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Annotation of sbbs/include/mozilla/nspr/prbit.h, revision 1.1

1.1     ! root        1: /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
        !             2: /* 
        !             3:  * The contents of this file are subject to the Mozilla Public
        !             4:  * License Version 1.1 (the "License"); you may not use this file
        !             5:  * except in compliance with the License. You may obtain a copy of
        !             6:  * the License at http://www.mozilla.org/MPL/
        !             7:  * 
        !             8:  * Software distributed under the License is distributed on an "AS
        !             9:  * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
        !            10:  * implied. See the License for the specific language governing
        !            11:  * rights and limitations under the License.
        !            12:  * 
        !            13:  * The Original Code is the Netscape Portable Runtime (NSPR).
        !            14:  * 
        !            15:  * The Initial Developer of the Original Code is Netscape
        !            16:  * Communications Corporation.  Portions created by Netscape are 
        !            17:  * Copyright (C) 1998-2000 Netscape Communications Corporation.  All
        !            18:  * Rights Reserved.
        !            19:  * 
        !            20:  * Contributor(s):
        !            21:  * 
        !            22:  * Alternatively, the contents of this file may be used under the
        !            23:  * terms of the GNU General Public License Version 2 or later (the
        !            24:  * "GPL"), in which case the provisions of the GPL are applicable 
        !            25:  * instead of those above.  If you wish to allow use of your 
        !            26:  * version of this file only under the terms of the GPL and not to
        !            27:  * allow others to use your version of this file under the MPL,
        !            28:  * indicate your decision by deleting the provisions above and
        !            29:  * replace them with the notice and other provisions required by
        !            30:  * the GPL.  If you do not delete the provisions above, a recipient
        !            31:  * may use your version of this file under either the MPL or the
        !            32:  * GPL.
        !            33:  */
        !            34: 
        !            35: #ifndef prbit_h___
        !            36: #define prbit_h___
        !            37: 
        !            38: #include "prtypes.h"
        !            39: PR_BEGIN_EXTERN_C
        !            40: 
        !            41: /*
        !            42: ** A prbitmap_t is a long integer that can be used for bitmaps
        !            43: */
        !            44: typedef unsigned long prbitmap_t;
        !            45: 
        !            46: #define PR_TEST_BIT(_map,_bit) \
        !            47:     ((_map)[(_bit)>>PR_BITS_PER_LONG_LOG2] & (1L << ((_bit) & (PR_BITS_PER_LONG-1))))
        !            48: #define PR_SET_BIT(_map,_bit) \
        !            49:     ((_map)[(_bit)>>PR_BITS_PER_LONG_LOG2] |= (1L << ((_bit) & (PR_BITS_PER_LONG-1))))
        !            50: #define PR_CLEAR_BIT(_map,_bit) \
        !            51:     ((_map)[(_bit)>>PR_BITS_PER_LONG_LOG2] &= ~(1L << ((_bit) & (PR_BITS_PER_LONG-1))))
        !            52: 
        !            53: /*
        !            54: ** Compute the log of the least power of 2 greater than or equal to n
        !            55: */
        !            56: NSPR_API(PRIntn) PR_CeilingLog2(PRUint32 i); 
        !            57: 
        !            58: /*
        !            59: ** Compute the log of the greatest power of 2 less than or equal to n
        !            60: */
        !            61: NSPR_API(PRIntn) PR_FloorLog2(PRUint32 i); 
        !            62: 
        !            63: /*
        !            64: ** Macro version of PR_CeilingLog2: Compute the log of the least power of
        !            65: ** 2 greater than or equal to _n. The result is returned in _log2.
        !            66: */
        !            67: #define PR_CEILING_LOG2(_log2,_n)   \
        !            68:   PR_BEGIN_MACRO                    \
        !            69:     PRUint32 j_ = (PRUint32)(_n);  \
        !            70:     (_log2) = 0;                    \
        !            71:     if ((j_) & ((j_)-1))            \
        !            72:    (_log2) += 1;               \
        !            73:     if ((j_) >> 16)                 \
        !            74:    (_log2) += 16, (j_) >>= 16; \
        !            75:     if ((j_) >> 8)                  \
        !            76:    (_log2) += 8, (j_) >>= 8;   \
        !            77:     if ((j_) >> 4)                  \
        !            78:    (_log2) += 4, (j_) >>= 4;   \
        !            79:     if ((j_) >> 2)                  \
        !            80:    (_log2) += 2, (j_) >>= 2;   \
        !            81:     if ((j_) >> 1)                  \
        !            82:    (_log2) += 1;               \
        !            83:   PR_END_MACRO
        !            84: 
        !            85: /*
        !            86: ** Macro version of PR_FloorLog2: Compute the log of the greatest power of
        !            87: ** 2 less than or equal to _n. The result is returned in _log2.
        !            88: **
        !            89: ** This is equivalent to finding the highest set bit in the word.
        !            90: */
        !            91: #define PR_FLOOR_LOG2(_log2,_n)   \
        !            92:   PR_BEGIN_MACRO                    \
        !            93:     PRUint32 j_ = (PRUint32)(_n);  \
        !            94:     (_log2) = 0;                    \
        !            95:     if ((j_) >> 16)                 \
        !            96:    (_log2) += 16, (j_) >>= 16; \
        !            97:     if ((j_) >> 8)                  \
        !            98:    (_log2) += 8, (j_) >>= 8;   \
        !            99:     if ((j_) >> 4)                  \
        !           100:    (_log2) += 4, (j_) >>= 4;   \
        !           101:     if ((j_) >> 2)                  \
        !           102:    (_log2) += 2, (j_) >>= 2;   \
        !           103:     if ((j_) >> 1)                  \
        !           104:    (_log2) += 1;               \
        !           105:   PR_END_MACRO
        !           106: 
        !           107: PR_END_EXTERN_C
        !           108: #endif /* prbit_h___ */

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