } elsif ($vers == 8 && defined $cjk && _isUIdeo($u, 0)) {
+ @ce = _uideoCE_8($u);
+ } else {
+ @ce = $der->($u);
+ }
+ }
+ return map $self->varCE($_), @ce;
+}
+
+
+##
+## string sortkey = getSortKey(string arg)
+##
+sub getSortKey
+{
+ my $self = shift;
+ my $orig = shift;
+ my $str = $self->process($orig);
+ my $rEnt = $self->splitEnt($str); # get an arrayref of JCPS
+ my $vers = $self->{UCA_Version};
+ my $term = $self->{hangul_terminator};
+ my $lev = $self->{level};
+ my $iden = $self->{identical};
+
+ my @buf; # weight arrays
+ if ($term) {
+ my $preHST = '';
+ my $termCE = $self->varCE(pack(VCE_TEMPLATE, NON_VAR, $term, 0,0,0));
+ foreach my $jcps (@$rEnt) {
+ # weird things like VL, TL-contraction are not considered!
+ my $curHST = join '', map getHST($_, $vers), split /;/, $jcps;
+ if ($preHST && !$curHST || # hangul before non-hangul
+ $preHST =~ /L\z/ && $curHST =~ /^T/ ||
+ $preHST =~ /V\z/ && $curHST =~ /^L/ ||
+ $preHST =~ /T\z/ && $curHST =~ /^[LV]/) {
+ push @buf, $termCE;
+ }
+ $preHST = $curHST;
+ push @buf, $self->getWt($jcps);
+ }
+ push @buf, $termCE if $preHST; # end at hangul
+ } else {
+ foreach my $jcps (@$rEnt) {
+ push @buf, $self->getWt($jcps);
+ }
+ }
+
+ my $rkey = $self->mk_SortKey(\@buf); ### XS only
+
+ if ($iden || $vers >= 26 && $lev == MaxLevel) {
+ $rkey .= LEVEL_SEP;
+ $rkey .= pack(TIE_TEMPLATE, unpack_U($str)) if $iden;
+ }
+ return $rkey;
+}
+
+
+##
+## int compare = cmp(string a, string b)
+##
+sub cmp { $_[0]->getSortKey($_[1]) cmp $_[0]->getSortKey($_[2]) }
+sub eq { $_[0]->getSortKey($_[1]) eq $_[0]->getSortKey($_[2]) }
+sub ne { $_[0]->getSortKey($_[1]) ne $_[0]->getSortKey($_[2]) }
+sub lt { $_[0]->getSortKey($_[1]) lt $_[0]->getSortKey($_[2]) }
+sub le { $_[0]->getSortKey($_[1]) le $_[0]->getSortKey($_[2]) }
+sub gt { $_[0]->getSortKey($_[1]) gt $_[0]->getSortKey($_[2]) }
+sub ge { $_[0]->getSortKey($_[1]) ge $_[0]->getSortKey($_[2]) }
+
+##
+## list[strings] sorted = sort(list[strings] arg)
+##
+sub sort {
+ my $obj = shift;
+ return
+ map { $_->[1] }
+ sort{ $a->[0] cmp $b->[0] }
+ map [ $obj->getSortKey($_), $_ ], @_;
+}
+
+
+##
+## bool _nonIgnorAtLevel(arrayref weights, int level)
+##
+sub _nonIgnorAtLevel($$)
+{
+ my $wt = shift;
+ return if ! defined $wt;
+ my $lv = shift;
+ return grep($wt->[$_-1] != 0, MinLevel..$lv) ? TRUE : FALSE;
+}
+
+##
+## bool _eqArray(
+## arrayref of arrayref[weights] source,
+## arrayref of arrayref[weights] substr,
+## int level)
+## * comparison of graphemes vs graphemes.
+## @$source >= @$substr must be true (check it before call this);
+##
+sub _eqArray($$$)
+{
+ my $source = shift;
+ my $substr = shift;
+ my $lev = shift;
+
+ for my $g (0..@$substr-1){
+ # Do the $g'th graphemes have the same number of AV weights?
+ return if @{ $source->[$g] } != @{ $substr->[$g] };
+
+ for my $w (0..@{ $substr->[$g] }-1) {
+ for my $v (0..$lev-1) {
+ return if $source->[$g][$w][$v] != $substr->[$g][$w][$v];
+ }
+ }
+ }
+ return 1;
+}
+
+##
+## (int position, int length)
+## int position = index(string, substring, position, [undoc'ed global])
+##
+## With "global" (only for the list context),
+## returns list of arrayref[position, length].
+##
+sub index
+{
+ my $self = shift;
+ $self->{preprocess} and
+ croak "Don't use Preprocess with index(), match(), etc.";
+ $self->{normCode} and
+ croak "Don't use Normalization with index(), match(), etc.";
+
+ my $str = shift;
+ my $len = length($str);
+ my $sub = shift;
+ my $subE = $self->splitEnt($sub);
+ my $pos = @_ ? shift : 0;
+ $pos = 0 if $pos < 0;
+ my $glob = shift;
+
+ my $lev = $self->{level};
+ my $v2i = $self->{UCA_Version} >= 9 &&
+ $self->{variable} ne 'non-ignorable';
+
+ if (! @$subE) {
+ my $temp = $pos <= 0 ? 0 : $len <= $pos ? $len : $pos;
+ return $glob
+ ? map([$_, 0], $temp..$len)
+ : wantarray ? ($temp,0) : $temp;
+ }
+ $len < $pos
+ and return wantarray ? () : NOMATCHPOS;
+ my $strE = $self->splitEnt($pos ? substr($str, $pos) : $str, TRUE);
+ @$strE
+ or return wantarray ? () : NOMATCHPOS;
+
+ my(@strWt, @iniPos, @finPos, @subWt, @g_ret);
+
+ my $last_is_variable;
+ for my $vwt (map $self->getWt($_), @$subE) {
+ my($var, @wt) = unpack(VCE_TEMPLATE, $vwt);
+ my $to_be_pushed = _nonIgnorAtLevel(\@wt,$lev);
+
+ # "Ignorable (L1, L2) after Variable" since track. v. 9
+ if ($v2i) {
+ if ($var) {
+ $last_is_variable = TRUE;
+ }
+ elsif (!$wt[0]) { # ignorable
+ $to_be_pushed = FALSE if $last_is_variable;
+ }
+ else {
+ $last_is_variable = FALSE;
+ }
+ }
+
+ if (@subWt && !$var && !$wt[0]) {
+ push @{ $subWt[-1] }, \@wt if $to_be_pushed;
+ } elsif ($to_be_pushed) {
+ push @subWt, [ \@wt ];
+ }
+ # else ===> skipped
+ }
+
+ my $count = 0;
+ my $end = @$strE - 1;
+
+ $last_is_variable = FALSE; # reuse
+ for (my $i = 0; $i <= $end; ) { # no $i++
+ my $found_base = 0;
+
+ # fetch a grapheme
+ while ($i <= $end && $found_base == 0) {
