+/**
+ * Finalize the hash computation and return the digest.
+ *
+ * \note This function must be called exactly once per each computation.
+ * Calling it twice leads to undefined behaviour.
+ *
+ * \note The pointer returned is within the hash context structure \a h, so it
+ * has the same lifetime as the hash instance. The data will be invalidated
+ * as soon as \a hash_begin is called again on the same instance.
+ */