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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* ***** 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 ***** */

#ifndef jsbit_h___
#define jsbit_h___

#include "jstypes.h"
#include "jsutil.h"

JS_BEGIN_EXTERN_C

/*
** A jsbitmap_t is a long integer that can be used for bitmaps
*/
typedef JSUword     jsbitmap_t;     /* NSPR name, a la Unix system types */
typedef jsbitmap_t  jsbitmap;       /* JS-style scalar typedef name */

#define JS_TEST_BIT(_map,_bit) \
    ((_map)[(_bit)>>JS_BITS_PER_WORD_LOG2] & (1L << ((_bit) & (JS_BITS_PER_WORD-1))))
#define JS_SET_BIT(_map,_bit) \
    ((_map)[(_bit)>>JS_BITS_PER_WORD_LOG2] |= (1L << ((_bit) & (JS_BITS_PER_WORD-1))))
#define JS_CLEAR_BIT(_map,_bit) \
    ((_map)[(_bit)>>JS_BITS_PER_WORD_LOG2] &= ~(1L << ((_bit) & (JS_BITS_PER_WORD-1))))

/*
** Compute the log of the least power of 2 greater than or equal to n
*/
extern JS_PUBLIC_API(JSIntn) JS_CeilingLog2(JSUint32 i);

/*
** Compute the log of the greatest power of 2 less than or equal to n
*/
extern JS_PUBLIC_API(JSIntn) JS_FloorLog2(JSUint32 i);

/*
 * Check if __builtin_clz is available which apeared first in GCC 3.4.
 * The built-in allows to speedup calculations of ceiling/floor log2,
 * see bug 327129.
 */
#if __GNUC__ >= 4 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
# define JS_HAS_GCC_BUILTIN_CLZ
#endif

/*
** Macro version of JS_CeilingLog2: Compute the log of the least power of
** 2 greater than or equal to _n. The result is returned in _log2.
*/
#ifdef JS_HAS_GCC_BUILTIN_CLZ
/*
 * Use __builtin_clz or count-leading-zeros to calculate ceil(log2(_n)).
 * The macro checks for "n <= 1" and not "n != 0" as __builtin_clz(0) is
 * undefined.
 */
# define JS_CEILING_LOG2(_log2,_n)                                            \
    JS_BEGIN_MACRO                                                            \
        JS_STATIC_ASSERT(sizeof(unsigned int) == sizeof(JSUint32));           \
        unsigned int j_ = (unsigned int)(_n);                                 \
        (_log2) = (j_ <= 1 ? 0 : 32 - __builtin_clz(j_ - 1));                 \
    JS_END_MACRO
#else
# define JS_CEILING_LOG2(_log2,_n)                                            \
    JS_BEGIN_MACRO                                                            \
        JSUint32 j_ = (JSUint32)(_n);                                         \
        (_log2) = 0;                                                          \
        if ((j_) & ((j_)-1))                                                  \
            (_log2) += 1;                                                     \
        if ((j_) >> 16)                                                       \
            (_log2) += 16, (j_) >>= 16;                                       \
        if ((j_) >> 8)                                                        \
            (_log2) += 8, (j_) >>= 8;                                         \
        if ((j_) >> 4)                                                        \
            (_log2) += 4, (j_) >>= 4;                                         \
        if ((j_) >> 2)                                                        \
            (_log2) += 2, (j_) >>= 2;                                         \
        if ((j_) >> 1)                                                        \
            (_log2) += 1;                                                     \
    JS_END_MACRO
#endif

/*
** Macro version of JS_FloorLog2: Compute the log of the greatest power of
** 2 less than or equal to _n. The result is returned in _log2.
**
** This is equivalent to finding the highest set bit in the word.
*/
#if JS_GCC_HAS_BUILTIN_CLZ
/*
 * Use __builtin_clz or count-leading-zeros to calculate floor(log2(_n)).
 * Since __builtin_clz(0) is undefined, the macro set the loweset bit to 1
 * to ensure 0 result when _n == 0.
 */
# define JS_FLOOR_LOG2(_log2,_n)                                              \
    JS_BEGIN_MACRO                                                            \
        JS_STATIC_ASSERT(sizeof(unsigned int) == sizeof(JSUint32));           \
        (_log2) = 31 - __builtin_clz(((unsigned int)(_n)) | 1);               \
    JS_END_MACRO
#else
# define JS_FLOOR_LOG2(_log2,_n)                                              \
    JS_BEGIN_MACRO                                                            \
        JSUint32 j_ = (JSUint32)(_n);                                         \
        (_log2) = 0;                                                          \
        if ((j_) >> 16)                                                       \
            (_log2) += 16, (j_) >>= 16;                                       \
        if ((j_) >> 8)                                                        \
            (_log2) += 8, (j_) >>= 8;                                         \
        if ((j_) >> 4)                                                        \
            (_log2) += 4, (j_) >>= 4;                                         \
        if ((j_) >> 2)                                                        \
            (_log2) += 2, (j_) >>= 2;                                         \
        if ((j_) >> 1)                                                        \
            (_log2) += 1;                                                     \
    JS_END_MACRO
#endif

/*
 * Internal function.
 * Compute the log of the least power of 2 greater than or equal to n.
 * This is a version of JS_CeilingLog2 that operates on jsuword with
 * CPU-dependant size.
 */
#define JS_CEILING_LOG2W(n) ((n) <= 1 ? 0 : 1 + JS_FLOOR_LOG2W((n) - 1))

/*
 * Internal function.
 * Compute the log of the greatest power of 2 less than or equal to n.
 * This is a version of JS_FloorLog2 that operates on jsuword with
 * CPU-dependant size and requires that n != 0.
 */
#define JS_FLOOR_LOG2W(n) (JS_ASSERT((n) != 0), js_FloorLog2wImpl(n))

#ifdef JS_HAS_GCC_BUILTIN_CLZ

# if JS_BYTES_PER_WORD == 4
JS_STATIC_ASSERT(sizeof(unsigned) == sizeof(JSUword));
#  define js_FloorLog2wImpl(n)                                                \
    ((JSUword)(JS_BITS_PER_WORD - 1 - __builtin_clz(n)))
# elif JS_BYTES_PER_WORD == 8
JS_STATIC_ASSERT(sizeof(unsigned long long) == sizeof(JSUword));
#  define js_FloorLog2wImpl(n)                                                \
    ((JSUword)(JS_BITS_PER_WORD - 1 - __builtin_clzll(n)))
# else
#  error "NOT SUPPORTED"
# endif

#else

# if JS_BYTES_PER_WORD == 4
#  define js_FloorLog2wImpl(n) ((JSUword)JS_FloorLog2(n))
# elif JS_BYTES_PER_WORD == 8
extern JSUword
js_FloorLog2wImpl(JSUword n);
# else
#  error "NOT SUPPORTED"
# endif

#endif


JS_END_EXTERN_C
#endif /* jsbit_h___ */

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