--- a/libtommath/bn_mp_div.c	Tue May 26 23:27:26 2020 +0800
+++ b/libtommath/bn_mp_div.c	Tue May 26 17:36:47 2020 +0200
@@ -1,69 +1,55 @@
 #include "tommath_private.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.
- *
- * SPDX-License-Identifier: Unlicense
- */
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
 
 #ifdef BN_MP_DIV_SMALL
 
 /* slower bit-bang division... also smaller */
-int mp_div(const mp_int *a, const mp_int *b, mp_int *c, mp_int *d)
+mp_err mp_div(const mp_int *a, const mp_int *b, mp_int *c, mp_int *d)
 {
    mp_int ta, tb, tq, q;
-   int    res, n, n2;
+   int     n, n2;
+   mp_err err;
 
    /* is divisor zero ? */
-   if (mp_iszero(b) == MP_YES) {
+   if (MP_IS_ZERO(b)) {
       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);
+         err = mp_copy(a, d);
       } else {
-         res = MP_OKAY;
+         err = MP_OKAY;
       }
       if (c != NULL) {
          mp_zero(c);
       }
-      return res;
+      return err;
    }
 
    /* init our temps */
-   if ((res = mp_init_multi(&ta, &tb, &tq, &q, NULL)) != MP_OKAY) {
-      return res;
+   if ((err = mp_init_multi(&ta, &tb, &tq, &q, NULL)) != MP_OKAY) {
+      return err;
    }
 
 
    mp_set(&tq, 1uL);
    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;
-   }
+   if ((err = mp_abs(a, &ta)) != MP_OKAY)                         goto LBL_ERR;
+   if ((err = mp_abs(b, &tb)) != MP_OKAY)                         goto LBL_ERR;
+   if ((err = mp_mul_2d(&tb, n, &tb)) != MP_OKAY)                 goto LBL_ERR;
+   if ((err = 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 ((err = mp_sub(&ta, &tb, &ta)) != MP_OKAY)            goto LBL_ERR;
+         if ((err = 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;
-      }
+      if ((err = mp_div_2d(&tb, 1, &tb, NULL)) != MP_OKAY)        goto LBL_ERR;
+      if ((err = mp_div_2d(&tq, 1, &tq, NULL)) != MP_OKAY)        goto LBL_ERR;
    }
 
    /* now q == quotient and ta == remainder */
@@ -71,15 +57,15 @@
    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;
+      c->sign  = MP_IS_ZERO(c) ? MP_ZPOS : n2;
    }
    if (d != NULL) {
       mp_exch(d, &ta);
-      d->sign = (mp_iszero(d) == MP_YES) ? MP_ZPOS : n;
+      d->sign = MP_IS_ZERO(d) ? MP_ZPOS : n;
    }
 LBL_ERR:
    mp_clear_multi(&ta, &tb, &tq, &q, NULL);
-   return res;
+   return err;
 }
 
 #else
@@ -97,64 +83,54 @@
  * The overall algorithm is as described as
  * 14.20 from HAC but fixed to treat these cases.
 */
-int mp_div(const mp_int *a, const mp_int *b, mp_int *c, mp_int *d)
+mp_err mp_div(const mp_int *a, const mp_int *b, mp_int *c, mp_int *d)
 {
    mp_int  q, x, y, t1, t2;
-   int     res, n, t, i, norm, neg;
+   int     n, t, i, norm;
+   mp_sign neg;
+   mp_err  err;
 
    /* is divisor zero ? */
-   if (mp_iszero(b) == MP_YES) {
+   if (MP_IS_ZERO(b)) {
       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);
+         err = mp_copy(a, d);
       } else {
-         res = MP_OKAY;
+         err = MP_OKAY;
       }
       if (c != NULL) {
          mp_zero(c);
       }
-      return res;
+      return err;
    }
 
-   if ((res = mp_init_size(&q, a->used + 2)) != MP_OKAY) {
-      return res;
+   if ((err = mp_init_size(&q, a->used + 2)) != MP_OKAY) {
+      return err;
    }
    q.used = a->used + 2;
 
-   if ((res = mp_init(&t1)) != MP_OKAY) {
-      goto LBL_Q;
-   }
+   if ((err = mp_init(&t1)) != MP_OKAY)                           goto LBL_Q;
 
