Add basic communication with a child process

src/plugin/bridge.cpp

@@ -1,5 +1,8 @@
 #include "bridge.h"
 
+#include <boost/dll/runtime_symbol_info.hpp>
+#include <boost/process/io.hpp>
+#include <boost/process/search_path.hpp>
 #include <iostream>
 #include <msgpack.hpp>
 
@@ -9,6 +12,22 @@
 //       implementation details, such as the use of intptr_t isntead of void*
 //       here.
 
+namespace bp = boost::process;
+namespace fs = boost::filesystem;
+
+constexpr auto yabridge_wine_host_name = "yabridge-host.exeTODO";
+
+fs::path find_wine_vst_host();
+
+Bridge::Bridge()
+    : vst_stdin(),
+      vst_stdout(),
+      vst_host(find_wine_vst_host(),
+               bp::std_in = vst_stdin,
+               bp::std_out = vst_stdout) {
+    // TODO: Wineprefix detection
+}
+
 /**
  * Handle an event sent by the VST host. Most of these opcodes will be passed
  * through to the winelib VST host.
@@ -36,6 +55,8 @@ intptr_t Bridge::dispatch(AEffect* /*plugin*/,
     switch (opcode) {
         case effClose:
             // TODO: Gracefully close the editor?
+            // XXX: Boost.Process will send SIGKILL to the process for us, is
+            //      there a way to manually send a SIGTERM signal instead?
 
             // The VST API does not have an explicit function for releasing
             // resources, so we'll have to do it here. The actual plugin
@@ -67,3 +88,34 @@ float Bridge::get_parameter(AEffect* /*plugin*/, int32_t /*index*/
     // TODO: Unimplmemented
     return 0.0f;
 }
+
+/**
+ * Finds the Wine VST hsot (named `yabridge-host.exe`). For this we will search
+ * in two places:
+ *
+ *   1. Alongside libyabridge.so if the file got symlinked. This is useful
+ *      when developing, as you can simply symlink the the libyabridge.so
+ *      file in the build directory without having to install anything to
+ *      /usr.
+ *   2. In the regular search path.
+ *
+ * @return The a path to the VST host, if found.
+ * @throw std::runtime_error If the Wine VST host could not be found.
+ */
+fs::path find_wine_vst_host() {
+    fs::path host_path = fs::canonical(boost::dll::this_line_location());
+    host_path.remove_filename().append(yabridge_wine_host_name);
+    if (fs::exists(host_path)) {
+        return host_path;
+    }
+
+    // Bosot will return an empty path if the file could not be found in the
+    // search path
+    fs::path vst_host_path = bp::search_path(yabridge_wine_host_name);
+    if (fs::is_empty(vst_host_path)) {
+        throw std::runtime_error("Could not locate '" +
+                                 std::string(yabridge_wine_host_name) + "'");
+    }
+
+    return vst_host_path;
+}