song/OptimizeFilter: optimization stage for filters

Makefile.am

@@ -1039,6 +1039,7 @@ libsong_a_SOURCES = \
 	src/song/AudioFormatSongFilter.cxx src/song/AudioFormatSongFilter.hxx \
 	src/song/AndSongFilter.cxx src/song/AndSongFilter.hxx \
 	src/song/NotSongFilter.hxx \
+	src/song/OptimizeFilter.cxx src/song/OptimizeFilter.hxx \
 	src/song/Filter.cxx src/song/Filter.hxx \
 	src/song/LightSong.cxx src/song/LightSong.hxx
 

src/command/DatabaseCommands.cxx

@@ -105,6 +105,7 @@ handle_match(Client &client, Request args, Response &r, bool fold_case)
 			GetFullMessage(std::current_exception()).c_str());
 		return CommandResult::ERROR;
 	}
+	filter.Optimize();
 
 	const DatabaseSelection selection("", true, &filter);
 
@@ -138,6 +139,7 @@ handle_match_add(Client &client, Request args, Response &r, bool fold_case)
 			GetFullMessage(std::current_exception()).c_str());
 		return CommandResult::ERROR;
 	}
+	filter.Optimize();
 
 	auto &partition = client.GetPartition();
 	const ScopeBulkEdit bulk_edit(partition);
@@ -172,6 +174,7 @@ handle_searchaddpl(Client &client, Request args, Response &r)
 			GetFullMessage(std::current_exception()).c_str());
 		return CommandResult::ERROR;
 	}
+	filter.Optimize();
 
 	const Database &db = client.GetDatabaseOrThrow();
 
@@ -206,6 +209,8 @@ handle_count(Client &client, Request args, Response &r)
 				GetFullMessage(std::current_exception()).c_str());
 			return CommandResult::ERROR;
 		}
+
+		filter.Optimize();
 	}
 
 	PrintSongCount(r, client.GetPartition(), "", &filter, group);
@@ -238,6 +243,7 @@ handle_list_file(Client &client, Request args, Response &r)
 				GetFullMessage(std::current_exception()).c_str());
 			return CommandResult::ERROR;
 		}
+		filter->Optimize();
 	}
 
 	PrintSongUris(r, client.GetPartition(), filter.get());
@@ -300,6 +306,7 @@ handle_list(Client &client, Request args, Response &r)
 				GetFullMessage(std::current_exception()).c_str());
 			return CommandResult::ERROR;
 		}
+		filter->Optimize();
 	}
 
 	if (group_mask.Test(tagType)) {

src/command/QueueCommands.cxx

@@ -272,6 +272,7 @@ handle_playlist_match(Client &client, Request args, Response &r,
 			GetFullMessage(std::current_exception()).c_str());
 		return CommandResult::ERROR;
 	}
+	filter.Optimize();
 
 	playlist_print_find(r, client.GetPlaylist(), filter);
 	return CommandResult::OK;

src/song/AndSongFilter.hxx

@@ -31,6 +31,9 @@
 class AndSongFilter final : public ISongFilter {
 	std::list<ISongFilterPtr> items;
 
+	friend void OptimizeSongFilter(AndSongFilter &) noexcept;
+	friend ISongFilterPtr OptimizeSongFilter(ISongFilterPtr) noexcept;
+
 public:
 	const auto &GetItems() const noexcept {
 		return items;

src/song/Filter.cxx

@@ -352,6 +352,12 @@ SongFilter::Parse(ConstBuffer<const char *> args, bool fold_case)
 	} while (!args.empty());
 }
 
+void
+SongFilter::Optimize() noexcept
+{
+	OptimizeSongFilter(and_filter);
+}
+
 bool
 SongFilter::Match(const LightSong &song) const noexcept
 {

src/song/Filter.hxx

@@ -68,6 +68,8 @@ public:
 	 */
 	void Parse(ConstBuffer<const char *> args, bool fold_case=false);
 
