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306 lines
12 KiB
C++
306 lines
12 KiB
C++
/* -*- 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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#ifndef jsbit_h___
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#define jsbit_h___
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#include "jstypes.h"
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#include "jscompat.h"
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#include "jsutil.h"
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JS_BEGIN_EXTERN_C
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/*
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** A jsbitmap_t is a long integer that can be used for bitmaps
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*/
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typedef jsuword jsbitmap_t; /* NSPR name, a la Unix system types */
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typedef jsbitmap_t jsbitmap; /* JS-style scalar typedef name */
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#define JS_BITMAP_SIZE(bits) (JS_HOWMANY(bits, JS_BITS_PER_WORD) * \
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sizeof(jsbitmap))
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#define JS_TEST_BIT(_map,_bit) ((_map)[(_bit)>>JS_BITS_PER_WORD_LOG2] & \
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((jsbitmap)1<<((_bit)&(JS_BITS_PER_WORD-1))))
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#define JS_SET_BIT(_map,_bit) ((_map)[(_bit)>>JS_BITS_PER_WORD_LOG2] |= \
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((jsbitmap)1<<((_bit)&(JS_BITS_PER_WORD-1))))
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#define JS_CLEAR_BIT(_map,_bit) ((_map)[(_bit)>>JS_BITS_PER_WORD_LOG2] &= \
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~((jsbitmap)1<<((_bit)&(JS_BITS_PER_WORD-1))))
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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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extern JS_PUBLIC_API(JSIntn) JS_CeilingLog2(JSUint32 i);
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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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*/
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extern JS_PUBLIC_API(JSIntn) JS_FloorLog2(JSUint32 i);
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/*
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* Replace bit-scanning code sequences with CPU-specific instructions to
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* speedup calculations of ceiling/floor log2.
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*
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* With GCC 3.4 or later we can use __builtin_clz for that, see bug 327129.
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*
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* SWS: Added MSVC intrinsic bitscan support. See bugs 349364 and 356856.
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*/
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#if defined(_WIN32) && (_MSC_VER >= 1300) && (defined(_M_IX86) || defined(_M_AMD64) || defined(_M_X64))
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unsigned char _BitScanForward(unsigned long * Index, unsigned long Mask);
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unsigned char _BitScanReverse(unsigned long * Index, unsigned long Mask);
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# pragma intrinsic(_BitScanForward,_BitScanReverse)
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__forceinline static int
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__BitScanForward32(unsigned int val)
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{
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unsigned long idx;
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_BitScanForward(&idx, (unsigned long)val);
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return (int)idx;
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}
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__forceinline static int
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__BitScanReverse32(unsigned int val)
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{
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unsigned long idx;
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_BitScanReverse(&idx, (unsigned long)val);
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return (int)(31-idx);
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}
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# define js_bitscan_ctz32(val) __BitScanForward32(val)
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# define js_bitscan_clz32(val) __BitScanReverse32(val)
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# define JS_HAS_BUILTIN_BITSCAN32
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#if defined(_M_AMD64) || defined(_M_X64)
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unsigned char _BitScanForward64(unsigned long * Index, unsigned __int64 Mask);
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unsigned char _BitScanReverse64(unsigned long * Index, unsigned __int64 Mask);
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# pragma intrinsic(_BitScanForward64,_BitScanReverse64)
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__forceinline static int
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__BitScanForward64(unsigned __int64 val)
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{
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unsigned long idx;
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_BitScanForward64(&idx, val);
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return (int)idx;
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}
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__forceinline static int
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__BitScanReverse64(unsigned __int64 val)
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{
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unsigned long idx;
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_BitScanReverse64(&idx, val);
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return (int)(63-idx);
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}
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# define js_bitscan_ctz64(val) __BitScanForward64(val)
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# define js_bitscan_clz64(val) __BitScanReverse64(val)
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# define JS_HAS_BUILTIN_BITSCAN64
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#endif
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#elif (__GNUC__ >= 4) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
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# define js_bitscan_ctz32(val) __builtin_ctz(val)
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# define js_bitscan_clz32(val) __builtin_clz(val)
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# define JS_HAS_BUILTIN_BITSCAN32
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# if (JS_BYTES_PER_WORD == 8)
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# define js_bitscan_ctz64(val) __builtin_ctzll(val)
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# define js_bitscan_clz64(val) __builtin_clzll(val)
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# define JS_HAS_BUILTIN_BITSCAN64
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# endif
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#endif
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/*
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** Macro version of JS_CeilingLog2: Compute the log of the least power of
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** 2 greater than or equal to _n. The result is returned in _log2.
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*/
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#ifdef JS_HAS_BUILTIN_BITSCAN32
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/*
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* Use intrinsic function or count-leading-zeros to calculate ceil(log2(_n)).
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* The macro checks for "n <= 1" and not "n != 0" as js_bitscan_clz32(0) is
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* undefined.
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*/
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# define JS_CEILING_LOG2(_log2,_n) \
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JS_BEGIN_MACRO \
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unsigned int j_ = (unsigned int)(_n); \
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(_log2) = (j_ <= 1 ? 0 : 32 - js_bitscan_clz32(j_ - 1)); \
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JS_END_MACRO
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#else
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# define JS_CEILING_LOG2(_log2,_n) \
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JS_BEGIN_MACRO \
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JSUint32 j_ = (JSUint32)(_n); \
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(_log2) = 0; \
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if ((j_) & ((j_)-1)) \
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(_log2) += 1; \
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if ((j_) >> 16) \
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(_log2) += 16, (j_) >>= 16; \
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if ((j_) >> 8) \
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(_log2) += 8, (j_) >>= 8; \
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if ((j_) >> 4) \
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(_log2) += 4, (j_) >>= 4; \
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if ((j_) >> 2) \
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(_log2) += 2, (j_) >>= 2; \
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if ((j_) >> 1) \
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(_log2) += 1; \
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JS_END_MACRO
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#endif
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/*
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** Macro version of JS_FloorLog2: Compute the log of the greatest power of
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** 2 less than or equal to _n. The result is returned in _log2.
