db/simple/Directory: LookupDirectory() return remaining URI

Code can now be reused in LookupSong().

src/db/plugins/simple/Directory.cxx

@@ -120,38 +120,49 @@ Directory::PruneEmpty()
 	}
 }
 
-Directory *
+Directory::LookupResult
 Directory::LookupDirectory(const char *uri)
 {
 	assert(holding_db_lock());
 	assert(uri != nullptr);
 
 	if (isRootDirectory(uri))
-		return this;
+		return { this, nullptr };
 
 	char *duplicated = xstrdup(uri), *name = duplicated;
 
 	Directory *d = this;
-	while (1) {
+	while (true) {
 		char *slash = strchr(name, '/');
-		if (slash == name) {
-			d = nullptr;
+		if (slash == name)
 			break;
-		}
 
 		if (slash != nullptr)
 			*slash = '\0';
 
-		d = d->FindChild(name);
-		if (d == nullptr || slash == nullptr)
+		Directory *tmp = d->FindChild(name);
+		if (tmp == nullptr)
+			/* not found */
 			break;
 
+		d = tmp;
+
+		if (slash == nullptr) {
+			/* found everything */
+			name = nullptr;
+			break;
+		}
+
 		name = slash + 1;
 	}
 
 	free(duplicated);
 
-	return d;
+	const char *rest = name == nullptr
+		? nullptr
+		: uri + (name - duplicated);
+
+	return { d, rest };
 }
 
 void
@@ -197,26 +208,16 @@ Directory::LookupSong(const char *uri)
 	assert(holding_db_lock());
 	assert(uri != nullptr);
 
-	char *duplicated = xstrdup(uri);
-	char *base = strrchr(duplicated, '/');
-
-	Directory *d = this;
-	if (base != nullptr) {
-		*base++ = 0;
-		d = d->LookupDirectory(duplicated);
-		if (d == nullptr) {
-			free(duplicated);
+	auto r = LookupDirectory(uri);
+	if (r.uri == nullptr)
+		/* it's a directory */
 		return nullptr;
-		}
-	} else
-		base = duplicated;
 
-	Song *song = d->FindSong(base);
-	assert(song == nullptr || song->parent == d);
-
-	free(duplicated);
-	return song;
+	if (strchr(r.uri, '/') != nullptr)
+		/* refers to a URI "below" the actual song */
+		return nullptr;
 
+	return r.directory->FindSong(r.uri);
 }
 
 static int

src/db/plugins/simple/Directory.hxx

@@ -149,6 +149,21 @@ public:
 		return child;
 	}
 
+	struct LookupResult {
+		/**
+		 * The last directory that was found.  If the given
+		 * URI could not be resolved at all, then this is the
+		 * root directory.
+		 */
+		Directory *directory;
+
+		/**
+		 * The remaining URI part (without leading slash) or
+		 * nullptr if the given URI was consumed completely.
+		 */
+		const char *uri;
+	};
+
 	/**
 	 * Looks up a directory by its relative URI.
 	 *
@@ -156,7 +171,7 @@ public:
 	 * @return the Directory, or nullptr if none was found
 	 */
 	gcc_pure
-	Directory *LookupDirectory(const char *uri);
+	LookupResult LookupDirectory(const char *uri);
 
 	gcc_pure
 	bool IsEmpty() const {

src/db/plugins/simple/SimpleDatabasePlugin.cxx

@@ -244,30 +244,35 @@ SimpleDatabase::Visit(const DatabaseSelection &selection,
 {
 	ScopeDatabaseLock protect;
 
-	const Directory *directory = root->LookupDirectory(selection.uri.c_str());
-	if (directory == nullptr) {
+	auto r = root->LookupDirectory(selection.uri.c_str());
+	if (r.uri == nullptr) {
+		/* it's a directory */
+
+		if (selection.recursive && visit_directory &&
+		    !visit_directory(r.directory->Export(), error))
+			return false;
+
+		return r.directory->Walk(selection.recursive, selection.filter,
+					 visit_directory, visit_song,
+					 visit_playlist,
+					 error);
+	}
+
+	if (strchr(r.uri, '/') == nullptr) {
 		if (visit_song) {
-			Song *song = root->LookupSong(selection.uri.c_str());
+			Song *song = r.directory->FindSong(r.uri);
 			if (song != nullptr) {
 				const LightSong song2 = song->Export();
 				return !selection.Match(song2) ||
 					visit_song(song2, error);
 			}
 		}
+	}
 
 	error.Set(db_domain, DB_NOT_FOUND, "No such directory");
 	return false;
 }
 
-	if (selection.recursive && visit_directory &&
-	    !visit_directory(directory->Export(), error))
-		return false;
-
-	return directory->Walk(selection.recursive, selection.filter,
-			       visit_directory, visit_song, visit_playlist,
-			       error);
-}
-
 bool
 SimpleDatabase::VisitUniqueTags(const DatabaseSelection &selection,
 				TagType tag_type,