1 | /* bitfield.h |
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2 | * |
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3 | * This include file contains all bit field manipulation routines. |
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4 | * |
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5 | * COPYRIGHT (c) 1989-1997. |
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6 | * On-Line Applications Research Corporation (OAR). |
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7 | * Copyright assigned to U.S. Government, 1994. |
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8 | * |
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9 | * The license and distribution terms for this file may in |
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10 | * the file LICENSE in this distribution or at |
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11 | * http://www.OARcorp.com/rtems/license.html. |
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12 | * |
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13 | * $Id$ |
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14 | */ |
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15 | |
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16 | #ifndef __RTEMS_BITFIELD_h |
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17 | #define __RTEMS_BITFIELD_h |
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18 | |
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19 | #ifdef __cplusplus |
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20 | extern "C" { |
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21 | #endif |
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22 | |
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23 | /* |
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24 | * _Bitfield_Find_first_bit |
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25 | * |
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26 | * DESCRIPTION: |
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27 | * |
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28 | * This routine returns the bit_number of the first bit set |
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29 | * in the specified value. The correspondence between bit_number |
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30 | * and actual bit position is processor dependent. The search for |
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31 | * the first bit set may run from most to least significant bit |
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32 | * or vice-versa. |
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33 | * |
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34 | * NOTE: |
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35 | * |
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36 | * This routine is used when the executing thread is removed |
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37 | * from the ready state and, as a result, its performance has a |
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38 | * significant impact on the performance of the executive as a whole. |
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39 | */ |
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40 | |
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41 | #if ( CPU_USE_GENERIC_BITFIELD_DATA == TRUE ) |
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42 | |
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43 | #ifndef SCORE_INIT |
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44 | extern const unsigned char __log2table[256]; |
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45 | #else |
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46 | const unsigned char __log2table[256] = { |
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47 | 7, 7, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4, |
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48 | 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, |
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49 | 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, |
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50 | 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, |
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51 | 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, |
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52 | 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, |
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53 | 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, |
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54 | 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, |
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55 | 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, |
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56 | 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, |
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57 | 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, |
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58 | 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, |
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59 | 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, |
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60 | 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, |
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61 | 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, |
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62 | 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 |
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63 | }; |
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64 | #endif |
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65 | |
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66 | #endif |
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67 | |
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68 | #if ( CPU_USE_GENERIC_BITFIELD_CODE == FALSE ) |
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69 | |
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70 | #define _Bitfield_Find_first_bit( _value, _bit_number ) \ |
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71 | _CPU_Bitfield_Find_first_bit( _value, _bit_number ) |
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72 | |
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73 | #else |
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74 | |
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75 | /* |
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76 | * The following must be a macro because if a CPU specific version |
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77 | * is used it will most likely use inline assembly. |
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78 | */ |
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79 | |
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80 | #define _Bitfield_Find_first_bit( _value, _bit_number ) \ |
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81 | { \ |
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82 | register unsigned32 __value = (unsigned32) (_value); \ |
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83 | register const unsigned char *__p = __log2table; \ |
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84 | \ |
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85 | if ( __value < 0x100 ) \ |
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86 | (_bit_number) = __p[ __value ] + 8; \ |
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87 | else \ |
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88 | (_bit_number) = __p[ __value >> 8 ]; \ |
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89 | } |
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90 | |
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91 | #endif |
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92 | |
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93 | #ifdef __cplusplus |
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94 | } |
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95 | #endif |
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96 | |
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97 | #endif |
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98 | /* end of include file */ |
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