refactor: add utils namespace

Author: vil02

math/ncr_modulo_p.cpp

@@ -25,6 +25,45 @@ namespace math {
  * implementation.
  */
 namespace ncr_modulo_p {
+
+namespace utils {
+/** Finds the value of x, y such that a*x + b*y = gcd(a,b)
+ *
+ * @params[in] the numbers 'a', 'b' and address of 'x' and 'y' from above
+ * equation
+ * @returns the gcd of a and b
+ */
+uint64_t gcdExtended(const uint64_t& a, const uint64_t& b, int64_t* x,
+                     int64_t* y) {
+    if (a == 0) {
+        *x = 0, *y = 1;
+        return b;
+    }
+
+    int64_t x1 = 0, y1 = 0;
+    uint64_t gcd = gcdExtended(b % a, a, &x1, &y1);
+
+    *x = y1 - (b / a) * x1;
+    *y = x1;
+    return gcd;
+}
+
+/** Find modular inverse of a with m i.e. a number x such that (a*x)%m = 1
+ *
+ * @params[in] the numbers 'a' and 'm' from above equation
+ * @returns the modular inverse of a
+ */
+int64_t modInverse(const uint64_t& a, const uint64_t& m) {
+    int64_t x = 0, y = 0;
+    uint64_t g = gcdExtended(a, m, &x, &y);
+    if (g != 1) {  // modular inverse doesn't exist
+        return -1;
+    } else {
+        int64_t res = ((x + m) % m);
+        return res;
+    }
+}
+};  // namespace utils
 /**
  * @brief Class which contains all methods required for calculating nCr mod p
  */
@@ -47,43 +86,6 @@ class NCRModuloP {
         }
     }
 
-    /** Finds the value of x, y such that a*x + b*y = gcd(a,b)
-     *
-     * @params[in] the numbers 'a', 'b' and address of 'x' and 'y' from above
-     * equation
-     * @returns the gcd of a and b
-     */
-    uint64_t gcdExtended(const uint64_t& a, const uint64_t& b, int64_t* x,
-                         int64_t* y) {
-        if (a == 0) {
-            *x = 0, *y = 1;
-            return b;
-        }
-
-        int64_t x1 = 0, y1 = 0;
-        uint64_t gcd = gcdExtended(b % a, a, &x1, &y1);
-
-        *x = y1 - (b / a) * x1;
-        *y = x1;
-        return gcd;
-    }
-
-    /** Find modular inverse of a with m i.e. a number x such that (a*x)%m = 1
-     *
-     * @params[in] the numbers 'a' and 'm' from above equation
-     * @returns the modular inverse of a
-     */
-    int64_t modInverse(const uint64_t& a, const uint64_t& m) {
-        int64_t x = 0, y = 0;
-        uint64_t g = gcdExtended(a, m, &x, &y);
-        if (g != 1) {  // modular inverse doesn't exist
-            return -1;
-        } else {
-            int64_t res = ((x + m) % m);
-            return res;
-        }
-    }
-
     /** Find nCr % p
      *
      * @params[in] the numbers 'n', 'r' and 'p'
@@ -101,11 +103,11 @@ class NCRModuloP {
             return 1;
         }
         // fac is a global array with fac[r] = (r! % p)
-        int64_t denominator = modInverse(fac[r], p);
+        int64_t denominator = utils::modInverse(fac[r], p);
         if (denominator < 0) {  // modular inverse doesn't exist
             return -1;
         }
-        denominator = (denominator * modInverse(fac[n - r], p)) % p;
+        denominator = (denominator * utils::modInverse(fac[n - r], p)) % p;
         if (denominator < 0) {  // modular inverse doesn't exist
             return -1;
         }