db_plugin: introducing a plugin API for the song database

Makefile.am

@@ -272,6 +272,8 @@ src_mpd_SOURCES = \
 	src/database.c \
 	src/db_save.c src/db_save.h \
 	src/db_print.c src/db_print.h \
+	src/db_plugin.h \
+	src/db/simple_db_plugin.c src/db/simple_db_plugin.h \
 	src/dirvec.c \
 	src/exclude.c \
 	src/fd_util.c \

src/database.c

@@ -20,8 +20,11 @@
 #include "config.h"
 #include "database.h"
 #include "db_save.h"
+#include "db_plugin.h"
+#include "db/simple_db_plugin.h"
 #include "directory.h"
 #include "stats.h"
+#include "conf.h"
 
 #include <glib.h>
 
@@ -35,11 +38,8 @@
 #undef G_LOG_DOMAIN
 #define G_LOG_DOMAIN "database"
 
-static char *database_path;
-
-static struct directory *music_root;
-
-static time_t database_mtime;
+static struct db *db;
+static bool db_is_open;
 
 /**
  * The quark used for GError.domain.
@@ -50,49 +50,50 @@ db_quark(void)
 	return g_quark_from_static_string("database");
 }
 
-void
-db_init(const char *path)
+bool
+db_init(const struct config_param *path, GError **error_r)
 {
-	database_path = g_strdup(path);
+	assert(db == NULL);
+	assert(!db_is_open);
 
-	if (path != NULL)
-		music_root = directory_new("", NULL);
-}
+	if (path == NULL)
+		return true;
 
-void
-db_finish(void)
-{
-	assert((database_path == NULL) == (music_root == NULL));
+	struct config_param *param = config_new_param("database", path->line);
+	config_add_block_param(param, "path", path->value, path->line);
+
+	db = db_plugin_new(&simple_db_plugin, param, error_r);
 
-	if (music_root != NULL)
-		directory_free(music_root);
+	config_param_free(param);
 
-	g_free(database_path);
+	return db != NULL;
 }
 
 void
-db_clear(void)
+db_finish(void)
 {
-	assert(music_root != NULL);
+	if (db_is_open)
+		db_plugin_close(db);
 
-	directory_free(music_root);
-	music_root = directory_new("", NULL);
+	if (db != NULL)
+		db_plugin_free(db);
 }
 
 struct directory *
 db_get_root(void)
 {
-	assert(music_root != NULL);
+	assert(db != NULL);
 
-	return music_root;
+	return simple_db_get_root(db);
 }
 
 struct directory *
 db_get_directory(const char *name)
 {
-	if (music_root == NULL)
+	if (db == NULL)
 		return NULL;
 
+	struct directory *music_root = db_get_root();
 	if (name == NULL)
 		return music_root;
 
@@ -106,9 +107,10 @@ db_get_song(const char *file)
 
 	g_debug("get song: %s", file);
 
-	if (music_root == NULL)
+	if (db == NULL)
 		return NULL;
 
+	struct directory *music_root = db_get_root();
 	return directory_lookup_song(music_root, file);
 }
 
@@ -119,7 +121,7 @@ db_walk(const char *name,
 {
 	struct directory *directory;
 
-	if (music_root == NULL)
+	if (db == NULL)
 		return -1;
 
 	if ((directory = db_get_directory(name)) == NULL) {
@@ -134,156 +136,35 @@ db_walk(const char *name,
 }
 
