/* bitfield.h
*
* This include file contains all bit field manipulation routines.
*
* COPYRIGHT (c) 1989-1998.
* On-Line Applications Research Corporation (OAR).
* Copyright assigned to U.S. Government, 1994.
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.OARcorp.com/rtems/license.html.
*
* $Id$
*/
#ifndef __RTEMS_BITFIELD_h
#define __RTEMS_BITFIELD_h
#ifdef __cplusplus
extern "C" {
#endif
/*
* _Bitfield_Find_first_bit
*
* DESCRIPTION:
*
* This routine returns the bit_number of the first bit set
* in the specified value. The correspondence between bit_number
* and actual bit position is processor dependent. The search for
* the first bit set may run from most to least significant bit
* or vice-versa.
*
* NOTE:
*
* This routine is used when the executing thread is removed
* from the ready state and, as a result, its performance has a
* significant impact on the performance of the executive as a whole.
*/
#if ( CPU_USE_GENERIC_BITFIELD_DATA == TRUE )
#ifndef SCORE_INIT
extern const unsigned char __log2table[256];
#else
const unsigned char __log2table[256] = {
7, 7, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4,
3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};
#endif
#endif
#if ( CPU_USE_GENERIC_BITFIELD_CODE == FALSE )
#define _Bitfield_Find_first_bit( _value, _bit_number ) \
_CPU_Bitfield_Find_first_bit( _value, _bit_number )
#else
/*
* The following must be a macro because if a CPU specific version
* is used it will most likely use inline assembly.
*/
#define _Bitfield_Find_first_bit( _value, _bit_number ) \
{ \
register unsigned32 __value = (unsigned32) (_value); \
register const unsigned char *__p = __log2table; \
\
if ( __value < 0x100 ) \
(_bit_number) = __p[ __value ] + 8; \
else \
(_bit_number) = __p[ __value >> 8 ]; \
}
#endif
#ifdef __cplusplus
}
#endif
#endif
/* end of include file */