1# Copyright (C) 2005, 2006, 2007, 2008 Nikolas Zimmermann <zimmermann@kde.org> 2# Copyright (C) 2006 Anders Carlsson <andersca@mac.com> 3# Copyright (C) 2006, 2007 Samuel Weinig <sam@webkit.org> 4# Copyright (C) 2006 Alexey Proskuryakov <ap@webkit.org> 5# Copyright (C) 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved. 6# Copyright (C) 2009 Cameron McCormack <cam@mcc.id.au> 7# Copyright (C) Research In Motion Limited 2010. All rights reserved. 8# Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies) 9# Copyright (C) 2011 Patrick Gansterer <paroga@webkit.org> 10# Copyright (C) 2012 Ericsson AB. All rights reserved. 11# 12# This library is free software; you can redistribute it and/or 13# modify it under the terms of the GNU Library General Public 14# License as published by the Free Software Foundation; either 15# version 2 of the License, or (at your option) any later version. 16# 17# This library is distributed in the hope that it will be useful, 18# but WITHOUT ANY WARRANTY; without even the implied warranty of 19# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 20# Library General Public License for more details. 21# 22# You should have received a copy of the GNU Library General Public License 23# along with this library; see the file COPYING.LIB. If not, write to 24# the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, 25# Boston, MA 02110-1301, USA. 26 27package Hasher; 28 29use strict; 30 31sub leftShift($$) { 32 my ($value, $distance) = @_; 33 return (($value << $distance) & 0xFFFFFFFF); 34} 35 36# Paul Hsieh's SuperFastHash 37# http://www.azillionmonkeys.com/qed/hash.html 38sub GenerateHashValue 39{ 40 my @chars = split(/ */, $_[0]); 41 42 # This hash is designed to work on 16-bit chunks at a time. But since the normal case 43 # (above) is to hash UTF-16 characters, we just treat the 8-bit chars as if they 44 # were 16-bit chunks, which should give matching results 45 46 my $EXP2_32 = 4294967296; 47 48 my $hash = 0x9e3779b9; 49 my $l = scalar @chars; #I wish this was in Ruby --- Maks 50 my $rem = $l & 1; 51 $l = $l >> 1; 52 53 my $s = 0; 54 55 # Main loop 56 for (; $l > 0; $l--) { 57 $hash += ord($chars[$s]); 58 my $tmp = leftShift(ord($chars[$s+1]), 11) ^ $hash; 59 $hash = (leftShift($hash, 16)% $EXP2_32) ^ $tmp; 60 $s += 2; 61 $hash += $hash >> 11; 62 $hash %= $EXP2_32; 63 } 64 65 # Handle end case 66 if ($rem != 0) { 67 $hash += ord($chars[$s]); 68 $hash ^= (leftShift($hash, 11)% $EXP2_32); 69 $hash += $hash >> 17; 70 } 71 72 # Force "avalanching" of final 127 bits 73 $hash ^= leftShift($hash, 3); 74 $hash += ($hash >> 5); 75 $hash = ($hash% $EXP2_32); 76 $hash ^= (leftShift($hash, 2)% $EXP2_32); 77 $hash += ($hash >> 15); 78 $hash = $hash% $EXP2_32; 79 $hash ^= (leftShift($hash, 10)% $EXP2_32); 80 81 # Save 8 bits for StringImpl to use as flags. 82 $hash &= 0xffffff; 83 84 # This avoids ever returning a hash code of 0, since that is used to 85 # signal "hash not computed yet". Setting the high bit maintains 86 # reasonable fidelity to a hash code of 0 because it is likely to yield 87 # exactly 0 when hash lookup masks out the high bits. 88 $hash = (0x80000000 >> 8) if ($hash == 0); 89 90 return $hash; 91} 92 931; 94