1 | /* emacs edit mode for this file is -*- C++ -*- */ |
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2 | |
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3 | /** |
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4 | * @file ffops.h |
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5 | * |
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6 | * operations in a finite prime field F_p. |
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7 | * The largest supported p is 536870909, i.e. the largest prime less than 2^29. |
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8 | * |
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9 | **/ |
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10 | |
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11 | #ifndef INCL_FFOPS_H |
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12 | #define INCL_FFOPS_H |
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13 | |
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14 | // #include "config.h" |
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15 | |
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16 | #include "cf_globals.h" |
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17 | #ifdef HAVE_NTL |
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18 | #include <NTL/config.h> |
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19 | #endif |
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20 | |
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21 | /* define type of your compilers 64 bit integer type */ |
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22 | #ifndef FACTORY_INT64 |
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23 | #if SIZEOF_LONG == 8 |
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24 | #define FACTORY_INT64 long int |
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25 | #else |
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26 | #define FACTORY_INT64 long long int |
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27 | #endif |
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28 | #endif |
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29 | |
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30 | EXTERN_VAR int ff_prime; |
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31 | EXTERN_VAR int ff_halfprime; |
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32 | EXTERN_VAR short * ff_invtab; |
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33 | EXTERN_VAR bool ff_big; |
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34 | |
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35 | int ff_newinv ( const int ); |
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36 | int ff_biginv ( const int ); |
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37 | void ff_setprime ( const int ); |
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38 | |
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39 | inline int ff_norm ( const int a ) |
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40 | { |
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41 | int n = a % ff_prime; |
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42 | #if defined(NTL_AVOID_BRANCHING) |
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43 | n += (n >> 31) & ff_prime; |
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44 | return n; |
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45 | #else |
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46 | if (n < 0) n += ff_prime; |
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47 | return n; |
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48 | #endif |
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49 | } |
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50 | |
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51 | inline long ff_norm ( const long a ) |
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52 | { |
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53 | long n = a % (long)ff_prime; |
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54 | #if defined(NTL_AVOID_BRANCHING) |
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55 | #if SIZEOF_LONG==8 |
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56 | n += (n >> 63) & ff_prime; |
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57 | #else |
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58 | n += (n >> 31) & ff_prime; |
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59 | #endif |
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60 | return n; |
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61 | #else |
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62 | if (n < 0) n += (long)ff_prime; |
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63 | return n; |
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64 | #endif |
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65 | } |
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66 | |
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67 | inline int ff_symmetric( const int a ) |
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68 | { |
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69 | if ( cf_glob_switches.isOn( SW_SYMMETRIC_FF ) ) |
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70 | return ( a > ff_halfprime ) ? a - ff_prime : a; |
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71 | else |
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72 | return a; |
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73 | } |
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74 | |
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75 | inline long ff_symmetric( const long a ) |
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76 | { |
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77 | if ( cf_glob_switches.isOn( SW_SYMMETRIC_FF ) ) |
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78 | return ( a > ff_halfprime ) ? a - ff_prime : a; |
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79 | else |
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80 | return a; |
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81 | } |
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82 | |
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83 | #if SIZEOF_LONG==4 |
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84 | inline int ff_bignorm ( const FACTORY_INT64 a ) |
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85 | { |
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86 | int n = (int)(a % (FACTORY_INT64)ff_prime); |
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87 | #if defined(NTL_AVOID_BRANCHING) |
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88 | n += (n >> 31) & ff_prime; |
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89 | return n; |
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90 | #else |
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91 | if (n < 0) n += ff_prime; |
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92 | return n; |
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93 | #endif |
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94 | } |
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95 | #endif |
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96 | |
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97 | inline int ff_add ( const int a, const int b ) |
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98 | { |
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99 | //return ff_norm( a + b ); |
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100 | #if defined(NTL_AVOID_BRANCHING) |
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101 | int r=( a + b ); |
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102 | r -= ff_prime; |
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103 | r += (r >> 31) & ff_prime; |
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104 | return r; |
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105 | #else |
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106 | int r=( a + b ); |
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107 | if (r >= ff_prime) r -= ff_prime; |
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108 | return r; |
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109 | #endif |
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110 | } |
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111 | |
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112 | inline int ff_sub ( const int a, const int b ) |
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113 | { |
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114 | //return ff_norm( a - b ); |
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115 | #if defined(NTL_AVOID_BRANCHING) |
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116 | int r=( a - b ); |
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117 | r += (r >> 31) & ff_prime; |
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118 | return r; |
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119 | #else |
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120 | int r=( a - b ); |
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121 | if (r < 0) r += ff_prime; |
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122 | return r; |
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123 | #endif |
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124 | } |
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125 | |
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126 | inline int ff_neg ( const int a ) |
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127 | { |
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128 | //return ff_norm( -a ); |
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129 | // EXPERIMENT |
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130 | #if defined(NTL_AVOID_BRANCHING) |
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131 | int r= -a; |
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132 | r += (r >> 31) & ff_prime; |
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133 | return r; |
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134 | #else |
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135 | return ( a == 0 ? 0 : ff_prime-a ); |
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136 | #endif |
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137 | } |
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138 | |
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139 | inline int ff_mul ( const int a, const int b ) |
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140 | { |
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141 | #if SIZEOF_LONG==4 |
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142 | if ( ff_big ) |
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143 | return ff_bignorm( (FACTORY_INT64)a * (FACTORY_INT64)b ); |
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144 | else |
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145 | #endif /* else: FACTORY_INT64 is long, i.e. ff_bignorm is the same as ff_norm(long) */ |
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146 | return ff_norm ( (long)a * (long)b ); |
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147 | } |
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148 | |
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149 | inline int ff_inv ( const int a ) |
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150 | { |
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151 | if ( ff_big ) |
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152 | return ff_biginv( a ); |
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153 | else { |
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154 | int b; |
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155 | if ( (b = (int)(ff_invtab[a])) ) |
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156 | return b; |
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157 | else |
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158 | return ff_newinv( a ); |
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159 | } |
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160 | |
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161 | } |
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162 | |
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163 | inline int ff_div ( const int a, const int b ) |
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164 | { |
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165 | return ff_mul( a, ff_inv( b ) ); |
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166 | } |
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167 | |
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168 | #endif /* ! INCL_FFOPS_H */ |
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