spielwiese
Last change
on this file since 08a955 was
362fc67,
checked in by Martin Lee <martinlee84@…>, 12 years ago
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chg: remove $Id$
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-
Property mode set to
100644
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File size:
1.8 KB
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1 | /* emacs edit mode for this file is -*- C++ -*- */ |
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2 | |
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3 | #include "config.h" |
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4 | |
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5 | #include <string.h> |
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6 | |
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7 | #include "cf_assert.h" |
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8 | |
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9 | #include "cf_defs.h" |
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10 | #include "ffops.h" |
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11 | |
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12 | int ff_prime = 0; |
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13 | int ff_halfprime = 0; |
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14 | bool ff_big = false; |
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15 | short * ff_invtab = new short [32767]; |
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16 | |
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17 | void ff_setprime ( const int p ) |
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18 | { |
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19 | if ( p != ff_prime ) { |
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20 | ff_prime = p; |
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21 | ff_halfprime = ff_prime / 2; |
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22 | if ( ! ff_big ) |
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23 | memset( ff_invtab, 0, ff_prime*sizeof(short) ); |
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24 | } |
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25 | } |
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26 | |
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27 | int ff_newinv ( const int a ) |
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28 | { |
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29 | int p, q, r1, r2, y1, y2; |
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30 | if (a < 2) |
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31 | return (ff_invtab[a] = a); |
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32 | r1 = p = ff_prime; |
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33 | q = r1 / a; |
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34 | y1 = -q; |
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35 | r1 -= a * q; |
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36 | if (r1 == 1) |
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37 | { |
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38 | y1 += p; |
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39 | ff_invtab[y1] = a; |
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40 | return (ff_invtab[a] = y1); |
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41 | } |
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42 | r2 = a; |
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43 | y2 = 1; |
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44 | for (;;) |
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45 | { |
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46 | q = r2 / r1; |
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47 | y2 -= y1 * q; |
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48 | r2 -= r1 * q; |
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49 | if (r2 == 1) |
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50 | { |
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51 | if (y2 < 0) |
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52 | y2 += p; |
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53 | ff_invtab[y2] = a; |
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54 | return (ff_invtab[a] = y2); |
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55 | } |
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56 | q = r1 / r2; |
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57 | y1 -= y2 * q; |
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58 | r1 -= r2 * q; |
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59 | if (r1 == 1) |
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60 | { |
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61 | if (y1 < 0) |
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62 | y1 += p; |
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63 | ff_invtab[y1] = a; |
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64 | return (ff_invtab[a] = y1); |
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65 | } |
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66 | } |
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67 | } |
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68 | |
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69 | int ff_biginv ( const int a ) |
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70 | { |
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71 | int p, q, r1, r2, y1, y2; |
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72 | if (a < 2) |
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73 | return a; |
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74 | r1 = p = ff_prime; |
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75 | q = r1 / a; |
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76 | y1 = -q; |
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77 | r1 -= a * q; |
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78 | if (r1 == 1) |
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79 | return p + y1; |
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80 | r2 = a; |
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81 | y2 = 1; |
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82 | for (;;) |
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83 | { |
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84 | q = r2 / r1; |
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85 | y2 -= y1 * q; |
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86 | r2 -= r1 * q; |
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87 | if (r2 == 1) |
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88 | { |
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89 | if (y2 > 0) |
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90 | return y2; |
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91 | else |
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92 | return p + y2; |
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93 | } |
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94 | q = r1 / r2; |
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95 | y1 -= y2 * q; |
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96 | r1 -= r2 * q; |
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97 | if (r1 == 1) |
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98 | { |
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99 | if (y1 > 0) |
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100 | return y1; |
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101 | else |
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102 | return p + y1; |
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103 | } |
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104 | } |
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105 | } |
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