manage tag string allocations in a pool

There are many duplicated strings in the tag database, e.g. many songs
having the same artist.  Don't allocate such strings twice, manage all
strings in a pool.

4 files changed, 200 insertions, 44 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index 176edf251..53342ff54 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -30,6 +30,7 @@ ncmpc_headers = \
   ncmpc.h\
   screen_browse.h\
   src_lyrics.h \
+	str_pool.h \
 	gcc.h
 
 # $Id$
@@ -62,7 +63,8 @@ ncmpc_SOURCES = \
   wreadln.c\
   strfsong.c\
   utils.c\
-  src_lyrics.c
+  src_lyrics.c \
+	str_pool.c
 
 if LEOSLYRICS_FIXED
 ncmpc_SOURCES+=lyrics_leoslyrics.c 
diff --git a/src/libmpdclient.c b/src/libmpdclient.c
index 48d7d4f5f..b0498445e 100644
--- a/src/libmpdclient.c
+++ b/src/libmpdclient.c
@@ -31,6 +31,7 @@
 */
 
 #include "libmpdclient.h"
+#include "str_pool.h"
 
 #include <errno.h>
 #include <sys/types.h>
@@ -279,15 +280,15 @@ static mpd_ReturnElement * mpd_newReturnElement(const char * name, const char *
 {
 	mpd_ReturnElement * ret = malloc(sizeof(mpd_ReturnElement));
 
-	ret->name = strdup(name);
-	ret->value = strdup(value);
+	ret->name = str_pool_get(name);
+	ret->value = str_pool_get(value);
 
 	return ret;
 }
 
 static void mpd_freeReturnElement(mpd_ReturnElement * re) {
-	free(re->name);
-	free(re->value);
+	str_pool_put(re->name);
+	str_pool_put(re->value);
 	free(re);
 }
 
@@ -930,17 +931,17 @@ static void mpd_initSong(mpd_Song * song) {
 }
 
 static void mpd_finishSong(mpd_Song * song) {
-	if(song->file) free(song->file);
-	if(song->artist) free(song->artist);
-	if(song->album) free(song->album);
-	if(song->title) free(song->title);
-	if(song->track) free(song->track);
-	if(song->name) free(song->name);
-	if(song->date) free(song->date);
-	if(song->genre) free(song->genre);
-	if(song->composer) free(song->composer);
-	if(song->disc) free(song->disc);
-	if(song->comment) free(song->comment);
+	if(song->file) str_pool_put(song->file);
+	if(song->artist) str_pool_put(song->artist);
+	if(song->album) str_pool_put(song->album);
+	if(song->title) str_pool_put(song->title);
+	if(song->track) str_pool_put(song->track);
+	if(song->name) str_pool_put(song->name);
+	if(song->date) str_pool_put(song->date);
+	if(song->genre) str_pool_put(song->genre);
+	if(song->composer) str_pool_put(song->composer);
+	if(song->disc) str_pool_put(song->disc);
+	if(song->comment) str_pool_put(song->comment);
 }
 
 mpd_Song * mpd_newSong(void) {
@@ -959,17 +960,17 @@ void mpd_freeSong(mpd_Song * song) {
 mpd_Song * mpd_songDup(mpd_Song * song) {
 	mpd_Song * ret = mpd_newSong();
 
-	if(song->file) ret->file = strdup(song->file);
-	if(song->artist) ret->artist = strdup(song->artist);
-	if(song->album) ret->album = strdup(song->album);
-	if(song->title) ret->title = strdup(song->title);
-	if(song->track) ret->track = strdup(song->track);
-	if(song->name) ret->name = strdup(song->name);
-	if(song->date) ret->date = strdup(song->date);
-	if(song->genre) ret->genre= strdup(song->genre);
-	if(song->composer) ret->composer= strdup(song->composer);
-	if(song->disc) ret->disc = strdup(song->disc);
-	if(song->comment) ret->comment = strdup(song->comment);
+	if(song->file) ret->file = str_pool_dup(song->file);
+	if(song->artist) ret->artist = str_pool_dup(song->artist);
+	if(song->album) ret->album = str_pool_dup(song->album);
+	if(song->title) ret->title = str_pool_dup(song->title);
+	if(song->track) ret->track = str_pool_dup(song->track);
+	if(song->name) ret->name = str_pool_dup(song->name);
+	if(song->date) ret->date = str_pool_dup(song->date);
+	if(song->genre) ret->genre= str_pool_dup(song->genre);
+	if(song->composer) ret->composer= str_pool_dup(song->composer);
+	if(song->disc) ret->disc = str_pool_dup(song->disc);
+	if(song->comment) ret->comment = str_pool_dup(song->comment);
 	ret->time = song->time;
 	ret->pos = song->pos;
 	ret->id = song->id;
@@ -983,7 +984,7 @@ static void mpd_initDirectory(mpd_Directory * directory) {
 
