Added two prime function to calculate the size of the cache when it n…

…eeds to be resized, since it blows up with a simple 'double its size' algorithm

src/prime.c

@@ -0,0 +1,32 @@
+#include <math.h>
+#include "prime.h"
+
+int is_prime(int n) {
+    if (n <= 1) {
+        return 0;
+    }
+
+    if (n == 2) {
+        return 1;
+    }
+
+    if (n % 2 == 0) {
+        return 0;
+    }
+
+    for (int i = 2; i < n; i++) {
+        if ((n % i) == 0) {
+            return 0;
+        }
+    }
+
+    return 1;
+}
+
+int next_prime(int x) {
+    while (is_prime(x) != 1) {
+        x++;
+    }
+
+    return x;
+}

src/prime.h

@@ -0,0 +1,8 @@
+#ifndef DUCKY_PRIME_H
+#define DUCKY_PRIME_H
+
+int is_prime(int n);
+
+int next_prime(int n);
+
+#endif

tests/prime_test.c

@@ -0,0 +1,48 @@
+#include "../lib/greatest.h"
+#include "../src/prime.h"
+
+TEST should_return_true_if_n_is_a_prime_number(void) {
+    ASSERT_EQ(1, is_prime(2));
+    ASSERT_EQ(1, is_prime(3));
+    ASSERT_EQ(1, is_prime(5));
+    ASSERT_EQ(1, is_prime(7));
+    ASSERT_EQ(1, is_prime(11));
+    ASSERT_EQ(1, is_prime(19));
+
+    PASS();
+}
+
+TEST should_return_false_if_n_is_a_not_a_prime_number(void) {
+    ASSERT_EQ(0, is_prime(-11));
+    ASSERT_EQ(0, is_prime(-1));
+    ASSERT_EQ(0, is_prime(1));
+    ASSERT_EQ(0, is_prime(4));
+    ASSERT_EQ(0, is_prime(6));
+    ASSERT_EQ(0, is_prime(6));
+    ASSERT_EQ(0, is_prime(15));
+    PASS();
+}
+
+TEST should_return_the_next_prime_number_unless_n_is_a_prime_number(void) {
+    ASSERT_EQ(2, next_prime(1));
+    ASSERT_EQ(2, next_prime(2));
+    ASSERT_EQ(3, next_prime(3));
+    ASSERT_EQ(5, next_prime(4));
+    ASSERT_EQ(7, next_prime(6));
+    ASSERT_EQ(11, next_prime(10));
+    PASS();
+}
+
+SUITE(suite) {
+    RUN_TEST(should_return_true_if_n_is_a_prime_number);
+    RUN_TEST(should_return_false_if_n_is_a_not_a_prime_number);
+    RUN_TEST(should_return_the_next_prime_number_unless_n_is_a_prime_number);
+}
+
+GREATEST_MAIN_DEFS();
+
+int main(int argc, char *argv[]) {
+    GREATEST_MAIN_BEGIN();
+    RUN_SUITE(suite);
+    GREATEST_MAIN_END();
+}