+	void Optimize() noexcept;
+
 	gcc_pure
 	bool Match(const LightSong &song) const noexcept;
 

src/song/NotSongFilter.hxx

@@ -28,6 +28,8 @@
 class NotSongFilter final : public ISongFilter {
 	ISongFilterPtr child;
 
+	friend ISongFilterPtr OptimizeSongFilter(ISongFilterPtr) noexcept;
+
 public:
 	template<typename C>
 	explicit NotSongFilter(C &&_child) noexcept

src/song/OptimizeFilter.cxx

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2003-2018 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 "config.h"
+#include "OptimizeFilter.hxx"
+#include "AndSongFilter.hxx"
+#include "NotSongFilter.hxx"
+#include "TagSongFilter.hxx"
+#include "UriSongFilter.hxx"
+
+void
+OptimizeSongFilter(AndSongFilter &af) noexcept
+{
+	for (auto i = af.items.begin(); i != af.items.end();) {
+		auto f = OptimizeSongFilter(std::move(*i));
+		if (auto *nested = dynamic_cast<AndSongFilter *>(f.get())) {
+			/* collapse nested #AndSongFilter instances */
+			af.items.splice(i, std::move(nested->items));
+			i = af.items.erase(i);
+		} else {
+			*i = std::move(f);
+			++i;
+		}
+	}
+}
+
+ISongFilterPtr
+OptimizeSongFilter(ISongFilterPtr f) noexcept
+{
+	if (auto *af = dynamic_cast<AndSongFilter *>(f.get())) {
+		/* first optimize all items */
+		OptimizeSongFilter(*af);
+
+		if (!af->items.empty() &&
+		    std::next(af->items.begin()) == af->items.end())
+			/* only one item: the containing
+			   #AndSongFilter can be removed */
+			return std::move(af->items.front());
+	} else if (auto *nf = dynamic_cast<NotSongFilter *>(f.get())) {
+		auto child = OptimizeSongFilter(std::move(nf->child));
+		if (auto *tf = dynamic_cast<TagSongFilter *>(child.get())) {
+			/* #TagSongFilter has its own "negated" flag,
+			   so we can drop the #NotSongFilter
+			   container */
+			tf->negated = !tf->negated;
+			return child;
+		} else if (auto *uf = dynamic_cast<UriSongFilter *>(child.get())) {
+			/* same for #UriSongFilter */
+			uf->negated = !uf->negated;
+			return child;
+		}
+
+		nf->child = std::move(child);
+	}
+
+	return f;
+}

src/song/OptimizeFilter.hxx

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2003-2018 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.
+ */
+
+#ifndef MPD_SONG_OPTIMIZE_FILTER_HXX
+#define MPD_SONG_OPTIMIZE_FILTER_HXX
+
+#include "ISongFilter.hxx"
+
+class AndSongFilter;
+
+void
+OptimizeSongFilter(AndSongFilter &af) noexcept;
+
+ISongFilterPtr
+OptimizeSongFilter(ISongFilterPtr f) noexcept;
+
+#endif

src/song/TagSongFilter.hxx

@@ -38,6 +38,8 @@ class TagSongFilter final : public ISongFilter {
 
 	StringFilter filter;
 
+	friend ISongFilterPtr OptimizeSongFilter(ISongFilterPtr) noexcept;
+
 public:
 	template<typename V>
 	TagSongFilter(TagType _type, V &&_value, bool fold_case, bool _negated)

src/song/UriSongFilter.hxx

@@ -28,6 +28,8 @@ class UriSongFilter final : public ISongFilter {
 
 	bool negated;
 
+	friend ISongFilterPtr OptimizeSongFilter(ISongFilterPtr) noexcept;
+
 public:
 	template<typename V>
 	UriSongFilter(V &&_value, bool fold_case, bool _negated)

test/ParseSongFilter.cxx

@@ -41,6 +41,7 @@ try {
 
 	SongFilter filter;
 	filter.Parse(ConstBuffer<const char *>(argv + 1, argc - 1));
+	filter.Optimize();
 
 	puts(filter.ToExpression().c_str());
 	return EXIT_SUCCESS;