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Annotation of Gnu-Mach/kern/log2.h, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 2014 Richard Braun.
        !             3:  *
        !             4:  * This program is free software: you can redistribute it and/or modify
        !             5:  * it under the terms of the GNU General Public License as published by
        !             6:  * the Free Software Foundation, either version 2 of the License, or
        !             7:  * (at your option) any later version.
        !             8:  *
        !             9:  * This program is distributed in the hope that it will be useful,
        !            10:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
        !            11:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
        !            12:  * GNU General Public License for more details.
        !            13:  *
        !            14:  * You should have received a copy of the GNU General Public License
        !            15:  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
        !            16:  *
        !            17:  *
        !            18:  * Integer base 2 logarithm operations.
        !            19:  */
        !            20: 
        !            21: #ifndef _KERN_LOG2_H
        !            22: #define _KERN_LOG2_H
        !            23: 
        !            24: #include <kern/assert.h>
        !            25: 
        !            26: #ifdef __LP64__
        !            27: #define LONG_BIT 64
        !            28: #else /* __LP64__ */
        !            29: #define LONG_BIT 32
        !            30: #endif /* __LP64__ */
        !            31: 
        !            32: static inline unsigned int
        !            33: ilog2(unsigned long x)
        !            34: {
        !            35:     assert(x != 0);
        !            36:     return LONG_BIT - __builtin_clzl(x) - 1;
        !            37: }
        !            38: 
        !            39: static inline unsigned int
        !            40: iorder2(unsigned long size)
        !            41: {
        !            42:     assert(size != 0);
        !            43: 
        !            44:     if (size == 1)
        !            45:         return 0;
        !            46: 
        !            47:     return ilog2(size - 1) + 1;
        !            48: }
        !            49: 
        !            50: #endif /* _KERN_LOG2_H */

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