build_OID_registry

#!/usr/bin/perl -w
#
# Build a static ASN.1 Object Identified (OID) registry
#
# Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
# Written by David Howells (dhowells@redhat.com)
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public Licence
# as published by the Free Software Foundation; either version
# 2 of the Licence, or (at your option) any later version.
#

use strict;

my @names = ();
my @oids = ();

if ($#ARGV != 1) {
    print STDERR "Format: ", $0, " <in-h-file> <out-c-file>\n";
    exit(2);
}

#
# Open the file to read from
#
open IN_FILE, "<$ARGV[0]" || die;
while (<IN_FILE>) {
    chomp;
    if (m!\s+OID_([a-zA-z][a-zA-Z0-9_]+),\s+/[*]\s+([012][.0-9]*)\s+[*]/!) {
	push @names, $1;
	push @oids, $2;
    }
}
close IN_FILE || die;

#
# Open the files to write into
#
open C_FILE, ">$ARGV[1]" or die;
print C_FILE "/*\n";
print C_FILE " * Automatically generated by ", $0, ".  Do not edit\n";
print C_FILE " */\n";

#
# Split the data up into separate lists and also determine the lengths of the
# encoded data arrays.
#
my @indices = ();
my @lengths = ();
my $total_length = 0;

print "Compiling ", $#names + 1, " OIDs\n";

for (my $i = 0; $i <= $#names; $i++) {
    my $name = $names[$i];
    my $oid = $oids[$i];

    my @components = split(/[.]/, $oid);

    # Determine the encoded length of this OID
    my $size = $#components;
    for (my $loop = 2; $loop <= $#components; $loop++) {
	my $c = $components[$loop];

	# We will base128 encode the number
	my $tmp = ($c == 0) ? 0 : int(log($c)/log(2));
	$tmp = int($tmp / 7);
	$size += $tmp;
    }
    push @lengths, $size;
    push @indices, $total_length;
    $total_length += $size;
}

#
# Emit the look-up-by-OID index table
#
print C_FILE "\n";
if ($total_length <= 255) {
    print C_FILE "static const unsigned char oid_index[OID__NR + 1] = {\n";
} else {
    print C_FILE "static const unsigned short oid_index[OID__NR + 1] = {\n";
}
for (my $i = 0; $i <= $#names; $i++) {
    print C_FILE "\t[OID_", $names[$i], "] = ", $indices[$i], ",\n"
}
print C_FILE "\t[OID__NR] = ", $total_length, "\n";
print C_FILE "};\n";

#
# Encode the OIDs
#
my @encoded_oids = ();

for (my $i = 0; $i <= $#names; $i++) {
    my @octets = ();

    my @components = split(/[.]/, $oids[$i]);

    push @octets, $components[0] * 40 + $components[1];

    for (my $loop = 2; $loop <= $#components; $loop++) {
	my $c = $components[$loop];

	# Base128 encode the number
	my $tmp = ($c == 0) ? 0 : int(log($c)/log(2));
	$tmp = int($tmp / 7);

	for (; $tmp > 0; $tmp--) {
	    push @octets, (($c >> $tmp * 7) & 0x7f) | 0x80;
	}
	push @octets, $c & 0x7f;
    }

    push @encoded_oids, \@octets;
}

#
# Create a hash value for each OID
#
my @hash_values = ();
for (my $i = 0; $i <= $#names; $i++) {
    my @octets = @{$encoded_oids[$i]};

    my $hash = $#octets;
    foreach (@octets) {
	$hash += $_ * 33;
    }

    $hash = ($hash >> 24) ^ ($hash >> 16) ^ ($hash >> 8) ^ ($hash);

    push @hash_values, $hash & 0xff;
}

#
# Emit the OID data
#
print C_FILE "\n";
print C_FILE "static const unsigned char oid_data[", $total_length, "] = {\n";
for (my $i = 0; $i <= $#names; $i++) {
    my @octets = @{$encoded_oids[$i]};
    print C_FILE "\t";
    print C_FILE $_, ", " foreach (@octets);
    print C_FILE "\t// ", $names[$i];
    print C_FILE "\n";
}
print C_FILE "};\n";

#
# Build the search index table (ordered by length then hash then content)
#
my @index_table = ( 0 .. $#names );

@index_table = sort {
    my @octets_a = @{$encoded_oids[$a]};
    my @octets_b = @{$encoded_oids[$b]};

    return $hash_values[$a] <=> $hash_values[$b]
	if ($hash_values[$a] != $hash_values[$b]);
    return $#octets_a <=> $#octets_b
	if ($#octets_a != $#octets_b);
    for (my $i = $#octets_a; $i >= 0; $i--) {
	return $octets_a[$i] <=> $octets_b[$i]
	    if ($octets_a[$i] != $octets_b[$i]);
    }
    return 0;

} @index_table;

#
# Emit the search index and hash value table
#
print C_FILE "\n";
print C_FILE "static const struct {\n";
print C_FILE "\tunsigned char hash;\n";
if ($#names <= 255) {
    print C_FILE "\tenum OID oid : 8;\n";
} else {
    print C_FILE "\tenum OID oid : 16;\n";
}
print C_FILE "} oid_search_table[OID__NR] = {\n";
for (my $i = 0; $i <= $#names; $i++) {
    my @octets = @{$encoded_oids[$index_table[$i]]};
    printf(C_FILE "\t[%3u] = { %3u, OID_%-35s }, // ",
	   $i,
	   $hash_values[$index_table[$i]],
	   $names[$index_table[$i]]);
    printf C_FILE "%02x", $_ foreach (@octets);
    print C_FILE "\n";
}
print C_FILE "};\n";

#
# Emit the OID debugging name table
#
#print C_FILE "\n";
#print C_FILE "const char *const oid_name_table[OID__NR + 1] = {\n";
#
#for (my $i = 0; $i <= $#names; $i++) {
#    print C_FILE "\t\"", $names[$i], "\",\n"
#}
#print C_FILE "\t\"Unknown-OID\"\n";
#print C_FILE "};\n";

#
# Polish off
#
close C_FILE or die;