GIOModule: Use unique names for load/unload symbols

GIO modules should include their name into their exported symbols to
make them unique. This avoids symbol clash when building modules
statically.

extract_name() function is copied from GStreamer which recently
switched to the same symbol naming scheme.

https://bugzilla.gnome.org/show_bug.cgi?id=684282

gio/giomodule-priv.c

@@ -0,0 +1,69 @@
+/* GIO - GLib Input, Output and Streaming Library
+ *
+ * Copyright (C) 2017 Collabora Inc.
+ *
+ * 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 2.1 of the License, 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, see <http://www.gnu.org/licenses/>.
+ *
+ * Author: Xavier Claessens <xavier.claessens@collabora.com>
+ */
+
+#include "config.h"
+#include "giomodule.h"
+#include "giomodule-priv.h"
+
+#include <string.h>
+
+/**
+ * _g_io_module_extract_name:
+ * @filename: filename of a GIOModule
+ *
+ * Extract the plugin name from its filename. It removes optional "lib" or
+ * "libgio" prefix, and removes everything after the first dot. For example:
+ * "libgiognutls.so" -> "gnutls".
+ *
+ * Returns: (transfer full): the module's name
+ */
+gchar *
+_g_io_module_extract_name (const char *filename)
+{
+  gchar *bname, *name;
+  const gchar *dot;
+  gsize prefix_len, len;
+  gsize i;
+
+  bname = g_path_get_basename (filename);
+  for (i = 0; bname[i]; ++i)
+    {
+      if (bname[i] == '-')
+        bname[i] = '_';
+    }
+
+  if (g_str_has_prefix (bname, "libgio"))
+    prefix_len = 6;
+  else if (g_str_has_prefix (bname, "lib"))
+    prefix_len = 3;
+  else
+    prefix_len = 0; /* use whole name (minus suffix) as plugin name */
+
+  dot = strchr (bname, '.');
+  if (dot != NULL)
+    len = dot - bname - prefix_len;
+  else
+    len = strlen (bname + prefix_len);
+
+  name = g_strndup (bname + prefix_len, len);
+  g_free (bname);
+
+  return name;
+}