Mercurial > dropbear
annotate bn_mp_mul_d.c @ 203:e109027b9edf libtommath LTM_DB_0.46 LTM_DB_0.47
Don't remove ~ files on make clean (and find -type was wrong anyway)
| author | Matt Johnston <matt@ucc.asn.au> |
|---|---|
| date | Wed, 11 May 2005 16:27:28 +0000 |
| parents | d8254fc979e9 |
| children |
| rev | line source |
|---|---|
| 142 | 1 #include <tommath.h> |
| 2 #ifdef BN_MP_MUL_D_C | |
| 2 | 3 /* LibTomMath, multiple-precision integer library -- Tom St Denis |
| 4 * | |
| 5 * LibTomMath is a library that provides multiple-precision | |
| 6 * integer arithmetic as well as number theoretic functionality. | |
| 7 * | |
| 8 * The library was designed directly after the MPI library by | |
| 9 * Michael Fromberger but has been written from scratch with | |
| 10 * additional optimizations in place. | |
| 11 * | |
| 12 * The library is free for all purposes without any express | |
| 13 * guarantee it works. | |
| 14 * | |
| 15 * Tom St Denis, [email protected], http://math.libtomcrypt.org | |
| 16 */ | |
| 17 | |
| 18 /* multiply by a digit */ | |
| 19 int | |
| 20 mp_mul_d (mp_int * a, mp_digit b, mp_int * c) | |
| 21 { | |
| 22 mp_digit u, *tmpa, *tmpc; | |
| 23 mp_word r; | |
| 24 int ix, res, olduse; | |
| 25 | |
| 26 /* make sure c is big enough to hold a*b */ | |
| 27 if (c->alloc < a->used + 1) { | |
| 28 if ((res = mp_grow (c, a->used + 1)) != MP_OKAY) { | |
| 29 return res; | |
| 30 } | |
| 31 } | |
| 32 | |
| 33 /* get the original destinations used count */ | |
| 34 olduse = c->used; | |
| 35 | |
| 36 /* set the sign */ | |
| 37 c->sign = a->sign; | |
| 38 | |
| 39 /* alias for a->dp [source] */ | |
| 40 tmpa = a->dp; | |
| 41 | |
| 42 /* alias for c->dp [dest] */ | |
| 43 tmpc = c->dp; | |
| 44 | |
| 45 /* zero carry */ | |
| 46 u = 0; | |
| 47 | |
| 48 /* compute columns */ | |
| 49 for (ix = 0; ix < a->used; ix++) { | |
| 50 /* compute product and carry sum for this term */ | |
| 51 r = ((mp_word) u) + ((mp_word)*tmpa++) * ((mp_word)b); | |
| 52 | |
| 53 /* mask off higher bits to get a single digit */ | |
| 54 *tmpc++ = (mp_digit) (r & ((mp_word) MP_MASK)); | |
| 55 | |
| 56 /* send carry into next iteration */ | |
| 57 u = (mp_digit) (r >> ((mp_word) DIGIT_BIT)); | |
| 58 } | |
| 59 | |
|
190
d8254fc979e9
Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
142
diff
changeset
|
60 /* store final carry [if any] and increment ix offset */ |
| 2 | 61 *tmpc++ = u; |
|
190
d8254fc979e9
Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
142
diff
changeset
|
62 ++ix; |
| 2 | 63 |
| 64 /* now zero digits above the top */ | |
| 65 while (ix++ < olduse) { | |
| 66 *tmpc++ = 0; | |
| 67 } | |
| 68 | |
| 69 /* set used count */ | |
| 70 c->used = a->used + 1; | |
| 71 mp_clamp(c); | |
| 72 | |
| 73 return MP_OKAY; | |
| 74 } | |
| 142 | 75 #endif |