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Annotation of Gnu-Mach/kern/log2.h, revision 1.1.1.1

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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