+ for my $vwt ($self->getWt($strE->[$i][0])) {
+ my($var, @wt) = unpack(VCE_TEMPLATE, $vwt);
+ my $to_be_pushed = _nonIgnorAtLevel(\@wt,$lev);
+
+ # "Ignorable (L1, L2) after Variable" since track. v. 9
+ if ($v2i) {
+ if ($var) {
+ $last_is_variable = TRUE;
+ }
+ elsif (!$wt[0]) { # ignorable
+ $to_be_pushed = FALSE if $last_is_variable;
+ }
+ else {
+ $last_is_variable = FALSE;
+ }
+ }
+
+ if (@strWt && !$var && !$wt[0]) {
+ push @{ $strWt[-1] }, \@wt if $to_be_pushed;
+ $finPos[-1] = $strE->[$i][2];
+ } elsif ($to_be_pushed) {
+ push @strWt, [ \@wt ];
+ push @iniPos, $found_base ? NOMATCHPOS : $strE->[$i][1];
+ $finPos[-1] = NOMATCHPOS if $found_base;
+ push @finPos, $strE->[$i][2];
+ $found_base++;
+ }
+ # else ===> no-op
+ }
+ $i++;
+ }
+
+ # try to match
+ while ( @strWt > @subWt || (@strWt == @subWt && $i > $end) ) {
+ if ($iniPos[0] != NOMATCHPOS &&
+ $finPos[$#subWt] != NOMATCHPOS &&
+ _eqArray(\@strWt, \@subWt, $lev)) {
+ my $temp = $iniPos[0] + $pos;
+
+ if ($glob) {
+ push @g_ret, [$temp, $finPos[$#subWt] - $iniPos[0]];
+ splice @strWt, 0, $#subWt;
+ splice @iniPos, 0, $#subWt;
+ splice @finPos, 0, $#subWt;
+ }
+ else {
+ return wantarray
+ ? ($temp, $finPos[$#subWt] - $iniPos[0])
+ : $temp;
+ }
+ }
+ shift @strWt;
+ shift @iniPos;
+ shift @finPos;
+ }
+ }
+
+ return $glob
+ ? @g_ret
+ : wantarray ? () : NOMATCHPOS;
+}
+
+##
+## scalarref to matching part = match(string, substring)
+##
+sub match
+{
+ my $self = shift;
+ if (my($pos,$len) = $self->index($_[0], $_[1])) {
+ my $temp = substr($_[0], $pos, $len);
+ return wantarray ? $temp : \$temp;
+ # An lvalue ref \substr should be avoided,
+ # since its value is affected by modification of its referent.
+ }
+ else {
+ return;
+ }
+}
+
+##
+## arrayref matching parts = gmatch(string, substring)
+##
+sub gmatch
+{
+ my $self = shift;
+ my $str = shift;
+ my $sub = shift;
+ return map substr($str, $_->[0], $_->[1]),
+ $self->index($str, $sub, 0, 'g');
+}
+
+##
+## bool subst'ed = subst(string, substring, replace)
+##
+sub subst
+{
+ my $self = shift;
+ my $code = ref $_[2] eq 'CODE' ? $_[2] : FALSE;
+
+ if (my($pos,$len) = $self->index($_[0], $_[1])) {
+ if ($code) {
+ my $mat = substr($_[0], $pos, $len);
+ substr($_[0], $pos, $len, $code->($mat));
+ } else {
+ substr($_[0], $pos, $len, $_[2]);
+ }
+ return TRUE;
+ }
+ else {
+ return FALSE;
+ }
+}
+
+##
+## int count = gsubst(string, substring, replace)
+##
+sub gsubst
+{
+ my $self = shift;
+ my $code = ref $_[2] eq 'CODE' ? $_[2] : FALSE;
+ my $cnt = 0;
+
+ # Replacement is carried out from the end, then use reverse.
+ for my $pos_len (reverse $self->index($_[0], $_[1], 0, 'g')) {
+ if ($code) {
+ my $mat = substr($_[0], $pos_len->[0], $pos_len->[1]);
+ substr($_[0], $pos_len->[0], $pos_len->[1], $code->($mat));
+ } else {
+ substr($_[0], $pos_len->[0], $pos_len->[1], $_[2]);
+ }
+ $cnt++;
+ }
+ return $cnt;
+}
+
+1;
+__END__
+
+=head1 NAME
+
+Unicode::Collate - Unicode Collation Algorithm
+
+=head1 SYNOPSIS
+
+ use Unicode::Collate;
+
+ #construct
+ $Collator = Unicode::Collate->new(%tailoring);
+
+ #sort
+ @sorted = $Collator->sort(@not_sorted);
+
+ #compare
+ $result = $Collator->cmp($a, $b); # returns 1, 0, or -1.
+
+B<Note:> Strings in C<@not_sorted>, C<$a> and C<$b> are interpreted
+according to Perl's Unicode support. See L<perlunicode>,
+L<perluniintro>, L<perlunitut>, L<perlunifaq>, L<utf8>.
+Otherwise you can use C<preprocess> or should decode them before.
+
+=head1 DESCRIPTION
+
+This module is an implementation of Unicode Technical Standard #10
+(a.k.a. UTS #10) - Unicode Collation Algorithm (a.k.a. UCA).
+
+=head2 Constructor and Tailoring
+
+The C<new> method returns a collator object. If new() is called
+with no parameters, the collator should do the default collation.
+
+ $Collator = Unicode::Collate->new(
+ UCA_Version => $UCA_Version,
+ alternate => $alternate, # alias for 'variable'
+ backwards => $levelNumber, # or \@levelNumbers
+ entry => $element,
+ hangul_terminator => $term_primary_weight,
+ highestFFFF => $bool,
+ identical => $bool,
+ ignoreName => qr/$ignoreName/,
+ ignoreChar => qr/$ignoreChar/,
+ ignore_level2 => $bool,
+ katakana_before_hiragana => $bool,
+ level => $collationLevel,
+ long_contraction => $bool,
+ minimalFFFE => $bool,
+ normalization => $normalization_form,
+ overrideCJK => \&overrideCJK,
+ overrideHangul => \&overrideHangul,
+ preprocess => \&preprocess,
+ rearrange => \@charList,
+ rewrite => \&rewrite,
+ suppress => \@charList,
+ table => $filename,
+ undefName => qr/$undefName/,
+ undefChar => qr/$undefChar/,
+ upper_before_lower => $bool,
+ variable => $variable,
+ );
+
+=over 4
+
+=item UCA_Version
+
+If the revision (previously "tracking version") number of UCA is given,
+behavior of that revision is emulated on collating.
+If omitted, the return value of C<UCA_Version()> is used.
+
+The following revisions are supported. The default is 34.
