[Global]: loading init

deps/libtommath/s_mp_mul_high.c

@@ -0,0 +1,56 @@
+#include "tommath_private.h"
+#ifdef S_MP_MUL_HIGH_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(const mp_int *a, const mp_int *b, mp_int *c, int digs)
+{
+   mp_int   t;
+   int      pa, pb, ix;
+   mp_err   err;
+
+   if (digs < 0) {
+      return MP_VAL;
+   }
+
+   /* can we use the fast multiplier? */
+   if (MP_HAS(S_MP_MUL_HIGH_COMBA)
+       && ((a->used + b->used + 1) < MP_WARRAY)
+       && (MP_MIN(a->used, b->used) < MP_MAX_COMBA)) {
+      return s_mp_mul_high_comba(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++) {
+      int iy;
+      mp_digit u = 0;
+
+      for (iy = digs - ix; iy < pb; iy++) {
+         /* calculate the double precision result */
+         mp_word r = (mp_word)t.dp[ix + iy] +
+                     ((mp_word)a->dp[ix] * (mp_word)b->dp[iy]) +
+                     (mp_word)u;
+
+         /* get the lower part */
+         t.dp[ix + iy] = (mp_digit)(r & (mp_word)MP_MASK);
+
+         /* carry the carry */
+         u       = (mp_digit)(r >> (mp_word)MP_DIGIT_BIT);
+      }
+      t.dp[ix + pb] = u;
+   }
+   mp_clamp(&t);
+   mp_exch(&t, c);
+   mp_clear(&t);
+   return MP_OKAY;
+}
+#endif