/* -*- 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 1.1 (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/NPL/
 *
 * 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 Netscape are
 * Copyright (C) 1998 Netscape Communications Corporation. All
 * Rights Reserved.
 *
 * Contributor(s): 
 *
 * Alternatively, the contents of this file may be used under the
 * terms of the GNU Public License (the "GPL"), in which case the
 * provisions of the GPL are applicable instead of those above.
 * If you wish to allow use of your version of this file only
 * under the terms of the GPL and not to allow others to use your
 * version of this file under the NPL, indicate your decision by
 * deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL.  If you do not delete
 * the provisions above, a recipient may use your version of this
 * file under either the NPL or the GPL.
 */

#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;
}