+
+ UCA Unicode Standard DUCET (@version)
+ -------------------------------------------------------
+ 8 3.1 3.0.1 (3.0.1d9)
+ 9 3.1 with Corrigendum 3 3.1.1 (3.1.1)
+ 11 4.0 4.0.0 (4.0.0)
+ 14 4.1.0 4.1.0 (4.1.0)
+ 16 5.0 5.0.0 (5.0.0)
+ 18 5.1.0 5.1.0 (5.1.0)
+ 20 5.2.0 5.2.0 (5.2.0)
+ 22 6.0.0 6.0.0 (6.0.0)
+ 24 6.1.0 6.1.0 (6.1.0)
+ 26 6.2.0 6.2.0 (6.2.0)
+ 28 6.3.0 6.3.0 (6.3.0)
+ 30 7.0.0 7.0.0 (7.0.0)
+ 32 8.0.0 8.0.0 (8.0.0)
+ 34 9.0.0 9.0.0 (9.0.0)
+ 36 10.0.0 10.0.0(10.0.0)
+
+* See below for C<long_contraction> with C<UCA_Version> 22 and 24.
+
+* Noncharacters (e.g. U+FFFF) are not ignored, and can be overridden
+since C<UCA_Version> 22.
+
+* Out-of-range codepoints (greater than U+10FFFF) are not ignored,
+and can be overridden since C<UCA_Version> 22.
+
+* Fully ignorable characters were ignored, and would not interrupt
+contractions with C<UCA_Version> 9 and 11.
+
+* Treatment of ignorables after variables and some behaviors
+were changed at C<UCA_Version> 9.
+
+* Characters regarded as CJK unified ideographs (cf. C<overrideCJK>)
+depend on C<UCA_Version>.
+
+* Many hangul jamo are assigned at C<UCA_Version> 20, that will affect
+C<hangul_terminator>.
+
+=item alternate
+
+-- see 3.2.2 Alternate Weighting, version 8 of UTS #10
+
+For backward compatibility, C<alternate> (old name) can be used
+as an alias for C<variable>.
+
+=item backwards
+
+-- see 3.4 Backward Accents, UTS #10.
+
+ backwards => $levelNumber or \@levelNumbers
+
+Weights in reverse order; ex. level 2 (diacritic ordering) in French.
+If omitted (or C<$levelNumber> is C<undef> or C<\@levelNumbers> is C<[]>),
+forwards at all the levels.
+
+=item entry
+
+-- see 5 Tailoring; 9.1 Allkeys File Format, UTS #10.
+
+If the same character (or a sequence of characters) exists
+in the collation element table through C<table>,
+mapping to collation elements is overridden.
+If it does not exist, the mapping is defined additionally.
+
+ entry => <<'ENTRY', # for DUCET v4.0.0 (allkeys-4.0.0.txt)
+0063 0068 ; [.0E6A.0020.0002.0063] # ch
+0043 0068 ; [.0E6A.0020.0007.0043] # Ch
+0043 0048 ; [.0E6A.0020.0008.0043] # CH
+006C 006C ; [.0F4C.0020.0002.006C] # ll
+004C 006C ; [.0F4C.0020.0007.004C] # Ll
+004C 004C ; [.0F4C.0020.0008.004C] # LL
+00F1 ; [.0F7B.0020.0002.00F1] # n-tilde
+006E 0303 ; [.0F7B.0020.0002.00F1] # n-tilde
+00D1 ; [.0F7B.0020.0008.00D1] # N-tilde
+004E 0303 ; [.0F7B.0020.0008.00D1] # N-tilde
+ENTRY
+
+ entry => <<'ENTRY', # for DUCET v4.0.0 (allkeys-4.0.0.txt)
+00E6 ; [.0E33.0020.0002.00E6][.0E8B.0020.0002.00E6] # ae ligature as <a><e>
+00C6 ; [.0E33.0020.0008.00C6][.0E8B.0020.0008.00C6] # AE ligature as <A><E>
+ENTRY
+
+B<NOTE:> The code point in the UCA file format (before C<';'>)
+B<must> be a Unicode code point (defined as hexadecimal),
+but not a native code point.
+So C<0063> must always denote C<U+0063>,
+but not a character of C<"\x63">.
+
+Weighting may vary depending on collation element table.
+So ensure the weights defined in C<entry> will be consistent with
+those in the collation element table loaded via C<table>.
+
+In DUCET v4.0.0, primary weight of C<C> is C<0E60>
+and that of C<D> is C<0E6D>. So setting primary weight of C<CH> to C<0E6A>
+(as a value between C<0E60> and C<0E6D>)
+makes ordering as C<C E<lt> CH E<lt> D>.
+Exactly speaking DUCET already has some characters between C<C> and C<D>:
+C<small capital C> (C<U+1D04>) with primary weight C<0E64>,
+C<c-hook/C-hook> (C<U+0188/U+0187>) with C<0E65>,
+and C<c-curl> (C<U+0255>) with C<0E69>.
+Then primary weight C<0E6A> for C<CH> makes C<CH>
+ordered between C<c-curl> and C<D>.
+
+=item hangul_terminator
+
+-- see 7.1.4 Trailing Weights, UTS #10.
+
+If a true value is given (non-zero but should be positive),
+it will be added as a terminator primary weight to the end of
+every standard Hangul syllable. Secondary and any higher weights
+for terminator are set to zero.
+If the value is false or C<hangul_terminator> key does not exist,
+insertion of terminator weights will not be performed.
+
+Boundaries of Hangul syllables are determined
+according to conjoining Jamo behavior in F<the Unicode Standard>
+and F<HangulSyllableType.txt>.
+
+B<Implementation Note:>
+(1) For expansion mapping (Unicode character mapped
+to a sequence of collation elements), a terminator will not be added
+between collation elements, even if Hangul syllable boundary exists there.
+Addition of terminator is restricted to the next position
+to the last collation element.
+
+(2) Non-conjoining Hangul letters
+(Compatibility Jamo, halfwidth Jamo, and enclosed letters) are not
+automatically terminated with a terminator primary weight.
+These characters may need terminator included in a collation element
+table beforehand.
+
+=item highestFFFF
+
+-- see 2.4 Tailored noncharacter weights, UTS #35 (LDML) Part 5: Collation.
+
+If the parameter is made true, C<U+FFFF> has a highest primary weight.
+When a boolean of C<$coll-E<gt>ge($str, "abc")> and
+C<$coll-E<gt>le($str, "abc\x{FFFF}")> is true, it is expected that C<$str>
+begins with C<"abc">, or another primary equivalent.
+C<$str> may be C<"abcd">, C<"abc012">, but should not include C<U+FFFF>
+such as C<"abc\x{FFFF}xyz">.
+
+C<$coll-E<gt>le($str, "abc\x{FFFF}")> works like C<$coll-E<gt>lt($str, "abd")>
+almost, but the latter has a problem that you should know which letter is
+next to C<c>. For a certain language where C<ch> as the next letter,
+C<"abch"> is greater than C<"abc\x{FFFF}">, but less than C<"abd">.
+
+Note:
+This is equivalent to C<(entry =E<gt> 'FFFF ; [.FFFE.0020.0005.FFFF]')>.
+Any other character than C<U+FFFF> can be tailored by C<entry>.
