/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/*
 * The contents of this file are subject to the Netscape Public License
 * Version 1.0 (the "NPL"); you may not use this file except in
 * compliance with the NPL.  You may obtain a copy of the NPL at
 * http://www.mozilla.org/NPL/
 * 
 * Software distributed under the NPL is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the NPL
 * for the specific language governing rights and limitations under the
 * NPL.
 * 
 * The Initial Developer of this code under the NPL is Netscape
 * Communications Corporation.  Portions created by Netscape are
 * Copyright (C) 1998 Netscape Communications Corporation.  All Rights
 * Reserved.
 */

#include "prbit.h"

/*
** Compute the log of the least power of 2 greater than or equal to n
*/
PR_IMPLEMENT(PRIntn) PR_CeilingLog2(PRUint32 n)
{
    PRIntn 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.
*/
PR_IMPLEMENT(PRIntn) PR_FloorLog2(PRUint32 n)
{
    PRIntn 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;
}