Pass callbacks back through to the host

Instead of using std::thread this can be done cleaner using recursive
async read functions. Everything withing those functions should of
course still remain synchronous.

src/plugin/bridge.cpp

@@ -51,20 +51,27 @@ bp::environment set_wineprefix();
 
 // TODO: When adding debug information, print both the path to the VST host and
 //       the chosen wineprefix
-Bridge::Bridge()
+Bridge::Bridge(AEffect* plugin, audioMasterCallback host_callback)
     : io_context(),
       socket_endpoint(generate_endpoint_name().string()),
       socket_acceptor(io_context, socket_endpoint),
       host_vst_dispatch(io_context),
+      vst_host_callback(io_context),
+      host_callback_function(host_callback),
       vst_host(find_wine_vst_host(),
-               // The Wine VST host needs to know which plugin to load and which
-               // Unix domain socket to connect to
+               // The Wine VST host needs to know which plugin to load and
+               // which Unix domain socket to connect to
                find_vst_plugin(),
                socket_endpoint.path(),
                bp::env = set_wineprefix()) {
     // It's very important that these sockets are connected to in the same order
     // in the Wine VST host
     socket_acceptor.accept(host_vst_dispatch);
+    socket_acceptor.accept(vst_host_callback);
+
+    // TODO: REmove
+    // After accepting the sockets
+    removeme = std::thread([&]() { return host_callback_loop(plugin); });
 }
 
 /**
@@ -213,6 +220,15 @@ fs::path generate_endpoint_name() {
     return candidate_endpoint;
 }
 
+// TODO: Replace blocking loop with async readers or threads for all of the
+//       sockets. Also extract this functionality somewhere since the host event
+//       callback needs to do exactly the same thing.
+void Bridge::host_callback_loop(AEffect* plugin) {
+    while (true) {
+        passthrough_event(vst_host_callback, plugin, host_callback_function);
+    }
+}
+
 /**
  * Locate the wineprefix and set the `WINEPREFIX` environment variable if found.
  * This way it's also possible to run .dll files outside of a wineprefix using

src/plugin/bridge.h

@@ -21,6 +21,8 @@
 #include <boost/asio/io_context.hpp>
 #include <boost/asio/local/stream_protocol.hpp>
 #include <boost/process/child.hpp>
+// TODO: Remove
+#include <thread>
 
 /**
  * This handles the communication between the Linux native VST plugin and the
@@ -36,10 +38,14 @@ class Bridge {
      * TODO: Figure out whether shared memory gives us better throughput and/or
      *       lower overhead than using a Unix domain socket would.
      *
+     * @param host_callback The callback function passed to the VST plugin by
+     *   the host.
+     *
      * @throw std::runtime_error Thrown when the VST host could not be found, or
      *   if it could not locate and load a VST .dll file.
      */
-    Bridge();
+    // TODO: The plugin struct should be created here, not passed in
+    Bridge(AEffect* plugin, audioMasterCallback host_callback);
 
     // The four below functions are the handlers from the VST2 API. They are
     // called through proxy functions in `plugin.cpp`.
@@ -61,6 +67,9 @@ class Bridge {
     void set_parameter(AEffect* plugin, int32_t index, float value);
     float get_parameter(AEffect* plugin, int32_t index);
 
+    // TODO: Remove debug loop
+    void host_callback_loop(AEffect* plugin);
+
    private:
     boost::asio::io_context io_context;
     boost::asio::local::stream_protocol::endpoint socket_endpoint;
@@ -71,6 +80,16 @@ class Bridge {
     // `AEffect.dispatch()` calls from the native VST host to the Windows VST
     // plugin (through the Wine VST host).
     boost::asio::local::stream_protocol::socket host_vst_dispatch;
+    boost::asio::local::stream_protocol::socket vst_host_callback;
 
+    /**
+     * The callback function passed by the host to the VST plugin instance.
+     */
+    audioMasterCallback host_callback_function;
+    // TODO: Remove
+    std::thread removeme;
+    /**
+     * The Wine process hosting the Windows VST plugin.
+     */
     boost::process::child vst_host;
 };

src/plugin/plugin.cpp

@@ -61,11 +61,13 @@ Bridge& get_bridge_instance(const AEffect& plugin) {
  * manual memory management. Clean up is done when we receive the `effClose`
  * opcode from the VST host (i.e. opcode 1).`
  */
-VST_EXPORT AEffect* VSTPluginMain(audioMasterCallback /*audioMaster*/) {
+VST_EXPORT AEffect* VSTPluginMain(audioMasterCallback host_callback) {
     try {
-        Bridge* bridge = new Bridge();
-
+        // TODO: Create the plugin instance in the bridge based on the received
+        //       parameters. We can then also use a smart pointer so we only
+        //       have to manually delete the bridge instance.
         AEffect* plugin = new AEffect();
+        Bridge* bridge = new Bridge(plugin, host_callback);
         plugin->ptr3 = bridge;
 
         plugin->dispatcher = dispatch_proxy;

src/wine-host/bridge.cpp

@@ -38,7 +38,8 @@ Bridge::Bridge(std::string plugin_dll_path, std::string socket_endpoint_path)
     : plugin_handle(LoadLibrary(plugin_dll_path.c_str()), &FreeLibrary),
       io_context(),
       socket_endpoint(socket_endpoint_path),
-      host_vst_dispatch(io_context) {
+      host_vst_dispatch(io_context),
+      vst_host_callback(io_context) {
     // Got to love these C APIs
     if (plugin_handle == nullptr) {
         throw std::runtime_error("Could not load a shared library at '" +
@@ -63,7 +64,10 @@ Bridge::Bridge(std::string plugin_dll_path, std::string socket_endpoint_path)
             "'.");
     }
 
+    // It's very important that these sockets are accepted to in the same order
+    // in the Linus plugin
     host_vst_dispatch.connect(socket_endpoint);
+    vst_host_callback.connect(socket_endpoint);
 
     // Initialize after communication has been set up We'll try to do the same
     // `get_bridge_isntance` trick as in `plugin/plugin.cpp`, but since the
@@ -90,14 +94,13 @@ void Bridge::dispatch_loop() {
     }
 }
 
-intptr_t Bridge::host_callback(AEffect* plugin,
+intptr_t Bridge::host_callback(AEffect* /*plugin*/,
                                int32_t opcode,
                                int32_t index,
                                intptr_t value,
                                void* data,
                                float option) {
-    // TODO
-    return 1;
+    return send_event(vst_host_callback, opcode, index, value, data, option);
 }
 
 intptr_t VST_CALL_CONV host_callback_proxy(AEffect* effect,

src/wine-host/bridge.h

@@ -74,4 +74,5 @@ class Bridge {
     // `AEffect.dispatch()` calls from the native VST host to the Windows VST
     // plugin (through the Wine VST host).
     boost::asio::local::stream_protocol::socket host_vst_dispatch;
+    boost::asio::local::stream_protocol::socket vst_host_callback;
 };