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prbit.h

/* -*- 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 the Netscape Portable Runtime (NSPR).
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1998-2000
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either 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
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#ifndef prbit_h___
#define prbit_h___

#include "prtypes.h"
PR_BEGIN_EXTERN_C

/*
** A prbitmap_t is a long integer that can be used for bitmaps
*/
typedef unsigned long prbitmap_t;

#define PR_TEST_BIT(_map,_bit) \
    ((_map)[(_bit)>>PR_BITS_PER_LONG_LOG2] & (1L << ((_bit) & (PR_BITS_PER_LONG-1))))
#define PR_SET_BIT(_map,_bit) \
    ((_map)[(_bit)>>PR_BITS_PER_LONG_LOG2] |= (1L << ((_bit) & (PR_BITS_PER_LONG-1))))
#define PR_CLEAR_BIT(_map,_bit) \
    ((_map)[(_bit)>>PR_BITS_PER_LONG_LOG2] &= ~(1L << ((_bit) & (PR_BITS_PER_LONG-1))))

/*
** Compute the log of the least power of 2 greater than or equal to n
*/
NSPR_API(PRIntn) PR_CeilingLog2(PRUint32 i); 

/*
** Compute the log of the greatest power of 2 less than or equal to n
*/
NSPR_API(PRIntn) PR_FloorLog2(PRUint32 i); 

/*
** Macro version of PR_CeilingLog2: Compute the log of the least power of
** 2 greater than or equal to _n. The result is returned in _log2.
*/
#define PR_CEILING_LOG2(_log2,_n)   \
  PR_BEGIN_MACRO                    \
    PRUint32 j_ = (PRUint32)(_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;               \
  PR_END_MACRO

/*
** Macro version of PR_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.
*/
#define PR_FLOOR_LOG2(_log2,_n)   \
  PR_BEGIN_MACRO                    \
    PRUint32 j_ = (PRUint32)(_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;               \
  PR_END_MACRO

PR_END_EXTERN_C
#endif /* prbit_h___ */

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