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comparison libtommath/bn_mp_sqrt.c @ 1739:13d834efc376 fuzz

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author Matt Johnston <matt@ucc.asn.au>
date Thu, 15 Oct 2020 19:55:15 +0800
parents 1051e4eea25a
children
comparison
equal deleted inserted replaced
1562:768ebf737aa0 1739:13d834efc376
1 #include <tommath_private.h> 1 #include "tommath_private.h"
2 #ifdef BN_MP_SQRT_C 2 #ifdef BN_MP_SQRT_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 /* this function is less generic than mp_n_root, simpler and faster */ 6 /* this function is less generic than mp_n_root, simpler and faster */
19 int mp_sqrt(mp_int *arg, mp_int *ret) 7 mp_err mp_sqrt(const mp_int *arg, mp_int *ret)
20 { 8 {
21 int res; 9 mp_err err;
22 mp_int t1,t2; 10 mp_int t1, t2;
23 11
24 /* must be positive */ 12 /* must be positive */
25 if (arg->sign == MP_NEG) { 13 if (arg->sign == MP_NEG) {
26 return MP_VAL; 14 return MP_VAL;
27 } 15 }
28 16
29 /* easy out */ 17 /* easy out */
30 if (mp_iszero(arg) == MP_YES) { 18 if (MP_IS_ZERO(arg)) {
31 mp_zero(ret); 19 mp_zero(ret);
32 return MP_OKAY; 20 return MP_OKAY;
33 } 21 }
34 22
35 if ((res = mp_init_copy(&t1, arg)) != MP_OKAY) { 23 if ((err = mp_init_copy(&t1, arg)) != MP_OKAY) {
36 return res; 24 return err;
37 } 25 }
38 26
39 if ((res = mp_init(&t2)) != MP_OKAY) { 27 if ((err = mp_init(&t2)) != MP_OKAY) {
40 goto E2; 28 goto E2;
41 } 29 }
42 30
43 /* First approx. (not very bad for large arg) */ 31 /* First approx. (not very bad for large arg) */
44 mp_rshd (&t1,t1.used/2); 32 mp_rshd(&t1, t1.used/2);
45 33
46 /* t1 > 0 */ 34 /* t1 > 0 */
47 if ((res = mp_div(arg,&t1,&t2,NULL)) != MP_OKAY) { 35 if ((err = mp_div(arg, &t1, &t2, NULL)) != MP_OKAY) {
48 goto E1;
49 }
50 if ((res = mp_add(&t1,&t2,&t1)) != MP_OKAY) {
51 goto E1;
52 }
53 if ((res = mp_div_2(&t1,&t1)) != MP_OKAY) {
54 goto E1;
55 }
56 /* And now t1 > sqrt(arg) */
57 do {
58 if ((res = mp_div(arg,&t1,&t2,NULL)) != MP_OKAY) {
59 goto E1; 36 goto E1;
60 } 37 }
61 if ((res = mp_add(&t1,&t2,&t1)) != MP_OKAY) { 38 if ((err = mp_add(&t1, &t2, &t1)) != MP_OKAY) {
62 goto E1; 39 goto E1;
63 } 40 }
64 if ((res = mp_div_2(&t1,&t1)) != MP_OKAY) { 41 if ((err = mp_div_2(&t1, &t1)) != MP_OKAY) {
65 goto E1; 42 goto E1;
66 } 43 }
67 /* t1 >= sqrt(arg) >= t2 at this point */ 44 /* And now t1 > sqrt(arg) */
68 } while (mp_cmp_mag(&t1,&t2) == MP_GT); 45 do {
46 if ((err = mp_div(arg, &t1, &t2, NULL)) != MP_OKAY) {
47 goto E1;
48 }
49 if ((err = mp_add(&t1, &t2, &t1)) != MP_OKAY) {
50 goto E1;
51 }
52 if ((err = mp_div_2(&t1, &t1)) != MP_OKAY) {
53 goto E1;
54 }
55 /* t1 >= sqrt(arg) >= t2 at this point */
56 } while (mp_cmp_mag(&t1, &t2) == MP_GT);
69 57
70 mp_exch(&t1,ret); 58 mp_exch(&t1, ret);
71 59
72 E1: mp_clear(&t2); 60 E1:
73 E2: mp_clear(&t1); 61 mp_clear(&t2);
74 return res; 62 E2:
63 mp_clear(&t1);
64 return err;
75 } 65 }
76 66
77 #endif 67 #endif
78
79 /* ref: $Format:%D$ */
80 /* git commit: $Format:%H$ */
81 /* commit time: $Format:%ai$ */