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**
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** This is equivalent to finding the highest set bit in the word.
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*/
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#ifdef JS_HAS_BUILTIN_BITSCAN32
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/*
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* Use js_bitscan_clz32 or count-leading-zeros to calculate floor(log2(_n)).
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* Since js_bitscan_clz32(0) is undefined, the macro set the loweset bit to 1
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* to ensure 0 result when _n == 0.
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*/
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# define JS_FLOOR_LOG2(_log2,_n) \
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JS_BEGIN_MACRO \
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(_log2) = 31 - js_bitscan_clz32(((unsigned int)(_n)) | 1); \
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JS_END_MACRO
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#else
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# define JS_FLOOR_LOG2(_log2,_n) \
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JS_BEGIN_MACRO \
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JSUint32 j_ = (JSUint32)(_n); \
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(_log2) = 0; \
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if ((j_) >> 16) \
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(_log2) += 16, (j_) >>= 16; \
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if ((j_) >> 8) \
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(_log2) += 8, (j_) >>= 8; \
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if ((j_) >> 4) \
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(_log2) += 4, (j_) >>= 4; \
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if ((j_) >> 2) \
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(_log2) += 2, (j_) >>= 2; \
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if ((j_) >> 1) \
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(_log2) += 1; \
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JS_END_MACRO
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#endif
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/*
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* Internal function.
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* Compute the log of the least power of 2 greater than or equal to n. This is
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* a version of JS_CeilingLog2 that operates on unsigned integers with
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* CPU-dependant size.
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*/
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#define JS_CEILING_LOG2W(n) ((n) <= 1 ? 0 : 1 + JS_FLOOR_LOG2W((n) - 1))
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/*
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* Internal function.
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* Compute the log of the greatest power of 2 less than or equal to n.
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* This is a version of JS_FloorLog2 that operates on unsigned integers with
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* CPU-dependant size and requires that n != 0.
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*/
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#define JS_FLOOR_LOG2W(n) (JS_ASSERT((n) != 0), js_FloorLog2wImpl(n))
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#if JS_BYTES_PER_WORD == 4
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# ifdef JS_HAS_BUILTIN_BITSCAN32
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# define js_FloorLog2wImpl(n) \
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((size_t)(JS_BITS_PER_WORD - 1 - js_bitscan_clz32(n)))
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# else
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# define js_FloorLog2wImpl(n) ((size_t)JS_FloorLog2(n))
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#endif
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#elif JS_BYTES_PER_WORD == 8
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# ifdef JS_HAS_BUILTIN_BITSCAN64
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# define js_FloorLog2wImpl(n) \
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((size_t)(JS_BITS_PER_WORD - 1 - js_bitscan_clz64(n)))
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# else
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extern size_t js_FloorLog2wImpl(size_t n);
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# endif
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#else
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# error "NOT SUPPORTED"
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#endif
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namespace js {
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inline size_t
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CountTrailingZeros(size_t n)
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{
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JS_ASSERT(n != 0);
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#if JS_BYTES_PER_WORD != 4 && JS_BYTES_PER_WORD != 8
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# error "NOT SUPPORTED"
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#endif
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#if JS_BYTES_PER_WORD == 4 && defined JS_HAS_BUILTIN_BITSCAN32
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return js_bitscan_ctz32(n);
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#elif JS_BYTES_PER_WORD == 8 && defined JS_HAS_BUILTIN_BITSCAN64
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return js_bitscan_ctz64(n);
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#else
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size_t count = 0;
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# if JS_BYTES_PER_WORD == 8
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if (!(n & size_t(0xFFFFFFFFU))) { count += 32; n >>= 32; }
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# endif
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if (!(n & 0xFFFF)) { count += 16; n >>= 16; }
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if (!(n & 0xFF)) { count += 8; n >>= 8; }
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if (!(n & 0xF)) { count += 4; n >>= 4; }
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if (!(n & 0x3)) { count += 2; n >>= 2; }
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if (!(n & 0x1)) { count += 1; n >>= 1; }
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return count + 1 - (n & 0x1);
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#endif
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}
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}
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/*
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* Macros for rotate left. There is no rotate operation in the C Language so
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* the construct (a << 4) | (a >> 28) is used instead. Most compilers convert
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* this to a rotate instruction but some versions of MSVC don't without a
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* little help. To get MSVC to generate a rotate instruction, we have to use
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* the _rotl intrinsic and use a pragma to make _rotl inline.
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*
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* MSVC in VS2005 will do an inline rotate instruction on the above construct.
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*/
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#if defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_AMD64) || \
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defined(_M_X64))
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#include <stdlib.h>
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#pragma intrinsic(_rotl)
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#define JS_ROTATE_LEFT32(a, bits) _rotl(a, bits)
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#else
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#define JS_ROTATE_LEFT32(a, bits) (((a) << (bits)) | ((a) >> (32 - (bits))))
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#endif
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JS_END_EXTERN_C
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#endif /* jsbit_h___ */
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