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phash.ph: yet another attempt at getting Perl to behave, arithmetically

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This commit is contained in:
H. Peter Anvin 2007-09-02 14:46:00 +00:00
parent 4768f5f6f2
commit e17a3cb29d
1 changed files with 15 additions and 7 deletions
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22
perllib/phash.ph
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@ -9,14 +9,23 @@
use Graph::Undirected;
require 'random_sv_vectors.ph';
#
# Truncate to 32-bit integer
#
sub int32($) {
my($x) = @_;
return int($x) % 4294967296;
}
#
# 32-bit rotate
#
sub rot($$) {
use integer;
my($v,$s) = @_;
return (($v << $s)+($v >> (32-$s))) & 0xffffffff;
$v = int32($v);
return int32(($v << $s)|($v >> (32-$s)));
}
#
@ -25,17 +34,16 @@ sub rot($$) {
# prehash(key, sv, N)
#
sub prehash($$$) {
use integer;
my($key, $n, $sv) = @_;
my $c;
my $k1 = 0, $k2 = 0;
my $kn1, $kn2;
my $ko1, $ko2;
my($s0, $s1, $s2, $s3) = @{$sv};
foreach $c (unpack("C*", $key)) {
$kn1 = (rot($k1,$s0)-rot($k2, $s1)+$c) & 0xffffffff;
$kn2 = (rot($k2,$s2)-rot($k1, $s3)+$c) & 0xffffffff;
$k1 = $kn1; $k2 = $kn2;
$ko1 = $k1; $ko2 = $k2;
$k1 = int32(rot($ko1,$s0)-rot($ko2, $s1)+$c);
$k2 = int32(rot($ko2,$s2)-rot($ko1, $s3)+$c);
}
# Create a bipartite graph...