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[eos/base.git] / util / src / TclTk / tcl8.6.12 / libtommath / bn_s_mp_add.c

diff --git a/util/src/TclTk/tcl8.6.12/libtommath/bn_s_mp_add.c b/util/src/TclTk/tcl8.6.12/libtommath/bn_s_mp_add.c
new file mode 100644 (file)
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--- /dev/null
+++ b/util/src/TclTk/tcl8.6.12/libtommath/bn_s_mp_add.c
@@ -0,0 +1,91 @@
+#include "tommath_private.h"
+#ifdef BN_S_MP_ADD_C
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
+
+/* low level addition, based on HAC pp.594, Algorithm 14.7 */
+mp_err s_mp_add(const mp_int *a, const mp_int *b, mp_int *c)
+{
+   const mp_int *x;
+   mp_err err;
+   int     olduse, min, max;
+
+   /* find sizes, we let |a| <= |b| which means we have to sort
+    * them.  "x" will point to the input with the most digits
+    */
+   if (a->used > b->used) {
+      min = b->used;
+      max = a->used;
+      x = a;
+   } else {
+      min = a->used;
+      max = b->used;
+      x = b;
+   }
+
+   /* init result */
+   if (c->alloc < (max + 1)) {
+      if ((err = mp_grow(c, max + 1)) != MP_OKAY) {
+         return err;
+      }
+   }
+
+   /* get old used digit count and set new one */
+   olduse = c->used;
+   c->used = max + 1;
+
+   {
+      mp_digit u, *tmpa, *tmpb, *tmpc;
+      int i;
+
+      /* alias for digit pointers */
+
+      /* first input */
+      tmpa = a->dp;
+
+      /* second input */
+      tmpb = b->dp;
+
+      /* destination */
+      tmpc = c->dp;
+
+      /* zero the carry */
+      u = 0;
+      for (i = 0; i < min; i++) {
+         /* Compute the sum at one digit, T[i] = A[i] + B[i] + U */
+         *tmpc = *tmpa++ + *tmpb++ + u;
+
+         /* U = carry bit of T[i] */
+         u = *tmpc >> (mp_digit)MP_DIGIT_BIT;
+
+         /* take away carry bit from T[i] */
+         *tmpc++ &= MP_MASK;
+      }
+
+      /* now copy higher words if any, that is in A+B
+       * if A or B has more digits add those in
+       */
+      if (min != max) {
+         for (; i < max; i++) {
+            /* T[i] = X[i] + U */
+            *tmpc = x->dp[i] + u;
+
+            /* U = carry bit of T[i] */
+            u = *tmpc >> (mp_digit)MP_DIGIT_BIT;
+
+            /* take away carry bit from T[i] */
+            *tmpc++ &= MP_MASK;
+         }
+      }
+
+      /* add carry */
+      *tmpc++ = u;
+
+      /* clear digits above oldused */
+      MP_ZERO_DIGITS(tmpc, olduse - c->used);
+   }
+
+   mp_clamp(c);
+   return MP_OKAY;
+}
+#endif