/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Mozilla Communicator client code, released
* March 31, 1998.
*
* The Initial Developer of the Original Code is
* Netscape Communications Corporation.
* Portions created by the Initial Developer are Copyright (C) 1998
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
*
* Alternatively, the contents of this file may be used under the terms of
* either of the GNU General Public License Version 2 or later (the "GPL"),
* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
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* ***** END LICENSE BLOCK ***** */
#include "jsstddef.h"
#include "jsbit.h"
/*
** Compute the log of the least power of 2 greater than or equal to n
*/
JS_PUBLIC_API(JSIntn) JS_CeilingLog2(JSUint32 n)
{
JSIntn log2 = 0;
if (n & (n-1))
log2++;
if (n >> 16)
log2 += 16, n >>= 16;
if (n >> 8)
log2 += 8, n >>= 8;
if (n >> 4)
log2 += 4, n >>= 4;
if (n >> 2)
log2 += 2, n >>= 2;
if (n >> 1)
log2++;
return log2;
}
/*
** Compute the log of the greatest power of 2 less than or equal to n.
** This really just finds the highest set bit in the word.
*/
JS_PUBLIC_API(JSIntn) JS_FloorLog2(JSUint32 n)
{
JSIntn log2 = 0;
if (n >> 16)
log2 += 16, n >>= 16;
if (n >> 8)
log2 += 8, n >>= 8;
if (n >> 4)
log2 += 4, n >>= 4;
if (n >> 2)
log2 += 2, n >>= 2;
if (n >> 1)
log2++;
return log2;
}