merge from main

--HG--
branch : fuzz

1 files changed, 93 insertions, 109 deletions

diff --git a/libtommath/bn_mp_montgomery_reduce.c b/libtommath/bn_mp_montgomery_reduce.c
index 05e8bfa..ffe8341 100644
--- a/libtommath/bn_mp_montgomery_reduce.c
+++ b/libtommath/bn_mp_montgomery_reduce.c
@@ -1,118 +1,102 @@
-#include <tommath_private.h>
+#include "tommath_private.h"
 #ifdef BN_MP_MONTGOMERY_REDUCE_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, tstdenis82@gmail.com, http://libtom.org
- */
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
 
 /* computes xR**-1 == x (mod N) via Montgomery Reduction */
-int
-mp_montgomery_reduce (mp_int * x, mp_int * n, mp_digit rho)
+mp_err mp_montgomery_reduce(mp_int *x, const mp_int *n, mp_digit rho)
 {
-  int     ix, res, digs;
-  mp_digit mu;
-
-  /* can the fast reduction [comba] method be used?
-   *
-   * Note that unlike in mul you're safely allowed *less*
-   * than the available columns [255 per default] since carries
-   * are fixed up in the inner loop.
-   */
-  digs = (n->used * 2) + 1;
-  if ((digs < MP_WARRAY) &&
-      (n->used <
-      (1 << ((CHAR_BIT * sizeof(mp_word)) - (2 * DIGIT_BIT))))) {
-    return fast_mp_montgomery_reduce (x, n, rho);
-  }
-
-  /* grow the input as required */
-  if (x->alloc < digs) {
-    if ((res = mp_grow (x, digs)) != MP_OKAY) {
-      return res;
-    }
-  }
-  x->used = digs;
-
-  for (ix = 0; ix < n->used; ix++) {
-    /* mu = ai * rho mod b
-     *
-     * The value of rho must be precalculated via
-     * montgomery_setup() such that
-     * it equals -1/n0 mod b this allows the
-     * following inner loop to reduce the
-     * input one digit at a time
-     */
-    mu = (mp_digit) (((mp_word)x->dp[ix] * (mp_word)rho) & MP_MASK);
-
-    /* a = a + mu * m * b**i */
-    {
-      int iy;
-      mp_digit *tmpn, *tmpx, u;
-      mp_word r;
-
-      /* alias for digits of the modulus */
-      tmpn = n->dp;
-
-      /* alias for the digits of x [the input] */
-      tmpx = x->dp + ix;
-
-      /* set the carry to zero */
-      u = 0;
-
-      /* Multiply and add in place */
-      for (iy = 0; iy < n->used; iy++) {
-        /* compute product and sum */
-        r       = ((mp_word)mu * (mp_word)*tmpn++) +
-                   (mp_word) u + (mp_word) *tmpx;
-
-        /* get carry */
-        u       = (mp_digit)(r >> ((mp_word) DIGIT_BIT));
-
-        /* fix digit */
-        *tmpx++ = (mp_digit)(r & ((mp_word) MP_MASK));
+   int      ix, digs;
+   mp_err   err;
+   mp_digit mu;
+
+   /* can the fast reduction [comba] method be used?
+    *
+    * Note that unlike in mul you're safely allowed *less*
+    * than the available columns [255 per default] since carries
+    * are fixed up in the inner loop.
+    */
+   digs = (n->used * 2) + 1;
+   if ((digs < MP_WARRAY) &&
+       (x->used <= MP_WARRAY) &&
+       (n->used < MP_MAXFAST)) {
+      return s_mp_montgomery_reduce_fast(x, n, rho);
+   }
+
+   /* grow the input as required */
+   if (x->alloc < digs) {
+      if ((err = mp_grow(x, digs)) != MP_OKAY) {
+         return err;
       }
-      /* At this point the ix'th digit of x should be zero */
+   }
+   x->used = digs;
+
+   for (ix = 0; ix < n->used; ix++) {
+      /* mu = ai * rho mod b
+       *
+       * The value of rho must be precalculated via
+       * montgomery_setup() such that
+       * it equals -1/n0 mod b this allows the
+       * following inner loop to reduce the
+       * input one digit at a time
+       */
+      mu = (mp_digit)(((mp_word)x->dp[ix] * (mp_word)rho) & MP_MASK);
+
+      /* a = a + mu * m * b**i */
+      {
+         int iy;
+         mp_digit *tmpn, *tmpx, u;
+         mp_word r;
+
+         /* alias for digits of the modulus */
+         tmpn = n->dp;
+
+         /* alias for the digits of x [the input] */
+         tmpx = x->dp + ix;
+
+         /* set the carry to zero */
+         u = 0;
+
+         /* Multiply and add in place */
+         for (iy = 0; iy < n->used; iy++) {
+            /* compute product and sum */
+            r       = ((mp_word)mu * (mp_word)*tmpn++) +
+                      (mp_word)u + (mp_word)*tmpx;
+
+            /* get carry */
+            u       = (mp_digit)(r >> (mp_word)MP_DIGIT_BIT);
+
+            /* fix digit */
+            *tmpx++ = (mp_digit)(r & (mp_word)MP_MASK);
+         }
+         /* At this point the ix'th digit of x should be zero */
+
+
+         /* propagate carries upwards as required*/
+         while (u != 0u) {
+            *tmpx   += u;
+            u        = *tmpx >> MP_DIGIT_BIT;
+            *tmpx++ &= MP_MASK;
+         }
+      }
+   }
 
+   /* at this point the n.used'th least
+    * significant digits of x are all zero
+    * which means we can shift x to the
+    * right by n.used digits and the
+    * residue is unchanged.
+    */
 
-      /* propagate carries upwards as required*/
-      while (u != 0) {
-        *tmpx   += u;
-        u        = *tmpx >> DIGIT_BIT;
-        *tmpx++ &= MP_MASK;
-      }
-    }
-  }
-
-  /* at this point the n.used'th least
-   * significant digits of x are all zero
-   * which means we can shift x to the
-   * right by n.used digits and the
-   * residue is unchanged.
-   */
-
-  /* x = x/b**n.used */
-  mp_clamp(x);
-  mp_rshd (x, n->used);
-
-  /* if x >= n then x = x - n */
-  if (mp_cmp_mag (x, n) != MP_LT) {
-    return s_mp_sub (x, n, x);
-  }
-
-  return MP_OKAY;
+   /* x = x/b**n.used */
+   mp_clamp(x);
+   mp_rshd(x, n->used);
+
+   /* if x >= n then x = x - n */
+   if (mp_cmp_mag(x, n) != MP_LT) {
+      return s_mp_sub(x, n, x);
+   }
+
+   return MP_OKAY;
 }
 #endif
-
-/* ref:         $Format:%D$ */
-/* git commit:  $Format:%H$ */
-/* commit time: $Format:%ai$ */