#! /usr/bin/perl
use strict;
use warnings;

my @trans;

print "\t/* -*- c -*- source code generated by ", join(" ", $0, @ARGV), " */\n";
while (<>) {
    s/#.*$//;
    next if /^\s*$/;
    my($code, $status, $mapping) = /^([[:xdigit:]]+);\s*([CFST]);\s*([[:xdigit:]]+(?:\s+[[:xdigit:]]+)*);\s*$/
	or warn("$ARGV:$.: weird line\n"), next;
    next unless $status eq "C" or $status eq "S";
    warn("$ARGV:$.: multi-char simple mapping\n"), next
	if $mapping =~ /\s/;
    $code = hex($code);
    $mapping = hex($mapping);
    $trans[$code] = $mapping;
} continue {
    close ARGV if eof;
}

sub gobble {
    my($begin, $step) = @_;
    my $diff = $trans[$begin] - $begin;
    my @codes;
    my @holes;
    my $probe = $begin;
    my $hole;
    while (1) {
	my @beyond;
	while (defined($trans[$probe]) && $trans[$probe] == $probe + $diff) {
	    push @beyond, $probe;
	    $probe += $step;
	}
	last unless @beyond >= 2;
	push @holes, $hole if defined $hole;
	push @codes, @beyond;
	$hole = $probe;
	$probe += $step;
    }
    return 0 unless @codes;

    # The following formula was tuned for i486-linux-gnu-gcc-4.0 -O1.
    if (@codes <= 2 + @holes) {
	print "if (", join(" || ", map { sprintf("c == 0x%X", $_) } @codes), ")\n";
    } else {
	printf "if (c >= 0x%X && c <= 0x%X", $codes[0], $codes[-1];
	printf " && c != 0x%X", $_ foreach @holes;
	if ($step == 2) { printf " && (c & 1) == %d", $begin & 1 }
	elsif ($step != 1) { printf " && c %% %d == %d", $step, $begin % $step }
	print ")\n";
    }
    if ($diff != 0) {
	if ($diff < 0) { printf "\t\tc -= "; $diff = -$diff }
	else { printf "\t\tc += " }
	if ($diff < 10) { printf "%d", $diff }
	else { printf "0x%X", $diff }
    }
    print ";\n";

    undef $trans[$_] foreach @codes;
    return 1;
}

my $first = 1;
for (my $code = 0; $code <= $#trans; ++$code) {
    next unless defined $trans[$code];

    print $first ? "\t" : "\telse ";
    gobble($code, 1) or gobble($code, 2) or gobble($code, 3) or gobble($code, 4)
	or printf "if (c == 0x%X)\n\t\tc = 0x%X;\n", $code, $trans[$code];
    $first = 0;
}
close STDOUT or die "$0: -: $!\n";

__END__

=head1 NAME

gen-case - Generate C source code for folding the case of a Unicode character.

=head1 SYNOPSIS

B<gen-case> CaseFolding.txt > ../src/intl/casefold.inc

=head1 DESCRIPTION

B<gen-case> reads F<CaseFolding.txt> of the Unicode Character Database
and generates C source code that implements the I<simple case folding>
as defined in that file.

The generated source code can then be used like this:

  unicode_val_T
  unicode_simple_case_fold(unicode_val_T c)
  {
  #include "casefold.inc"
          return c;
  }

=head1 BUGS

Does not support B<--help> nor B<--version>.

=head1 AUTHOR

Kalle Olavi Niemitalo <kon@iki.fi>

=head1 COPYRIGHT AND LICENSE

Copyright (c) 2006 Kalle Olavi Niemitalo.

This program is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.  In addition:

=over

Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
to deal in the Software without restriction, including without limitation
the rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.

=back