 bool
-db_check(GError **error_r)
-{
-	struct stat st;
-
-	assert(database_path != NULL);
-
-	/* Check if the file exists */
-	if (access(database_path, F_OK)) {
-		/* If the file doesn't exist, we can't check if we can write
-		 * it, so we are going to try to get the directory path, and
-		 * see if we can write a file in that */
-		char *dirPath = g_path_get_dirname(database_path);
-
-		/* Check that the parent part of the path is a directory */
-		if (stat(dirPath, &st) < 0) {
-			g_free(dirPath);
-			g_set_error(error_r, db_quark(), errno,
-				    "Couldn't stat parent directory of db file "
-				    "\"%s\": %s",
-				    database_path, g_strerror(errno));
-			return false;
-		}
-
-		if (!S_ISDIR(st.st_mode)) {
-			g_free(dirPath);
-			g_set_error(error_r, db_quark(), 0,
-				    "Couldn't create db file \"%s\" because the "
-				    "parent path is not a directory",
-				    database_path);
-			return false;
-		}
-
-		/* Check if we can write to the directory */
-		if (access(dirPath, X_OK | W_OK)) {
-			g_set_error(error_r, db_quark(), errno,
-				    "Can't create db file in \"%s\": %s",
-				    dirPath, g_strerror(errno));
-			g_free(dirPath);
-			return false;
-		}
-
-		g_free(dirPath);
-
-		return true;
-	}
-
-	/* Path exists, now check if it's a regular file */
-	if (stat(database_path, &st) < 0) {
-		g_set_error(error_r, db_quark(), errno,
-			    "Couldn't stat db file \"%s\": %s",
-			    database_path, g_strerror(errno));
-		return false;
-	}
-
-	if (!S_ISREG(st.st_mode)) {
-		g_set_error(error_r, db_quark(), 0,
-			    "db file \"%s\" is not a regular file",
-			    database_path);
-		return false;
-	}
-
-	/* And check that we can write to it */
-	if (access(database_path, R_OK | W_OK)) {
-		g_set_error(error_r, db_quark(), errno,
-			    "Can't open db file \"%s\" for reading/writing: %s",
-			    database_path, g_strerror(errno));
-		return false;
-	}
-
-	return true;
-}
-
-bool
 db_save(GError **error_r)
 {
-	FILE *fp;
-	struct stat st;
-
-	assert(database_path != NULL);
-	assert(music_root != NULL);
-
-	g_debug("removing empty directories from DB");
-	directory_prune_empty(music_root);
-
-	g_debug("sorting DB");
-
-	directory_sort(music_root);
-
-	g_debug("writing DB");
-
-	fp = fopen(database_path, "w");
-	if (!fp) {
-		g_set_error(error_r, db_quark(), errno,
-			    "unable to write to db file \"%s\": %s",
-			    database_path, g_strerror(errno));
-		return false;
-	}
+	assert(db != NULL);
+	assert(db_is_open);
 
-	db_save_internal(fp, music_root);
-
-	if (ferror(fp)) {
-		g_set_error(error_r, db_quark(), errno,
-			    "Failed to write to database file: %s",
-			    g_strerror(errno));
-		fclose(fp);
-		return false;
-	}
-
-	fclose(fp);
-
-	if (stat(database_path, &st) == 0)
-		database_mtime = st.st_mtime;
-
-	return true;
+	return simple_db_save(db, error_r);
 }
 
 bool
 db_load(GError **error)
 {
-	FILE *fp = NULL;
-	struct stat st;
+	assert(db != NULL);
+	assert(!db_is_open);
 
-	assert(database_path != NULL);
-	assert(music_root != NULL);
-
-	fp = fopen(database_path, "r");
-	if (fp == NULL) {
-		g_set_error(error, db_quark(), errno,
-			    "Failed to open database file \"%s\": %s",
-			    database_path, strerror(errno));
+	if (!db_plugin_open(db, error))
 		return false;
-	}
 
-	if (!db_load_internal(fp, music_root, error)) {
-		fclose(fp);
-		return false;
-	}
-
-	fclose(fp);
+	db_is_open = true;
 
 	stats_update();
 
-	if (stat(database_path, &st) == 0)
-		database_mtime = st.st_mtime;
-
 	return true;
 }
 
 time_t
 db_get_mtime(void)
 {
-	return database_mtime;
+	assert(db != NULL);
+	assert(db_is_open);
+
+	return simple_db_get_mtime(db);
 }

src/database.h

@@ -25,6 +25,7 @@
 #include <sys/time.h>
 #include <stdbool.h>
 
+struct config_param;
 struct directory;
 
 /**
@@ -32,19 +33,13 @@ struct directory;
  *
  * @param path the absolute path of the database file
  */
-void
-db_init(const char *path);
+bool
+db_init(const struct config_param *path, GError **error_r);
 
 void
 db_finish(void);
 
