added shortcuts for mp_radix_size and fixed mp_radix_sizeinbase for negative input

Author: czurnieden

bn_mp_radix_size.c

@@ -8,7 +8,7 @@ mp_err mp_radix_size(const mp_int *a, int radix, int *size)
 {
    mp_err err;
    mp_int a_, b;
-
+   int rem, bit_count, ln2;
 
    *size = 0;
 
@@ -22,12 +22,41 @@ mp_err mp_radix_size(const mp_int *a, int radix, int *size)
       return MP_OKAY;
    }
 
-   /* special case for binary */
-   if (radix == 2) {
-      *size = mp_count_bits(a) + ((a->sign == MP_NEG) ? 1 : 0) + 1;
+   /* A small shortcut for powers of two. */
+   switch (radix) {
+   case 4:
+      ln2 = 2;
+      break;
+   case 8:
+      ln2 = 3;
+      break;
+   case 16:
+      ln2 = 4;
+      break;
+   case 32:
+      ln2 = 5;
+      break;
+   case 64:
+      ln2 = 6;
+      break;
+   default:
+      ln2 = 0;
+      break;
+   }
+   if (ln2 != 0) {
+      bit_count = mp_count_bits(a) + 1;
+      *size = bit_count/ln2;
+      rem = bit_count - (*size) * ln2;
+      /* Add 1 for the remainder if any and 1 for "\0". */
+      *size += (rem == 0) ? 1 : 2;
+      /* And one extra character for the minus sign */
+      if (a->sign == MP_NEG) {
+        (*size)++;
+      }
       return MP_OKAY;
    }
 
+
    if ((err = mp_init(&b)) != MP_OKAY) {
       goto LBL_ERR;
    }
@@ -43,7 +72,7 @@ mp_err mp_radix_size(const mp_int *a, int radix, int *size)
    /* mp_ilogb truncates to zero, hence we need one extra put on top. */
    (*size)++;
 
-   /* if it's negative add one for the sign */
+   /* The sign needs to have a place to live, too*/
    if (a->sign == MP_NEG) {
       (*size)++;
    }

bn_mp_radix_sizeinbase.c

@@ -203,7 +203,7 @@ mp_err mp_radix_sizeinbase(const mp_int *a, const int base, int *size)
 #if ( (defined MP_8BIT) || (defined MP_16BIT) )
    mp_int bi_k_bis;
 #endif
-   int ln2 = 0, rem, bit_count;
+   int ln2, rem, bit_count;
    mp_err e = MP_OKAY;
 
    if ((base < 2) || (base > 64)) {
@@ -240,13 +240,18 @@ mp_err mp_radix_sizeinbase(const mp_int *a, const int base, int *size)
       ln2 = 6;
       break;
    default:
+      ln2 = 0;
       break;
    }
    if (ln2 != 0) {
       *size = bit_count/ln2;
       rem = bit_count - (*size) * ln2;
       /* Add 1 for the remainder if any and 1 for "\0". */
       *size += (rem == 0) ? 1 : 2;
+      /* And one extra character for the minus sign */
+      if (a->sign == MP_NEG) {
+        (*size)++;
+      }
       return MP_OKAY;
    }
 
@@ -305,6 +310,11 @@ mp_err mp_radix_sizeinbase(const mp_int *a, const int base, int *size)
    *size += 2;
 #endif
 
+   /* And before we forget it: one extra character for the minus sign */
+   if (a->sign == MP_NEG) {
+      (*size)++;
+   }
+
 LTM_E1:
    mp_clear_multi(&bi_bit_count, &bi_k, NULL);
 #if ( (defined MP_8BIT) || (defined MP_16BIT) )