db/simple/Song: convert "uri" to a std::string

No longer allocate it as a "VarSize".  This used to be a clever trick
to save memory 10 years ago, but these days, keeping the code
maintainable seems more important than saving a few kilobytes of
memory.

src/db/plugins/simple/Directory.cxx

@@ -20,7 +20,6 @@
 #include "Directory.hxx"
 #include "SongSort.hxx"
 #include "Song.hxx"
-#include "Disposer.hxx"
 #include "Mount.hxx"
 #include "db/LightDirectory.hxx"
 #include "song/LightSong.hxx"
@@ -51,7 +50,7 @@ Directory::~Directory() noexcept
 		mounted_database.reset();
 	}
 
-	songs.clear_and_dispose(SongDisposer());
+	songs.clear_and_dispose(DeleteDisposer());
 	children.clear_and_dispose(DeleteDisposer());
 }
 
@@ -192,7 +191,7 @@ Directory::FindSong(const char *name_utf8) const noexcept
 	for (auto &song : songs) {
 		assert(song.parent == this);
 
-		if (strcmp(song.uri, name_utf8) == 0)
+		if (song.uri == name_utf8)
 			return &song;
 	}
 

src/db/plugins/simple/Disposer.hxx

@@ -1,29 +0,0 @@
-/*
- * Copyright 2003-2019 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_DISPOSER_HXX
-#define MPD_SONG_DISPOSER_HXX
-
-struct Song;
-
-struct SongDisposer {
-	void operator()(Song *song) const noexcept;
-};
-
-#endif

src/db/plugins/simple/Ptr.hxx

@@ -20,10 +20,10 @@
 #ifndef MPD_SONG_PTR_HXX
 #define MPD_SONG_PTR_HXX
 
-#include "Disposer.hxx"
-
 #include <memory>
 
-using SongPtr = std::unique_ptr<Song, SongDisposer>;
+struct Song;
+
+using SongPtr = std::unique_ptr<Song>;
 
 #endif

src/db/plugins/simple/Song.cxx

@@ -18,36 +18,22 @@
  */
 
 #include "Song.hxx"
-#include "Disposer.hxx"
 #include "Directory.hxx"
 #include "tag/Tag.hxx"
-#include "util/VarSize.hxx"
 #include "song/DetachedSong.hxx"
 #include "song/LightSong.hxx"
 #include "util/StringView.hxx"
 
-#include <assert.h>
-#include <string.h>
-
 inline
 Song::Song(StringView _uri, Directory &_parent) noexcept
-	:parent(&_parent)
-{
-	memcpy(uri, _uri.data, _uri.size + 1);
-}
-
-inline
-Song::~Song() noexcept
+	:parent(&_parent), uri(_uri.data, _uri.size)
 {
 }
 
 static SongPtr
 song_alloc(StringView uri, Directory &parent) noexcept
 {
-	auto *song = NewVarSize<Song>(sizeof(Song::uri),
-				      uri.size + 1,
-				      uri, parent);
-	return SongPtr(song);
+	return std::make_unique<Song>(uri, parent);
 }
 
 SongPtr
@@ -67,30 +53,16 @@ Song::NewFile(const char *path, Directory &parent) noexcept
 	return SongPtr(song_alloc(path, parent));
 }
 
-void
-Song::Free() noexcept
-{
-	DeleteVarSize(this);
-}
-
-void
-SongDisposer::operator()(Song *song) const noexcept
-{
-	song->Free();
-}
-
 std::string
 Song::GetURI() const noexcept
 {
-	assert(*uri);
-
 	if (parent->IsRoot())
-		return std::string(uri);
+		return uri;
 	else {
 		const char *path = parent->GetPath();
 
 		std::string result;
-		result.reserve(strlen(path) + 1 + strlen(uri));
+		result.reserve(strlen(path) + 1 + uri.length());
 		result.assign(path);
 		result.push_back('/');
 		result.append(uri);
@@ -101,7 +73,7 @@ Song::GetURI() const noexcept
 LightSong
 Song::Export() const noexcept
 {
-	LightSong dest(uri, tag);
+	LightSong dest(uri.c_str(), tag);
 	dest.directory = parent->IsRoot()
 		? nullptr : parent->GetPath();
 	dest.real_uri = nullptr;

src/db/plugins/simple/Song.hxx

@@ -92,10 +92,9 @@ struct Song {
 	/**
 	 * The file name.
 	 */
-	char uri[sizeof(int)];
+	std::string uri;
 
 	Song(StringView _uri, Directory &parent) noexcept;
-	~Song() noexcept;
 
 	static SongPtr NewFrom(DetachedSong &&other, Directory &parent) noexcept;
 
@@ -115,8 +114,6 @@ struct Song {
 	static SongPtr LoadFile(Storage &storage, const char *name_utf8,
 				Directory &parent);
 
-	void Free() noexcept;
-
 	/**
 	 * Throws on error.
 	 *

src/db/plugins/simple/SongSort.cxx

@@ -96,7 +96,7 @@ song_cmp(const Song &a, const Song &b) noexcept
 		return ret < 0;
 
 	/* still no difference?  compare file name */
-	return IcuCollate(a.uri, b.uri) < 0;
+	return IcuCollate(a.uri.c_str(), b.uri.c_str()) < 0;
 }
 
 void