 static void mpd_finishDirectory(mpd_Directory * directory) {
 	if (directory->path)
-		free(directory->path);
+		str_pool_put(directory->path);
 }
 
 mpd_Directory * mpd_newDirectory(void) {
@@ -1004,7 +1005,7 @@ mpd_Directory * mpd_directoryDup(mpd_Directory * directory) {
 	mpd_Directory * ret = mpd_newDirectory();
 
 	if (directory->path)
-		ret->path = strdup(directory->path);
+		ret->path = str_pool_dup(directory->path);
 
 	return ret;
 }
@@ -1015,7 +1016,7 @@ static void mpd_initPlaylistFile(mpd_PlaylistFile * playlist) {
 
 static void mpd_finishPlaylistFile(mpd_PlaylistFile * playlist) {
 	if (playlist->path)
-		free(playlist->path);
+		str_pool_put(playlist->path);
 }
 
 mpd_PlaylistFile * mpd_newPlaylistFile(void) {
@@ -1035,7 +1036,7 @@ mpd_PlaylistFile * mpd_playlistFileDup(mpd_PlaylistFile * playlist) {
 	mpd_PlaylistFile * ret = mpd_newPlaylistFile();
 
 	if (playlist->path)
-		ret->path = strdup(playlist->path);
+		ret->path = str_pool_dup(playlist->path);
 
