add feature detection macros MP_DEFINED and MP_HAS

additionally, make bn_mp_mul private

Author: minad

bn_mp_invmod.c

@@ -11,17 +11,13 @@ int mp_invmod(const mp_int *a, const mp_int *b, mp_int *c)
       return MP_VAL;
    }
 
-#ifdef BN_FAST_MP_INVMOD_C
    /* if the modulus is odd we can use a faster routine instead */
-   if (IS_ODD(b)) {
+   if (MP_HAS(FAST_MP_INVMOD) && IS_ODD(b)) {
       return fast_mp_invmod(a, b, c);
    }
-#endif
 
-#ifdef BN_MP_INVMOD_SLOW_C
-   return mp_invmod_slow(a, b, c);
-#else
-   return MP_VAL;
-#endif
+   return MP_HAS(MP_INVMOD_SLOW)
+       ? mp_invmod_slow(a, b, c)
+       : MP_VAL;
 }
 #endif

bn_mp_mul.c

@@ -6,82 +6,48 @@
 /* high level multiplication (handles sign) */
 int mp_mul(const mp_int *a, const mp_int *b, mp_int *c)
 {
-   int     res, neg;
-#ifdef BN_MP_BALANCE_MUL_C
-   int len_b, len_a;
-#endif
+   int res, neg, min_len, max_len, digs;
+   min_len = MIN(a->used, b->used);
+   max_len = MAX(a->used, b->used);
+   digs = a->used + b->used + 1;
    neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG;
-#ifdef BN_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 ((MIN(len_a, len_b) < KARATSUBA_MUL_CUTOFF)
-       || ((MAX(len_a, len_b)) / 2 < KARATSUBA_MUL_CUTOFF)) {
-      goto GO_ON;
-   }
-   /*
-    * Not much effect was observed below a ratio of 1:2, but again: YMMV.
-    */
-   if ((MAX(len_a, len_b) /  MIN(len_a, len_b)) < 2) {
-      goto GO_ON;
-   }
-
-   res = 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) {
+   if (MP_HAS(MP_BALANCE_MUL) &&
+       /* 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.
+        */
+       (min_len >= KARATSUBA_MUL_CUTOFF) &&
+       (max_len / 2 >= KARATSUBA_MUL_CUTOFF) &&
+       /* Not much effect was observed below a ratio of 1:2, but again: YMMV. */
+       (max_len >= (2 * min_len))) {
+      res = mp_balance_mul(a,b,c);
+   } else if (MP_HAS(MP_TOOM_MUL) &&
+              min_len >= TOOM_MUL_CUTOFF) {
       res = mp_toom_mul(a, b, c);
-   } else
-#endif
-#ifdef BN_MP_KARATSUBA_MUL_C
-      /* use Karatsuba? */
-      if (MIN(a->used, b->used) >= KARATSUBA_MUL_CUTOFF) {
-         res = mp_karatsuba_mul(a, b, c);
-      } else
-#endif
-      {
-         /* can we use the fast multiplier?
-          *
-          * The fast multiplier can be used if the output will
-          * have less than MP_WARRAY digits and the number of
-          * digits won't affect carry propagation
-          */
-         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 << ((CHAR_BIT * sizeof(mp_word)) - (2u * (size_t)DIGIT_BIT))))) {
-            res = fast_s_mp_mul_digs(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 */
-#else
-            res = MP_VAL;
-#endif
-         }
-      }
-END:
+   } else if (MP_HAS(MP_KARATSUBA_MUL) &&
+              min_len >= KARATSUBA_MUL_CUTOFF) {
+      res = mp_karatsuba_mul(a, b, c);
+   } else if (MP_HAS(FAST_S_MP_MUL_DIGS) &&
+              /* can we use the fast multiplier?
+               *
+               * The fast multiplier can be used if the output will
+               * have less than MP_WARRAY digits and the number of
+               * digits won't affect carry propagation
+               */
+              (digs < (int)MP_WARRAY) &&
+              (min_len <=
+               (int)(1u << ((CHAR_BIT * sizeof(mp_word)) - (2u * (size_t)DIGIT_BIT))))) {
+      res = fast_s_mp_mul_digs(a, b, c, digs);
+   } else if (MP_HAS(S_MP_MUL_DIGS)) {
+      res = s_mp_mul(a, b, c); /* uses s_mp_mul_digs */
+   } else {
+      res = MP_VAL;
+   }
    c->sign = (c->used > 0) ? neg : MP_ZPOS;
    return res;
 }
 #endif
-