-   if ((res = mp_init(&t2)) != MP_OKAY) {
-      goto LBL_T1;
-   }
+   if ((err = mp_init(&t2)) != MP_OKAY)                           goto LBL_T1;
 
-   if ((res = mp_init_copy(&x, a)) != MP_OKAY) {
-      goto LBL_T2;
-   }
+   if ((err = mp_init_copy(&x, a)) != MP_OKAY)                    goto LBL_T2;
 
-   if ((res = mp_init_copy(&y, b)) != MP_OKAY) {
-      goto LBL_X;
-   }
+   if ((err = 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 < (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;
-      }
+   /* normalize both x and y, ensure that y >= b/2, [b == 2**MP_DIGIT_BIT] */
+   norm = mp_count_bits(&y) % MP_DIGIT_BIT;
+   if (norm < (MP_DIGIT_BIT - 1)) {
+      norm = (MP_DIGIT_BIT - 1) - norm;
+      if ((err = mp_mul_2d(&x, norm, &x)) != MP_OKAY)             goto LBL_Y;
+      if ((err = mp_mul_2d(&y, norm, &y)) != MP_OKAY)             goto LBL_Y;
    } else {
       norm = 0;
    }
@@ -164,15 +140,12 @@
    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;
-   }
+   /* y = y*b**{n-t} */
+   if ((err = mp_lshd(&y, n - t)) != MP_OKAY)                     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;
-      }
+      if ((err = mp_sub(&x, &y, &x)) != MP_OKAY)                  goto LBL_Y;
    }
 
    /* reset y by shifting it back down */
@@ -187,10 +160,10 @@
       /* 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 << (mp_digit)DIGIT_BIT) - (mp_digit)1;
+         q.dp[(i - t) - 1] = ((mp_digit)1 << (mp_digit)MP_DIGIT_BIT) - (mp_digit)1;
       } else {
          mp_word tmp;
-         tmp = (mp_word)x.dp[i] << (mp_word)DIGIT_BIT;
+         tmp = (mp_word)x.dp[i] << (mp_word)MP_DIGIT_BIT;
          tmp |= (mp_word)x.dp[i - 1];
          tmp /= (mp_word)y.dp[t];
          if (tmp > (mp_word)MP_MASK) {
@@ -213,41 +186,27 @@
          t1.dp[0] = ((t - 1) < 0) ? 0u : 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;
-         }
+         if ((err = mp_mul_d(&t1, q.dp[(i - t) - 1], &t1)) != MP_OKAY) goto LBL_Y;
 
          /* find right hand */
          t2.dp[0] = ((i - 2) < 0) ? 0u : x.dp[i - 2];
-         t2.dp[1] = ((i - 1) < 0) ? 0u : x.dp[i - 1];
+         t2.dp[1] = x.dp[i - 1]; /* i >= 1 always holds */
          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 ((err = 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 ((err = mp_lshd(&t1, (i - t) - 1)) != MP_OKAY)           goto LBL_Y;
 
-      if ((res = mp_sub(&x, &t1, &x)) != MP_OKAY) {
-         goto LBL_Y;
-      }
+      if ((err = 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;
-         }
+         if ((err = mp_copy(&y, &t1)) != MP_OKAY)                 goto LBL_Y;
+         if ((err = mp_lshd(&t1, (i - t) - 1)) != MP_OKAY)        goto LBL_Y;
+         if ((err = mp_add(&x, &t1, &x)) != MP_OKAY)              goto LBL_Y;
 
          q.dp[(i - t) - 1] = (q.dp[(i - t) - 1] - 1uL) & MP_MASK;
       }
@@ -267,13 +226,11 @@
    }
 
    if (d != NULL) {
-      if ((res = mp_div_2d(&x, norm, &x, NULL)) != MP_OKAY) {
-         goto LBL_Y;
-      }
+      if ((err = mp_div_2d(&x, norm, &x, NULL)) != MP_OKAY)       goto LBL_Y;
       mp_exch(&x, d);
    }
 
-   res = MP_OKAY;
+   err = MP_OKAY;
 
 LBL_Y:
    mp_clear(&y);
@@ -285,13 +242,9 @@
    mp_clear(&t1);
 LBL_Q:
    mp_clear(&q);
-   return res;
+   return err;
 }
 
 #endif
 
 #endif
-
-/* ref:         HEAD -> master, tag: v1.1.0 */
-/* git commit:  08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
-/* commit time: 2019-01-28 20:32:32 +0100 */