Improve big integer tests, fix bugs, add quick digit multiplication

include/bh/bigint.h

@@ -84,6 +84,10 @@ int bh_bigint_mul(bh_bigint_t *to,
                   bh_bigint_t *left,
                   bh_bigint_t *right);
 
+int bh_bigint_mul_digit(bh_bigint_t *to,
+                        bh_bigint_t *left,
+                        bh_int16_t right);
+
 int bh_bigint_pow(bh_bigint_t *to,
                   bh_bigint_t *from,
                   bh_uint32_t power);

include/bh/internal/bh.h

@@ -5,3 +5,4 @@
 #include <bh/internal/config.h>
 
 #endif /* BH_INTERNAL_H */
+

src/bigint.c

@@ -496,9 +496,14 @@ int bh_bigint_add(bh_bigint_t *to,
     else
         code = bh_bigint_sub_base(to, most, least);
 
-    /* Set result sign */
     if (!code)
+    {
+        /* Set result sign or zero */
+        if (to->size)
             to->type = type;
+        else
+            to->type = 0;
+    }
 
     /* Return result code */
     return code;
@@ -538,9 +543,14 @@ int bh_bigint_sub(bh_bigint_t *to,
     else
         code = bh_bigint_add_base(to, most, least);
 
-    /* Set result sign */
     if (!code)
+    {
+        /* Set result sign or zero */
+        if (to->size)
             to->type = type;
+        else
+            to->type = 0;
+    }
 
     /* Return result code */
     return code;
@@ -639,6 +649,73 @@ int bh_bigint_mul(bh_bigint_t *to,
     return BH_OK;
 }
 
+int bh_bigint_mul_digit(bh_bigint_t *to,
+                        bh_bigint_t *left,
+                        bh_int16_t right)
+{
+    BH_BIGINT_TYPE carry;
+    BH_BIGINT_TMP tmp;
+    size_t i, size;
+
+    /* Shortcut - one of the arguments has error flag set */
+    if (left->error)
+    {
+        to->error = 1;
+        return BH_ERROR;
+    }
+
+    /* Clear up result error flag */
+    to->error = 0;
+
+    /* Shortcut - multiplication by zero */
+    if (left->type == 0 || right == 0)
+    {
+        to->type = 0;
+        to->size = 0;
+        return BH_OK;
+    }
+
+    /* Reserve space for result */
+    if (to->capacity < (left->size + 1))
+    {
+        if (bh_bigint_reserve(to, left->size + 1))
+        {
+            to->error = 1;
+            return BH_OOM;
+        }
+    }
+
+    /* Determine sign */
+    if ((left->type > 0 && right < 0) || (left->type < 0 && right > 0))
+        to->type = -1;
+    else
+        to->type = 1;
+
+    if (right < 0)
+        right = -right;
+
+    /* Prepare variables */
+    carry = 0;
+
+    /* Multiplication loop */
+    for (i = 0; i < left->size; i++)
+    {
+        tmp = (BH_BIGINT_TMP)left->data[i] * (BH_BIGINT_TMP)right + carry;
+        carry = tmp >> BH_BIGINT_BITS;
+        to->data[i] = tmp & BH_BIGINT_MASK;
+    }
+    to->data[i] = carry;
+
+    /* Truncate multiplication result size */
+    size = left->size + 1;
+    while (size && !to->data[size - 1]) size--;
+
+    /* Update size */
+    to->size = size;
+
+    return BH_OK;
+}
+
 int bh_bigint_pow(bh_bigint_t *to,
                   bh_bigint_t *from,
                   bh_uint32_t power)
@@ -732,7 +809,7 @@ int bh_bigint_powm(bh_bigint_t *to,
     code = BH_OK;
 
     /* Shortcut - one of the arguments has error flag set */
-    if (left->error || right->error)
+    if (left->error || right->error || mod->error)
     {
         to->error = 1;
         return BH_ERROR;
@@ -993,7 +1070,8 @@ static int bh_bigint_div_base(bh_bigint_t *quotient,
         }
 
         /* Calculate remainder */
-        bh_bigint_sub(remainder, remainder, tmp);
+        /* Prevent using addition logic and use subtraction */
+        bh_bigint_sub_base(remainder, remainder, tmp);
 
         if (!nleft->size)
             break;
@@ -1020,6 +1098,9 @@ finish:
     return code;
 }
 
+/**
+ * This follows C99 model (a/b)*b + a%b
+ */
 int bh_bigint_divmod(bh_bigint_t *quotient,
                      bh_bigint_t *remainder,
                      bh_bigint_t *left,
@@ -1111,6 +1192,9 @@ int bh_bigint_divmod(bh_bigint_t *quotient,
     code = bh_bigint_div_base(quotient, tmp, left, right, &shift);
     if (!code)
     {
+        /* Remainder should use sign of the left operand */
+        tmp->type = left->type;
+
         /* If remainder required - normilize it */
         if (tmp == remainder)
             bh_bigint_rsh(remainder, remainder, shift);
@@ -1358,10 +1442,16 @@ int bh_bigint_or(bh_bigint_t *to,
         to->data[i] = tmp;
     }
 
+    /* Shrink size */
+    while (size && !to->data[size - 1]) size--;
+
     /* Update fields */
     to->type = 1;
     to->size = size;
 
+    if (!size)
+        to->type = 0;
+
     return BH_OK;
 }
 
@@ -1401,10 +1491,16 @@ int bh_bigint_and(bh_bigint_t *to,
         to->data[i] = tmp;
     }
 
+    /* Shrink size */
+    while (size && !to->data[size - 1]) size--;
+
     /* Update fields */
     to->type = 1;
     to->size = size;
 
+    if (!size)
+        to->type = 0;
+
     return BH_OK;
 }
 
@@ -1444,10 +1540,16 @@ int bh_bigint_xor(bh_bigint_t *to,
         to->data[i] = tmp;
     }
 
+    /* Shrink size */
+    while (size && !to->data[size - 1]) size--;
+
     /* Update fields */
     to->type = 1;
     to->size = size;
 
+    if (!size)
+        to->type = 0;
+
     return BH_OK;
 }
 
@@ -1472,10 +1574,7 @@ int bh_bigint_negate(bh_bigint_t *to,
     }
 
     /* Change the sign */
-    if (to->type < 0)
+    to->type = 0 - to->type;
-        to->type = 1;
-    else if (to->type > 0)
-        to->type = -1;
 
     return BH_OK;
 }