Pass through processReplacing

Should work, almost does.

src/common/communication.h

@@ -160,23 +160,29 @@ struct ParameterResult {
  * A buffer of audio for the plugin to process, or the response of that
  * processing. The number of samples is encoded in each audio buffer's length.
  */
-struct AudioBuffer {
+struct AudioBuffers {
     // When sending data we could use a vector of the right size, but when
     // receiving data we don't know how large this vector should be in advance
     // (or without sending the message length first)
     using buffer_type =
-        ArrayBuffer<max_audio_channels * max_buffer_size * sizeof(float)>;
+        ArrayBuffer<max_audio_channels * max_buffer_size * sizeof(float) + 16>;
 
     /**
-     * An audio buffer for each of the plugin's audio channels. The number of
-     * samples is equal to `buffers[0].size()`.
+     * An audio buffer for each of the plugin's audio channels.
      */
     std::vector<std::vector<float>> buffers;
 
+    /**
+     * The number of frames in a sample. If buffers is not empty, then
+     * `buffers[0].size() == sample_frames`.
+     */
+    int sample_frames;
+
     template <typename S>
     void serialize(S& s) {
         s.container(buffers, max_audio_channels,
                     [](S& s, auto& v) { s.container4b(v, max_buffer_size); });
+        s.value4b(sample_frames);
     }
 };
 
@@ -296,12 +302,12 @@ inline T read_object(Socket& socket) {
  *
  * @relates passthrough_event
  */
-intptr_t send_event(boost::asio::local::stream_protocol::socket& socket,
-                    int32_t opcode,
-                    int32_t index,
-                    intptr_t value,
-                    void* data,
-                    float option) {
+inline intptr_t send_event(boost::asio::local::stream_protocol::socket& socket,
+                           int32_t opcode,
+                           int32_t index,
+                           intptr_t value,
+                           void* data,
+                           float option) {
     auto payload =
         data == nullptr
             ? std::nullopt

src/plugin/host-bridge.cpp

@@ -24,8 +24,6 @@
 #include <iostream>
 #include <random>
 
-#include "../common/communication.h"
-
 // TODO: I should track down the VST2 SDK for clarification on some of the
 //       implementation details, such as the use of intptr_t isntead of void*
 //       here.
@@ -73,6 +71,7 @@ HostBridge::HostBridge(audioMasterCallback host_callback)
       host_vst_dispatch(io_context),
       vst_host_callback(io_context),
       host_vst_parameters(io_context),
+      host_vst_process_replacing(io_context),
       vst_host_aeffect(io_context),
       host_callback_function(host_callback),
       vst_host(find_wine_vst_host(),
@@ -80,12 +79,14 @@ HostBridge::HostBridge(audioMasterCallback host_callback)
                // which Unix domain socket to connect to
                find_vst_plugin(),
                socket_endpoint.path(),
-               bp::env = set_wineprefix()) {
+               bp::env = set_wineprefix()),
+      process_buffer(std::make_unique<AudioBuffers::buffer_type>()) {
     // 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);
     socket_acceptor.accept(host_vst_parameters);
+    socket_acceptor.accept(host_vst_process_replacing);
     socket_acceptor.accept(vst_host_aeffect);
 
     // Set up all pointers for our `AEffect` struct. We will fill this with data
@@ -147,24 +148,39 @@ intptr_t HostBridge::dispatch(AEffect* /*plugin*/,
     return send_event(host_vst_dispatch, opcode, index, value, data, option);
 }
 
