Torne (Richard Coles) | 926b001 | 2013-03-28 15:32:48 +0000 | [diff] [blame] | 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 | |
| 27 | package Hasher; |
| 28 | |
| 29 | use strict; |
| 30 | |
| 31 | sub 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 |
| 38 | sub 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 | |
| 93 | 1; |