modify wire plugin load logic to use reference counting

src/wire/wire.c

@@ -1,6 +1,6 @@
 /*
   This file is part of TALER
-  (C) 2015, 2016, 2017 GNUnet e.V.
+  (C) 2015, 2016, 2017, 2018 GNUnet e.V.
 
   TALER 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
@@ -23,6 +23,50 @@
 #include "taler_util.h"
 #include "taler_wire_lib.h"
 
+
+/**
+ * A wire plugin that we have loaded.
+ */
+struct WirePlugin
+{
+  /**
+   * We keep these in a DLL.
+   */
+  struct WirePlugin *next;
+
+  /**
+   * We keep these in a DLL.
+   */
+  struct WirePlugin *prev;
+
+  /**
+   * Type of this wire plugin.
+   */
+  char *type;
+
+  /**
+   * Wire plugin
+   */
+  struct TALER_WIRE_Plugin *plugin;
+
+  /**
+   * Reference counter for the plugin.
+   */
+  unsigned int rc;
+};
+
+
+/**
+ * Head of the DLL of loaded wire plugins.
+ */
+static struct WirePlugin *wp_head;
+
+/**
+ * Tail of the DLL of loaded wire plugins.
+ */
+static struct WirePlugin *wp_tail;
+
+
 /**
  * Load a WIRE plugin.
  *
@@ -36,7 +80,15 @@ TALER_WIRE_plugin_load (const struct GNUNET_CONFIGURATION_Handle *cfg,
 {
   char *lib_name;
   struct TALER_WIRE_Plugin *plugin;
+  struct WirePlugin *wp;
 
+  for (wp = wp_head; NULL != wp; wp = wp->next)
+    if (0 == strcasecmp (plugin_name,
+                         wp->type))
+    {
+      wp->rc++;
+      return wp->plugin;
+    }
   (void) GNUNET_asprintf (&lib_name,
                           "libtaler_plugin_wire_%s",
                           plugin_name);
@@ -46,6 +98,15 @@ TALER_WIRE_plugin_load (const struct GNUNET_CONFIGURATION_Handle *cfg,
     plugin->library_name = lib_name;
   else
     GNUNET_free (lib_name);
+  if (NULL == plugin)
+    return NULL;
+  wp = GNUNET_new (struct WirePlugin);
+  wp->plugin = plugin;
+  wp->type = GNUNET_strdup (plugin_name);
+  GNUNET_CONTAINER_DLL_insert (wp_head,
+                               wp_tail,
+                               wp);
+  wp->rc = 1;
   return plugin;
 }
 
@@ -58,10 +119,26 @@ TALER_WIRE_plugin_load (const struct GNUNET_CONFIGURATION_Handle *cfg,
 void
 TALER_WIRE_plugin_unload (struct TALER_WIRE_Plugin *plugin)
 {
+  struct WirePlugin *wp;
   char *lib_name;
 
   if (NULL == plugin)
     return;
+  for (wp = wp_head; NULL != wp; wp = wp->next)
+  {
+    if (plugin == wp->plugin)
+    {
+      wp->rc--;
+      if (0 < wp->rc)
+        return;
+      GNUNET_CONTAINER_DLL_remove (wp_head,
+                                   wp_tail,
+                                   wp);
+      GNUNET_free (wp->type);
+      GNUNET_free (wp);
+      break;
+    }
+  }
   lib_name = plugin->library_name;
   GNUNET_assert (NULL == GNUNET_PLUGIN_unload (lib_name,
                                                plugin));