bn_mp_reduce.c

@@ -25,21 +25,15 @@ int mp_reduce(mp_int *x, const mp_int *m, const mp_int *mu)
       if ((res = mp_mul(&q, mu, &q)) != MP_OKAY) {
          goto CLEANUP;
       }
+   } else if (MP_HAS(S_MP_MUL_HIGH_DIGS) &&
+              (res = s_mp_mul_high_digs(&q, mu, &q, um)) != MP_OKAY) {
+      goto CLEANUP;
+   } else if (MP_HAS(FAST_S_MP_MUL_HIGH_DIGS) &&
+              (res = fast_s_mp_mul_high_digs(&q, mu, &q, um)) != MP_OKAY) {
+      goto CLEANUP;
    } else {
-#ifdef BN_S_MP_MUL_HIGH_DIGS_C
-      if ((res = s_mp_mul_high_digs(&q, mu, &q, um)) != MP_OKAY) {
-         goto CLEANUP;
-      }
-#elif defined(BN_FAST_S_MP_MUL_HIGH_DIGS_C)
-      if ((res = fast_s_mp_mul_high_digs(&q, mu, &q, um)) != MP_OKAY) {
-         goto CLEANUP;
-      }
-#else
-      {
-         res = MP_VAL;
-         goto CLEANUP;
-      }
-#endif
+      res = MP_VAL;
+      goto CLEANUP;
    }
 
    /* q3 = q2 / b**(k+1) */

bn_s_mp_exptmod.c

@@ -34,11 +34,9 @@ int s_mp_exptmod(const mp_int *G, const mp_int *X, const mp_int *P, mp_int *Y, i
       winsize = 8;
    }
 
-#ifdef MP_LOW_MEM
-   if (winsize > 5) {
+   if (MP_DEFINED(MP_LOW_MEM) && winsize > 5) {
       winsize = 5;
    }
-#endif
 
    /* init M array */
    /* init first cell */

demo/test.c

@@ -1,5 +1,8 @@
 #include "shared.h"
 
+/* We can also test the private API here */
+#include "tommath_private.h"
+
 static int test_trivial_stuff(void)
 {
    mp_int a, b, c, d;
@@ -1624,7 +1627,7 @@ static int test_mp_balance_mul(void)
       goto LTM_ERR;
    }
 
-   if ((e = mp_mul(&a, &b, &c)) != MP_OKAY) {
+   if ((e = mp_balance_mul(&a, &b, &c)) != MP_OKAY) {
       goto LTM_ERR;
    }
 

tommath.h

@@ -335,7 +335,6 @@ int mp_sub(const mp_int *a, const mp_int *b, mp_int *c);
 
 /* c = a * b */
 int mp_mul(const mp_int *a, const mp_int *b, mp_int *c);
-int mp_balance_mul(const mp_int *a, const mp_int *b, mp_int *c);
 
 /* b = a*a  */
 int mp_sqr(const mp_int *a, mp_int *b);

tommath_private.h

@@ -33,6 +33,14 @@ extern void *XCALLOC(size_t nmemb, size_t size);
 extern void XFREE(void *mem, size_t size);
 #endif
 
+/* feature detection macro */
+#define MP_HAS(x)               MP_DEFINED(BN_##x##_C)
+#define MP_DEFINED(x)           _MP_DEFINED1(x)
+#define _MP_DEFINED1(x)         _MP_DEFINED2(_MP_DEFINED_TEST##x)
+#define _MP_DEFINED2(x)         _MP_DEFINED3(x 1, 0)
+#define _MP_DEFINED3(x, y, ...) y
+#define _MP_DEFINED_TEST        ,
+
 /* ---> Basic Manipulations <--- */
 #define IS_ZERO(a) ((a)->used == 0)
 #define IS_EVEN(a) (((a)->used == 0) || (((a)->dp[0] & 1u) == 0u))
@@ -48,6 +56,7 @@ int fast_s_mp_mul_high_digs(const mp_int *a, const mp_int *b, mp_int *c, int dig
 int s_mp_mul_high_digs(const mp_int *a, const mp_int *b, mp_int *c, int digs);
 int fast_s_mp_sqr(const mp_int *a, mp_int *b);
 int s_mp_sqr(const mp_int *a, mp_int *b);
+int mp_balance_mul(const mp_int *a, const mp_int *b, mp_int *c);
 int mp_karatsuba_mul(const mp_int *a, const mp_int *b, mp_int *c);
 int mp_toom_mul(const mp_int *a, const mp_int *b, mp_int *c);
 int mp_karatsuba_sqr(const mp_int *a, mp_int *b);