--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/bn_mp_div.c	Wed Mar 08 13:16:18 2006 +0000
@@ -0,0 +1,288 @@
+#include <tommath.h>
+#ifdef BN_MP_DIV_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, [email protected], http://math.libtomcrypt.org
+ */
+
+#ifdef BN_MP_DIV_SMALL
+
+/* slower bit-bang division... also smaller */
+int mp_div(mp_int * a, mp_int * b, mp_int * c, mp_int * d)
+{
+   mp_int ta, tb, tq, q;
+   int    res, n, n2;
+
+  /* is divisor zero ? */
+  if (mp_iszero (b) == 1) {
+    return MP_VAL;
+  }
+
+  /* if a < b then q=0, r = a */
+  if (mp_cmp_mag (a, b) == MP_LT) {
+    if (d != NULL) {
+      res = mp_copy (a, d);
+    } else {
+      res = MP_OKAY;
+    }
+    if (c != NULL) {
+      mp_zero (c);
+    }
+    return res;
+  }
+	
+  /* init our temps */
+  if ((res = mp_init_multi(&ta, &tb, &tq, &q, NULL) != MP_OKAY)) {
+     return res;
+  }
+
+
+  mp_set(&tq, 1);
+  n = mp_count_bits(a) - mp_count_bits(b);
+  if (((res = mp_abs(a, &ta)) != MP_OKAY) ||
+      ((res = mp_abs(b, &tb)) != MP_OKAY) || 
+      ((res = mp_mul_2d(&tb, n, &tb)) != MP_OKAY) ||
+      ((res = mp_mul_2d(&tq, n, &tq)) != MP_OKAY)) {
+      goto LBL_ERR;
+  }
+
+  while (n-- >= 0) {
+     if (mp_cmp(&tb, &ta) != MP_GT) {
+        if (((res = mp_sub(&ta, &tb, &ta)) != MP_OKAY) ||
+            ((res = mp_add(&q, &tq, &q)) != MP_OKAY)) {
+           goto LBL_ERR;
+        }
+     }
+     if (((res = mp_div_2d(&tb, 1, &tb, NULL)) != MP_OKAY) ||
+         ((res = mp_div_2d(&tq, 1, &tq, NULL)) != MP_OKAY)) {
+           goto LBL_ERR;
+     }
+  }
+
+  /* now q == quotient and ta == remainder */
+  n  = a->sign;
+  n2 = (a->sign == b->sign ? MP_ZPOS : MP_NEG);
+  if (c != NULL) {
+     mp_exch(c, &q);
+     c->sign  = (mp_iszero(c) == MP_YES) ? MP_ZPOS : n2;
+  }
+  if (d != NULL) {
+     mp_exch(d, &ta);
+     d->sign = (mp_iszero(d) == MP_YES) ? MP_ZPOS : n;
+  }
+LBL_ERR:
+   mp_clear_multi(&ta, &tb, &tq, &q, NULL);
+   return res;
+}
+
+#else
+
+/* integer signed division. 
+ * c*b + d == a [e.g. a/b, c=quotient, d=remainder]
+ * HAC pp.598 Algorithm 14.20
+ *
+ * Note that the description in HAC is horribly 
+ * incomplete.  For example, it doesn't consider 
+ * the case where digits are removed from 'x' in 
+ * the inner loop.  It also doesn't consider the 
+ * case that y has fewer than three digits, etc..
+ *
+ * The overall algorithm is as described as 
+ * 14.20 from HAC but fixed to treat these cases.
+*/
+int mp_div (mp_int * a, mp_int * b, mp_int * c, mp_int * d)
+{
+  mp_int  q, x, y, t1, t2;
+  int     res, n, t, i, norm, neg;
+
+  /* is divisor zero ? */
+  if (mp_iszero (b) == 1) {
+    return MP_VAL;
+  }
+
+  /* if a < b then q=0, r = a */
+  if (mp_cmp_mag (a, b) == MP_LT) {
+    if (d != NULL) {
+      res = mp_copy (a, d);
+    } else {
+      res = MP_OKAY;
+    }
+    if (c != NULL) {
+      mp_zero (c);
+    }
+    return res;
+  }
+
+  if ((res = mp_init_size (&q, a->used + 2)) != MP_OKAY) {
+    return res;
+  }
+  q.used = a->used + 2;
+
+  if ((res = mp_init (&t1)) != MP_OKAY) {
+    goto LBL_Q;
+  }
+
+  if ((res = mp_init (&t2)) != MP_OKAY) {
+    goto LBL_T1;
+  }
+
+  if ((res = mp_init_copy (&x, a)) != MP_OKAY) {
+    goto LBL_T2;
+  }
+
+  if ((res = mp_init_copy (&y, b)) != MP_OKAY) {
+    goto LBL_X;
+  }
+
+  /* fix the sign */
+  neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG;
+  x.sign = y.sign = MP_ZPOS;
+
+  /* normalize both x and y, ensure that y >= b/2, [b == 2**DIGIT_BIT] */
