-#include <tommath.h>
+#include "tommath_private.h"
#ifdef BN_S_MP_MUL_DIGS_C
-/* LibTomMath, multiple-precision integer library -- Tom St Denis
- *
- * LibTomMath is a library that provides multiple-precision
- * integer arithmetic as well as number theoretic functionality.
- *
- * The library was designed directly after the MPI library by
- * Michael Fromberger but has been written from scratch with
- * additional optimizations in place.
- *
- * The library is free for all purposes without any express
- * guarantee it works.
- *
- * Tom St Denis, tomstdenis@gmail.com, http://libtom.org
- */
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
/* multiplies |a| * |b| and only computes upto digs digits of result
* HAC pp. 595, Algorithm 14.12 Modified so you can control how
* many digits of output are created.
*/
-int s_mp_mul_digs (mp_int * a, mp_int * b, mp_int * c, int digs)
+mp_err s_mp_mul_digs(const mp_int *a, const mp_int *b, mp_int *c, int digs)
{
- mp_int t;
- int res, pa, pb, ix, iy;
- mp_digit u;
- mp_word r;
- mp_digit tmpx, *tmpt, *tmpy;
+ mp_int t;
+ mp_err err;
+ int pa, pb, ix, iy;
+ mp_digit u;
+ mp_word r;
+ mp_digit tmpx, *tmpt, *tmpy;
- /* can we use the fast multiplier? */
- if (((digs) < MP_WARRAY) &&
- MIN (a->used, b->used) <
- (1 << ((CHAR_BIT * sizeof (mp_word)) - (2 * DIGIT_BIT)))) {
- return fast_s_mp_mul_digs (a, b, c, digs);
- }
+ /* can we use the fast multiplier? */
+ if ((digs < MP_WARRAY) &&
+ (MP_MIN(a->used, b->used) < MP_MAXFAST)) {
+ return s_mp_mul_digs_fast(a, b, c, digs);
+ }
- if ((res = mp_init_size (&t, digs)) != MP_OKAY) {
- return res;
- }
- t.used = digs;
+ if ((err = mp_init_size(&t, digs)) != MP_OKAY) {
+ return err;
+ }
+ t.used = digs;
- /* compute the digits of the product directly */
- pa = a->used;
- for (ix = 0; ix < pa; ix++) {
- /* set the carry to zero */
- u = 0;
+ /* compute the digits of the product directly */
+ pa = a->used;
+ for (ix = 0; ix < pa; ix++) {
+ /* set the carry to zero */
+ u = 0;
- /* limit ourselves to making digs digits of output */
- pb = MIN (b->used, digs - ix);
+ /* limit ourselves to making digs digits of output */
+ pb = MP_MIN(b->used, digs - ix);
- /* setup some aliases */
- /* copy of the digit from a used within the nested loop */
- tmpx = a->dp[ix];
+ /* setup some aliases */
+ /* copy of the digit from a used within the nested loop */
+ tmpx = a->dp[ix];
- /* an alias for the destination shifted ix places */
- tmpt = t.dp + ix;
+ /* an alias for the destination shifted ix places */
+ tmpt = t.dp + ix;
- /* an alias for the digits of b */
- tmpy = b->dp;
+ /* an alias for the digits of b */
+ tmpy = b->dp;
- /* compute the columns of the output and propagate the carry */
- for (iy = 0; iy < pb; iy++) {
- /* compute the column as a mp_word */
- r = ((mp_word)*tmpt) +
- ((mp_word)tmpx) * ((mp_word)*tmpy++) +
- ((mp_word) u);
+ /* compute the columns of the output and propagate the carry */
+ for (iy = 0; iy < pb; iy++) {
+ /* compute the column as a mp_word */
+ r = (mp_word)*tmpt +
+ ((mp_word)tmpx * (mp_word)*tmpy++) +
+ (mp_word)u;
- /* the new column is the lower part of the result */
- *tmpt++ = (mp_digit) (r & ((mp_word) MP_MASK));
+ /* the new column is the lower part of the result */
+ *tmpt++ = (mp_digit)(r & (mp_word)MP_MASK);
- /* get the carry word from the result */
- u = (mp_digit) (r >> ((mp_word) DIGIT_BIT));
- }
- /* set carry if it is placed below digs */
- if (ix + iy < digs) {
- *tmpt = u;
- }
- }
+ /* get the carry word from the result */
+ u = (mp_digit)(r >> (mp_word)MP_DIGIT_BIT);
+ }
+ /* set carry if it is placed below digs */
+ if ((ix + iy) < digs) {
+ *tmpt = u;
+ }
+ }
- mp_clamp (&t);
- mp_exch (&t, c);
+ mp_clamp(&t);
+ mp_exch(&t, c);
- mp_clear (&t);
- return MP_OKAY;
+ mp_clear(&t);
+ return MP_OKAY;
}
#endif
-
-/* $Source: /cvs/libtom/libtommath/bn_s_mp_mul_digs.c,v $ */
-/* $Revision: 1.4 $ */
-/* $Date: 2006/12/28 01:25:13 $ */
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