Add test uuid4 implementation

uuid4.c

@@ -0,0 +1,43 @@
+#include "intern/wapp/src/common/wapp_common.h"
+#include "intern/wapp/src/prng/wapp_prng.h"
+#include <inttypes.h>
+#include <stdio.h>
+
+typedef struct uuid4 UUID4;
+struct uuid4 {
+  u64 high;
+  u64 low;
+};
+
+UUID4 gen_uuid4(XOR256State *state);
+void print_uuid4(UUID4 uuid);
+
+int main(void) {
+  XOR256State state = wapp_init_xor_256_state();
+
+	for (int i = 0; i < 100000; ++i) {
+		UUID4 uuid = gen_uuid4(&state);
+		print_uuid4(uuid);
+	}
+
+  return 0;
+}
+
+UUID4 gen_uuid4(XOR256State *state) {
+	persistent u64 and_mask = 0xffffffffffff0fff;
+	persistent u64 or_mask  = 0x0000000000004000;
+	UUID4 uuid = { .high = wapp_xorshift_256_generate(state), .low = wapp_xorshift_256_generate(state) };
+	uuid.high &= and_mask;
+	uuid.high |= or_mask;
+	return uuid;
+}
+
+void print_uuid4(UUID4 uuid) {
+	u64 a = uuid.high >> 32;
+	u64 b = (uuid.high << 32) >> 48;
+	u64 c = (uuid.high << 48) >> 48;
+	u64 d = uuid.low >> 48;
+	u64 e = (uuid.low << 16) >> 16;
+
+	printf("%.8llx-%.4llx-%.4llx-%.4llx-%.12llx\n", a, b, c, d, e);
+}