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95 lines
2.8 KiB
C
95 lines
2.8 KiB
C
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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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/* ***** BEGIN LICENSE BLOCK *****
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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*
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* The contents of this file are subject to the Mozilla Public License Version
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* 1.1 (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is Mozilla Communicator client code, released
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* March 31, 1998.
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*
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* The Initial Developer of the Original Code is
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* Netscape Communications Corporation.
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* Portions created by the Initial Developer are Copyright (C) 1998
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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*
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* Alternatively, the contents of this file may be used under the terms of
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* either of the GNU General Public License Version 2 or later (the "GPL"),
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* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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* in which case the provisions of the GPL or the LGPL are applicable instead
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* of those above. If you wish to allow use of your version of this file only
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* under the terms of either the GPL or the LGPL, and not to allow others to
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* use your version of this file under the terms of the MPL, indicate your
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* decision by deleting the provisions above and replace them with the notice
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* and other provisions required by the GPL or the LGPL. If you do not delete
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* the provisions above, a recipient may use your version of this file under
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* the terms of any one of the MPL, the GPL or the LGPL.
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*
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* ***** END LICENSE BLOCK ***** */
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#include "jsstddef.h"
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#include "jsbit.h"
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#include "jsutil.h"
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/*
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** Compute the log of the least power of 2 greater than or equal to n
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*/
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JS_PUBLIC_API(JSIntn) JS_CeilingLog2(JSUint32 n)
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{
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JSIntn log2;
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JS_CEILING_LOG2(log2, n);
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return log2;
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}
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/*
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** Compute the log of the greatest power of 2 less than or equal to n.
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** This really just finds the highest set bit in the word.
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*/
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JS_PUBLIC_API(JSIntn) JS_FloorLog2(JSUint32 n)
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{
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JSIntn log2;
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JS_FLOOR_LOG2(log2, n);
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return log2;
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}
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/*
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* js_FloorLog2wImpl has to be defined only for 64-bit non-GCC case.
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*/
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#if !defined(JS_HAS_GCC_BUILTIN_CLZ) && JS_BYTES_PER_WORD == 8
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JSUword
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js_FloorLog2wImpl(JSUword n)
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{
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JSUword log2, m;
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JS_ASSERT(n != 0);
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log2 = 0;
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m = n >> 32;
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if (m != 0) { n = m; log2 = 32; }
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m = n >> 16;
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if (m != 0) { n = m; log2 |= 16; }
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m = n >> 8;
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if (m != 0) { n = m; log2 |= 8; }
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m = n >> 4;
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if (m != 0) { n = m; log2 |= 4; }
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m = n >> 2;
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if (m != 0) { n = m; log2 |= 2; }
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log2 |= (n >> 1);
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return log2;
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}
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#endif
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