Mercurial > dropbear
view libtommath/bn_s_mp_mul_high_digs.c @ 1695:93e738ef0d9d
Avoid oss-fuzz $SANITIZER causing wrong build
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=22608
author | Matt Johnston <matt@ucc.asn.au> |
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date | Wed, 27 May 2020 20:33:45 +0800 |
parents | 1051e4eea25a |
children |
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#include "tommath_private.h" #ifdef BN_S_MP_MUL_HIGH_DIGS_C /* LibTomMath, multiple-precision integer library -- Tom St Denis */ /* SPDX-License-Identifier: Unlicense */ /* multiplies |a| * |b| and does not compute the lower digs digits * [meant to get the higher part of the product] */ mp_err s_mp_mul_high_digs(const mp_int *a, const mp_int *b, mp_int *c, int digs) { mp_int t; int pa, pb, ix, iy; mp_err err; mp_digit u; mp_word r; mp_digit tmpx, *tmpt, *tmpy; /* can we use the fast multiplier? */ if (MP_HAS(S_MP_MUL_HIGH_DIGS_FAST) && ((a->used + b->used + 1) < MP_WARRAY) && (MP_MIN(a->used, b->used) < MP_MAXFAST)) { return s_mp_mul_high_digs_fast(a, b, c, digs); } if ((err = mp_init_size(&t, a->used + b->used + 1)) != MP_OKAY) { return err; } t.used = a->used + b->used + 1; pa = a->used; pb = b->used; for (ix = 0; ix < pa; ix++) { /* clear the carry */ u = 0; /* left hand side of A[ix] * B[iy] */ tmpx = a->dp[ix]; /* alias to the address of where the digits will be stored */ tmpt = &(t.dp[digs]); /* alias for where to read the right hand side from */ tmpy = b->dp + (digs - ix); for (iy = digs - ix; iy < pb; iy++) { /* calculate the double precision result */ r = (mp_word)*tmpt + ((mp_word)tmpx * (mp_word)*tmpy++) + (mp_word)u; /* get the lower part */ *tmpt++ = (mp_digit)(r & (mp_word)MP_MASK); /* carry the carry */ u = (mp_digit)(r >> (mp_word)MP_DIGIT_BIT); } *tmpt = u; } mp_clamp(&t); mp_exch(&t, c); mp_clear(&t); return MP_OKAY; } #endif