+
+=item identical
+
+-- see A.3 Deterministic Comparison, UTS #10.
+
+By default, strings whose weights are equal should be equal,
+even though their code points are not equal.
+Completely ignorable characters are ignored.
+
+If the parameter is made true, a final, tie-breaking level is used.
+If no difference of weights is found after the comparison through
+all the level specified by C<level>, the comparison with code points
+will be performed.
+For the tie-breaking comparison, the sort key has code points
+of the original string appended.
+Completely ignorable characters are not ignored.
+
+If C<preprocess> and/or C<normalization> is applied, the code points
+of the string after them (in NFD by default) are used.
+
+=item ignoreChar
+
+=item ignoreName
+
+-- see 3.6 Variable Weighting, UTS #10.
+
+Makes the entry in the table completely ignorable;
+i.e. as if the weights were zero at all level.
+
+Through C<ignoreChar>, any character matching C<qr/$ignoreChar/>
+will be ignored. Through C<ignoreName>, any character whose name
+(given in the C<table> file as a comment) matches C<qr/$ignoreName/>
+will be ignored.
+
+E.g. when 'a' and 'e' are ignorable,
+'element' is equal to 'lament' (or 'lmnt').
+
+=item ignore_level2
+
+-- see 5.1 Parametric Tailoring, UTS #10.
+
+By default, case-sensitive comparison (that is level 3 difference)
+won't ignore accents (that is level 2 difference).
+
+If the parameter is made true, accents (and other primary ignorable
+characters) are ignored, even though cases are taken into account.
+
+B<NOTE>: C<level> should be 3 or greater.
+
+=item katakana_before_hiragana
+
+-- see 7.2 Tertiary Weight Table, UTS #10.
+
+By default, hiragana is before katakana.
+If the parameter is made true, this is reversed.
+
+B<NOTE>: This parameter simplemindedly assumes that any hiragana/katakana
+distinctions must occur in level 3, and their weights at level 3 must be
+same as those mentioned in 7.3.1, UTS #10.
+If you define your collation elements which violate this requirement,
+this parameter does not work validly.
+
+=item level
+
+-- see 4.3 Form Sort Key, UTS #10.
+
+Set the maximum level.
+Any higher levels than the specified one are ignored.
+
+ Level 1: alphabetic ordering
+ Level 2: diacritic ordering
+ Level 3: case ordering
+ Level 4: tie-breaking (e.g. in the case when variable is 'shifted')
+
+ ex.level => 2,
+
+If omitted, the maximum is the 4th.
+
+B<NOTE:> The DUCET includes weights over 0xFFFF at the 4th level.
+But this module only uses weights within 0xFFFF.
+When C<variable> is 'blanked' or 'non-ignorable' (other than 'shifted'
+and 'shift-trimmed'), the level 4 may be unreliable.
+
+See also C<identical>.
+
+=item long_contraction
+
+-- see 3.8.2 Well-Formedness of the DUCET, 4.2 Produce Array, UTS #10.
+
+If the parameter is made true, for a contraction with three or more
+characters (here nicknamed "long contraction"), initial substrings
+will be handled.
+For example, a contraction ABC, where A is a starter, and B and C
+are non-starters (character with non-zero combining character class),
+will be detected even if there is not AB as a contraction.
+
+B<Default:> Usually false.
+If C<UCA_Version> is 22 or 24, and the value of C<long_contraction>
+is not specified in C<new()>, a true value is set implicitly.
+This is a workaround to pass Conformance Tests for Unicode 6.0.0 and 6.1.0.
+
+C<change()> handles C<long_contraction> explicitly only.
+If C<long_contraction> is not specified in C<change()>, even though
+C<UCA_Version> is changed, C<long_contraction> will not be changed.
+
+B<Limitation:> Scanning non-starters is one-way (no back tracking).
+If AB is found but not ABC is not found, other long contraction where
+the first character is A and the second is not B may not be found.
+
+Under C<(normalization =E<gt> undef)>, detection step of discontiguous
+contractions will be skipped.
+
+B<Note:> The following contractions in DUCET are not considered
+in steps S2.1.1 to S2.1.3, where they are discontiguous.
+
+ 0FB2 0F71 0F80 (TIBETAN VOWEL SIGN VOCALIC RR)
+ 0FB3 0F71 0F80 (TIBETAN VOWEL SIGN VOCALIC LL)
+
+For example C<TIBETAN VOWEL SIGN VOCALIC RR> with C<COMBINING TILDE OVERLAY>
+(C<U+0344>) is C<0FB2 0344 0F71 0F80> in NFD.
+In this case C<0FB2 0F80> (C<TIBETAN VOWEL SIGN VOCALIC R>) is detected,
+instead of C<0FB2 0F71 0F80>.
+Inserted C<0344> makes C<0FB2 0F71 0F80> discontiguous and lack of
+contraction C<0FB2 0F71> prohibits C<0FB2 0F71 0F80> from being detected.
+
+=item minimalFFFE
+
+-- see 1.1.1 U+FFFE, UTS #35 (LDML) Part 5: Collation.
+
+If the parameter is made true, C<U+FFFE> has a minimal primary weight.
+The comparison between C<"$a1\x{FFFE}$a2"> and C<"$b1\x{FFFE}$b2">
+first compares C<$a1> and C<$b1> at level 1, and
+then C<$a2> and C<$b2> at level 1, as followed.
+
+ "ab\x{FFFE}a"
+ "Ab\x{FFFE}a"
+ "ab\x{FFFE}c"
+ "Ab\x{FFFE}c"
+ "ab\x{FFFE}xyz"
+ "abc\x{FFFE}def"
+ "abc\x{FFFE}xYz"
+ "aBc\x{FFFE}xyz"
+ "abcX\x{FFFE}def"
+ "abcx\x{FFFE}xyz"
+ "b\x{FFFE}aaa"
+ "bbb\x{FFFE}a"
+
+Note:
+This is equivalent to C<(entry =E<gt> 'FFFE ; [.0001.0020.0005.FFFE]')>.
+Any other character than C<U+FFFE> can be tailored by C<entry>.
+
+=item normalization
+
+-- see 4.1 Normalize, UTS #10.
+
+If specified, strings are normalized before preparation of sort keys
+(the normalization is executed after preprocess).
+
+A form name C<Unicode::Normalize::normalize()> accepts will be applied
+as C<$normalization_form>.
+Acceptable names include C<'NFD'>, C<'NFC'>, C<'NFKD'>, and C<'NFKC'>.
+See C<Unicode::Normalize::normalize()> for detail.
+If omitted, C<'NFD'> is used.
+
+C<normalization> is performed after C<preprocess> (if defined).
+
+Furthermore, special values, C<undef> and C<"prenormalized">, can be used,
+though they are not concerned with C<Unicode::Normalize::normalize()>.
+
+If C<undef> (not a string C<"undef">) is passed explicitly
+as the value for this key,
+any normalization is not carried out (this may make tailoring easier
+if any normalization is not desired). Under C<(normalization =E<gt> undef)>,
+only contiguous contractions are resolved;
+e.g. even if C<A-ring> (and C<A-ring-cedilla>) is ordered after C<Z>,
+C<A-cedilla-ring> would be primary equal to C<A>.
