Encapsulate the STDOUT/STDERR capturing

src/wine-host/bridges/group.cpp

@@ -0,0 +1,44 @@
+// yabridge: a Wine VST bridge
+// Copyright (C) 2020  Robbert van der Helm
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+#include "group.h"
+
+#include <unistd.h>
+
+StdIoCapture::StdIoCapture(boost::asio::io_context& io_context,
+                           int file_descriptor)
+    : pipe(io_context),
+      target_fd(file_descriptor),
+      original_fd_copy(dup(file_descriptor)) {
+    // We'll use the second element of these two file descriptors to reopen
+    // `file_descriptor`, and the first one to read the captured contents from
+    ::pipe(pipe_fd);
+
+    // We've already created a copy of the original file descriptor, so we can
+    // reopen it using the newly created pipe
+    dup2(pipe_fd[1], target_fd);
+    close(pipe_fd[1]);
+
+    pipe.assign(pipe_fd[0]);
+}
+
+StdIoCapture::~StdIoCapture() {
+    // Restore the original file descriptor and close the pipe. The other wend
+    // was already closed in the constructor.
+    dup2(original_fd_copy, target_fd);
+    close(original_fd_copy);
+    close(pipe_fd[0]);
+}