-/************************************************************************
- Weak Hash Tables
- ************************************************************************/
-
-/* Sweep weak hash table H. REMOVE_ENTRIES_P means remove
- entries from the table that don't survive the current GC.
- !REMOVE_ENTRIES_P means mark entries that are in use. Value is
- true if anything was marked. */
-
-static bool
-sweep_weak_table (struct Lisp_Hash_Table *h, bool remove_entries_p)
-{
- ptrdiff_t bucket, n;
- bool marked;
-
- n = ASIZE (h->index) & ~ARRAY_MARK_FLAG;
- marked = 0;
-
- for (bucket = 0; bucket < n; ++bucket)
- {
- Lisp_Object idx, next, prev;
-
- /* Follow collision chain, removing entries that
- don't survive this garbage collection. */
- prev = Qnil;
- for (idx = HASH_INDEX (h, bucket); !NILP (idx); idx = next)
- {
- ptrdiff_t i = XFASTINT (idx);
- bool key_known_to_survive_p = survives_gc_p (HASH_KEY (h, i));
- bool value_known_to_survive_p = survives_gc_p (HASH_VALUE (h, i));
- bool remove_p;
-
- if (EQ (h->weak, Qkey))
- remove_p = !key_known_to_survive_p;
- else if (EQ (h->weak, Qvalue))
- remove_p = !value_known_to_survive_p;
- else if (EQ (h->weak, Qkey_or_value))
- remove_p = !(key_known_to_survive_p || value_known_to_survive_p);
- else if (EQ (h->weak, Qkey_and_value))
- remove_p = !(key_known_to_survive_p && value_known_to_survive_p);
- else
- emacs_abort ();
-
- next = HASH_NEXT (h, i);
-
- if (remove_entries_p)
- {
- if (remove_p)
- {
- /* Take out of collision chain. */
- if (NILP (prev))
- set_hash_index_slot (h, bucket, next);
- else
- set_hash_next_slot (h, XFASTINT (prev), next);
-
- /* Add to free list. */
- set_hash_next_slot (h, i, h->next_free);
- h->next_free = idx;
-
- /* Clear key, value, and hash. */
- set_hash_key_slot (h, i, Qnil);
- set_hash_value_slot (h, i, Qnil);
- set_hash_hash_slot (h, i, Qnil);
-
- h->count--;
- }
- else
- {
- prev = idx;
- }
- }
- else
- {
- if (!remove_p)
- {
- /* Make sure key and value survive. */
- if (!key_known_to_survive_p)
- {
- mark_object (HASH_KEY (h, i));
- marked = 1;
- }
-
- if (!value_known_to_survive_p)
- {
- mark_object (HASH_VALUE (h, i));
- marked = 1;
- }
- }
- }
- }
- }
-
- return marked;
-}
-
-/* Remove elements from weak hash tables that don't survive the
- current garbage collection. Remove weak tables that don't survive
- from Vweak_hash_tables. Called from gc_sweep. */
-
-void
-sweep_weak_hash_tables (void)
-{
- struct Lisp_Hash_Table *h, *used, *next;
- bool marked;
-
- /* Mark all keys and values that are in use. Keep on marking until
- there is no more change. This is necessary for cases like
- value-weak table A containing an entry X -> Y, where Y is used in a
- key-weak table B, Z -> Y. If B comes after A in the list of weak
- tables, X -> Y might be removed from A, although when looking at B
- one finds that it shouldn't. */
- do
- {
- marked = 0;
- for (h = weak_hash_tables; h; h = h->next_weak)
- {
- if (h->header.size & ARRAY_MARK_FLAG)
- marked |= sweep_weak_table (h, 0);
- }
- }
- while (marked);
-
- /* Remove tables and entries that aren't used. */
- for (h = weak_hash_tables, used = NULL; h; h = next)
- {
- next = h->next_weak;
-
- if (h->header.size & ARRAY_MARK_FLAG)
- {
- /* TABLE is marked as used. Sweep its contents. */
- if (h->count > 0)
- sweep_weak_table (h, 1);
-
- /* Add table to the list of used weak hash tables. */
- h->next_weak = used;
- used = h;
- }
- }
-
- weak_hash_tables = used;
-}
-
-
-\f
HCoop / bpt / emacs.git / blobdiff