+In this point,
+C<(normalization =E<gt> undef, preprocess =E<gt> sub { NFD(shift) })>
+B<is not> equivalent to C<(normalization =E<gt> 'NFD')>.
+
+In the case of C<(normalization =E<gt> "prenormalized")>,
+any normalization is not performed, but
+discontiguous contractions with combining characters are performed.
+Therefore
+C<(normalization =E<gt> 'prenormalized', preprocess =E<gt> sub { NFD(shift) })>
+B<is> equivalent to C<(normalization =E<gt> 'NFD')>.
+If source strings are finely prenormalized,
+C<(normalization =E<gt> 'prenormalized')> may save time for normalization.
+
+Except C<(normalization =E<gt> undef)>,
+B<Unicode::Normalize> is required (see also B<CAVEAT>).
+
+=item overrideCJK
+
+-- see 7.1 Derived Collation Elements, UTS #10.
+
+By default, CJK unified ideographs are ordered in Unicode codepoint
+order, but those in the CJK Unified Ideographs block are less than
+those in the CJK Unified Ideographs Extension A etc.
+
+ In the CJK Unified Ideographs block:
+ U+4E00..U+9FA5 if UCA_Version is 8, 9 or 11.
+ U+4E00..U+9FBB if UCA_Version is 14 or 16.
+ U+4E00..U+9FC3 if UCA_Version is 18.
+ U+4E00..U+9FCB if UCA_Version is 20 or 22.
+ U+4E00..U+9FCC if UCA_Version is 24 to 30.
+ U+4E00..U+9FD5 if UCA_Version is 32 or 34.
+ U+4E00..U+9FEA if UCA_Version is 36.
+
+ In the CJK Unified Ideographs Extension blocks:
+ Ext.A (U+3400..U+4DB5) and Ext.B (U+20000..U+2A6D6) in any UCA_Version.
+ Ext.C (U+2A700..U+2B734) if UCA_Version is 20 or later.
+ Ext.D (U+2B740..U+2B81D) if UCA_Version is 22 or later.
+ Ext.E (U+2B820..U+2CEA1) if UCA_Version is 32 or later.
+ Ext.F (U+2CEB0..U+2EBE0) if UCA_Version is 36.
+
+Through C<overrideCJK>, ordering of CJK unified ideographs (including
+extensions) can be overridden.
+
+ex. CJK unified ideographs in the JIS code point order.
+
+ overrideCJK => sub {
+ my $u = shift; # get a Unicode codepoint
+ my $b = pack('n', $u); # to UTF-16BE
+ my $s = your_unicode_to_sjis_converter($b); # convert
+ my $n = unpack('n', $s); # convert sjis to short
+ [ $n, 0x20, 0x2, $u ]; # return the collation element
+ },
+
+The return value may be an arrayref of 1st to 4th weights as shown
+above. The return value may be an integer as the primary weight
+as shown below. If C<undef> is returned, the default derived
+collation element will be used.
+
+ overrideCJK => sub {
+ my $u = shift; # get a Unicode codepoint
+ my $b = pack('n', $u); # to UTF-16BE
+ my $s = your_unicode_to_sjis_converter($b); # convert
+ my $n = unpack('n', $s); # convert sjis to short
+ return $n; # return the primary weight
+ },
+
+The return value may be a list containing zero or more of
+an arrayref, an integer, or C<undef>.
+
+ex. ignores all CJK unified ideographs.
+
+ overrideCJK => sub {()}, # CODEREF returning empty list
+
+ # where ->eq("Pe\x{4E00}rl", "Perl") is true
+ # as U+4E00 is a CJK unified ideograph and to be ignorable.
+
+If a false value (including C<undef>) is passed, C<overrideCJK>
+has no effect.
+C<$Collator-E<gt>change(overrideCJK =E<gt> 0)> resets the old one.
+
+But assignment of weight for CJK unified ideographs
+in C<table> or C<entry> is still valid.
+If C<undef> is passed explicitly as the value for this key,
+weights for CJK unified ideographs are treated as undefined.
+However when C<UCA_Version> E<gt> 8, C<(overrideCJK =E<gt> undef)>
+has no special meaning.
+
+B<Note:> In addition to them, 12 CJK compatibility ideographs (C<U+FA0E>,
+C<U+FA0F>, C<U+FA11>, C<U+FA13>, C<U+FA14>, C<U+FA1F>, C<U+FA21>, C<U+FA23>,
+C<U+FA24>, C<U+FA27>, C<U+FA28>, C<U+FA29>) are also treated as CJK unified
+ideographs. But they can't be overridden via C<overrideCJK> when you use
+DUCET, as the table includes weights for them. C<table> or C<entry> has
+priority over C<overrideCJK>.
+
+=item overrideHangul
+
+-- see 7.1 Derived Collation Elements, UTS #10.
+
+By default, Hangul syllables are decomposed into Hangul Jamo,
+even if C<(normalization =E<gt> undef)>.
+But the mapping of Hangul syllables may be overridden.
+
+This parameter works like C<overrideCJK>, so see there for examples.
+
+If you want to override the mapping of Hangul syllables,
+NFD and NFKD are not appropriate, since NFD and NFKD will decompose
+Hangul syllables before overriding. FCD may decompose Hangul syllables
+as the case may be.
+
+If a false value (but not C<undef>) is passed, C<overrideHangul>
+has no effect.
+C<$Collator-E<gt>change(overrideHangul =E<gt> 0)> resets the old one.
+
+If C<undef> is passed explicitly as the value for this key,
+weight for Hangul syllables is treated as undefined
+without decomposition into Hangul Jamo.
+But definition of weight for Hangul syllables
+in C<table> or C<entry> is still valid.
+
+=item overrideOut
+
+-- see 7.1.1 Handling Ill-Formed Code Unit Sequences, UTS #10.
+
+Perl seems to allow out-of-range values (greater than 0x10FFFF).
+By default, out-of-range values are replaced with C<U+FFFD>
+(REPLACEMENT CHARACTER) when C<UCA_Version> E<gt>= 22,
+or ignored when C<UCA_Version> E<lt>= 20.
+
+When C<UCA_Version> E<gt>= 22, the weights of out-of-range values
+can be overridden. Though C<table> or C<entry> are available for them,
+out-of-range values are too many.
+
+C<overrideOut> can perform it algorithmically.
+This parameter works like C<overrideCJK>, so see there for examples.
+
+ex. ignores all out-of-range values.
+
+ overrideOut => sub {()}, # CODEREF returning empty list
+
+If a false value (including C<undef>) is passed, C<overrideOut>
+has no effect.
+C<$Collator-E<gt>change(overrideOut =E<gt> 0)> resets the old one.
+
+B<NOTE ABOUT U+FFFD:>
+
+UCA recommends that out-of-range values should not be ignored for security
+reasons. Say, C<"pe\x{110000}rl"> should not be equal to C<"perl">.
