Latest libtommath's "develop" branch adapted for Tcl 8.6. And Tcl 8.6 adapted for changes in libtommath

1 files changed, 53 insertions, 31 deletions

diff --git a/libtommath/bn_mp_mul.c b/libtommath/bn_mp_mul.c
index f83b1b7..f0ca04a 100644
--- a/libtommath/bn_mp_mul.c
+++ b/libtommath/bn_mp_mul.c
@@ -1,33 +1,59 @@
 #include "tommath_private.h"
 #ifdef BN_MP_MUL_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.
- *
- * SPDX-License-Identifier: Unlicense
- */
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
 
 /* high level multiplication (handles sign) */
-int mp_mul(const mp_int *a, const mp_int *b, mp_int *c)
+mp_err mp_mul(const mp_int *a, const mp_int *b, mp_int *c)
 {
-   int     res, neg;
+   mp_err  err;
+   mp_sign neg;
+#ifdef BN_S_MP_BALANCE_MUL_C
+   int len_b, len_a;
+#endif
    neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG;
+#ifdef BN_S_MP_BALANCE_MUL_C
+   len_a = a->used;
+   len_b = b->used;
+
+   if (len_a == len_b) {
+      goto GO_ON;
+   }
+   /*
+    * Check sizes. The smaller one needs to be larger than the Karatsuba cut-off.
+    * The bigger one needs to be at least about one KARATSUBA_MUL_CUTOFF bigger
+    * to make some sense, but it depends on architecture, OS, position of the
+    * stars... so YMMV.
+    * Using it to cut the input into slices small enough for fast_s_mp_mul_digs
+    * was actually slower on the author's machine, but YMMV.
+    */
+   if ((MP_MIN(len_a, len_b) < MP_KARATSUBA_MUL_CUTOFF)
+       || ((MP_MAX(len_a, len_b) / 2) < MP_KARATSUBA_MUL_CUTOFF)) {
+      goto GO_ON;
+   }
+   /*
+    * Not much effect was observed below a ratio of 1:2, but again: YMMV.
+    */
+   if ((MP_MAX(len_a, len_b) /  MP_MIN(len_a, len_b)) < 2) {
+      goto GO_ON;
+   }
+
+   err = s_mp_balance_mul(a,b,c);
+   goto END;
+
+GO_ON:
+#endif
 
    /* use Toom-Cook? */
-#ifdef BN_MP_TOOM_MUL_C
-   if (MIN(a->used, b->used) >= TOOM_MUL_CUTOFF) {
-      res = mp_toom_mul(a, b, c);
+#ifdef BN_S_MP_TOOM_MUL_C
+   if (MP_MIN(a->used, b->used) >= MP_TOOM_MUL_CUTOFF) {
+      err = s_mp_toom_mul(a, b, c);
    } else
 #endif
-#ifdef BN_MP_KARATSUBA_MUL_C
+#ifdef BN_S_MP_KARATSUBA_MUL_C
       /* use Karatsuba? */
-      if (MIN(a->used, b->used) >= KARATSUBA_MUL_CUTOFF) {
-         res = mp_karatsuba_mul(a, b, c);
+      if (MP_MIN(a->used, b->used) >= MP_KARATSUBA_MUL_CUTOFF) {
+         err = s_mp_karatsuba_mul(a, b, c);
       } else
 #endif
       {
@@ -39,26 +65,22 @@ int mp_mul(const mp_int *a, const mp_int *b, mp_int *c)
           */
          int     digs = a->used + b->used + 1;
 
-#ifdef BN_FAST_S_MP_MUL_DIGS_C
-         if ((digs < (int)MP_WARRAY) &&
-             (MIN(a->used, b->used) <=
-              (int)(1u << (((size_t)CHAR_BIT * sizeof(mp_word)) - (2u * (size_t)DIGIT_BIT))))) {
-            res = fast_s_mp_mul_digs(a, b, c, digs);
+#ifdef BN_S_MP_MUL_DIGS_FAST_C
+         if ((digs < MP_WARRAY) &&
+             (MP_MIN(a->used, b->used) <= MP_MAXFAST)) {
+            err = s_mp_mul_digs_fast(a, b, c, digs);
          } else
 #endif
          {
 #ifdef BN_S_MP_MUL_DIGS_C
-            res = s_mp_mul(a, b, c); /* uses s_mp_mul_digs */
+            err = s_mp_mul_digs(a, b, c, a->used + b->used + 1);
 #else
-            res = MP_VAL;
+            err = MP_VAL;
 #endif
          }
       }
+END:
    c->sign = (c->used > 0) ? neg : MP_ZPOS;
-   return res;
+   return err;
 }
 #endif
-
-/* ref:         $Format:%D$ */
-/* git commit:  $Format:%H$ */
-/* commit time: $Format:%ai$ */