Add plugin library.

1 files changed, 66 insertions, 0 deletions

diff --git a/plugin/include/plugin.h b/plugin/include/plugin.h
new file mode 100644
index 0000000..abca9b5
--- /dev/null
+++ b/plugin/include/plugin.h
@@ -0,0 +1,66 @@
+/*
+ * Plugin engine for loading plugins and watching plugin updates.
+ *
+ * The plugin engine allows the client to load plugins and call their functions.
+ *
+ * Plugins can also be associated with a state. The engine does not create the
+ * plugin's state because this may require other application-specific state.
+ *
+ * Plugin files are watched for updates. Upon an update, the engine reloads the
+ * plugin into memory and notifies the client. The client should then typically
+ * re-create the plugin's state.
+ */
+#pragma once
+
+#include <stdbool.h>
+
+#include <dlfcn.h>
+
+typedef struct Plugin       Plugin;
+typedef struct PluginEngine PluginEngine;
+
+/// Plugin engine creation depluginor.
+typedef struct PluginEngineDesc {
+  const char* plugins_dir;
+} PluginEngineDesc;
+
+/// Create a new plugin engine.
+PluginEngine* new_plugin_engine(const PluginEngineDesc*);
+
+/// Destroy the plugin engine.
+void delete_plugin_engine(PluginEngine**);
+
+/// Update the plugin engine.
+///
+/// This looks for any plugins that have been modified and reloads them.
+void plugin_engine_update(PluginEngine*);
+
+/// Load a plugin.
+Plugin* load_plugin(PluginEngine*, const char* filename);
+
+/// Delete the plugin.
+///
+/// This unloads the plugin from memory and removes it from the engine.
+void delete_plugin(Plugin**);
+
+/// Set the plugin's state.
+///
+/// The plugin's previous state is deleted if non-null.
+void set_plugin_state(Plugin*, void* state);
+
+/// Get the plugin's state. Return null if the plugin has no state.
+void* get_plugin_state(Plugin*);
+
+/// Return true if the plugin has been reloaded.
+///
+/// If the plugin has been reloaded, subsequent calls to this function return
+/// false until the plugin is reloaded again.
+bool plugin_reloaded(Plugin*);
+
+/// Resolve a function in the plugin.
+#define plugin_resolve(plugin, func_sig, func_name) \
+  (func_sig)(dlsym(*((void**)(plugin)), func_name))
+
+/// Call a function in the plugin.
+#define plugin_call(plugin, func_sig, func_name, ...) \
+  (*plugin_resolve(plugin, func_sig, func_name))(__VA_ARGS__)