+However, C<U+FFFD> is wrongly mapped to a variable collation element
+in DUCET for Unicode 6.0.0 to 6.2.0, that means out-of-range values will be
+ignored when C<variable> isn't C<Non-ignorable>.
+
+The mapping of C<U+FFFD> is corrected in Unicode 6.3.0.
+see L<http://www.unicode.org/reports/tr10/tr10-28.html#Trailing_Weights>
+(7.1.4 Trailing Weights). Such a correction is reproduced by this.
+
+ overrideOut => sub { 0xFFFD }, # CODEREF returning a very large integer
+
+This workaround is unnecessary since Unicode 6.3.0.
+
+=item preprocess
+
+-- see 5.4 Preprocessing, UTS #10.
+
+If specified, the coderef is used to preprocess each string
+before the formation of sort keys.
+
+ex. dropping English articles, such as "a" or "the".
+Then, "the pen" is before "a pencil".
+
+ preprocess => sub {
+ my $str = shift;
+ $str =~ s/\b(?:an?|the)\s+//gi;
+ return $str;
+ },
+
+C<preprocess> is performed before C<normalization> (if defined).
+
+ex. decoding strings in a legacy encoding such as shift-jis:
+
+ $sjis_collator = Unicode::Collate->new(
+ preprocess => \&your_shiftjis_to_unicode_decoder,
+ );
+ @result = $sjis_collator->sort(@shiftjis_strings);
+
+B<Note:> Strings returned from the coderef will be interpreted
+according to Perl's Unicode support. See L<perlunicode>,
+L<perluniintro>, L<perlunitut>, L<perlunifaq>, L<utf8>.
+
+=item rearrange
+
+-- see 3.5 Rearrangement, UTS #10.
+
+Characters that are not coded in logical order and to be rearranged.
+If C<UCA_Version> is equal to or less than 11, default is:
+
+ rearrange => [ 0x0E40..0x0E44, 0x0EC0..0x0EC4 ],
+
+If you want to disallow any rearrangement, pass C<undef> or C<[]>
+(a reference to empty list) as the value for this key.
+
+If C<UCA_Version> is equal to or greater than 14, default is C<[]>
+(i.e. no rearrangement).
+
+B<According to the version 9 of UCA, this parameter shall not be used;
+but it is not warned at present.>
+
+=item rewrite
+
+If specified, the coderef is used to rewrite lines in C<table> or C<entry>.
+The coderef will get each line, and then should return a rewritten line
+according to the UCA file format.
+If the coderef returns an empty line, the line will be skipped.
+
+e.g. any primary ignorable characters into tertiary ignorable:
+
+ rewrite => sub {
+ my $line = shift;
+ $line =~ s/\[\.0000\..{4}\..{4}\./[.0000.0000.0000./g;
+ return $line;
+ },
+
+This example shows rewriting weights. C<rewrite> is allowed to
+affect code points, weights, and the name.
+
+B<NOTE>: C<table> is available to use another table file;
+preparing a modified table once would be more efficient than
+rewriting lines on reading an unmodified table every time.
+
+=item suppress
+
+-- see 3.12 Special-Purpose Commands, UTS #35 (LDML) Part 5: Collation.
+
+Contractions beginning with the specified characters are suppressed,
+even if those contractions are defined in C<table>.
+
+An example for Russian and some languages using the Cyrillic script:
+
+ suppress => [0x0400..0x0417, 0x041A..0x0437, 0x043A..0x045F],
+
+where 0x0400 stands for C<U+0400>, CYRILLIC CAPITAL LETTER IE WITH GRAVE.
+
+B<NOTE>: Contractions via C<entry> will not be suppressed.
+
+=item table
+
+-- see 3.8 Default Unicode Collation Element Table, UTS #10.
+
+You can use another collation element table if desired.
+
+The table file should locate in the F<Unicode/Collate> directory
+on C<@INC>. Say, if the filename is F<Foo.txt>,
+the table file is searched as F<Unicode/Collate/Foo.txt> in C<@INC>.
+
+By default, F<allkeys.txt> (as the filename of DUCET) is used.
+If you will prepare your own table file, any name other than F<allkeys.txt>
+may be better to avoid namespace conflict.
+
+B<NOTE>: When XSUB is used, the DUCET is compiled on building this
+module, and it may save time at the run time.
+Explicit saying C<(table =E<gt> 'allkeys.txt')>, or using another table,
+or using C<ignoreChar>, C<ignoreName>, C<undefChar>, C<undefName> or
+C<rewrite> will prevent this module from using the compiled DUCET.
+
+If C<undef> is passed explicitly as the value for this key,
+no file is read (but you can define collation elements via C<entry>).
+
+A typical way to define a collation element table
+without any file of table:
+
+ $onlyABC = Unicode::Collate->new(
+ table => undef,
+ entry => << 'ENTRIES',
+0061 ; [.0101.0020.0002.0061] # LATIN SMALL LETTER A
+0041 ; [.0101.0020.0008.0041] # LATIN CAPITAL LETTER A
+0062 ; [.0102.0020.0002.0062] # LATIN SMALL LETTER B
+0042 ; [.0102.0020.0008.0042] # LATIN CAPITAL LETTER B
+0063 ; [.0103.0020.0002.0063] # LATIN SMALL LETTER C
+0043 ; [.0103.0020.0008.0043] # LATIN CAPITAL LETTER C
+ENTRIES
+ );
+
+If C<ignoreName> or C<undefName> is used, character names should be
+specified as a comment (following C<#>) on each line.
+
+=item undefChar
+
+=item undefName
+
+-- see 6.3.3 Reducing the Repertoire, UTS #10.
+
+Undefines the collation element as if it were unassigned in the C<table>.
+This reduces the size of the table.
+If an unassigned character appears in the string to be collated,
+the sort key is made from its codepoint
+as a single-character collation element,
+as it is greater than any other assigned collation elements
+(in the codepoint order among the unassigned characters).
+But, it'd be better to ignore characters
+unfamiliar to you and maybe never used.
+
+Through C<undefChar>, any character matching C<qr/$undefChar/>
+will be undefined. Through C<undefName>, any character whose name
+(given in the C<table> file as a comment) matches C<qr/$undefName/>
+will be undefined.
+
+ex. Collation weights for beyond-BMP characters are not stored in object:
+
+ undefChar => qr/[^\0-\x{fffd}]/,
+
+=item upper_before_lower
+
+-- see 6.6 Case Comparisons, UTS #10.
+
+By default, lowercase is before uppercase.
+If the parameter is made true, this is reversed.
+
+B<NOTE>: This parameter simplemindedly assumes that any lowercase/uppercase
+distinctions must occur in level 3, and their weights at level 3 must be
+same as those mentioned in 7.3.1, UTS #10.
+If you define your collation elements which differs from this requirement,
+this parameter doesn't work validly.
+
+=item variable
+
+-- see 3.6 Variable Weighting, UTS #10.
