invbloom: singleton callback for when destroying a singleton, too.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

ccan/invbloom/invbloom.c

@@ -34,7 +34,7 @@ struct invbloom *invbloom_new_(const tal_t *ctx,
 
 void invbloom_singleton_cb_(struct invbloom *ib,
 			    void (*cb)(struct invbloom *,
-				       size_t bucket, void *),
+				       size_t bucket, bool, void *),
 			    void *data)
 {
 	ib->singleton = cb;
@@ -51,7 +51,7 @@ static u8 *idsum_ptr(const struct invbloom *ib, size_t bucket)
 	return (u8 *)ib->idsum + bucket * ib->id_size;
 }
 
-static void check_for_singleton(struct invbloom *ib, size_t bucket)
+static void check_for_singleton(struct invbloom *ib, size_t bucket, bool before)
 {
 	if (!ib->singleton)
 		return;
@@ -59,7 +59,7 @@ static void check_for_singleton(struct invbloom *ib, size_t bucket)
 	if (ib->count[bucket] != 1 && ib->count[bucket] != -1)
 		return;
 
-	ib->singleton(ib, bucket, ib->singleton_data);
+	ib->singleton(ib, bucket, before, ib->singleton_data);
 }
 
 static void add_to_bucket(struct invbloom *ib, size_t n, const u8 *id)
@@ -67,12 +67,14 @@ static void add_to_bucket(struct invbloom *ib, size_t n, const u8 *id)
 	size_t i;
 	u8 *idsum = idsum_ptr(ib, n);
 	
+	check_for_singleton(ib, n, true);
+
 	ib->count[n]++;
 
 	for (i = 0; i < ib->id_size; i++)
 		idsum[i] ^= id[i];
 
-	check_for_singleton(ib, n);
+	check_for_singleton(ib, n, false);
 }
 
 static void remove_from_bucket(struct invbloom *ib, size_t n, const u8 *id)
@@ -80,11 +82,13 @@ static void remove_from_bucket(struct invbloom *ib, size_t n, const u8 *id)
 	size_t i;
 	u8 *idsum = idsum_ptr(ib, n);
 
+	check_for_singleton(ib, n, true);
+
 	ib->count[n]--;
 	for (i = 0; i < ib->id_size; i++)
 		idsum[i] ^= id[i];
 
-	check_for_singleton(ib, n);
+	check_for_singleton(ib, n, false);
 }
 
 void invbloom_insert(struct invbloom *ib, const void *id)
@@ -175,12 +179,15 @@ void invbloom_subtract(struct invbloom *ib1, const struct invbloom *ib2)
 	assert(ib1->id_size == ib2->id_size);
 	assert(ib1->salt == ib2->salt);
 
+	for (i = 0; i < ib1->n_elems; i++)
+		check_for_singleton(ib1, i, true);
+
 	for (i = 0; i < ib1->n_elems * ib1->id_size; i++)
 		ib1->idsum[i] ^= ib2->idsum[i];
 
 	for (i = 0; i < ib1->n_elems; i++) {
 		ib1->count[i] -= ib2->count[i];
-		check_for_singleton(ib1, i);
+		check_for_singleton(ib1, i, false);
 	}
 }
 

ccan/invbloom/invbloom.h

@@ -11,7 +11,7 @@ struct invbloom {
 	u32 salt;
 	s32 *count; /* [n_elems] */
 	u8 *idsum; /* [n_elems][id_size] */
-	void (*singleton)(struct invbloom *ib, size_t elem, void *);
+	void (*singleton)(struct invbloom *ib, size_t elem, bool, void *);
 	void *singleton_data;
 };
 
@@ -31,7 +31,7 @@ struct invbloom *invbloom_new_(const tal_t *ctx,
 			       size_t n_elems, u32 salt);
 
