util/hash_table: Rework the API to know about hashing

Previously, the hash_table API required the user to do all of the hashing
of keys as it passed them in.  Since the hashing function is intrinsically
tied to the comparison function, it makes sense for the hash table to know
about it.  Also, it makes for a somewhat clumsy API as the user is
constantly calling hashing functions many of which have long names.  This
is especially bad when the standard call looks something like

_mesa_hash_table_insert(ht, _mesa_pointer_hash(key), key, data);

In the above case, there is no reason why the hash table shouldn't do the
hashing for you.  We leave the option for you to do your own hashing if
it's more efficient, but it's no longer needed.  Also, if you do do your
own hashing, the hash table will assert that your hash matches what it
expects out of the hashing function.  This should make it harder to mess up
your hashing.

v2: change to call the old entrypoint "pre_hashed" rather than
    "with_hash", like cworth's equivalent change upstream (change by
    anholt, acked-in-general by Jason).

Signed-off-by: Jason Ekstrand <[email protected]>
Signed-off-by: Eric Anholt <[email protected]>
Reviewed-by: Eric Anholt <[email protected]>

1 files changed, 55 insertions, 20 deletions

diff --git a/src/util/hash_table.c b/src/util/hash_table.c
index 920bdfd3317..e85ebe345f8 100644
--- a/src/util/hash_table.c
+++ b/src/util/hash_table.c
@@ -42,6 +42,7 @@
 
 #include <stdlib.h>
 #include <string.h>
+#include <assert.h>
 
 #include "hash_table.h"
 #include "ralloc.h"
@@ -110,6 +111,7 @@ entry_is_present(const struct hash_table *ht, struct hash_entry *entry)
 
 struct hash_table *
 _mesa_hash_table_create(void *mem_ctx,
+                        uint32_t (*key_hash_function)(const void *key),
                         bool (*key_equals_function)(const void *a,
                                                     const void *b))
 {
@@ -123,6 +125,7 @@ _mesa_hash_table_create(void *mem_ctx,
    ht->size = hash_sizes[ht->size_index].size;
    ht->rehash = hash_sizes[ht->size_index].rehash;
    ht->max_entries = hash_sizes[ht->size_index].max_entries;
+   ht->key_hash_function = key_hash_function;
    ht->key_equals_function = key_equals_function;
    ht->table = rzalloc_array(ht, struct hash_entry, ht->size);
    ht->entries = 0;
@@ -176,15 +179,8 @@ _mesa_hash_table_set_deleted_key(struct hash_table *ht, const void *deleted_key)
    ht->deleted_key = deleted_key;
 }
 
-/**
- * Finds a hash table entry with the given key and hash of that key.
- *
- * Returns NULL if no entry is found.  Note that the data pointer may be
- * modified by the user.
- */
-struct hash_entry *
-_mesa_hash_table_search(struct hash_table *ht, uint32_t hash,
-                        const void *key)
+static struct hash_entry *
+hash_table_search(struct hash_table *ht, uint32_t hash, const void *key)
 {
    uint32_t start_hash_address = hash % ht->size;
    uint32_t hash_address = start_hash_address;
@@ -210,6 +206,31 @@ _mesa_hash_table_search(struct hash_table *ht, uint32_t hash,
    return NULL;
 }
 
+/**
+ * Finds a hash table entry with the given key and hash of that key.
+ *
+ * Returns NULL if no entry is found.  Note that the data pointer may be
+ * modified by the user.
+ */
+struct hash_entry *
+_mesa_hash_table_search(struct hash_table *ht, const void *key)
+{
+   assert(ht->key_hash_function);
+   return hash_table_search(ht, ht->key_hash_function(key), key);
+}
+
+struct hash_entry *
+_mesa_hash_table_search_pre_hashed(struct hash_table *ht, uint32_t hash,
+                                  const void *key)
+{
+   assert(ht->key_hash_function == NULL || hash == ht->key_hash_function(key));
+   return hash_table_search(ht, hash, key);
+}
+
+static struct hash_entry *
+hash_table_insert(struct hash_table *ht, uint32_t hash,
+                  const void *key, void *data);
+
 static void
 _mesa_hash_table_rehash(struct hash_table *ht, int new_size_index)
 {
@@ -235,22 +256,15 @@ _mesa_hash_table_rehash(struct hash_table *ht, int new_size_index)
    ht->deleted_entries = 0;
 
    hash_table_foreach(&old_ht, entry) {
-      _mesa_hash_table_insert(ht, entry->hash,
-                              entry->key, entry->data);
+      hash_table_insert(ht, entry->hash, entry->key, entry->data);
    }
 
    ralloc_free(old_ht.table);
 }
 
-/**
- * Inserts the key with the given hash into the table.
- *
- * Note that insertion may rearrange the table on a resize or rehash,
- * so previously found hash_entries are no longer valid after this function.
- */
-struct hash_entry *
-_mesa_hash_table_insert(struct hash_table *ht, uint32_t hash,
-                        const void *key, void *data)
+static struct hash_entry *
+hash_table_insert(struct hash_table *ht, uint32_t hash,
+                  const void *key, void *data)
 {
    uint32_t start_hash_address, hash_address;
 
@@ -307,6 +321,27 @@ _mesa_hash_table_insert(struct hash_table *ht, uint32_t hash,
 }
 
 /**
+ * Inserts the key with the given hash into the table.
+ *
+ * Note that insertion may rearrange the table on a resize or rehash,
+ * so previously found hash_entries are no longer valid after this function.
+ */
+struct hash_entry *
+_mesa_hash_table_insert(struct hash_table *ht, const void *key, void *data)
+{
+   assert(ht->key_hash_function);
+   hash_table_insert(ht, ht->key_hash_function(key), key, data);
+}
+
+struct hash_entry *
+_mesa_hash_table_insert_with_hash(struct hash_table *ht, uint32_t hash,
+                                  const void *key, void *data)
+{
+   assert(ht->key_hash_function == NULL || hash == ht->key_hash_function(key));
+   hash_table_insert(ht, hash, key, data);
+}
+
+/**
  * This function deletes the given hash table entry.
  *
  * Note that deletion doesn't otherwise modify the table, so an iteration over