91 lines
1.9 KiB
C
91 lines
1.9 KiB
C
#include "tommath_private.h"
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#ifdef BN_MP_TC_XOR_C
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/* LibTomMath, multiple-precision integer library -- Tom St Denis
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*
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* LibTomMath is a library that provides multiple-precision
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* integer arithmetic as well as number theoretic functionality.
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*
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* The library was designed directly after the MPI library by
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* Michael Fromberger but has been written from scratch with
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* additional optimizations in place.
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*
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* SPDX-License-Identifier: Unlicense
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*/
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/* two complement xor */
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int mp_tc_xor(const mp_int *a, const mp_int *b, mp_int *c)
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{
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int res = MP_OKAY, bits, abits, bbits;
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int sa = a->sign, sb = b->sign;
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mp_int *mx = NULL, _mx, acpy, bcpy;
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if ((sa == MP_NEG) || (sb == MP_NEG)) {
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abits = mp_count_bits(a);
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bbits = mp_count_bits(b);
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bits = MAX(abits, bbits);
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res = mp_init_set_int(&_mx, 1uL);
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if (res != MP_OKAY) {
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goto end;
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}
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mx = &_mx;
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res = mp_mul_2d(mx, bits + 1, mx);
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if (res != MP_OKAY) {
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goto end;
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}
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if (sa == MP_NEG) {
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res = mp_init(&acpy);
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if (res != MP_OKAY) {
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goto end;
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}
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res = mp_add(mx, a, &acpy);
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if (res != MP_OKAY) {
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mp_clear(&acpy);
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goto end;
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}
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a = &acpy;
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}
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if (sb == MP_NEG) {
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res = mp_init(&bcpy);
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if (res != MP_OKAY) {
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goto end;
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}
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res = mp_add(mx, b, &bcpy);
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if (res != MP_OKAY) {
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mp_clear(&bcpy);
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goto end;
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}
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b = &bcpy;
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}
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}
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res = mp_xor(a, b, c);
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if ((sa != sb) && (res == MP_OKAY)) {
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res = mp_sub(c, mx, c);
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}
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end:
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if (a == &acpy) {
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mp_clear(&acpy);
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}
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if (b == &bcpy) {
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mp_clear(&bcpy);
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}
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if (mx == &_mx) {
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mp_clear(mx);
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}
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return res;
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}
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#endif
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/* ref: $Format:%D$ */
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/* git commit: $Format:%H$ */
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/* commit time: $Format:%ai$ */
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