 /**
- * Clear the database.
- */
-void
-db_clear(void);
-
-/**
  * Returns the root directory object.  Returns NULL if there is no
  * configured music directory.
  */

src/db/simple_db_plugin.c

+/*
+ * Copyright (C) 2003-2011 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 "simple_db_plugin.h"
+#include "db_internal.h"
+#include "db_save.h"
+#include "conf.h"
+#include "glib_compat.h"
+#include "directory.h"
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <errno.h>
+
+struct simple_db {
+	struct db base;
+
+	char *path;
+
+	struct directory *root;
+
+	time_t mtime;
+};
+
+G_GNUC_CONST
+static inline GQuark
+simple_db_quark(void)
+{
+	return g_quark_from_static_string("simple_db");
+}
+
+static struct db *
+simple_db_init(const struct config_param *param, GError **error_r)
+{
+	struct simple_db *db = g_malloc(sizeof(*db));
+	db_base_init(&db->base, &simple_db_plugin);
+
+	GError *error = NULL;
+	db->path = config_dup_block_path(param, "path", error_r);
+	if (db->path == NULL) {
+		g_free(db);
+		if (error != NULL)
+			g_propagate_error(error_r, error);
+		else
+			g_set_error(error_r, simple_db_quark(), 0,
+				    "No \"path\" parameter specified");
+		return NULL;
+	}
+
+	return &db->base;
+}
+
+static void
+simple_db_finish(struct db *_db)
+{
+	struct simple_db *db = (struct simple_db *)_db;
+
+	g_free(db->path);
+	g_free(db);
+}
+
+static bool
+simple_db_check(struct simple_db *db, GError **error_r)
+{
+	assert(db != NULL);
+	assert(db->path != NULL);
+
+	/* Check if the file exists */
+	if (access(db->path, F_OK)) {
+		/* If the file doesn't exist, we can't check if we can write
+		 * it, so we are going to try to get the directory path, and
+		 * see if we can write a file in that */
+		char *dirPath = g_path_get_dirname(db->path);
+
+		/* Check that the parent part of the path is a directory */
+		struct stat st;
+		if (stat(dirPath, &st) < 0) {
+			g_free(dirPath);
+			g_set_error(error_r, simple_db_quark(), errno,
+				    "Couldn't stat parent directory of db file "
+				    "\"%s\": %s",
+				    db->path, g_strerror(errno));
+			return false;
+		}
+
+		if (!S_ISDIR(st.st_mode)) {
+			g_free(dirPath);
+			g_set_error(error_r, simple_db_quark(), 0,
+				    "Couldn't create db file \"%s\" because the "
+				    "parent path is not a directory",
+				    db->path);
+			return false;
+		}
+
+		/* Check if we can write to the directory */
+		if (access(dirPath, X_OK | W_OK)) {
+			g_set_error(error_r, simple_db_quark(), errno,
+				    "Can't create db file in \"%s\": %s",
+				    dirPath, g_strerror(errno));
+			g_free(dirPath);
+			return false;
+		}
+
+		g_free(dirPath);
+
+		return true;
+	}
+
+	/* Path exists, now check if it's a regular file */
+	struct stat st;
+	if (stat(db->path, &st) < 0) {
+		g_set_error(error_r, simple_db_quark(), errno,
+			    "Couldn't stat db file \"%s\": %s",
+			    db->path, g_strerror(errno));
+		return false;
+	}
+
+	if (!S_ISREG(st.st_mode)) {
+		g_set_error(error_r, simple_db_quark(), 0,
