Mercurial > dropbear
annotate libtommath/bn_mp_reduce_2k_l.c @ 1507:d54bbb645f02 coverity
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author | Matt Johnston <matt@ucc.asn.au> |
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date | Sat, 10 Feb 2018 19:03:54 +0800 |
parents | 8bba51a55704 |
children | f52919ffd3b1 |
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1436 | 1 #include <tommath_private.h> |
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2 #ifdef BN_MP_REDUCE_2K_L_C |
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3 /* LibTomMath, multiple-precision integer library -- Tom St Denis |
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4 * |
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5 * LibTomMath is a library that provides multiple-precision |
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6 * integer arithmetic as well as number theoretic functionality. |
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7 * |
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8 * The library was designed directly after the MPI library by |
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9 * Michael Fromberger but has been written from scratch with |
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10 * additional optimizations in place. |
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11 * |
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12 * The library is free for all purposes without any express |
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13 * guarantee it works. |
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14 * |
1436 | 15 * Tom St Denis, [email protected], http://libtom.org |
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16 */ |
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17 |
1436 | 18 /* reduces a modulo n where n is of the form 2**p - d |
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19 This differs from reduce_2k since "d" can be larger |
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20 than a single digit. |
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21 */ |
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22 int mp_reduce_2k_l(mp_int *a, mp_int *n, mp_int *d) |
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23 { |
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24 mp_int q; |
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25 int p, res; |
1436 | 26 |
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27 if ((res = mp_init(&q)) != MP_OKAY) { |
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28 return res; |
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29 } |
1436 | 30 |
31 p = mp_count_bits(n); | |
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32 top: |
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33 /* q = a/2**p, a = a mod 2**p */ |
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34 if ((res = mp_div_2d(a, p, &q, a)) != MP_OKAY) { |
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35 goto ERR; |
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36 } |
1436 | 37 |
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38 /* q = q * d */ |
1436 | 39 if ((res = mp_mul(&q, d, &q)) != MP_OKAY) { |
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40 goto ERR; |
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41 } |
1436 | 42 |
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43 /* a = a + q */ |
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44 if ((res = s_mp_add(a, &q, a)) != MP_OKAY) { |
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45 goto ERR; |
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46 } |
1436 | 47 |
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48 if (mp_cmp_mag(a, n) != MP_LT) { |
1436 | 49 if ((res = s_mp_sub(a, n, a)) != MP_OKAY) { |
50 goto ERR; | |
51 } | |
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52 goto top; |
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53 } |
1436 | 54 |
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55 ERR: |
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56 mp_clear(&q); |
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57 return res; |
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58 } |
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59 |
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60 #endif |
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61 |
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Update to libtommath v1.0.1
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62 /* ref: $Format:%D$ */ |
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63 /* git commit: $Format:%H$ */ |
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64 /* commit time: $Format:%ai$ */ |