1af0de1f91
* same behavior for positive numbers * generalisation for negative numbers, treating them as two complement * improve algorithm, iterate once over the digits, manually perform two complement * simplify mp_add_d, mp_sub_d * functions are safe in case of a==c or b==c * renamed mp_tc_div_2d to mp_signed_rsh (signed right shift)
23 lines
553 B
C
23 lines
553 B
C
#include "tommath_private.h"
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#ifdef BN_MP_SIGNED_RSH_C
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/* LibTomMath, multiple-precision integer library -- Tom St Denis */
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/* SPDX-License-Identifier: Unlicense */
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/* shift right by a certain bit count with sign extension */
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mp_err mp_signed_rsh(const mp_int *a, int b, mp_int *c)
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{
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mp_err res;
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if (a->sign == MP_ZPOS) {
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return mp_div_2d(a, b, c, NULL);
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}
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res = mp_add_d(a, 1uL, c);
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if (res != MP_OKAY) {
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return res;
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}
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res = mp_div_2d(c, b, c, NULL);
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return (res == MP_OKAY) ? mp_sub_d(c, 1uL, c) : res;
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}
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#endif
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