-void HostBridge::process(AEffect* /*plugin*/,
-                         float** /*inputs*/,
-                         float** /*outputs*/,
-                         int32_t /*sample_frames*/) {
-    // TODO: Unimplmemented
-}
-
 void HostBridge::process_replacing(AEffect* /*plugin*/,
-                                   float** /*inputs*/,
-                                   float** /*outputs*/,
-                                   int /*sample_frames*/) {
-    // TODO: Unimplmemented
+                                   float** inputs,
+                                   float** outputs,
+                                   int sample_frames) {
+    // The inputs and outputs arrays should be `[num_inputs][sample_frames]` and
+    // `[num_outputs][sample_frames]` floats large respectfully.
+    std::vector<std::vector<float>> input_buffers(
+        plugin.numInputs, std::vector<float>(sample_frames));
+    for (int channel = 0; channel < plugin.numInputs; channel++) {
+        std::copy(inputs[channel], inputs[channel] + sample_frames + 1,
+                  input_buffers[channel].begin());
+    }
+
+    const AudioBuffers request{input_buffers, sample_frames};
+    write_object(host_vst_process_replacing, request, *process_buffer);
+
+    // /Write the results back to the `outputs` arrays
+    AudioBuffers response;
+    response =
+        read_object(host_vst_process_replacing, response, *process_buffer);
+
+    // TODO: Doesn't quite work yet, not sure which side is causing problems
+    assert(response.buffers.size() == static_cast<size_t>(plugin.numOutputs));
+    for (int channel = 0; channel < plugin.numOutputs; channel++) {
+        std::copy(response.buffers[channel].begin(),
+                  response.buffers[channel].end(), outputs[channel]);
+    }
 }
 
 void HostBridge::set_parameter(AEffect* /*plugin*/,
                                int32_t index,
                                float value) {
-    Parameter request{index, value};
+    const Parameter request{index, value};
     write_object(host_vst_parameters, request);
 
     // This should not contain any values and just serve as an acknowledgement
@@ -173,7 +189,7 @@ void HostBridge::set_parameter(AEffect* /*plugin*/,
 }
 
 float HostBridge::get_parameter(AEffect* /*plugin*/, int32_t index) {
-    Parameter request{index, std::nullopt};
+    const Parameter request{index, std::nullopt};
     write_object(host_vst_parameters, request);
 
     const auto response = read_object<ParameterResult>(host_vst_parameters);
@@ -316,8 +332,8 @@ void process_proxy(AEffect* plugin,
                    float** inputs,
                    float** outputs,
                    int32_t sample_frames) {
-    return get_bridge_instance(*plugin).process(plugin, inputs, outputs,
-                                                sample_frames);
+    return get_bridge_instance(*plugin).process_replacing(
+        plugin, inputs, outputs, sample_frames);
 }
 
 void process_replacing_proxy(AEffect* plugin,

src/plugin/host-bridge.h

@@ -23,6 +23,8 @@
 #include <boost/process/child.hpp>
 #include <thread>
 
+#include "../common/communication.h"
+
 /**
  * This handles the communication between the Linux native VST plugin and the
  * Wine VST host. The functions below should be used as callback functions in an
@@ -55,10 +57,10 @@ class HostBridge {
                       intptr_t value,
                       void* data,
                       float option);
-    void process(AEffect* plugin,
-                 float** inputs,
-                 float** outputs,
-                 int32_t sample_frames);
+    /**
+     * Ask the VST plugin to process audio for us. This should also be used for
+     * the deprecated 'process' function.
+     */
     void process_replacing(AEffect* plugin,
                            float** inputs,
                            float** outputs,
@@ -92,6 +94,7 @@ class HostBridge {
      *       would cause a race condition.
      */
     boost::asio::local::stream_protocol::socket host_vst_parameters;
+    boost::asio::local::stream_protocol::socket host_vst_process_replacing;
 
     /**
      * This socket only handles updates of the `AEffect` struct instead of
@@ -113,4 +116,10 @@ class HostBridge {
      * The Wine process hosting the Windows VST plugin.
      */
     boost::process::child vst_host;
+
+    /**
+     * A scratch buffer for sending and receiving data during `process` and
+     * `processReplacing` calls.
+     */
+    std::unique_ptr<AudioBuffers::buffer_type> process_buffer;
 };

src/wine-host/plugin-bridge.cpp

@@ -16,8 +16,6 @@
 
 #include "plugin-bridge.h"
 