 /**
- * invbloom_singleton_cb - set callback for when a singleton is found.
+ * invbloom_singleton_cb - set callback for a singleton created/destroyed.
  * @ib: the invertable bloom lookup table.
  * @cb: the function to call (or NULL for none)
  * @data: the data to hand to the function.
@@ -40,15 +40,21 @@ struct invbloom *invbloom_new_(const tal_t *ctx,
  * possibly multiple times for a single call.  The particular
  * @ib bucket will be consistent, but the rest of the table may
  * not be.
+ *
+ * @cb is of form "void @cb(struct invbloom *ib, size_t bucket, bool
+ * before, data)".  @before is true if the call is done before the
+ * singleton in @bucket is removed (ie. ib->counts[bucket] is -1 or 1,
+ * but is about to change).  @before is false if the call is done
+ * after the operation, and the bucket is now a singleton.
  */
 #define invbloom_singleton_cb(ib, cb, data)			\
 	invbloom_singleton_cb_((ib),				\
 	       typesafe_cb_preargs(void, void *, (cb), (data),  \
-				   struct invbloom *, size_t), (data))
+				   struct invbloom *, size_t, bool), (data))
 
 void invbloom_singleton_cb_(struct invbloom *ib,
 			    void (*cb)(struct invbloom *,
-				       size_t bucket, void *),
+				       size_t bucket, bool before, void *),
 			    void *data);
 
 /**

ccan/invbloom/test/run-singletoncb.c

@@ -3,11 +3,11 @@
 #include <ccan/invbloom/invbloom.c>
 #include <ccan/tap/tap.h>
 
-static void singleton_cb(struct invbloom *ib, size_t n,
+static void singleton_cb(struct invbloom *ib, size_t n, bool before,
 			 unsigned *count)
 {
 	ok1(ib->count[n] == 1 || ib->count[n] == -1);
-	(*count)++;
+	count[before]++;
 }	
 
 int main(void)
@@ -15,48 +15,54 @@ int main(void)
 	struct invbloom *ib;
 	const tal_t *ctx = tal(NULL, char);
 	int val;
-	unsigned singleton_count;
+	unsigned singleton_count[2];
 
 	/* This is how many tests you plan to run */
-	plan_tests(10 + 3 + NUM_HASHES * 2);
+	plan_tests(16 + 6 + NUM_HASHES * 3);
 
 	/* Single entry ib table keeps it simple. */
 	ib = invbloom_new(ctx, int, 1, 100);
-	invbloom_singleton_cb(ib, singleton_cb, &singleton_count);
+	invbloom_singleton_cb(ib, singleton_cb, singleton_count);
 
 	val = 0;
-	singleton_count = 0;
+	singleton_count[false] = singleton_count[true] = 0;
 	invbloom_insert(ib, &val);
 	ok1(ib->count[0] == NUM_HASHES);
-	ok1(singleton_count == 1);
+	ok1(singleton_count[true] == 1);
+	ok1(singleton_count[false] == 1);
 	ok1(!invbloom_empty(ib));
 
 	/* First delete takes it via singleton. */
 	invbloom_delete(ib, &val);
-	ok1(singleton_count == 2);
+	ok1(singleton_count[true] == 2);
+	ok1(singleton_count[false] == 2);
 	ok1(invbloom_empty(ib));
 
 	/* Second delete creates negative singleton. */
 	invbloom_delete(ib, &val);
-	ok1(singleton_count == 3);
+	ok1(singleton_count[true] == 3);
+	ok1(singleton_count[false] == 3);
 
 	/* Now a larger table: this seed set so entries don't clash */
 	ib = invbloom_new(ctx, int, 1024, 0);
-	singleton_count = 0;
-	invbloom_singleton_cb(ib, singleton_cb, &singleton_count);
+	singleton_count[false] = singleton_count[true] = 0;
+	invbloom_singleton_cb(ib, singleton_cb, singleton_count);
 
 	val = 0;
 	invbloom_insert(ib, &val);
-	ok1(singleton_count == NUM_HASHES);
+	ok1(singleton_count[true] == 0);
+	ok1(singleton_count[false] == NUM_HASHES);
 
-	/* First delete does nothing. */
+	/* First delete removes singletons. */
 	invbloom_delete(ib, &val);
-	ok1(singleton_count == NUM_HASHES);
+	ok1(singleton_count[true] == NUM_HASHES);
+	ok1(singleton_count[false] == NUM_HASHES);
 	ok1(invbloom_empty(ib));
 
 	/* Second delete creates negative singletons. */
 	invbloom_delete(ib, &val);
-	ok1(singleton_count == NUM_HASHES * 2);
+	ok1(singleton_count[true] == NUM_HASHES);
+	ok1(singleton_count[false] == NUM_HASHES * 2);
 
 	tal_free(ctx);