My Project  debian-1:4.1.2-p1+ds-2
ffops.cc
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1 /* emacs edit mode for this file is -*- C++ -*- */
2 
3 
4 #include "config.h"
5 
6 
7 #include <string.h>
8 
9 #include "cf_assert.h"
10 
11 #include "cf_defs.h"
12 #include "ffops.h"
13 
14 VAR int ff_prime = 0;
15 VAR int ff_halfprime = 0;
16 VAR bool ff_big = false;
17 VAR short * ff_invtab = new short [32767];
18 
19 void ff_setprime ( const int p )
20 {
21  if ( p != ff_prime )
22  {
23  ff_prime = p;
24  ff_halfprime = ff_prime / 2;
25  if ( ! ff_big )
26  memset( ff_invtab, 0, ff_prime*sizeof(short) );
27  }
28 }
29 
30 int ff_newinv ( const int a )
31 {
32  if (a < 2)
33  return (ff_invtab[a] = a);
34  int p, q, r1, r2, y1, y2;
35  r1 = p = ff_prime;
36  q = r1 / a;
37  y1 = -q;
38  r1 -= a * q;
39  if (r1 == 1)
40  {
41  y1 += p;
42  ff_invtab[y1] = a;
43  return (ff_invtab[a] = y1);
44  }
45  r2 = a;
46  y2 = 1;
47  for (;;)
48  {
49  q = r2 / r1;
50  y2 -= y1 * q;
51  r2 -= r1 * q;
52  if (r2 == 1)
53  {
54  if (y2 < 0)
55  y2 += p;
56  ff_invtab[y2] = a;
57  return (ff_invtab[a] = y2);
58  }
59  q = r1 / r2;
60  y1 -= y2 * q;
61  r1 -= r2 * q;
62  if (r1 == 1)
63  {
64  if (y1 < 0)
65  y1 += p;
66  ff_invtab[y1] = a;
67  return (ff_invtab[a] = y1);
68  }
69  }
70 }
71 
72 int ff_biginv ( const int a )
73 {
74  if (a < 2)
75  return a;
76  int p, q, r1, r2, y1, y2;
77  r1 = p = ff_prime;
78  q = r1 / a;
79  y1 = -q;
80  r1 -= a * q;
81  if (r1 == 1)
82  return p + y1;
83  r2 = a;
84  y2 = 1;
85  for (;;)
86  {
87  q = r2 / r1;
88  y2 -= y1 * q;
89  r2 -= r1 * q;
90  if (r2 == 1)
91  {
92  if (y2 > 0)
93  return y2;
94  else
95  return p + y2;
96  }
97  q = r1 / r2;
98  y1 -= y2 * q;
99  r1 -= r2 * q;
100  if (r1 == 1)
101  {
102  if (y1 > 0)
103  return y1;
104  else
105  return p + y1;
106  }
107  }
108 }
ff_halfprime
VAR int ff_halfprime
Definition: ffops.cc:15
ff_prime
VAR int ff_prime
Definition: ffops.cc:14
ff_invtab
VAR short * ff_invtab
Definition: ffops.cc:17
cf_defs.h
VAR
#define VAR
Definition: globaldefs.h:5
ff_newinv
int ff_newinv(const int a)
Definition: ffops.cc:30
ff_big
VAR bool ff_big
Definition: ffops.cc:16
cf_assert.h
p
int p
Definition: cfModGcd.cc:4019
ff_biginv
int ff_biginv(const int a)
Definition: ffops.cc:72
ffops.h
ff_setprime
void ff_setprime(const int p)
Definition: ffops.cc:19