Import code from previous AssetBuilder version

thirdparty/libtommath/bn_mp_add_d.c

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+#include "tommath_private.h"
+#ifdef BN_MP_ADD_D_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
+ */
+
+/* single digit addition */
+int mp_add_d(const mp_int *a, mp_digit b, mp_int *c)
+{
+   int     res, ix, oldused;
+   mp_digit *tmpa, *tmpc, mu;
+
+   /* grow c as required */
+   if (c->alloc < (a->used + 1)) {
+      if ((res = mp_grow(c, a->used + 1)) != MP_OKAY) {
+         return res;
+      }
+   }
+
+   /* if a is negative and |a| >= b, call c = |a| - b */
+   if ((a->sign == MP_NEG) && ((a->used > 1) || (a->dp[0] >= b))) {
+      mp_int a_ = *a;
+      /* temporarily fix sign of a */
+      a_.sign = MP_ZPOS;
+
+      /* c = |a| - b */
+      res = mp_sub_d(&a_, b, c);
+
+      /* fix sign  */
+      c->sign = MP_NEG;
+
+      /* clamp */
+      mp_clamp(c);
+
+      return res;
+   }
+
+   /* old number of used digits in c */
+   oldused = c->used;
+
+   /* source alias */
+   tmpa    = a->dp;
+
+   /* destination alias */
+   tmpc    = c->dp;
+
+   /* if a is positive */
+   if (a->sign == MP_ZPOS) {
+      /* add digit, after this we're propagating
+       * the carry.
+       */
+      *tmpc   = *tmpa++ + b;
+      mu      = *tmpc >> DIGIT_BIT;
+      *tmpc++ &= MP_MASK;
+
+      /* now handle rest of the digits */
+      for (ix = 1; ix < a->used; ix++) {
+         *tmpc   = *tmpa++ + mu;
+         mu      = *tmpc >> DIGIT_BIT;
+         *tmpc++ &= MP_MASK;
+      }
+      /* set final carry */
+      ix++;
+      *tmpc++  = mu;
+
+      /* setup size */
+      c->used = a->used + 1;
+   } else {
+      /* a was negative and |a| < b */
+      c->used  = 1;
+
+      /* the result is a single digit */
+      if (a->used == 1) {
+         *tmpc++  =  b - a->dp[0];
+      } else {
+         *tmpc++  =  b;
+      }
+
+      /* setup count so the clearing of oldused
+       * can fall through correctly
+       */
+      ix       = 1;
+   }
+
+   /* sign always positive */
+   c->sign = MP_ZPOS;
+
+   /* now zero to oldused */
+   while (ix++ < oldused) {
+      *tmpc++ = 0;
+   }
+   mp_clamp(c);
+
+   return MP_OKAY;
+}
+
+#endif
+
+/* ref:         HEAD -> master, tag: v1.1.0 */
+/* git commit:  08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
+/* commit time: 2019-01-28 20:32:32 +0100 */