52 lines
1.6 KiB
C
52 lines
1.6 KiB
C
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#include "tommath_private.h"
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#ifdef S_MP_DIV_SMALL_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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/* slower bit-bang division... also smaller */
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mp_err s_mp_div_small(const mp_int *a, const mp_int *b, mp_int *c, mp_int *d)
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{
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mp_int ta, tb, tq, q;
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int n;
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bool neg;
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mp_err err;
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/* init our temps */
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if ((err = mp_init_multi(&ta, &tb, &tq, &q, NULL)) != MP_OKAY) {
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return err;
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}
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mp_set(&tq, 1uL);
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n = mp_count_bits(a) - mp_count_bits(b);
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if ((err = mp_abs(a, &ta)) != MP_OKAY) goto LBL_ERR;
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if ((err = mp_abs(b, &tb)) != MP_OKAY) goto LBL_ERR;
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if ((err = mp_mul_2d(&tb, n, &tb)) != MP_OKAY) goto LBL_ERR;
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if ((err = mp_mul_2d(&tq, n, &tq)) != MP_OKAY) goto LBL_ERR;
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while (n-- >= 0) {
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if (mp_cmp(&tb, &ta) != MP_GT) {
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if ((err = mp_sub(&ta, &tb, &ta)) != MP_OKAY) goto LBL_ERR;
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if ((err = mp_add(&q, &tq, &q)) != MP_OKAY) goto LBL_ERR;
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}
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if ((err = mp_div_2d(&tb, 1, &tb, NULL)) != MP_OKAY) goto LBL_ERR;
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if ((err = mp_div_2d(&tq, 1, &tq, NULL)) != MP_OKAY) goto LBL_ERR;
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}
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/* now q == quotient and ta == remainder */
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neg = (a->sign != b->sign);
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if (c != NULL) {
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mp_exch(c, &q);
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c->sign = ((neg && !mp_iszero(c)) ? MP_NEG : MP_ZPOS);
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}
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if (d != NULL) {
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mp_exch(d, &ta);
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d->sign = (mp_iszero(d) ? MP_ZPOS : a->sign);
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}
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LBL_ERR:
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mp_clear_multi(&ta, &tb, &tq, &q, NULL);
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return err;
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}
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#endif
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