Mercurial > dropbear
view libtommath/bn_mp_div_d.c @ 1723:5386011b740d
Disable toom and karatsuba for new libtommath
author | Matt Johnston <matt@ucc.asn.au> |
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date | Thu, 18 Jun 2020 19:12:07 +0800 |
parents | 1051e4eea25a |
children |
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#include "tommath_private.h" #ifdef BN_MP_DIV_D_C /* LibTomMath, multiple-precision integer library -- Tom St Denis */ /* SPDX-License-Identifier: Unlicense */ /* single digit division (based on routine from MPI) */ mp_err mp_div_d(const mp_int *a, mp_digit b, mp_int *c, mp_digit *d) { mp_int q; mp_word w; mp_digit t; mp_err err; int ix; /* cannot divide by zero */ if (b == 0u) { return MP_VAL; } /* quick outs */ if ((b == 1u) || MP_IS_ZERO(a)) { if (d != NULL) { *d = 0; } if (c != NULL) { return mp_copy(a, c); } return MP_OKAY; } /* power of two ? */ if ((b & (b - 1u)) == 0u) { ix = 1; while ((ix < MP_DIGIT_BIT) && (b != (((mp_digit)1)<<ix))) { ix++; } if (d != NULL) { *d = a->dp[0] & (((mp_digit)1<<(mp_digit)ix) - 1uL); } if (c != NULL) { return mp_div_2d(a, ix, c, NULL); } return MP_OKAY; } /* three? */ if (MP_HAS(MP_DIV_3) && (b == 3u)) { return mp_div_3(a, c, d); } /* no easy answer [c'est la vie]. Just division */ if ((err = mp_init_size(&q, a->used)) != MP_OKAY) { return err; } q.used = a->used; q.sign = a->sign; w = 0; for (ix = a->used - 1; ix >= 0; ix--) { w = (w << (mp_word)MP_DIGIT_BIT) | (mp_word)a->dp[ix]; if (w >= b) { t = (mp_digit)(w / b); w -= (mp_word)t * (mp_word)b; } else { t = 0; } q.dp[ix] = t; } if (d != NULL) { *d = (mp_digit)w; } if (c != NULL) { mp_clamp(&q); mp_exch(&q, c); } mp_clear(&q); return err; } #endif