+
+This key allows for variable weighting of variable collation elements,
+which are marked with an ASTERISK in the table
+(NOTE: Many punctuation marks and symbols are variable in F<allkeys.txt>).
+
+ variable => 'blanked', 'non-ignorable', 'shifted', or 'shift-trimmed'.
+
+These names are case-insensitive.
+By default (if specification is omitted), 'shifted' is adopted.
+
+ 'Blanked' Variable elements are made ignorable at levels 1 through 3;
+ considered at the 4th level.
+
+ 'Non-Ignorable' Variable elements are not reset to ignorable.
+
+ 'Shifted' Variable elements are made ignorable at levels 1 through 3
+ their level 4 weight is replaced by the old level 1 weight.
+ Level 4 weight for Non-Variable elements is 0xFFFF.
+
+ 'Shift-Trimmed' Same as 'shifted', but all FFFF's at the 4th level
+ are trimmed.
+
+=back
+
+=head2 Methods for Collation
+
+=over 4
+
+=item C<@sorted = $Collator-E<gt>sort(@not_sorted)>
+
+Sorts a list of strings.
+
+=item C<$result = $Collator-E<gt>cmp($a, $b)>
+
+Returns 1 (when C<$a> is greater than C<$b>)
+or 0 (when C<$a> is equal to C<$b>)
+or -1 (when C<$a> is less than C<$b>).
+
+=item C<$result = $Collator-E<gt>eq($a, $b)>
+
+=item C<$result = $Collator-E<gt>ne($a, $b)>
+
+=item C<$result = $Collator-E<gt>lt($a, $b)>
+
+=item C<$result = $Collator-E<gt>le($a, $b)>
+
+=item C<$result = $Collator-E<gt>gt($a, $b)>
+
+=item C<$result = $Collator-E<gt>ge($a, $b)>
+
+They works like the same name operators as theirs.
+
+ eq : whether $a is equal to $b.
+ ne : whether $a is not equal to $b.
+ lt : whether $a is less than $b.
+ le : whether $a is less than $b or equal to $b.
+ gt : whether $a is greater than $b.
+ ge : whether $a is greater than $b or equal to $b.
+
+=item C<$sortKey = $Collator-E<gt>getSortKey($string)>
+
+-- see 4.3 Form Sort Key, UTS #10.
+
+Returns a sort key.
+
+You compare the sort keys using a binary comparison
+and get the result of the comparison of the strings using UCA.
+
+ $Collator->getSortKey($a) cmp $Collator->getSortKey($b)
+
+ is equivalent to
+
+ $Collator->cmp($a, $b)
+
+=item C<$sortKeyForm = $Collator-E<gt>viewSortKey($string)>
+
+Converts a sorting key into its representation form.
+If C<UCA_Version> is 8, the output is slightly different.
+
+ use Unicode::Collate;
+ my $c = Unicode::Collate->new();
+ print $c->viewSortKey("Perl"),"\n";
+
+ # output:
+ # [0B67 0A65 0B7F 0B03 | 0020 0020 0020 0020 | 0008 0002 0002 0002 | FFFF FFFF FFFF FFFF]
+ # Level 1 Level 2 Level 3 Level 4
+
+=back
+
+=head2 Methods for Searching
+
+The C<match>, C<gmatch>, C<subst>, C<gsubst> methods work
+like C<m//>, C<m//g>, C<s///>, C<s///g>, respectively,
+but they are not aware of any pattern, but only a literal substring.
+
+B<DISCLAIMER:> If C<preprocess> or C<normalization> parameter is true
+for C<$Collator>, calling these methods (C<index>, C<match>, C<gmatch>,
+C<subst>, C<gsubst>) is croaked, as the position and the length might
+differ from those on the specified string.
+
+C<rearrange> and C<hangul_terminator> parameters are neglected.
+C<katakana_before_hiragana> and C<upper_before_lower> don't affect
+matching and searching, as it doesn't matter whether greater or less.
+
+=over 4
+
+=item C<$position = $Collator-E<gt>index($string, $substring[, $position])>
+
+=item C<($position, $length) = $Collator-E<gt>index($string, $substring[, $position])>
+
+If C<$substring> matches a part of C<$string>, returns
+the position of the first occurrence of the matching part in scalar context;
+in list context, returns a two-element list of
+the position and the length of the matching part.
+
+If C<$substring> does not match any part of C<$string>,
+returns C<-1> in scalar context and
+an empty list in list context.
+
+e.g. when the content of C<$str> is C<"Ich mu>E<szlig>C< studieren Perl.">,
+you say the following where C<$sub> is C<"M>E<uuml>C<SS">,
+
+ my $Collator = Unicode::Collate->new( normalization => undef, level => 1 );
+ # (normalization => undef) is REQUIRED.
+ my $match;
+ if (my($pos,$len) = $Collator->index($str, $sub)) {
+ $match = substr($str, $pos, $len);
+ }
+
+and get C<"mu>E<szlig>C<"> in C<$match>, since C<"mu>E<szlig>C<">
+is primary equal to C<"M>E<uuml>C<SS">.
+
+=item C<$match_ref = $Collator-E<gt>match($string, $substring)>
+
+=item C<($match) = $Collator-E<gt>match($string, $substring)>
+
+If C<$substring> matches a part of C<$string>, in scalar context, returns
+B<a reference to> the first occurrence of the matching part
+(C<$match_ref> is always true if matches,
+since every reference is B<true>);
+in list context, returns the first occurrence of the matching part.
+
+If C<$substring> does not match any part of C<$string>,
+returns C<undef> in scalar context and
+an empty list in list context.
+
+e.g.
+
+ if ($match_ref = $Collator->match($str, $sub)) { # scalar context
+ print "matches [$$match_ref].\n";
+ } else {
+ print "doesn't match.\n";
+ }
+
+ or
+
+ if (($match) = $Collator->match($str, $sub)) { # list context
+ print "matches [$match].\n";
+ } else {
+ print "doesn't match.\n";
+ }
+
+=item C<@match = $Collator-E<gt>gmatch($string, $substring)>
+
+If C<$substring> matches a part of C<$string>, returns
+all the matching parts (or matching count in scalar context).
+
+If C<$substring> does not match any part of C<$string>,
+returns an empty list.
+
+=item C<$count = $Collator-E<gt>subst($string, $substring, $replacement)>
+
+If C<$substring> matches a part of C<$string>,
+the first occurrence of the matching part is replaced by C<$replacement>
+(C<$string> is modified) and C<$count> (always equals to C<1>) is returned.
+
+C<$replacement> can be a C<CODEREF>,
+taking the matching part as an argument,
+and returning a string to replace the matching part
+(a bit similar to C<s/(..)/$coderef-E<gt>($1)/e>).
+
+=item C<$count = $Collator-E<gt>gsubst($string, $substring, $replacement)>
+
+If C<$substring> matches a part of C<$string>,
+all the occurrences of the matching part are replaced by C<$replacement>
+(C<$string> is modified) and C<$count> is returned.
