1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
|
/****************************************************************************
**
** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the QtTest module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL21$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Digia. For licensing terms and
** conditions see http://qt.digia.com/licensing. For further information
** use the contact form at http://qt.digia.com/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 or version 3 as published by the Free
** Software Foundation and appearing in the file LICENSE.LGPLv21 and
** LICENSE.LGPLv3 included in the packaging of this file. Please review the
** following information to ensure the GNU Lesser General Public License
** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Digia gives you certain additional
** rights. These rights are described in the Digia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** $QT_END_LICENSE$
**
****************************************************************************/
#include "main.h"
QT_BEGIN_NAMESPACE
uint qHash(const Qt4String &str)
{
int n = str.length();
const QChar *p = str.unicode();
uint h = 0;
while (n--) {
h = (h << 4) + (*p++).unicode();
h ^= (h & 0xf0000000) >> 23;
h &= 0x0fffffff;
}
return h;
}
uint qHash(const Qt50String &key, uint seed)
{
const QChar *p = key.unicode();
int len = key.size();
uint h = seed;
for (int i = 0; i < len; ++i)
h = 31 * h + p[i].unicode();
return h;
}
// The Java's hashing algorithm for strings is a variation of D. J. Bernstein
// hashing algorithm appeared here http://cr.yp.to/cdb/cdb.txt
// and informally known as DJB33XX - DJB's 33 Times Xor.
// Java uses DJB31XA, that is, 31 Times Add.
// The original algorithm was a loop around "(h << 5) + h ^ c",
// which is indeed "h * 33 ^ c"; it was then changed to
// "(h << 5) - h ^ c", so "h * 31 ^ c", and the XOR changed to a sum:
// "(h << 5) - h + c", which can save some assembly instructions.
// Still, we can avoid writing the multiplication as "(h << 5) - h"
// -- the compiler will turn it into a shift and an addition anyway
// (for instance, gcc 4.4 does that even at -O0).
uint qHash(const JavaString &str)
{
const unsigned short *p = (unsigned short *)str.constData();
const int len = str.size();
uint h = 0;
for (int i = 0; i < len; ++i)
h = 31 * h + p[i];
return h;
}
QT_END_NAMESPACE
|
