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/**
* @file rtems/score/bitfield.h
*
* This include file contains all bit field manipulation routines.
*/
/*
* COPYRIGHT (c) 1989-2006.
* On-Line Applications Research Corporation (OAR).
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.com/license/LICENSE.
*
* $Id$
*/
#ifndef _RTEMS_SCORE_BITFIELD_H
#define _RTEMS_SCORE_BITFIELD_H
/**
* @defgroup ScoreBitfield Bitfield Handler
*
* This handler encapsulates functionality that is used to manipulate the
* priority bitfields used to lookup which priority has the highest
* priority ready to execute thread.
*/
/**@{*/
#ifdef __cplusplus
extern "C" {
#endif
#if ( CPU_USE_GENERIC_BITFIELD_DATA == TRUE )
/**
* This table is used by the generic bitfield routines to perform
* a highly optimized bit scan without the use of special CPU
* instructions.
*/
#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
/**
* This routine returns the @a _bit_number of the first bit set
* in the specified value. The correspondence between @a _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.
*
* @param[in] _value is the value to bit scan.
* @param[in] _bit_number is the position of the first bit set.
*
* @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.
*
* @note This routine must be a macro because if a CPU specific version
* is used it will most likely use inline assembly.
*/
#if ( CPU_USE_GENERIC_BITFIELD_CODE == FALSE )
#define _Bitfield_Find_first_bit( _value, _bit_number ) \
_CPU_Bitfield_Find_first_bit( _value, _bit_number )
#else
#define _Bitfield_Find_first_bit( _value, _bit_number ) \
{ \
register uint32_t __value = (uint32_t ) (_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 */
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