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comparison libtommath/bn_s_mp_add.c @ 1733:d529a52b2f7c coverity coverity

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merge coverity from main
author Matt Johnston <matt@ucc.asn.au>
date Fri, 26 Jun 2020 21:07:34 +0800
parents 1051e4eea25a
children
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1643:b59623a64678 1733:d529a52b2f7c
1 #include <tommath_private.h> 1 #include "tommath_private.h"
2 #ifdef BN_S_MP_ADD_C 2 #ifdef BN_S_MP_ADD_C
3 /* LibTomMath, multiple-precision integer library -- Tom St Denis 3 /* LibTomMath, multiple-precision integer library -- Tom St Denis */
4 * 4 /* SPDX-License-Identifier: Unlicense */
5 * LibTomMath is a library that provides multiple-precision
6 * integer arithmetic as well as number theoretic functionality.
7 *
8 * The library was designed directly after the MPI library by
9 * Michael Fromberger but has been written from scratch with
10 * additional optimizations in place.
11 *
12 * The library is free for all purposes without any express
13 * guarantee it works.
14 *
15 * Tom St Denis, [email protected], http://libtom.org
16 */
17 5
18 /* low level addition, based on HAC pp.594, Algorithm 14.7 */ 6 /* low level addition, based on HAC pp.594, Algorithm 14.7 */
19 int 7 mp_err s_mp_add(const mp_int *a, const mp_int *b, mp_int *c)
20 s_mp_add (mp_int * a, mp_int * b, mp_int * c)
21 { 8 {
22 mp_int *x; 9 const mp_int *x;
23 int olduse, res, min, max; 10 mp_err err;
11 int olduse, min, max;
24 12
25 /* find sizes, we let |a| <= |b| which means we have to sort 13 /* find sizes, we let |a| <= |b| which means we have to sort
26 * them. "x" will point to the input with the most digits 14 * them. "x" will point to the input with the most digits
27 */ 15 */
28 if (a->used > b->used) { 16 if (a->used > b->used) {
29 min = b->used; 17 min = b->used;
30 max = a->used; 18 max = a->used;
31 x = a; 19 x = a;
32 } else { 20 } else {
33 min = a->used; 21 min = a->used;
34 max = b->used; 22 max = b->used;
35 x = b; 23 x = b;
36 } 24 }
37 25
38 /* init result */ 26 /* init result */
39 if (c->alloc < (max + 1)) { 27 if (c->alloc < (max + 1)) {
40 if ((res = mp_grow (c, max + 1)) != MP_OKAY) { 28 if ((err = mp_grow(c, max + 1)) != MP_OKAY) {
41 return res; 29 return err;
42 } 30 }
43 } 31 }
44 32
45 /* get old used digit count and set new one */ 33 /* get old used digit count and set new one */
46 olduse = c->used; 34 olduse = c->used;
47 c->used = max + 1; 35 c->used = max + 1;
48 36
49 { 37 {
50 mp_digit u, *tmpa, *tmpb, *tmpc; 38 mp_digit u, *tmpa, *tmpb, *tmpc;
51 int i; 39 int i;
52 40
53 /* alias for digit pointers */ 41 /* alias for digit pointers */
54 42
55 /* first input */ 43 /* first input */
56 tmpa = a->dp; 44 tmpa = a->dp;
57 45
58 /* second input */ 46 /* second input */
59 tmpb = b->dp; 47 tmpb = b->dp;
60 48
61 /* destination */ 49 /* destination */
62 tmpc = c->dp; 50 tmpc = c->dp;
63 51
64 /* zero the carry */ 52 /* zero the carry */
65 u = 0; 53 u = 0;
66 for (i = 0; i < min; i++) { 54 for (i = 0; i < min; i++) {
67 /* Compute the sum at one digit, T[i] = A[i] + B[i] + U */ 55 /* Compute the sum at one digit, T[i] = A[i] + B[i] + U */
68 *tmpc = *tmpa++ + *tmpb++ + u; 56 *tmpc = *tmpa++ + *tmpb++ + u;
69 57
70 /* U = carry bit of T[i] */ 58 /* U = carry bit of T[i] */
71 u = *tmpc >> ((mp_digit)DIGIT_BIT); 59 u = *tmpc >> (mp_digit)MP_DIGIT_BIT;
72 60
73 /* take away carry bit from T[i] */ 61 /* take away carry bit from T[i] */
74 *tmpc++ &= MP_MASK; 62 *tmpc++ &= MP_MASK;
75 } 63 }
76 64
77 /* now copy higher words if any, that is in A+B 65 /* now copy higher words if any, that is in A+B
78 * if A or B has more digits add those in 66 * if A or B has more digits add those in
79 */ 67 */
80 if (min != max) { 68 if (min != max) {
81 for (; i < max; i++) { 69 for (; i < max; i++) {
82 /* T[i] = X[i] + U */ 70 /* T[i] = X[i] + U */
83 *tmpc = x->dp[i] + u; 71 *tmpc = x->dp[i] + u;
84 72
85 /* U = carry bit of T[i] */ 73 /* U = carry bit of T[i] */
86 u = *tmpc >> ((mp_digit)DIGIT_BIT); 74 u = *tmpc >> (mp_digit)MP_DIGIT_BIT;
87 75
88 /* take away carry bit from T[i] */ 76 /* take away carry bit from T[i] */
89 *tmpc++ &= MP_MASK; 77 *tmpc++ &= MP_MASK;
78 }
90 } 79 }
91 }
92 80
93 /* add carry */ 81 /* add carry */
94 *tmpc++ = u; 82 *tmpc++ = u;
95 83
96 /* clear digits above oldused */ 84 /* clear digits above oldused */
97 for (i = c->used; i < olduse; i++) { 85 MP_ZERO_DIGITS(tmpc, olduse - c->used);
98 *tmpc++ = 0; 86 }
99 }
100 }
101 87
102 mp_clamp (c); 88 mp_clamp(c);
103 return MP_OKAY; 89 return MP_OKAY;
104 } 90 }
105 #endif 91 #endif
106
107 /* ref: $Format:%D$ */
108 /* git commit: $Format:%H$ */
109 /* commit time: $Format:%ai$ */