/* -*- 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;
}
