Pass all events to the plugin

src/common/communication.h

@@ -22,6 +22,13 @@
 #include <msgpack.hpp>
 #include <optional>
 
+/**
+ * The maximum size in bytes of a string or buffer passed through a void pointer
+ * in one of the dispatch functions. This is used as a buffer size and also as a
+ * cutoff for checking if c-style strings behind a `char*` have changed.
+ */
+constexpr size_t max_string_size = 128;
+
 /**
  * An event as dispatched by the VST host. These events will get forwarded to
  * the VST host process running under Wine. The fields here mirror those
@@ -34,8 +41,15 @@ struct Event {
     //       dereferenced?
     intptr_t value;
     float option;
+    /**
+     * The event dispatch function has a void pointer parameter that's used to
+     * either send string messages to the event (e.g. for `effCanDo`) or to
+     * write a string back into. This value will contain an (empty) string if
+     * the void* parameter for the dispatch function was not a null pointer.
+     */
+    std::optional<std::string> data;
 
-    MSGPACK_DEFINE(opcode, parameter, value, option)
+    MSGPACK_DEFINE(opcode, parameter, value, option, data)
 };
 
 /**
@@ -50,11 +64,11 @@ struct EventResult {
      * If present, this should get written into the void pointer passed to the
      * dispatch function.
      */
-    std::optional<std::string> result;
+    std::optional<std::string> data;
 
     // TODO: Add missing return value fields;
 
-    MSGPACK_DEFINE(return_value, result)
+    MSGPACK_DEFINE(return_value, data)
 };
 
 /**
@@ -89,9 +103,9 @@ inline void write_object(Socket& socket, const T& object) {
  */
 template <typename T, typename Socket>
 inline T read_object(Socket& socket) {
-    // TODO: Reuse buffers
+    // TODO: Reuse buffers, also this is way too large right now
     // TODO: Use boost's buffers directly after switching to bitsery
-    char buffer[65536];
+    char buffer[4096];
     auto message_length = socket.receive(boost::asio::buffer(buffer));
 
     return msgpack::unpack(buffer, message_length).get().convert();

src/plugin/bridge.cpp

@@ -76,7 +76,7 @@ intptr_t Bridge::dispatch(AEffect* /*plugin*/,
                           int32_t opcode,
                           int32_t parameter,
                           intptr_t value,
-                          void* result,
+                          void* data,
                           float option) {
     // Some events need some extra handling
     // TODO: Handle other things such as GUI itneraction
@@ -97,13 +97,18 @@ intptr_t Bridge::dispatch(AEffect* /*plugin*/,
             break;
     }
 
-    const Event event{opcode, parameter, value, option};
+    auto payload =
+        data == nullptr
+            ? std::nullopt
+            : std::make_optional(std::string(static_cast<char*>(data)));
+
+    const Event event{opcode, parameter, value, option, payload};
     write_object(host_vst_dispatch, event);
 
     const auto response = read_object<EventResult>(host_vst_dispatch);
-    if (response.result) {
-        std::copy(response.result->begin(), response.result->end(),
-                  static_cast<char*>(result));
+    if (response.data.has_value()) {
+        std::copy(response.data->begin(), response.data->end(),
+                  static_cast<char*>(data));
     }
 
     return response.return_value;

src/plugin/bridge.h

@@ -52,7 +52,7 @@ class Bridge {
                       int32_t opcode,
                       int32_t parameter,
                       intptr_t value,
-                      void* result,
+                      void* data,
                       float option);
     void process(AEffect* plugin,
                  float** inputs,

src/plugin/plugin.cpp

@@ -95,10 +95,10 @@ intptr_t dispatch(AEffect* plugin,
                   int32_t opcode,
                   int32_t parameter,
                   intptr_t value,
-                  void* result,
+                  void* data,
                   float option) {
     return get_bridge_instance(*plugin).dispatch(plugin, opcode, parameter,
-                                                 value, result, option);
+                                                 value, data, option);
 }
 
 void process(AEffect* plugin,

src/wine-host/native-includes.h

@@ -34,6 +34,7 @@
 #undef __WIN32__
 #undef _WIN64
 
+#include <boost/algorithm/string/predicate.hpp>
 #include <boost/asio/io_context.hpp>
 #include <boost/asio/local/stream_protocol.hpp>
 #include <msgpack.hpp>

src/wine-host/vst-host.cpp

@@ -59,12 +59,6 @@ int main(int argc, char* argv[]) {
     // TODO: Check whether this returned a null pointer
     AEffect* plugin = vst_entry_point(host_callback);
 
-    // TODO: Check the spec, how large should this be?
-    std::vector<char> buffer(2048, 0);
-    plugin->dispatcher(plugin, effGetEffectName, 0, 0, buffer.data(), 0.0);
-
-    std::string plugin_title(buffer.data());
-
     // Connect to the sockets for communication once the plugin has finished
     // loading
     // TODO: The program should terminate gracefully when one of the sockets
@@ -85,18 +79,41 @@ int main(int argc, char* argv[]) {
 
     // TODO: Remove debug, we're just reporting the plugin's name we retrieved
     //       above
+    std::array<char, max_string_size> buffer;
     while (true) {
         auto event = read_object<Event>(host_vst_dispatch);
 
-        EventResult response;
-        if (event.opcode == effGetEffectName) {
-            response.result = plugin_title;
-            response.return_value = 1;
-        } else {
-            response.return_value = 0;
+        // The void pointer argument for the dispatch function is used for
+        // either:
+        //  - Not at all, in which case it will be a null pointer
+        //  - For passing strings as input to the event
+        //  - For providing a buffer for the event to write results back into
+        char* payload = nullptr;
+        if (event.data.has_value()) {
+            // If the data parameter was an empty string, then we're going to
+            // pass a larger buffer to the dispatch function instead..
+            if (!event.data->empty()) {
+                payload = const_cast<char*>(event.data->c_str());
+            } else {
+                payload = buffer.data();
+            }
         }
 
-        write_object(host_vst_dispatch, response);
+        const intptr_t return_value =
+            plugin->dispatcher(plugin, event.opcode, event.option,
+                               event.parameter, payload, event.option);
+
+        // Only write back the value from `payload` if we were passed an empty
+        // buffer to write into
+        bool is_updated = event.data.has_value() && event.data->empty();
+
+        if (is_updated) {
+            EventResult response{return_value, payload};
+            write_object(host_vst_dispatch, response);
+        } else {
+            EventResult response{return_value, std::nullopt};
+            write_object(host_vst_dispatch, response);
+        }
     }
 }
 
@@ -105,7 +122,7 @@ intptr_t VST_CALL_CONV host_callback(AEffect* plugin,
                                      int32_t opcode,
                                      int32_t parameter,
                                      intptr_t value,
-                                     void* result,
+                                     void* data,
                                      float option) {
     return 1;
 }