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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* ***** 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
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
#include "jsstdint.h"
#include "jsbit.h"
#include "jsutil.h"
/*
* Check that we can use js_bitscan_clz32 to implement JS_FLOOR_LOG2 and
* JS_FLOOR_LOG2W and js_bitscan_clz64 to implement JS_FLOOR_LOG2W on 64-bit
* systems.
*/
#ifdef JS_HAS_BUILTIN_BITSCAN32
JS_STATIC_ASSERT(sizeof(unsigned int) == sizeof(JSUint32));
JS_STATIC_ASSERT_IF(JS_BYTES_PER_WORD == 4,
sizeof(unsigned int) == sizeof(JSUword));
#endif
#ifdef JS_HAS_BUILTIN_BITSCAN64
JS_STATIC_ASSERT_IF(JS_BYTES_PER_WORD == 8,
sizeof(unsigned long long) == sizeof(JSUword));
#endif
/*
* 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;
JS_CEILING_LOG2(log2, n);
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;
JS_FLOOR_LOG2(log2, n);
return log2;
}
/*
* js_FloorLog2wImpl has to be defined only for 64-bit non-GCC case.
*/
#if !defined(JS_HAS_BUILTIN_BITSCAN64) && JS_BYTES_PER_WORD == 8
JSUword
js_FloorLog2wImpl(JSUword n)
{
JSUword log2, m;
JS_ASSERT(n != 0);
log2 = 0;
m = n >> 32;
if (m != 0) { n = m; log2 = 32; }
m = n >> 16;
if (m != 0) { n = m; log2 |= 16; }
m = n >> 8;
if (m != 0) { n = m; log2 |= 8; }
m = n >> 4;
if (m != 0) { n = m; log2 |= 4; }
m = n >> 2;
if (m != 0) { n = m; log2 |= 2; }
log2 |= (n >> 1);
return log2;
}
#endif
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