-#include "../common/communication.h"
-
 /**
  * A function pointer to what should be the entry point of a VST plugin.
  */
@@ -58,7 +56,9 @@ PluginBridge::PluginBridge(std::string plugin_dll_path,
       host_vst_dispatch(io_context),
       vst_host_callback(io_context),
       host_vst_parameters(io_context),
-      vst_host_aeffect(io_context) {
+      host_vst_process_replacing(io_context),
+      vst_host_aeffect(io_context),
+      process_buffer(std::make_unique<AudioBuffers::buffer_type>()) {
     // Got to love these C APIs
     if (plugin_handle == nullptr) {
         throw std::runtime_error("Could not load a shared library at '" +
@@ -88,6 +88,7 @@ PluginBridge::PluginBridge(std::string plugin_dll_path,
     host_vst_dispatch.connect(socket_endpoint);
     vst_host_callback.connect(socket_endpoint);
     host_vst_parameters.connect(socket_endpoint);
+    host_vst_process_replacing.connect(socket_endpoint);
     vst_host_aeffect.connect(socket_endpoint);
 
     // Initialize after communication has been set up We'll try to do the same
@@ -143,10 +144,42 @@ PluginBridge::PluginBridge(std::string plugin_dll_path,
             }
         }
     });
+
+    process_replacing_handler = std::thread([&]() {
+        while (true) {
+            AudioBuffers request;
+            request = read_object(host_vst_process_replacing, request,
+                                  *process_buffer);
+
+            // TODO: Check if the plugin doesn't support `processReplacing` and
+            //       call the legacy `process` function instead
+            std::vector<std::vector<float>> output_buffers(
+                plugin->numOutputs, std::vector<float>(request.sample_frames));
+
+            // The process functions expect a `float**` for their inputs and
+            // their outputs
+            std::vector<float*> inputs;
+            for (auto& buffer : request.buffers) {
+                inputs.push_back(buffer.data());
+            }
+            std::vector<float*> outputs;
+            for (auto& buffer : output_buffers) {
+                outputs.push_back(buffer.data());
+            }
+
+            plugin->process(plugin, inputs.data(), outputs.data(),
+                            request.sample_frames);
+
+            AudioBuffers response{output_buffers, request.sample_frames};
+            write_object(host_vst_process_replacing, response, *process_buffer);
+        }
+    });
 }
 
 void PluginBridge::wait() {
     dispatch_handler.join();
+    parameters_handler.join();
+    process_replacing_handler.join();
 }
 
 intptr_t PluginBridge::host_callback(AEffect* /*plugin*/,

src/wine-host/plugin-bridge.h

@@ -26,6 +26,8 @@
 
 #include <thread>
 
+#include "../common/communication.h"
+
 /**
  * This handles the communication between the Linux native VST plugin and the
  * Wine VST host. The functions below should be used as callback functions in an
@@ -82,6 +84,7 @@ class PluginBridge {
      * overlap.
      */
     boost::asio::local::stream_protocol::socket host_vst_parameters;
+    boost::asio::local::stream_protocol::socket host_vst_process_replacing;
 
     /**
      * This socket only handles updates of the `AEffect` struct instead of
@@ -98,6 +101,14 @@ class PluginBridge {
      * The thread that responds to `getParameter` and `setParameter` requests.
      */
     std::thread parameters_handler;
+    /**
+     * The t thread that handles calls to `processReplacing` (and `process`).
+     */
+    std::thread process_replacing_handler;
 
-    // TODO: Set up process and processReplacing callback handlers
+    /**
+     * A scratch buffer for sending and receiving data during `process` and
+     * `processReplacing` calls.
+     */
+    std::unique_ptr<AudioBuffers::buffer_type> process_buffer;
 };