+  norm = mp_count_bits(&y) % DIGIT_BIT;
+  if (norm < (int)(DIGIT_BIT-1)) {
+     norm = (DIGIT_BIT-1) - norm;
+     if ((res = mp_mul_2d (&x, norm, &x)) != MP_OKAY) {
+       goto LBL_Y;
+     }
+     if ((res = mp_mul_2d (&y, norm, &y)) != MP_OKAY) {
+       goto LBL_Y;
+     }
+  } else {
+     norm = 0;
+  }
+
+  /* note hac does 0 based, so if used==5 then its 0,1,2,3,4, e.g. use 4 */
+  n = x.used - 1;
+  t = y.used - 1;
+
+  /* while (x >= y*b**n-t) do { q[n-t] += 1; x -= y*b**{n-t} } */
+  if ((res = mp_lshd (&y, n - t)) != MP_OKAY) { /* y = y*b**{n-t} */
+    goto LBL_Y;
+  }
+
+  while (mp_cmp (&x, &y) != MP_LT) {
+    ++(q.dp[n - t]);
+    if ((res = mp_sub (&x, &y, &x)) != MP_OKAY) {
+      goto LBL_Y;
+    }
+  }
+
+  /* reset y by shifting it back down */
+  mp_rshd (&y, n - t);
+
+  /* step 3. for i from n down to (t + 1) */
+  for (i = n; i >= (t + 1); i--) {
+    if (i > x.used) {
+      continue;
+    }
+
+    /* step 3.1 if xi == yt then set q{i-t-1} to b-1, 
+     * otherwise set q{i-t-1} to (xi*b + x{i-1})/yt */
+    if (x.dp[i] == y.dp[t]) {
+      q.dp[i - t - 1] = ((((mp_digit)1) << DIGIT_BIT) - 1);
+    } else {
+      mp_word tmp;
+      tmp = ((mp_word) x.dp[i]) << ((mp_word) DIGIT_BIT);
+      tmp |= ((mp_word) x.dp[i - 1]);
+      tmp /= ((mp_word) y.dp[t]);
+      if (tmp > (mp_word) MP_MASK)
+        tmp = MP_MASK;
+      q.dp[i - t - 1] = (mp_digit) (tmp & (mp_word) (MP_MASK));
+    }
+
+    /* while (q{i-t-1} * (yt * b + y{t-1})) > 
+             xi * b**2 + xi-1 * b + xi-2 
+     
+       do q{i-t-1} -= 1; 
+    */
+    q.dp[i - t - 1] = (q.dp[i - t - 1] + 1) & MP_MASK;
+    do {
+      q.dp[i - t - 1] = (q.dp[i - t - 1] - 1) & MP_MASK;
+
+      /* find left hand */
+      mp_zero (&t1);
+      t1.dp[0] = (t - 1 < 0) ? 0 : y.dp[t - 1];
+      t1.dp[1] = y.dp[t];
+      t1.used = 2;
+      if ((res = mp_mul_d (&t1, q.dp[i - t - 1], &t1)) != MP_OKAY) {
+        goto LBL_Y;
+      }
+
+      /* find right hand */
+      t2.dp[0] = (i - 2 < 0) ? 0 : x.dp[i - 2];
+      t2.dp[1] = (i - 1 < 0) ? 0 : x.dp[i - 1];
+      t2.dp[2] = x.dp[i];
+      t2.used = 3;
+    } while (mp_cmp_mag(&t1, &t2) == MP_GT);
+
+    /* step 3.3 x = x - q{i-t-1} * y * b**{i-t-1} */
+    if ((res = mp_mul_d (&y, q.dp[i - t - 1], &t1)) != MP_OKAY) {
+      goto LBL_Y;
+    }
+
+    if ((res = mp_lshd (&t1, i - t - 1)) != MP_OKAY) {
+      goto LBL_Y;
+    }
+
+    if ((res = mp_sub (&x, &t1, &x)) != MP_OKAY) {
+      goto LBL_Y;
+    }
+
+    /* if x < 0 then { x = x + y*b**{i-t-1}; q{i-t-1} -= 1; } */
+    if (x.sign == MP_NEG) {
+      if ((res = mp_copy (&y, &t1)) != MP_OKAY) {
+        goto LBL_Y;
+      }
+      if ((res = mp_lshd (&t1, i - t - 1)) != MP_OKAY) {
+        goto LBL_Y;
+      }
+      if ((res = mp_add (&x, &t1, &x)) != MP_OKAY) {
+        goto LBL_Y;
+      }
+
+      q.dp[i - t - 1] = (q.dp[i - t - 1] - 1UL) & MP_MASK;
+    }
+  }
+
+  /* now q is the quotient and x is the remainder 
+   * [which we have to normalize] 
+   */
+  
+  /* get sign before writing to c */
+  x.sign = x.used == 0 ? MP_ZPOS : a->sign;
+
+  if (c != NULL) {
+    mp_clamp (&q);
+    mp_exch (&q, c);
+    c->sign = neg;
+  }
+
+  if (d != NULL) {
+    mp_div_2d (&x, norm, &x, NULL);
+    mp_exch (&x, d);
+  }
+
+  res = MP_OKAY;
+
+LBL_Y:mp_clear (&y);
+LBL_X:mp_clear (&x);
+LBL_T2:mp_clear (&t2);
+LBL_T1:mp_clear (&t1);
+LBL_Q:mp_clear (&q);
+  return res;
+}
+
+#endif
+
+#endif