clean up and factor out the 'shm' code

Remove the shm code from the engine and the service and put it in a
separate convenience library in shm/.

Remove the vestigial shmdir weirdness from the service (since shmdir is
now always relative to XDG_RUNTIME_DIR and has been for some time).

The purpose of this is so that dconf-engine can be properly unit-tested.
dconf-engine now has five points of contact with the world (excluding
the users of the engine themselves):

  - the DCONF_PROFILE environment variable

  - fopen() of profile files

  - shm

  - gvdb

  - dbus

The environment variable is quite easily controlled.  fopen() is
intercepted in the engine testcase with a interpose of the libc symbol.

With this commit now each of dbus, gvdb and shm are implemented in
separate utility modules that can be mocked from the testcases.

4 files changed, 186 insertions, 0 deletions

diff --git a/shm/.gitignore b/shm/.gitignore
new file mode 100644
index 0000000..16d8712
--- /dev/null
+++ b/shm/.gitignore
@@ -0,0 +1,2 @@
+libdconf-shm.a
+libdconf-shm-shared.a
diff --git a/shm/Makefile.am b/shm/Makefile.am
new file mode 100644
index 0000000..b3068cb
--- /dev/null
+++ b/shm/Makefile.am
@@ -0,0 +1,12 @@
+include $(top_srcdir)/Makefile.gtester
+
+noinst_LIBRARIES = libdconf-shm.a libdconf-shm-shared.a
+libdconf_shm_a_CFLAGS = -Wall
+INCLUDES = $(glib_CFLAGS)
+
+libdconf_shm_a_SOURCES = \
+	dconf-shm.h		\
+	dconf-shm.c
+
+libdconf_shm_shared_a_CFLAGS = -fPIC -DPIC $(libdconf_shm_a_CFLAGS)
+libdconf_shm_shared_a_SOURCES = $(libdconf_shm_a_SOURCES)
diff --git a/shm/dconf-shm.c b/shm/dconf-shm.c
new file mode 100644
index 0000000..62439a0
--- /dev/null
+++ b/shm/dconf-shm.c
@@ -0,0 +1,138 @@
+/*
+ * Copyright © 2010 Codethink Limited
+ * Copyright © 2012 Canonical Limited
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the licence, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ *
+ * Author: Ryan Lortie <desrt@desrt.ca>
+ */
+
+#include "dconf-shm.h"
+
+#include <sys/mman.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+
+static gchar *
+dconf_shm_get_shmdir (void)
+{
+  static gchar *shmdir;
+
+  if (g_once_init_enter (&shmdir))
+    g_once_init_leave (&shmdir, g_build_filename (g_get_user_runtime_dir (), "dconf", NULL));
+
+  return shmdir;
+}
+
+void
+dconf_shm_close (guint8 *shm)
+{
+  if (shm)
+    munmap (shm, 1);
+}
+
+guint8 *
+dconf_shm_open (const gchar *name)
+{
+  const gchar *shmdir;
+  gchar *filename;
+  void *memory;
+  gint fd;
+
+  shmdir = dconf_shm_get_shmdir ();
+  filename = g_build_filename (shmdir, name, NULL);
+  memory = NULL;
+  fd = -1;
+
+  if (g_mkdir_with_parents (shmdir, 0700) != 0)
+    {
+      g_critical ("unable to create directory '%s': %s.  dconf will not work properly.", shmdir, g_strerror (errno));
+      goto out;
+    }
+
+  fd = open (filename, O_RDWR | O_CREAT, 0600);
+  if (fd == -1)
+    {
+      g_critical ("unable to create file '%s': %s.  dconf will not work properly.", filename, g_strerror (errno));
+      goto out;
+    }
+
+  if (ftruncate (fd, 1) != 0)
+    {
+      g_critical ("failed to allocate file '%s': %s.  dconf will not work properly.", filename, g_strerror (errno));
+      goto out;
+    }
+
+  memory = mmap (NULL, 1, PROT_READ, MAP_SHARED, fd, 0);
+  g_assert (memory != NULL);
+
+  if (memory == MAP_FAILED)
+    {
+      g_critical ("failed to mmap file '%s': %s.  dconf will not work properly.", filename, g_strerror (errno));
+      memory = NULL;
+      goto out;
+    }
+
+ out:
+  g_free (filename);
+  close (fd);
+
+  return memory;
+}
+
+void
+dconf_shm_flag (const gchar *name)
+{
+  const gchar *shmdir;
+  gchar *filename;
+  gint fd;
+
+  shmdir = dconf_shm_get_shmdir ();
+  filename = g_build_filename (shmdir, name, NULL);
+
+  fd = open (filename, O_WRONLY);
+  if (fd >= 0)
+    {
+      guint8 *shm;
+
+      /* Easiest thing to do here would be write(fd, "\1", 1); but this
+       * causes problems on kernels (ie: OpenBSD) that don't sync up
+       * their filesystem cache with mmap()ed regions.
+       *
+       * Using mmap() works everywhere.
+       */
+      shm = mmap (NULL, 1, PROT_WRITE, MAP_SHARED, fd, 0);
+
+      if (shm != MAP_FAILED)
+        {
+          *shm = 1;
+
+          munmap (shm, 1);
+        }
+      else
+        g_warning ("failed to invalidate mmap file '%s': %s.", filename, g_strerror (errno));
+
+      close (fd);
+
+      unlink (filename);
+    }
+
+  else if (errno != ENOENT)
+    unlink (filename);
+
+  g_free (filename);
+}
diff --git a/shm/dconf-shm.h b/shm/dconf-shm.h
new file mode 100644
index 0000000..407375a
--- /dev/null
+++ b/shm/dconf-shm.h
@@ -0,0 +1,34 @@
+/*
+ * Copyright © 2010 Codethink Limited
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the licence, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ *
+ * Author: Ryan Lortie <desrt@desrt.ca>
+ */
+
+#ifndef __dconf_shm_h__
+#define __dconf_shm_h__
+
+#include <glib.h>
+
+G_GNUC_INTERNAL
+guint8 *                dconf_shm_open                                  (const gchar *name);
+G_GNUC_INTERNAL
+void                    dconf_shm_close                                 (guint8      *shm);
+G_GNUC_INTERNAL
+void                    dconf_shm_flag                                  (const gchar *name);
+
+#endif /* __dconf_shm_h__ */