core/database: Replace database iterators with db_for_each()

This function is similar to Linux's list_for_each_safe(), and lets you
iterate over a database even if the current item is removed.

Signed-off-by: Anna Schumaker <Anna@OcarinaProject.net>

core/tags/track.cpp

@@ -171,11 +171,11 @@ void tags :: remove_track(Track *track)
 
 void tags :: remove_library_tracks(Library *library)
 {
-	database<Track>::iterator it;
+	Track *it, *next;
 
-	for (it = track_db.begin(); it != track_db.end(); it = track_db.next(it)) {
-		if ((*it)->library() == library)
-			db_remove(&track_db, *it);
+	db_for_each(it, next, &track_db) {
+		if (it->library() == library)
+			db_remove(&track_db, it);
 	}
 	tags :: commit_track_db();
 }

include/core/database.h

@@ -86,10 +86,6 @@ struct database {
 	std::vector<T *> db_entries;
 	std::map<const std::string, unsigned int> db_keys;
 
-	/** Iterator access for our backing std::vector */
-	typedef typename std::vector<T *>::iterator iterator;
-	/** Const iterator access for our backing std::vector */
-	typedef typename std::vector<T *>::const_iterator const_iterator;
 
 	/**
 	 * Initialize a Database using filepath as a location to store data
@@ -107,23 +103,6 @@ struct database {
 	 * Deletes all remaining entries in a Database to prevent memory leaks.
 	 */
 	~database();
-
-
-	/**
-	 * @return An iterator pointing to the first valid entry in the Database.
-	 * @return Return Database::end() if there are no valid entries.
-	 */
-	iterator begin();
-
-	/**
-	 * @return An iterator pointing past the end of the database.
-	 */
-	iterator end();
-
-	/**
-	 * @return An iterator pointing to the next valid item in the database.
-	 */
-	iterator next(iterator &);
 };
 
 
@@ -171,6 +150,21 @@ T *db_get(struct database<T> *, const gchar *);
 template <class T>
 T *db_find(struct database<T> *, const gchar *);
 
+/* Returns the first valid database item. */
+template <class T>
+T *db_first(const struct database<T> *);
+
+/* Returns the next valid database item. */
+template <class T>
+T *db_next(const struct database<T> *, T *);
+
+
+#define db_for_each(ent, next, db)				\
+	for (ent = db_first(db), next = db_next(db, ent);	\
+	     ent != NULL;					\
+	     ent = next, next = db_next(db, ent))
+
+
 #include "database.hpp"
 
 #endif /* OCARINA_CORE_DATABASE_H */

include/core/database.hpp

@@ -17,9 +17,9 @@ database<T> :: database(std::string filepath, bool autosave)
 template <class T>
 database<T> :: ~database()
 {
-	iterator it;
-	for (it = begin(); it != end(); it = next(it))
-		delete (*it);
+	T *t, *u;
+	db_for_each(t, u, this)
+		delete t;
 }
 
 template <class T>
@@ -114,30 +114,27 @@ unsigned int db_actual_size(const struct database<T> *db)
 }
 
 template <class T>
-typename database<T>::iterator database<T> :: begin()
+T *__db_next(const struct database<T> *db, unsigned int index)
 {
-	if (db_size == 0)
-		return end();
-
-	iterator it = db_entries.begin();
-	if ( (*it) != NULL )
-		return it;
-	return next(it);
+	for (; index < db->db_entries.size(); index++) {
+		if (db->db_entries[index])
+			return db->db_entries[index];
+	}
+	return NULL;
 }
 
 template <class T>
-typename database<T>::iterator database<T> :: end()
+T *db_first(const struct database<T> *db)
 {
-	return db_entries.end();
+	return __db_next(db, 0);
 }
 
 template <class T>
-typename database<T>::iterator database<T> :: next(iterator &it)
+T *db_next(const struct database<T> *db, T *ent)
 {
-	do {
-		it++;
-	} while ((it != end()) && (*it) == NULL);
-	return it;
+	if (ent)
+		return __db_next(db, ent->index() + 1);
+	return NULL;
 }
 
 template <class T>

tests/core/database.cpp

@@ -72,9 +72,8 @@ static void test_init()
 static void test_stress(unsigned int N)
 {
 	database<struct int_entry> db("stress.db", false);
-	database<struct int_entry>::iterator it;
 	std::vector<struct int_entry *> ptrs;
-	struct int_entry *dbe, rmv(42);
+	struct int_entry *dbe, *next, rmv(42);
 	unsigned int i;
 	gchar *key;
 
@@ -142,12 +141,19 @@ static void test_stress(unsigned int N)
 	test_equal(db.db_size, N / 2);
 	test_equal(db_actual_size(&db), N + 1);
 
-	/* database.first(), database.next(), database.end() */
+	/* db_for_each() (db_first() / db_next()) */
 	i = 1;
-	for (it = db.begin(); it != db.end(); it = db.next(it)) {
-		test_loop_not_equal(*it, NULL, i);
-		test_loop_equal(*it, ptrs.at(i), i);
-		test_loop_equal((*it)->ie_val, i, i);
+	db_for_each(dbe, next, &db) {
+		test_loop_not_equal(dbe, NULL, i);
+		if (i == (N - 1)) {
+			test_loop_equal(next, NULL, i);
+		} else {
+			test_loop_not_equal(next, NULL, i);
+			test_loop_equal(next->ie_val, i + 2, i);
+		}
+		test_loop_equal(dbe, ptrs.at(i), i);
+		test_loop_equal(dbe->ie_val, i, i);
+		test_loop_equal(db_next(&db, dbe), next, i);
 		i += 2;
 	} test_loop_passed();
 	test_equal(i, N + 1);