Add functions to encapsulate serialization

meson.build

@@ -25,20 +25,12 @@ msgpack_dep = dependency('msgpack')
 
 include_dir = include_directories('src/include')
 
-common_src = []
-
-linux_plugin_src = [
-  'src/plugin/bridge.cpp',
-  'src/plugin/plugin.cpp',
-]
-
-wine_host_src = [
-  'src/wine-host/vst-host.cpp',
-]
-
 shared_library(
   'yabridge',
-  linux_plugin_src + common_src,
+  [
+    'src/plugin/bridge.cpp',
+    'src/plugin/plugin.cpp',
+  ],
   native : true,
   include_directories : include_dir,
   dependencies : [boost_dep, msgpack_dep],
@@ -47,7 +39,9 @@ shared_library(
 
 executable(
   'yabridge-host',
-  wine_host_src + common_src,
+  [
+    'src/wine-host/vst-host.cpp',
+  ],
   native : false,
   include_directories : include_dir,
   dependencies : [],

src/common/communication.h

@@ -0,0 +1,81 @@
+#pragma once
+
+#include <cinttypes>
+#include <msgpack.hpp>
+#include <optional>
+
+/**
+ * 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
+ * arguments sent to the `AEffect::dispatch` function.
+ */
+struct Event {
+    int32_t opcode;
+    int32_t parameter;
+    // TODO: This is an intptr_t, is this actually a poitner that should be
+    //       dereferenced?
+    intptr_t value;
+    float option;
+
+    MSGPACK_DEFINE(opcode, parameter, value, option)
+};
+
+/**
+ * AN instance of this should be sent back as a response to an incoming event.
+ */
+struct EventResult {
+    /**
+     * The result that should be returned from the dispatch function.
+     */
+    intptr_t return_value;
+    /**
+     * If present, this should get written into the void pointer passed to the
+     * dispatch function.
+     */
+    std::optional<std::string> result;
+
+    // TODO: Add missing return value fields;
+
+    MSGPACK_DEFINE(return_value, result)
+};
+
+/**
+ * Serialize an object and write it to a stream. This function prefixes the
+ * output with the length of the serialized object in bytes since msgpack
+ * doesn't handle this on its own.
+ *
+ * @param stream An ostream that can be written to.
+ * @param object The object to write to the stream.
+ *
+ * @relates read_object
+ */
+template <typename Stream, typename T>
+inline void write_object(Stream& stream, const T& object) {
+    // TODO: Reuse buffers
+    msgpack::sbuffer buffer;
+    msgpack::pack(buffer, object);
+
+    stream << buffer.size();
+    stream << buffer.data();
+    stream.flush();
+}
+
+/**
+ * Deserialize an object by reading it from a stream. This should be used
+ * together with `write_object`. This will block until the object is
+ available.
+ *
+ * @param stream The stream to read from.
+ *
+ * @relates write_object
+ */
+template <typename Stream>
+inline EventResult read_object(Stream& stream) {
+    size_t message_length;
+    stream >> message_length;
+
+    // TODO: Reuse buffers
+    std::vector<char> buffer(message_length);
+    stream.read(buffer.data(), message_length);
+    return msgpack::unpack(buffer.data(), message_length).get().convert();
+}

src/common/events.h

@@ -1,40 +0,0 @@
-#pragma once
-
-#include <cinttypes>
-#include <msgpack.hpp>
-#include <optional>
-
-/**
- * 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
- * arguments sent to the `AEffect::dispatch` function.
- */
-struct Event {
-    int32_t opcode;
-    int32_t parameter;
-    // TODO: This is an intptr_t, is this actually a poitner that should be
-    //       dereferenced?
-    intptr_t value;
-    float option;
-
-    MSGPACK_DEFINE(opcode, parameter, value, option)
-};
-
-/**
- * AN instance of this should be sent back as a response to an incoming event.
- */
-struct EventResult {
-    /**
-     * The result that should be returned from the dispatch function.
-     */
-    intptr_t return_value;
-    /**
-     * If present, this should get written into the void pointer passed to the
-     * dispatch function.
-     */
-    std::optional<std::string> result;
-
-    // TODO: Add missing return value fields;
-
-    MSGPACK_DEFINE(return_value, result)
-};

src/plugin/bridge.cpp

@@ -6,7 +6,7 @@
 #include <iostream>
 #include <msgpack.hpp>
 
-#include "../common/events.h"
+#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*
@@ -38,13 +38,10 @@ intptr_t Bridge::dispatch(AEffect* /*plugin*/,
                           intptr_t value,
                           void* result,
                           float option) {
-    // TODO: Send to the Wine process
     Event event{opcode, parameter, value, option};
-    msgpack::sbuffer buffer;
+    write_object(vst_stdin, event);
-    msgpack::pack(buffer, event);
 
-    // TODO: Read the response
+    EventResult response = read_object(vst_stdout);
-    EventResult response;
     if (response.result) {
         std::copy(response.result->begin(), response.result->end(),
                   static_cast<char*>(result));