+			    "db file \"%s\" is not a regular file",
+			    db->path);
+		return false;
+	}
+
+	/* And check that we can write to it */
+	if (access(db->path, R_OK | W_OK)) {
+		g_set_error(error_r, simple_db_quark(), errno,
+			    "Can't open db file \"%s\" for reading/writing: %s",
+			    db->path, g_strerror(errno));
+		return false;
+	}
+
+	return true;
+}
+
+static bool
+simple_db_load(struct simple_db *db, GError **error_r)
+{
+	assert(db != NULL);
+	assert(db->path != NULL);
+	assert(db->root != NULL);
+
+	FILE *fp = fopen(db->path, "r");
+	if (fp == NULL) {
+		g_set_error(error_r, simple_db_quark(), errno,
+			    "Failed to open database file \"%s\": %s",
+			    db->path, g_strerror(errno));
+		return false;
+	}
+
+	if (!db_load_internal(fp, db->root, error_r)) {
+		fclose(fp);
+		return false;
+	}
+
+	fclose(fp);
+
+	struct stat st;
+	if (stat(db->path, &st) == 0)
+		db->mtime = st.st_mtime;
+
+	return true;
+}
+
+static bool
+simple_db_open(struct db *_db, G_GNUC_UNUSED GError **error_r)
+{
+	struct simple_db *db = (struct simple_db *)_db;
+
+	db->root = directory_new("", NULL);
+	db->mtime = 0;
+
+	GError *error = NULL;
+	if (!simple_db_load(db, &error)) {
+		directory_free(db->root);
+
+		g_warning("Failed to load database: %s", error->message);
+		g_error_free(error);
+
+		if (!simple_db_check(db, error_r))
+			return false;
+
+		db->root = directory_new("", NULL);
+	}
+
+	return true;
+}
+
+static void
+simple_db_close(struct db *_db)
+{
+	struct simple_db *db = (struct simple_db *)_db;
+
+	assert(db->root != NULL);
+
+	directory_free(db->root);
+}
+
+const struct db_plugin simple_db_plugin = {
+	.name = "simple",
+	.init = simple_db_init,
+	.finish = simple_db_finish,
+	.open = simple_db_open,
+	.close = simple_db_close,
+};
+
+struct directory *
+simple_db_get_root(struct db *_db)
+{
+	struct simple_db *db = (struct simple_db *)_db;
+
+	assert(db != NULL);
+	assert(db->root != NULL);
+
+	return db->root;
+}
+
+bool
+simple_db_save(struct db *_db, GError **error_r)
+{
+	struct simple_db *db = (struct simple_db *)_db;
+	struct directory *music_root = db->root;
+
+	g_debug("removing empty directories from DB");
+	directory_prune_empty(music_root);
+
+	g_debug("sorting DB");
+
+	directory_sort(music_root);
+
+	g_debug("writing DB");
+
+	FILE *fp = fopen(db->path, "w");
+	if (!fp) {
+		g_set_error(error_r, simple_db_quark(), errno,
+			    "unable to write to db file \"%s\": %s",
+			    db->path, g_strerror(errno));
+		return false;
+	}
+
+	db_save_internal(fp, music_root);
+
+	if (ferror(fp)) {
+		g_set_error(error_r, simple_db_quark(), errno,
+			    "Failed to write to database file: %s",
+			    g_strerror(errno));
+		fclose(fp);
+		return false;
+	}
+
+	fclose(fp);
+
+	struct stat st;
+	if (stat(db->path, &st) == 0)
+		db->mtime = st.st_mtime;
+
+	return true;
+}
+
+time_t
+simple_db_get_mtime(const struct db *_db)
+{
+	const struct simple_db *db = (const struct simple_db *)_db;
+
+	assert(db != NULL);
+	assert(db->root != NULL);
+
+	return db->mtime;
+}