 	return ret;
 }
@@ -1091,7 +1092,7 @@ mpd_InfoEntity * mpd_getNextInfoEntity(mpd_Connection * connection) {
 			entity->type = MPD_INFO_ENTITY_TYPE_SONG;
 			entity->info.song = mpd_newSong();
 			entity->info.song->file =
-				strdup(connection->returnElement->value);
+				str_pool_dup(connection->returnElement->value);
 		}
 		else if(strcmp(connection->returnElement->name,
 					"directory")==0) {
@@ -1099,14 +1100,14 @@ mpd_InfoEntity * mpd_getNextInfoEntity(mpd_Connection * connection) {
 			entity->type = MPD_INFO_ENTITY_TYPE_DIRECTORY;
 			entity->info.directory = mpd_newDirectory();
 			entity->info.directory->path =
-				strdup(connection->returnElement->value);
+				str_pool_dup(connection->returnElement->value);
 		}
 		else if(strcmp(connection->returnElement->name,"playlist")==0) {
 			entity = mpd_newInfoEntity();
 			entity->type = MPD_INFO_ENTITY_TYPE_PLAYLISTFILE;
 			entity->info.playlistFile = mpd_newPlaylistFile();
 			entity->info.playlistFile->path =
-				strdup(connection->returnElement->value);
+				str_pool_dup(connection->returnElement->value);
 		}
 		else if(strcmp(connection->returnElement->name, "cpos") == 0){
 			entity = mpd_newInfoEntity();
@@ -1135,23 +1136,23 @@ mpd_InfoEntity * mpd_getNextInfoEntity(mpd_Connection * connection) {
 				strlen(re->value)) {
 			if(!entity->info.song->artist &&
 					strcmp(re->name,"Artist")==0) {
-				entity->info.song->artist = strdup(re->value);
+				entity->info.song->artist = str_pool_dup(re->value);
 			}
 			else if(!entity->info.song->album &&
 					strcmp(re->name,"Album")==0) {
-				entity->info.song->album = strdup(re->value);
+				entity->info.song->album = str_pool_dup(re->value);
 			}
 			else if(!entity->info.song->title &&
 					strcmp(re->name,"Title")==0) {
-				entity->info.song->title = strdup(re->value);
+				entity->info.song->title = str_pool_dup(re->value);
 			}
 			else if(!entity->info.song->track &&
 					strcmp(re->name,"Track")==0) {
-				entity->info.song->track = strdup(re->value);
+				entity->info.song->track = str_pool_dup(re->value);
 			}
 			else if(!entity->info.song->name &&
 					strcmp(re->name,"Name")==0) {
-				entity->info.song->name = strdup(re->value);
+				entity->info.song->name = str_pool_dup(re->value);
 			}
 			else if(entity->info.song->time==MPD_SONG_NO_TIME &&
 					strcmp(re->name,"Time")==0) {
@@ -1167,23 +1168,23 @@ mpd_InfoEntity * mpd_getNextInfoEntity(mpd_Connection * connection) {
 			}
 			else if(!entity->info.song->date &&
 					strcmp(re->name, "Date") == 0) {
-				entity->info.song->date = strdup(re->value);
+				entity->info.song->date = str_pool_dup(re->value);
 			}
 			else if(!entity->info.song->genre &&
 					strcmp(re->name, "Genre") == 0) {
-				entity->info.song->genre = strdup(re->value);
+				entity->info.song->genre = str_pool_dup(re->value);
 			}
 			else if(!entity->info.song->composer &&
 					strcmp(re->name, "Composer") == 0) {
-				entity->info.song->composer = strdup(re->value);
+				entity->info.song->composer = str_pool_dup(re->value);
 			}
 			else if(!entity->info.song->disc &&
 					strcmp(re->name, "Disc") == 0) {
-				entity->info.song->disc = strdup(re->value);
+				entity->info.song->disc = str_pool_dup(re->value);
 			}
 			else if(!entity->info.song->comment &&
 					strcmp(re->name, "Comment") == 0) {
-				entity->info.song->comment = strdup(re->value);
+				entity->info.song->comment = str_pool_dup(re->value);
 			}
 		}
 		else if(entity->type == MPD_INFO_ENTITY_TYPE_DIRECTORY) {
diff --git a/src/str_pool.c b/src/str_pool.c
new file mode 100644
index 000000000..74839b59d
--- /dev/null
+++ b/src/str_pool.c
@@ -0,0 +1,125 @@
+/* ncmpc
+ * Copyright (C) 2008 Max Kellermann <max@duempel.org>
+ * This project's homepage is: 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include "str_pool.h"
+
+#include <assert.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define NUM_SLOTS 4096
+
+struct slot {
+	struct slot *next;
+	unsigned char ref;
+	char value[1];
+} __attribute__((packed));
+
+struct slot *slots[NUM_SLOTS];
+
+static inline unsigned
+calc_hash(const char *p)
+{
+	unsigned hash = 5381;
+
+	assert(p != NULL);
+
+	while (*p != 0)
+		hash = (hash << 5) + hash + *p++;
+
+	return hash;
+}
+
+static inline struct slot *
+value_to_slot(char *value)
+{
+	return (struct slot*)(value - offsetof(struct slot, value));
+}
+
+static struct slot *slot_alloc(struct slot *next, const char *value)
+{
+	size_t length = strlen(value);
+	struct slot *slot = malloc(sizeof(*slot) + length);
+	if (slot == NULL)
+		abort(); /* XXX */
+
+	slot->next = next;
+	slot->ref = 1;
+	memcpy(slot->value, value, length + 1);
+	return slot;
+}
+
+char *str_pool_get(const char *value)
+{
+	struct slot **slot_p, *slot;
+
+	slot_p = &slots[calc_hash(value) % NUM_SLOTS];
+	for (slot = *slot_p; slot != NULL; slot = slot->next) {
+		if (strcmp(value, slot->value) == 0 && slot->ref < 0xff) {
+			assert(slot->ref > 0);
+			++slot->ref;
+			return slot->value;
+		}
+	}
+
+	slot = slot_alloc(*slot_p, value);
+	*slot_p = slot;
+	return slot->value;
+}
+
+char *str_pool_dup(char *value)
+{
+	struct slot *slot = value_to_slot(value);
+
+	assert(slot->ref > 0);
+
+	if (slot->ref < 0xff) {
+		++slot->ref;
+		return value;
+	} else {
+		/* the reference counter overflows above 0xff;
+		   duplicate the value, and start with 1 */
+		struct slot **slot_p =
+			&slots[calc_hash(slot->value) % NUM_SLOTS];
+		slot = slot_alloc(*slot_p, slot->value);
+		*slot_p = slot;
+		return slot->value;
+	}
+}
+
+void str_pool_put(char *value)
+{
+	struct slot **slot_p, *slot;
+
+	slot = value_to_slot(value);
+	assert(slot->ref > 0);
+	--slot->ref;
+
+	if (slot->ref > 0)
+		return;
+
+	for (slot_p = &slots[calc_hash(value) % NUM_SLOTS];
+	     *slot_p != slot;
+	     slot_p = &(*slot_p)->next) {
+		assert(*slot_p != NULL);
+	}
+
+	*slot_p = slot->next;
+	free(slot);
+}
diff --git a/src/str_pool.h b/src/str_pool.h
new file mode 100644
index 000000000..4a0ad12d8
--- /dev/null
+++ b/src/str_pool.h
@@ -0,0 +1,28 @@
+/* ncmpc
+ * Copyright (C) 2008 Max Kellermann <max@duempel.org>
+ * This project's homepage is: 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#ifndef STR_POOL_H
+#define STR_POOL_H
+
+char *str_pool_get(const char *value);
+
+char *str_pool_dup(char *value);
+
+void str_pool_put(char *value);
+
+#endif