#! /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.

Permission to use, copy, modify, and/or distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.