+
+C<$replacement> can be a C<CODEREF>,
+taking the matching part as an argument,
+and returning a string to replace the matching part
+(a bit similar to C<s/(..)/$coderef-E<gt>($1)/eg>).
+
+e.g.
+
+ my $Collator = Unicode::Collate->new( normalization => undef, level => 1 );
+ # (normalization => undef) is REQUIRED.
+ my $str = "Camel donkey zebra came\x{301}l CAMEL horse cam\0e\0l...";
+ $Collator->gsubst($str, "camel", sub { "<b>$_[0]</b>" });
+
+ # now $str is "<b>Camel</b> donkey zebra <b>came\x{301}l</b> <b>CAMEL</b> horse <b>cam\0e\0l</b>...";
+ # i.e., all the camels are made bold-faced.
+
+ Examples: levels and ignore_level2 - what does camel match?
+ ---------------------------------------------------------------------------
+ level ignore_level2 | camel Camel came\x{301}l c-a-m-e-l cam\0e\0l
+ -----------------------|---------------------------------------------------
+ 1 false | yes yes yes yes yes
+ 2 false | yes yes no yes yes
+ 3 false | yes no no yes yes
+ 4 false | yes no no no yes
+ -----------------------|---------------------------------------------------
+ 1 true | yes yes yes yes yes
+ 2 true | yes yes yes yes yes
+ 3 true | yes no yes yes yes
+ 4 true | yes no yes no yes
+ ---------------------------------------------------------------------------
+ note: if variable => non-ignorable, camel doesn't match c-a-m-e-l
+ at any level.
+
+=back
+
+=head2 Other Methods
+
+=over 4
+
+=item C<%old_tailoring = $Collator-E<gt>change(%new_tailoring)>
+
+=item C<$modified_collator = $Collator-E<gt>change(%new_tailoring)>
+
+Changes the value of specified keys and returns the changed part.
+
+ $Collator = Unicode::Collate->new(level => 4);
+
+ $Collator->eq("perl", "PERL"); # false
+
+ %old = $Collator->change(level => 2); # returns (level => 4).
+
+ $Collator->eq("perl", "PERL"); # true
+
+ $Collator->change(%old); # returns (level => 2).
+
+ $Collator->eq("perl", "PERL"); # false
+
+Not all C<(key,value)>s are allowed to be changed.
+See also C<@Unicode::Collate::ChangeOK> and C<@Unicode::Collate::ChangeNG>.
+
+In the scalar context, returns the modified collator
+(but it is B<not> a clone from the original).
+
+ $Collator->change(level => 2)->eq("perl", "PERL"); # true
+
+ $Collator->eq("perl", "PERL"); # true; now max level is 2nd.
+
+ $Collator->change(level => 4)->eq("perl", "PERL"); # false
+
+=item C<$version = $Collator-E<gt>version()>
+
+Returns the version number (a string) of the Unicode Standard
+which the C<table> file used by the collator object is based on.
+If the table does not include a version line (starting with C<@version>),
+returns C<"unknown">.
+
+=item C<UCA_Version()>
+
+Returns the revision number of UTS #10 this module consults,
+that should correspond with the DUCET incorporated.
+
+=item C<Base_Unicode_Version()>
+
+Returns the version number of UTS #10 this module consults,
+that should correspond with the DUCET incorporated.
+
+=back
+
+=head1 EXPORT
+
+No method will be exported.
+
+=head1 INSTALL
+
+Though this module can be used without any C<table> file,
+to use this module easily, it is recommended to install a table file
+in the UCA format, by copying it under the directory
+<a place in @INC>/Unicode/Collate.
+
+The most preferable one is "The Default Unicode Collation Element Table"
+(aka DUCET), available from the Unicode Consortium's website:
+
+ http://www.unicode.org/Public/UCA/
+
+ http://www.unicode.org/Public/UCA/latest/allkeys.txt
+ (latest version)
+
+If DUCET is not installed, it is recommended to copy the file
+from http://www.unicode.org/Public/UCA/latest/allkeys.txt
+to <a place in @INC>/Unicode/Collate/allkeys.txt
+manually.
+
+=head1 CAVEATS
+
+=over 4
+
+=item Normalization
+
+Use of the C<normalization> parameter requires the B<Unicode::Normalize>
+module (see L<Unicode::Normalize>).
+
+If you need not it (say, in the case when you need not
+handle any combining characters),
+assign C<(normalization =E<gt> undef)> explicitly.
+
+-- see 6.5 Avoiding Normalization, UTS #10.
+
+=item Conformance Test
+
+The Conformance Test for the UCA is available
+under L<http://www.unicode.org/Public/UCA/>.
+
+For F<CollationTest_SHIFTED.txt>,
+a collator via C<Unicode::Collate-E<gt>new( )> should be used;
+for F<CollationTest_NON_IGNORABLE.txt>, a collator via
+C<Unicode::Collate-E<gt>new(variable =E<gt> "non-ignorable", level =E<gt> 3)>.
+
+If C<UCA_Version> is 26 or later, the C<identical> level is preferred;
+C<Unicode::Collate-E<gt>new(identical =E<gt> 1)> and
+C<Unicode::Collate-E<gt>new(identical =E<gt> 1,>
+C<variable =E<gt> "non-ignorable", level =E<gt> 3)> should be used.
+
+B<Unicode::Normalize is required to try The Conformance Test.>
+
+=back
+
+=head1 AUTHOR, COPYRIGHT AND LICENSE
+
+The Unicode::Collate module for perl was written by SADAHIRO Tomoyuki,
+<SADAHIRO@cpan.org>. This module is Copyright(C) 2001-2017,
+SADAHIRO Tomoyuki. Japan. All rights reserved.
+
+This module is free software; you can redistribute it and/or
+modify it under the same terms as Perl itself.
+
+The file Unicode/Collate/allkeys.txt was copied verbatim
+from L<http://www.unicode.org/Public/UCA/9.0.0/allkeys.txt>.
+For this file, Copyright (c) 2016 Unicode, Inc.; distributed
+under the Terms of Use in L<http://www.unicode.org/terms_of_use.html>
+
+=head1 SEE ALSO
+
+=over 4
+
+=item Unicode Collation Algorithm - UTS #10
+
+L<http://www.unicode.org/reports/tr10/>
+
+=item The Default Unicode Collation Element Table (DUCET)
+
+L<http://www.unicode.org/Public/UCA/latest/allkeys.txt>
+
+=item The conformance test for the UCA
+
+L<http://www.unicode.org/Public/UCA/latest/CollationTest.html>
+
+L<http://www.unicode.org/Public/UCA/latest/CollationTest.zip>
+
+=item Hangul Syllable Type
+
+L<http://www.unicode.org/Public/UNIDATA/HangulSyllableType.txt>
+
+=item Unicode Normalization Forms - UAX #15
+
+L<http://www.unicode.org/reports/tr15/>
+
+=item Unicode Locale Data Markup Language (LDML) - UTS #35
+
+L<http://www.unicode.org/reports/tr35/>
+
+=back
+
+=cut