1 files changed, 95 insertions, 0 deletions
diff --git a/src/lib/subsys/subsys.h b/src/lib/subsys/subsys.h
new file mode 100644
index 0000000000..241ad7829c
--- /dev/null
+++ b/src/lib/subsys/subsys.h
@@ -0,0 +1,95 @@
+/* Copyright (c) 2003-2004, Roger Dingledine
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2019, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#ifndef TOR_SUBSYS_T
+#define TOR_SUBSYS_T
+
+#include <stdbool.h>
+
+struct dispatch_connector_t;
+
+/**
+ * A subsystem is a part of Tor that is initialized, shut down, configured,
+ * and connected to other parts of Tor.
+ *
+ * All callbacks are optional -- if a callback is set to NULL, the subsystem
+ * manager will treat it as a no-op.
+ *
+ * You should use c99 named-field initializers with this structure: we
+ * will be adding more fields, often in the middle of the structure.
+ **/
+typedef struct subsys_fns_t {
+  /**
+   * The name of this subsystem.  It should be a programmer-readable
+   * identifier.
+   **/
+  const char *name;
+
+  /**
+   * Whether this subsystem is supported -- that is, whether it is compiled
+   * into Tor.  For most subsystems, this should be true.
+   **/
+  bool supported;
+
+  /**
+   * The 'initialization level' for the subsystem.  It should run from -100
+   * through +100.  The subsystems are initialized from lowest level to
+   * highest, and shut down from highest level to lowest.
+   **/
+  int level;
+
+  /**
+   * Initialize any global components of this subsystem.
+   *
+   * This function MAY rely on any lower-level subsystem being initialized.
+   *
+   * This function MUST NOT rely on any runtime configuration information;
+   * it is only for global state or pre-configuration state.
+   *
+   * (If you need to do any setup that depends on configuration, you'll need
+   * to declare a configuration callback. (Not yet designed))
+   *
+   * This function MUST NOT have any parts that can fail.
+   **/
+  int (*initialize)(void);
+
+  /**
+   * Connect a subsystem to the message dispatch system.
+   **/
+  int (*add_pubsub)(struct dispatch_connector_t *);
+
+  /**
+   * Perform any necessary pre-fork cleanup.  This function may not fail.
+   */
+  void (*prefork)(void);
+
+  /**
+   * Perform any necessary post-fork setup. This function may not fail.
+   */
+  void (*postfork)(void);
+
+  /**
+   * Free any thread-local resources held by this subsystem. Called before
+   * the thread exits.
+   */
+  void (*thread_cleanup)(void);
+
+  /**
+   * Free all resources held by this subsystem.
+   *
+   * This function is not allowed to fail.
+   **/
+  void (*shutdown)(void);
+
+} subsys_fns_t;
+
+#define MIN_SUBSYS_LEVEL -100
+#define MAX_SUBSYS_LEVEL 100
+
+/* All tor "libraries" (in src/libs) should have a subsystem level equal to or
+ * less than this value. */
+#define SUBSYS_LEVEL_LIBS -10
+
+#endif