tests: rename remaining C unit tests to .cpp (no content changes)

tests/test_ipset_reference_cpp.cpp

@@ -0,0 +1,59 @@
+/* Optional migration differential test. Link against the pre-migration ipset
+ * and cork archives; these are intentionally not production dependencies. */
+#include <assert.h>
+#include <stdio.h>
+#include <string.h>
+#include <ipset/ipset.h>
+#include "ipset.h"
+int verbose = 0;
+static uint32_t state = 0x725cab91;
+static uint32_t next_random(void)
+{
+    state ^= state << 13;
+    state ^= state >> 17;
+    state ^= state << 5;
+    return state;
+}
+static void check_family(unsigned width)
+{
+    struct ss_ipset current = {0};
+    struct ip_set reference;
+    ipset_init(&reference);
+    for (unsigned round = 0; round < 2000; round++) {
+        uint8_t bytes[16];
+        for (unsigned i = 0; i < sizeof(bytes); i++) bytes[i] = (uint8_t)next_random();
+        unsigned prefix = next_random() % (width + 1);
+        bool present = (next_random() & 1) != 0;
+        ss_ipset_assign(&current, bytes, width, prefix, present);
+        struct cork_ipv4 v4;
+        struct cork_ipv6 v6;
+        memcpy(v4._.u8, bytes, sizeof(v4._.u8));
+        memcpy(v6._.u8, bytes, sizeof(v6._.u8));
+        if (width == 32) {
+            if (present) ipset_ipv4_add_network(&reference, &v4, prefix);
+            else ipset_ipv4_remove_network(&reference, &v4, prefix);
+        } else {
+            if (present) ipset_ipv6_add_network(&reference, &v6, prefix);
+            else ipset_ipv6_remove_network(&reference, &v6, prefix);
+        }
+        for (unsigned sample = 0; sample < 257; sample++) {
+            if (sample != 0) {
+                for (unsigned i = 0; i < sizeof(bytes); i++) bytes[i] = (uint8_t)next_random();
+            }
+            memcpy(v4._.u8, bytes, sizeof(v4._.u8));
+            memcpy(v6._.u8, bytes, sizeof(v6._.u8));
+            bool old = width == 32 ? ipset_contains_ipv4(&reference, &v4) : ipset_contains_ipv6(&reference, &v6);
+            assert(old == ss_ipset_contains(&current, bytes, width));
+        }
+    }
+    ipset_done(&reference);
+    ss_ipset_clear(&current);
+}
+int main(void)
+{
+    ipset_init_library();
+    check_family(32);
+    check_family(128);
+    puts("1,028,000 IPv4/IPv6 membership comparisons matched the original libipset");
+    return 0;
+}