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simplesshd/dropbear/libtommath/bn_mp_signed_rsh.c

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2020-12-28 21:40:37 +00:00
#include "tommath_private.h"
#ifdef BN_MP_SIGNED_RSH_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */
/* shift right by a certain bit count with sign extension */
mp_err mp_signed_rsh(const mp_int *a, int b, mp_int *c)
{
mp_err res;
if (a->sign == MP_ZPOS) {
return mp_div_2d(a, b, c, NULL);
}
res = mp_add_d(a, 1uL, c);
if (res != MP_OKAY) {
return res;
}
res = mp_div_2d(c, b, c, NULL);
return (res == MP_OKAY) ? mp_sub_d(c, 1uL, c) : res;
}
#endif