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Annotation of Gnu-Mach/include/mach/proc_ops.h, revision 1.1.1.1

1.1       root        1: /*
                      2:  * Copyright (c) 1994 The University of Utah and
                      3:  * the Center for Software Science (CSS).  All rights reserved.
                      4:  *
                      5:  * Permission to use, copy, modify and distribute this software and its
                      6:  * documentation is hereby granted, provided that both the copyright
                      7:  * notice and this permission notice appear in all copies of the
                      8:  * software, derivative works or modified versions, and any portions
                      9:  * thereof, and that both notices appear in supporting documentation.
                     10:  *
                     11:  * THE UNIVERSITY OF UTAH AND CSS ALLOW FREE USE OF THIS SOFTWARE IN ITS "AS
                     12:  * IS" CONDITION.  THE UNIVERSITY OF UTAH AND CSS DISCLAIM ANY LIABILITY OF
                     13:  * ANY KIND FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
                     14:  *
                     15:  * CSS requests users of this software to return to [email protected] any
                     16:  * improvements that they make and grant CSS redistribution rights.
                     17:  *
                     18:  *      Author: Bryan Ford, University of Utah CSS
                     19:  */
                     20: /*
                     21:  * Simple operations that don't exist as primitives in C,
                     22:  * but which processors often implement directly.
                     23:  * This file contains default, "dumb" implementations;
                     24:  * machine-independent code can override these with smarter implementations.
                     25:  */
                     26: #ifndef _MACH_PROC_OPS_H_
                     27: #define _MACH_PROC_OPS_H_
                     28: 
                     29: #include <mach/machine/vm_types.h>
                     30: #include <mach/inline.h>
                     31: 
                     32: /* Returns the bit number of the most-significant set bit in `val',
                     33:    e.g. 0 for 1, 1 for 2-3, 2 for 4-7, etc.
                     34:    If `val' is 0 (i.e. no bits are set), the behavior is undefined.  */
                     35: MACH_INLINE int find_msb_set(natural_t val)
                     36: {
                     37:        int msb;
                     38:        for (msb = sizeof(val)*8-1; (val & ((natural_t)1 << msb)) == 0; msb--);
                     39:        return msb;
                     40: }
                     41: 
                     42: /* Returns the bit number of the least-significant set bit in `val'.
                     43:    If `val' is 0 (i.e. no bits are set), the behavior is undefined.  */
                     44: MACH_INLINE int find_lsb_set(natural_t val)
                     45: {
                     46:        int lsb;
                     47:        for (lsb = 0; (val & ((natural_t)1 << lsb)) == 0; lsb++);
                     48:        return lsb;
                     49: }
                     50: 
                     51: #endif _MACH_PROC_OPS_H_

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