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1 /* ********************************************************************* |
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2 * |
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3 * Sun elects to have this file available under and governed by the |
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4 * Mozilla Public License Version 1.1 ("MPL") (see |
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5 * http://www.mozilla.org/MPL/ for full license text). For the avoidance |
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6 * of doubt and subject to the following, Sun also elects to allow |
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7 * licensees to use this file under the MPL, the GNU General Public |
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8 * License version 2 only or the Lesser General Public License version |
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9 * 2.1 only. Any references to the "GNU General Public License version 2 |
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10 * or later" or "GPL" in the following shall be construed to mean the |
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11 * GNU General Public License version 2 only. Any references to the "GNU |
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12 * Lesser General Public License version 2.1 or later" or "LGPL" in the |
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13 * following shall be construed to mean the GNU Lesser General Public |
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14 * License version 2.1 only. However, the following notice accompanied |
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15 * the original version of this file: |
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16 * |
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17 * |
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18 * Bitwise logical operations on MPI values |
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19 * |
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20 * Version: MPL 1.1/GPL 2.0/LGPL 2.1 |
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21 * |
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22 * The contents of this file are subject to the Mozilla Public License Version |
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23 * 1.1 (the "License"); you may not use this file except in compliance with |
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24 * the License. You may obtain a copy of the License at |
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25 * http://www.mozilla.org/MPL/ |
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26 * |
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27 * Software distributed under the License is distributed on an "AS IS" basis, |
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28 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License |
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29 * for the specific language governing rights and limitations under the |
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30 * License. |
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31 * |
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32 * The Original Code is the MPI Arbitrary Precision Integer Arithmetic library. |
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33 * |
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34 * The Initial Developer of the Original Code is |
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35 * Michael J. Fromberger. |
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36 * Portions created by the Initial Developer are Copyright (C) 1998 |
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37 * the Initial Developer. All Rights Reserved. |
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38 * |
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39 * Contributor(s): |
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40 * |
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41 * Alternatively, the contents of this file may be used under the terms of |
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42 * either the GNU General Public License Version 2 or later (the "GPL"), or |
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43 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"), |
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44 * in which case the provisions of the GPL or the LGPL are applicable instead |
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45 * of those above. If you wish to allow use of your version of this file only |
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46 * under the terms of either the GPL or the LGPL, and not to allow others to |
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47 * use your version of this file under the terms of the MPL, indicate your |
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48 * decision by deleting the provisions above and replace them with the notice |
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49 * and other provisions required by the GPL or the LGPL. If you do not delete |
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50 * the provisions above, a recipient may use your version of this file under |
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51 * the terms of any one of the MPL, the GPL or the LGPL. |
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52 * |
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53 *********************************************************************** */ |
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54 /* |
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55 * Copyright 2007 Sun Microsystems, Inc. All rights reserved. |
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56 * Use is subject to license terms. |
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57 */ |
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58 |
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59 #pragma ident "%Z%%M% %I% %E% SMI" |
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60 |
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61 /* $Id: mplogic.c,v 1.15 2004/04/27 23:04:36 gerv%gerv.net Exp $ */ |
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62 |
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63 #include "mpi-priv.h" |
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64 #include "mplogic.h" |
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65 |
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66 /* {{{ Lookup table for population count */ |
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67 |
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68 static unsigned char bitc[] = { |
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69 0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4, |
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70 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, |
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71 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, |
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72 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, |
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73 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, |
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74 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, |
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75 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, |
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76 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, |
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77 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, |
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78 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, |
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79 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, |
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80 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, |
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81 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, |
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82 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, |
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83 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, |
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84 4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8 |
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85 }; |
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86 |
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87 /* }}} */ |
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88 |
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89 /* |
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90 mpl_rsh(a, b, d) - b = a >> d |
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91 mpl_lsh(a, b, d) - b = a << d |
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92 */ |
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93 |
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94 /* {{{ mpl_rsh(a, b, d) */ |
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95 |
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96 mp_err mpl_rsh(const mp_int *a, mp_int *b, mp_digit d) |
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97 { |
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98 mp_err res; |
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99 |
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100 ARGCHK(a != NULL && b != NULL, MP_BADARG); |
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101 |
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102 if((res = mp_copy(a, b)) != MP_OKAY) |
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103 return res; |
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104 |
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105 s_mp_div_2d(b, d); |
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106 |
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107 return MP_OKAY; |
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108 |
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109 } /* end mpl_rsh() */ |
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110 |
