Fully implement CLAP audio processing

src/common/serialization/clap/README.md

@@ -9,6 +9,7 @@ Yabridge currently tracks CLAP 1.1.1. The implementation status for CLAP's core
 | core feature                              | status                                                 |
 | ----------------------------------------- | ------------------------------------------------------ |
 | Core plugin and host functionality        | :warning: Everything but actual audio processing works |
+| Audio processing                          | :heavy_check_mark:                                     |
 | Events                                    | :heavy_check_mark:                                     |
 | Streams                                   | :heavy_check_mark:                                     |
 | `clap.plugin-factory`                     | :heavy_check_mark:                                     |

src/plugin/bridges/clap-impls/plugin-proxy.cpp

@@ -223,11 +223,59 @@ clap_plugin_proxy::plugin_reset(const struct clap_plugin* plugin) {
 clap_process_status CLAP_ABI
 clap_plugin_proxy::plugin_process(const struct clap_plugin* plugin,
                                   const clap_process_t* process) {
-    assert(plugin && plugin->plugin_data);
-    auto self = static_cast<const clap_plugin_proxy*>(plugin->plugin_data);
+    assert(plugin && plugin->plugin_data && process);
+    auto self = static_cast<clap_plugin_proxy*>(plugin->plugin_data);
 
-    // TODO: Implement
-    return CLAP_PROCESS_ERROR;
+    // We'll synchronize the scheduling priority of the audio thread on the Wine
+    // plugin host with that of the host's audio thread every once in a while
+    std::optional<int> new_realtime_priority = std::nullopt;
+    time_t now = time(nullptr);
+    if (now > self->last_audio_thread_priority_synchronization_ +
+                  audio_thread_priority_synchronization_interval) {
+        new_realtime_priority = get_realtime_priority();
+        self->last_audio_thread_priority_synchronization_ = now;
+    }
+
+    // We reuse this existing object to avoid allocations.
+    // `clap::process::Process::repopulate()` will write the input audio to the
+    // shared audio buffers, so they're not stored within the request object
+    // itself.
+    assert(self->process_buffers_);
+    self->process_request_.instance_id = self->instance_id();
+    self->process_request_.process.repopulate(*process,
+                                              *self->process_buffers_);
+    self->process_request_.new_realtime_priority = new_realtime_priority;
+
+    // HACK: This is a bit ugly. This `clap::process::Process::Response` object
+    //       actually contains pointers to the corresponding `YaProcessData`
+    //       fields in this object, so we can only send back the fields that are
+    //       actually relevant. This is necessary to avoid allocating copies or
+    //       moves on the Wine side. This `create_response()` function creates a
+    //       response object that points to the fields in
+    //       `process_request_.data`, so when we deserialize into
+    //       `process_response_` we end up actually writing to the actual
+    //       `process_request_.data` object. Thus we can also call
+    //       `process_request_.data.write_back_outputs()` later.
+    //
+    //       `clap::process::Process::Response::serialize()` should make this a
+    //       lot clearer.
+    self->process_response_.output_data =
+        self->process_request_.process.create_response();
+
+    // We'll also receive the response into an existing object so we can also
+    // avoid heap allocations there
+    self->bridge_.receive_audio_thread_message_into(
+        MessageReference<clap::plugin::Process>(self->process_request_),
+        self->process_response_);
+
+    // At this point the shared audio buffers should contain the output audio,
+    // so we'll write that back to the host along with any metadata (which in
+    // practice are only the silence flags), as well as any output parameter
+    // changes and events
+    self->process_request_.process.write_back_outputs(*process,
+                                                      *self->process_buffers_);
+
+    return self->process_response_.result;
 }
 
 const void* CLAP_ABI

src/plugin/bridges/clap-impls/plugin-proxy.h

@@ -266,6 +266,13 @@ class clap_plugin_proxy {
     size_t instance_id_;
     clap::plugin::Descriptor descriptor_;
 
+    /**
+     * We'll periodically synchronize the Wine host's audio thread priority with
+     * that of the host. Since the overhead from doing so does add up, we'll
+     * only do this every once in a while.
+     */
+    time_t last_audio_thread_priority_synchronization_ = 0;
+
     /**
      * A shared memory object to share audio buffers between the native plugin
      * and the Wine plugin host. Copying audio is the most significant source of
@@ -277,6 +284,29 @@ class clap_plugin_proxy {
      */
     std::optional<AudioShmBuffer> process_buffers_;
 
+    /**
+     * We'll reuse the request objects for the process call so we can keep the
+     * process data object (which contains vectors and other heap allocated data
+     * structure) alive. We'll then just fill this object with new data every
+     * processing cycle to prevent allocations. Then, we pass a
+     * `MessageReference<clap::plugin::Process>` to our sockets. This together
+     * with `bitisery::ext::MessageReference` will let us serialize from and to
+     * existing objects without having to copy or reallocate them.
+     *
+     * To reduce the amount of copying during audio processing we'll write the
+     * audio data to a shared memory object stored in `process_buffers_` first.
+     */
+    clap::plugin::Process process_request_;
+
+    /**
+     * The response object we'll get in return when we send the
+     * `process_request_` object above to the Wine plugin host. This object also
+     * contains heap data, so we also want to reuse this. This is initialized to
+     * contain the `process_request_`'s response object so the response can be
+     * deserialized in place.
+     */
+    clap::plugin::ProcessResponse process_response_;
+
     /**
      * The vtable for `clap_plugin`, requires that this object is never moved or
      * copied. We'll use the host data pointer instead of placing this vtable at

src/plugin/bridges/clap.h

@@ -125,21 +125,21 @@ class ClapPluginBridge : PluginBridge<ClapSockets<std::jthread>> {
             object, std::pair<ClapLogger&, bool>(logger_, true));
     }
 
-    // /**
-    //  * Send an audio thread control message to a specific plugin instance,
-    //  * receiving the results into an existing object. This is similar to the
-    //  * `send_audio_thread_message()` above, but this lets us avoid
-    //  allocations
-    //  * in response objects that contain heap data.
-    //  */
-    // template <typename T>
-    // typename T::Response& receive_audio_thread_message_into(
-    //     const T& object,
-    //     typename T::Response& response_object) {
-    //     return sockets_.receive_audio_processor_message_into(
-    //         object, response_object,
-    //         std::pair<ClapLogger&, bool>(logger_, true));
-    // }
+    /**
+     * Send an audio thread control message to a specific plugin instance,
+     * receiving the results into an existing object. This is similar to the
+     * `send_audio_thread_message()` above, but this lets us avoid
+     allocations
+     * in response objects that contain heap data.
+     */
+    template <typename T>
+    typename T::Response& receive_audio_thread_message_into(
+        const T& object,
+        typename T::Response& response_object) {
+        return sockets_.receive_audio_thread_control_message_into(
+            object, response_object,
+            std::pair<ClapLogger&, bool>(logger_, true));
+    }
 
     // TODO: Do we need this for CLAP? If we do, update the docstring
     // /**