util/hash_table: add u64 foreach macro

needs some nontrivial wrapping but can mostly fallback to the regular impl.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27762>

src/.clang-format

@@ -57,6 +57,7 @@ ForEachMacros:
 
   - hash_table_foreach
   - hash_table_foreach_remove
+  - hash_table_u64_foreach
 
   - rb_tree_foreach
   - rb_tree_foreach_rev

src/util/hash_table.c

@@ -960,3 +960,49 @@ _mesa_hash_table_u64_remove(struct hash_table_u64 *ht, uint64_t key)
       FREE(_key);
    }
 }
+
+
+/*
+ * Iterates in order ("freed key", "deleted key", regular entries...)
+ */
+struct hash_entry_u64
+_mesa_hash_table_u64_next_entry(struct hash_table_u64 *ht,
+                                struct hash_entry_u64 *ent)
+{
+   /* First entry: freed key */
+   if (!ent && ht->freed_key_data) {
+      return (struct hash_entry_u64){
+         .key = FREED_KEY_VALUE,
+         .data = ht->freed_key_data,
+      };
+   }
+
+   /* Second entry: deleted key */
+   if ((!ent || ent->key == FREED_KEY_VALUE) && ht->deleted_key_data) {
+      return (struct hash_entry_u64){
+         .key = DELETED_KEY_VALUE,
+         .data = ht->deleted_key_data,
+      };
+   }
+
+   /* All other entries: regular */
+   struct hash_entry *next =
+      _mesa_hash_table_next_entry(ht->table, ent ? ent->_entry : NULL);
+
+   if (!next)
+      return (struct hash_entry_u64){.data = NULL};
+
+   uint64_t key;
+   if (sizeof(void *) == 8) {
+      key = (uintptr_t)next->key;
+   } else {
+      const struct hash_key_u64 *_key = next->key;
+      key = _key->value;
+   }
+
+   return (struct hash_entry_u64){
+      .key = key,
+      .data = next->data,
+      ._entry = next,
+   };
+}

src/util/hash_table.h

@@ -171,6 +171,12 @@ struct hash_table_u64 {
    void *deleted_key_data;
 };
 
+struct hash_entry_u64 {
+   uint64_t key;
+   void *data;
+   struct hash_entry *_entry;
+};
+
 struct hash_table_u64 *
 _mesa_hash_table_u64_create(void *mem_ctx);
 
@@ -190,6 +196,22 @@ _mesa_hash_table_u64_remove(struct hash_table_u64 *ht, uint64_t key);
 void
 _mesa_hash_table_u64_clear(struct hash_table_u64 *ht);
 
+struct hash_entry_u64
+_mesa_hash_table_u64_next_entry(struct hash_table_u64 *ht,
+                                struct hash_entry_u64 *ent);
+
+/**
+ * This foreach function is safe against deletion (which just replaces
+ * an entry's data with the deleted marker), but not against insertion
+ * (which may rehash the table, making entry a dangling pointer).
+ */
+#define hash_table_u64_foreach(ht, entry)                                      \
+   for (struct hash_entry_u64 entry =                                          \
+         _mesa_hash_table_u64_next_entry(ht, NULL);                            \
+        entry.data != NULL;                                                    \
+        entry = _mesa_hash_table_u64_next_entry(ht, &entry))
+
+
 #ifdef __cplusplus
 } /* extern C */
 #endif