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111 /* }}} */ |
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112 |
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113 /* {{{ mpl_lsh(a, b, d) */ |
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114 |
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115 mp_err mpl_lsh(const mp_int *a, mp_int *b, mp_digit d) |
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116 { |
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117 mp_err res; |
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118 |
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119 ARGCHK(a != NULL && b != NULL, MP_BADARG); |
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120 |
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121 if((res = mp_copy(a, b)) != MP_OKAY) |
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122 return res; |
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123 |
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124 return s_mp_mul_2d(b, d); |
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125 |
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126 } /* end mpl_lsh() */ |
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127 |
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128 /* }}} */ |
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129 |
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130 /*------------------------------------------------------------------------*/ |
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131 /* |
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132 mpl_set_bit |
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133 |
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134 Returns MP_OKAY or some error code. |
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135 Grows a if needed to set a bit to 1. |
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136 */ |
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137 mp_err mpl_set_bit(mp_int *a, mp_size bitNum, mp_size value) |
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138 { |
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139 mp_size ix; |
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140 mp_err rv; |
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141 mp_digit mask; |
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142 |
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143 ARGCHK(a != NULL, MP_BADARG); |
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144 |
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145 ix = bitNum / MP_DIGIT_BIT; |
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146 if (ix + 1 > MP_USED(a)) { |
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147 rv = s_mp_pad(a, ix + 1); |
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148 if (rv != MP_OKAY) |
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149 return rv; |
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150 } |
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151 |
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152 bitNum = bitNum % MP_DIGIT_BIT; |
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153 mask = (mp_digit)1 << bitNum; |
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154 if (value) |
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155 MP_DIGIT(a,ix) |= mask; |
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156 else |
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157 MP_DIGIT(a,ix) &= ~mask; |
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158 s_mp_clamp(a); |
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159 return MP_OKAY; |
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160 } |
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161 |
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162 /* |
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163 mpl_get_bit |
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164 |
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165 returns 0 or 1 or some (negative) error code. |
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166 */ |
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167 mp_err mpl_get_bit(const mp_int *a, mp_size bitNum) |
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168 { |
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169 mp_size bit, ix; |
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170 mp_err rv; |
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171 |
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172 ARGCHK(a != NULL, MP_BADARG); |
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173 |
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174 ix = bitNum / MP_DIGIT_BIT; |
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175 ARGCHK(ix <= MP_USED(a) - 1, MP_RANGE); |
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176 |
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177 bit = bitNum % MP_DIGIT_BIT; |
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178 rv = (mp_err)(MP_DIGIT(a, ix) >> bit) & 1; |
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179 return rv; |
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180 } |
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181 |
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182 /* |
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183 mpl_get_bits |
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184 - Extracts numBits bits from a, where the least significant extracted bit |
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185 is bit lsbNum. Returns a negative value if error occurs. |
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186 - Because sign bit is used to indicate error, maximum number of bits to |
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187 be returned is the lesser of (a) the number of bits in an mp_digit, or |
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188 (b) one less than the number of bits in an mp_err. |
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189 - lsbNum + numbits can be greater than the number of significant bits in |
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190 integer a, as long as bit lsbNum is in the high order digit of a. |
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191 */ |
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192 mp_err mpl_get_bits(const mp_int *a, mp_size lsbNum, mp_size numBits) |
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193 { |
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194 mp_size rshift = (lsbNum % MP_DIGIT_BIT); |
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195 mp_size lsWndx = (lsbNum / MP_DIGIT_BIT); |
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196 mp_digit * digit = MP_DIGITS(a) + lsWndx; |
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197 mp_digit mask = ((1 << numBits) - 1); |
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198 |
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199 ARGCHK(numBits < CHAR_BIT * sizeof mask, MP_BADARG); |
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200 ARGCHK(MP_HOWMANY(lsbNum, MP_DIGIT_BIT) <= MP_USED(a), MP_RANGE); |
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201 |
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202 if ((numBits + lsbNum % MP_DIGIT_BIT <= MP_DIGIT_BIT) || |
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203 (lsWndx + 1 >= MP_USED(a))) { |
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204 mask &= (digit[0] >> rshift); |
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205 } else { |
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206 mask &= ((digit[0] >> rshift) | (digit[1] << (MP_DIGIT_BIT - rshift))); |
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207 } |
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208 return (mp_err)mask; |
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209 } |
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210 |
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211 /* |
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212 mpl_significant_bits |
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213 returns number of significnant bits in abs(a). |
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214 returns 1 if value is zero. |
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215 */ |
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216 mp_err mpl_significant_bits(const mp_int *a) |
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217 { |
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218 mp_err bits = 0; |
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219 int ix; |
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220 |
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221 ARGCHK(a != NULL, MP_BADARG); |
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222 |
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223 ix = MP_USED(a); |
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224 for (ix = MP_USED(a); ix > 0; ) { |
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225 mp_digit d; |
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226 d = MP_DIGIT(a, --ix); |
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227 if (d) { |
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228 while (d) { |
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229 ++bits; |
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230 d >>= 1; |
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231 } |
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232 break; |
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233 } |
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234 } |
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235 bits += ix * MP_DIGIT_BIT; |
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236 if (!bits) |
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237 bits = 1; |
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238 return bits; |
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239 } |
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240 |
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241 /*------------------------------------------------------------------------*/ |
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242 /* HERE THERE BE DRAGONS */ |