queue/Selection: wrap SongFilter in a new struct

meson.build

@@ -332,6 +332,7 @@ sources = [
   'src/queue/Queue.cxx',
   'src/queue/Print.cxx',
   'src/queue/Save.cxx',
+  'src/queue/Selection.cxx',
   'src/queue/Playlist.cxx',
   'src/queue/PlaylistControl.cxx',
   'src/queue/PlaylistEdit.cxx',

src/PlaylistPrint.cxx

@@ -77,9 +77,9 @@ playlist_print_current(Response &r, const playlist &playlist)
 
 void
 playlist_print_find(Response &r, const playlist &playlist,
-		    const SongFilter &filter)
+		    const QueueSelection &selection)
 {
-	queue_find(r, playlist.queue, filter);
+	PrintQueue(r, playlist.queue, selection);
 }
 
 void

src/PlaylistPrint.hxx

@@ -24,7 +24,7 @@
 
 struct playlist;
 struct RangeArg;
-class SongFilter;
+struct QueueSelection;
 class Response;
 
 /**
@@ -65,7 +65,7 @@ playlist_print_current(Response &r, const playlist &playlist);
  */
 void
 playlist_print_find(Response &r, const playlist &playlist,
-		    const SongFilter &filter);
+		    const QueueSelection &selection);
 
 /**
  * Print detailed changes since the specified playlist version.

src/command/QueueCommands.cxx

@@ -29,6 +29,7 @@
 #include "song/DetachedSong.hxx"
 #include "LocateUri.hxx"
 #include "queue/Playlist.hxx"
+#include "queue/Selection.hxx"
 #include "PlaylistPrint.hxx"
 #include "client/Client.hxx"
 #include "client/Response.hxx"
@@ -299,7 +300,10 @@ handle_playlist_match(Client &client, Request args, Response &r,
 	}
 	filter.Optimize();
 
-	playlist_print_find(r, client.GetPlaylist(), filter);
+	QueueSelection selection;
+	selection.filter = &filter;
+
+	playlist_print_find(r, client.GetPlaylist(), selection);
 	return CommandResult::OK;
 }
 

src/queue/Print.cxx

@@ -19,6 +19,7 @@
 
 #include "Print.hxx"
 #include "Queue.hxx"
+#include "Selection.hxx"
 #include "song/Filter.hxx"
 #include "SongPrint.hxx"
 #include "song/DetachedSong.hxx"
@@ -100,13 +101,11 @@ queue_print_changes_position(Response &r, const Queue &queue,
 }
 
 void
-queue_find(Response &r, const Queue &queue,
-	   const SongFilter &filter)
+PrintQueue(Response &r, const Queue &queue,
+	   const QueueSelection &selection)
 {
 	for (unsigned i = 0; i < queue.GetLength(); i++) {
-		const LightSong song{queue.Get(i)};
-
-		if (filter.Match(song))
+		if (selection.MatchPosition(queue, i))
 			queue_print_song_info(r, queue, i);
 	}
 }

src/queue/Print.hxx

@@ -27,7 +27,7 @@
 #include <cstdint>
 
 struct Queue;
-class SongFilter;
+struct QueueSelection;
 class Response;
 
 void
@@ -49,5 +49,5 @@ queue_print_changes_position(Response &r, const Queue &queue,
 			     unsigned start, unsigned end);
 
 void
-queue_find(Response &response, const Queue &queue,
-	   const SongFilter &filter);
+PrintQueue(Response &response, const Queue &queue,
+	   const QueueSelection &selection);

src/queue/Selection.cxx

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2003-2021 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "Selection.hxx"
+#include "Queue.hxx"
+#include "song/DetachedSong.hxx"
+#include "song/Filter.hxx"
+#include "song/LightSong.hxx"
+
+bool
+QueueSelection::MatchPosition(const Queue &queue,
+			      unsigned position) const noexcept
+{
+	if (filter != nullptr) {
+		const LightSong song{queue.Get(position)};
+		if (!filter->Match(song))
+			return false;
+	}
+
+	return true;
+}

src/queue/Selection.hxx

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2003-2021 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#pragma once
+
+struct Queue;
+class SongFilter;
+
+/**
+ * Describes what part of and how the client wishes to see the queue.
+ */
+struct QueueSelection {
+	/**
+	 * An optional pointer to a #SongFilter (not owned by this
+	 * object).
+	 */
+	const SongFilter *filter = nullptr;
+
+	[[gnu::pure]]
+	bool MatchPosition(const Queue &queue,
+			   unsigned position) const noexcept;
+};