spielwiese
Last change
on this file since fd80670 was
362fc67,
checked in by Martin Lee <martinlee84@…>, 12 years ago
|
chg: remove $Id$
|
-
Property mode set to
100644
|
File size:
1.8 KB
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Rev | Line | |
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[493c477] | 1 | /* emacs edit mode for this file is -*- C++ -*- */ |
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[2dd068] | 2 | |
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[e4fe2b] | 3 | #include "config.h" |
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[84250a6] | 4 | |
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[071a57] | 5 | #include <string.h> |
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| 6 | |
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[650f2d8] | 7 | #include "cf_assert.h" |
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[84250a6] | 8 | |
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[2dd068] | 9 | #include "cf_defs.h" |
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| 10 | #include "ffops.h" |
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| 11 | |
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[a43bd1] | 12 | int ff_prime = 0; |
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| 13 | int ff_halfprime = 0; |
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[02af91] | 14 | bool ff_big = false; |
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[cfa45e] | 15 | short * ff_invtab = new short [32767]; |
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[2dd068] | 16 | |
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| 17 | void ff_setprime ( const int p ) |
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| 18 | { |
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[0eb89c] | 19 | if ( p != ff_prime ) { |
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[806c18] | 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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[0eb89c] | 24 | } |
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[2dd068] | 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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[b7c8bd] | 29 | int p, q, r1, r2, y1, y2; |
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| 30 | if (a < 2) |
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[806c18] | 31 | return (ff_invtab[a] = a); |
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[b7c8bd] | 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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[02af91] | 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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[b7c8bd] | 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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[2dd068] | 104 | } |
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| 105 | } |
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