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/js/lib/Socket.IO-node/support/expresso/deps/jscoverage/js/jslog2.cpp

http://github.com/onedayitwillmake/RealtimeMultiplayerNodeJs
C++ | 94 lines | 36 code | 11 blank | 47 comment | 13 complexity | 7d9741b11f97c6ef5cf1caeab2bdd399 MD5 | raw file
 1/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
 2/* ***** BEGIN LICENSE BLOCK *****
 3 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 4 *
 5 * The contents of this file are subject to the Mozilla Public License Version
 6 * 1.1 (the "License"); you may not use this file except in compliance with
 7 * the License. You may obtain a copy of the License at
 8 * http://www.mozilla.org/MPL/
 9 *
10 * Software distributed under the License is distributed on an "AS IS" basis,
11 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
12 * for the specific language governing rights and limitations under the
13 * License.
14 *
15 * The Original Code is Mozilla Communicator client code, released
16 * March 31, 1998.
17 *
18 * The Initial Developer of the Original Code is
19 * Netscape Communications Corporation.
20 * Portions created by the Initial Developer are Copyright (C) 1998
21 * the Initial Developer. All Rights Reserved.
22 *
23 * Contributor(s):
24 *
25 * Alternatively, the contents of this file may be used under the terms of
26 * either of the GNU General Public License Version 2 or later (the "GPL"),
27 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
28 * in which case the provisions of the GPL or the LGPL are applicable instead
29 * of those above. If you wish to allow use of your version of this file only
30 * under the terms of either the GPL or the LGPL, and not to allow others to
31 * use your version of this file under the terms of the MPL, indicate your
32 * decision by deleting the provisions above and replace them with the notice
33 * and other provisions required by the GPL or the LGPL. If you do not delete
34 * the provisions above, a recipient may use your version of this file under
35 * the terms of any one of the MPL, the GPL or the LGPL.
36 *
37 * ***** END LICENSE BLOCK ***** */
38
39#include "jsstddef.h"
40#include "jsbit.h"
41#include "jsutil.h"
42
43/*
44** Compute the log of the least power of 2 greater than or equal to n
45*/
46JS_PUBLIC_API(JSIntn) JS_CeilingLog2(JSUint32 n)
47{
48    JSIntn log2;
49
50    JS_CEILING_LOG2(log2, n);
51    return log2;
52}
53
54/*
55** Compute the log of the greatest power of 2 less than or equal to n.
56** This really just finds the highest set bit in the word.
57*/
58JS_PUBLIC_API(JSIntn) JS_FloorLog2(JSUint32 n)
59{
60    JSIntn log2;
61
62    JS_FLOOR_LOG2(log2, n);
63    return log2;
64}
65
66/*
67 * js_FloorLog2wImpl has to be defined only for 64-bit non-GCC case.
68 */
69#if !defined(JS_HAS_BUILTIN_BITSCAN64) && JS_BYTES_PER_WORD == 8
70
71JSUword
72js_FloorLog2wImpl(JSUword n)
73{
74    JSUword log2, m;
75
76    JS_ASSERT(n != 0);
77
78    log2 = 0;
79    m = n >> 32;
80    if (m != 0) { n = m; log2 = 32; }
81    m = n >> 16;
82    if (m != 0) { n = m; log2 |= 16; }
83    m = n >> 8;
84    if (m != 0) { n = m; log2 |= 8; }
85    m = n >> 4;
86    if (m != 0) { n = m; log2 |= 4; }
87    m = n >> 2;
88    if (m != 0) { n = m; log2 |= 2; }
89    log2 |= (n >> 1);
90
91    return log2;
92}
93
94#endif