utils: Add ref_cur() to retrieve the current value of a reference counter

On many architectures it is safe to read the value directly (those
using cache coherency protocols, and with atomic loads for 32-bit
values) but it is not if that's not the case or if we ever decide to
make refcount_t 64-bit (load not atomic on x86).

So make sure the operation is actually atomic and that users do not
have to care about the size of refcount_t.

src/libstrongswan/utils/utils.c

@@ -528,7 +528,6 @@ refcount_t ref_get(refcount_t *ref)
 	pthread_mutex_lock(&ref_mutex);
 	current = ++(*ref);
 	pthread_mutex_unlock(&ref_mutex);
-
 	return current;
 }
 
@@ -545,6 +544,19 @@ bool ref_put(refcount_t *ref)
 	return !more_refs;
 }
 
+/**
+ * Current refcount
+ */
+refcount_t ref_cur(refcount_t *ref)
+{
+	refcount_t current;
+
+	pthread_mutex_lock(&ref_mutex);
+	current = *ref;
+	pthread_mutex_unlock(&ref_mutex);
+	return current;
+}
+
 /**
  * Single mutex for all compare and swap operations.
  */