src/db/simple_db_plugin.h

+/*
+ * Copyright (C) 2003-2011 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_SIMPLE_DB_PLUGIN_H
+#define MPD_SIMPLE_DB_PLUGIN_H
+
+#include <glib.h>
+#include <stdbool.h>
+#include <time.h>
+
+extern const struct db_plugin simple_db_plugin;
+
+struct db;
+
+G_GNUC_PURE
+struct directory *
+simple_db_get_root(struct db *db);
+
+bool
+simple_db_save(struct db *db, GError **error_r);
+
+G_GNUC_PURE
+time_t
+simple_db_get_mtime(const struct db *db);
+
+#endif

src/db_internal.h

+/*
+ * Copyright (C) 2003-2011 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_DB_INTERNAL_H
+#define MPD_DB_INTERNAL_H
+
+#include "db_plugin.h"
+
+#include <assert.h>
+
+static inline void
+db_base_init(struct db *db, const struct db_plugin *plugin)
+{
+	assert(plugin != NULL);
+
+	db->plugin = plugin;
+}
+
+#endif

src/db_plugin.h

+/*
+ * Copyright (C) 2003-2011 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.
+ */
+
+/** \file
+ *
+ * This header declares the db_plugin class.  It describes a
+ * plugin API for databases of song metadata.
+ */
+
+#ifndef MPD_DB_PLUGIN_H
+#define MPD_DB_PLUGIN_H
+
+#include <glib.h>
+#include <assert.h>
+#include <stdbool.h>
+
+struct config_param;
+
+struct db {
+	const struct db_plugin *plugin;
+};
+
+struct db_plugin {
+	const char *name;
+
+	/**
+         * Allocates and configures a database.
+	 */
+	struct db *(*init)(const struct config_param *param, GError **error_r);
+
+	/**
+	 * Free instance data.
+         */
+	void (*finish)(struct db *db);
+
+	/**
+         * Open the database.  Read it into memory if applicable.
+	 */
+	bool (*open)(struct db *db, GError **error_r);
+
+	/**
+         * Close the database, free allocated memory.
+	 */
+	void (*close)(struct db *db);
+};
+
+G_GNUC_MALLOC
+static inline struct db *
+db_plugin_new(const struct db_plugin *plugin, const struct config_param *param,
+	      GError **error_r)
+{
+	assert(plugin != NULL);
+	assert(plugin->init != NULL);
+	assert(plugin->finish != NULL);
+	assert(error_r == NULL || *error_r == NULL);
+
+	struct db *db = plugin->init(param, error_r);
+	assert(db == NULL || db->plugin == plugin);
+	assert(db != NULL || error_r == NULL || *error_r != NULL);
+
+	return db;
+}
+
+static inline void
+db_plugin_free(struct db *db)
+{
+	assert(db != NULL);
+	assert(db->plugin != NULL);
+	assert(db->plugin->finish != NULL);
+
+	db->plugin->finish(db);
+}
+
+static inline bool
+db_plugin_open(struct db *db, GError **error_r)
+{
+	assert(db != NULL);
+	assert(db->plugin != NULL);
+
+	return db->plugin->open != NULL
+		? db->plugin->open(db, error_r)
+		: true;
+}
+
+static inline void
+db_plugin_close(struct db *db)
+{
+	assert(db != NULL);
+	assert(db->plugin != NULL);
+
+	if (db->plugin->close != NULL)
+		db->plugin->close(db);
+}
+
+#endif

src/main.c

@@ -156,44 +156,31 @@ glue_mapper_init(GError **error_r)
 static bool
 glue_db_init_and_load(void)
 {
-	GError *error = NULL;
-	char *path = config_dup_path(CONF_DB_FILE, &error);
-	if (path == NULL && error != NULL)
-		MPD_ERROR("%s", error->message);
+	const struct config_param *path = config_get_param(CONF_DB_FILE);
 
+	GError *error = NULL;
 	bool ret;
 
 	if (!mapper_has_music_directory()) {
-		g_free(path);
 		if (path != NULL)
 			g_message("Found " CONF_DB_FILE " setting without "
 				  CONF_MUSIC_DIR " - disabling database");
-		db_init(NULL);
+		db_init(NULL, NULL);
 		return true;
 	}
 
 	if (path == NULL)
 		MPD_ERROR(CONF_DB_FILE " setting missing");
 
-	db_init(path);
-	g_free(path);
+	if (!db_init(path, &error))
+		MPD_ERROR("%s", error->message);
 
 	ret = db_load(&error);
-	if (!ret) {
-		g_warning("Failed to load database: %s", error->message);
-		g_error_free(error);
-		error = NULL;
-
-		if (!db_check(&error))
-			MPD_ERROR("%s", error->message);
-
-		db_clear();
-
-		/* run database update after daemonization */
-		return false;
-	}
+	if (!ret)
+		MPD_ERROR("%s", error->message);
 
-	return true;
+	/* run database update after daemonization? */
+	return db_exists();
 }
 
 /**