libdpkg: Add new dbdir module

lib/dpkg/Makefile.am

@@ -7,6 +7,7 @@ pkgconfdir = $(sysconfdir)/@PACKAGE@
 AM_CPPFLAGS = \
 	-DLOCALEDIR=\"$(localedir)\" \
 	-DCONFIGDIR=\"$(pkgconfdir)\" \
+	-DADMINDIR=\"$(admindir)\" \
 	-idirafter $(top_srcdir)/lib/compat \
 	-I$(top_builddir) \
 	-I$(top_srcdir)/lib
@@ -28,6 +29,7 @@ libdpkg_a_SOURCES = \
 	cleanup.c \
 	command.c \
 	compress.c \
+	dbdir.c \
 	dbmodify.c \
 	debug.c \
 	dir.c \

lib/dpkg/dbdir.c

@@ -0,0 +1,92 @@
+/*
+ * libdpkg - Debian packaging suite library routines
+ * dbdir.c - on-disk database directory functions
+ *
+ * Copyright © 2011 Guillem Jover <guillem@debian.org>
+ *
+ * This 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 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, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+#include <compat.h>
+
+#include <sys/types.h>
+
+#include <stdlib.h>
+
+#include <dpkg/dpkg.h>
+#include <dpkg/dpkg-db.h>
+
+static const char *db_dir = ADMINDIR;
+
+/**
+ * Set current on-disk database directory.
+ *
+ * The directory is initially set to ADMINDIR, this function can be used to
+ * set the directory to a new value, or to set it to a default value if dir
+ * is NULL. For the latter the order is, value from environment variable
+ * DPKG_ADMINDIR, and then the built-in default ADMINDIR,
+ *
+ * @param dir The new databse directory, or NULL to set to default.
+ *
+ * @return The new database directory.
+ */
+const char *
+dpkg_db_set_dir(const char *dir)
+{
+	if (dir == NULL) {
+		const char *env;
+
+		env = getenv("DPKG_ADMINDIR");
+		if (env)
+			db_dir = env;
+		else
+			db_dir = ADMINDIR;
+	} else {
+		db_dir = dir;
+	}
+
+	return db_dir;
+}
+
+/**
+ * Get current on-disk database directory.
+ *
+ * @return The current database directory.
+ */
+const char *
+dpkg_db_get_dir(void)
+{
+	return db_dir;
+}
+
+/**
+ * Get a pathname to the current on-disk database directory.
+ *
+ * This function returns an allocated string, which should be freed with
+ * free(2).
+ *
+ * @param pathpart The pathpart to append to the new pathnme.
+ *
+ * @return The newly allocated pathname.
+ */
+char *
+dpkg_db_get_path(const char *pathpart)
+{
+	char *pathname;
+
+	m_asprintf(&pathname, "%s/%s", db_dir, pathpart);
+
+	return pathname;
+}

lib/dpkg/dpkg-db.h

@@ -207,6 +207,12 @@ struct pkginfo {
   struct trigpend *trigpend_head;
 };
 
+/*** from dbdir.c ***/
+
+const char *dpkg_db_set_dir(const char *dir);
+const char *dpkg_db_get_dir(void);
+char *dpkg_db_get_path(const char *pathpart);
+
 /*** from dbmodify.c ***/
 
 enum modstatdb_rw {