+void
+hash_reset_tuning (Hash_tuning *tuning)
+{
+ *tuning = default_tuning;
+}
+
+/* If the user passes a NULL hasher, we hash the raw pointer. */
+static size_t
+raw_hasher (const void *data, size_t n)
+{
+ /* When hashing unique pointers, it is often the case that they were
+ generated by malloc and thus have the property that the low-order
+ bits are 0. As this tends to give poorer performance with small
+ tables, we rotate the pointer value before performing division,
+ in an attempt to improve hash quality. */
+ size_t val = rotr_sz ((size_t) data, 3);
+ return val % n;
+}
+
+/* If the user passes a NULL comparator, we use pointer comparison. */
+static bool
+raw_comparator (const void *a, const void *b)
+{
+ return a == b;
+}
+
+
+/* For the given hash TABLE, check the user supplied tuning structure for
+ reasonable values, and return true if there is no gross error with it.
+ Otherwise, definitively reset the TUNING field to some acceptable default
+ in the hash table (that is, the user loses the right of further modifying
+ tuning arguments), and return false. */
+
+static bool
+check_tuning (Hash_table *table)
+{
+ const Hash_tuning *tuning = table->tuning;
+ float epsilon;
+ if (tuning == &default_tuning)
+ return true;
+
+ /* Be a bit stricter than mathematics would require, so that
+ rounding errors in size calculations do not cause allocations to
+ fail to grow or shrink as they should. The smallest allocation
+ is 11 (due to next_prime's algorithm), so an epsilon of 0.1
+ should be good enough. */
+ epsilon = 0.1f;
+
+ if (epsilon < tuning->growth_threshold
+ && tuning->growth_threshold < 1 - epsilon
+ && 1 + epsilon < tuning->growth_factor
+ && 0 <= tuning->shrink_threshold
+ && tuning->shrink_threshold + epsilon < tuning->shrink_factor
+ && tuning->shrink_factor <= 1
+ && tuning->shrink_threshold + epsilon < tuning->growth_threshold)
+ return true;