libcamera: Add Process and ProcessManager classes

Add a Process class to abstract a process, and a ProcessManager singleton
to monitor and manage the processes.

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/libcamera/include/process.h

@@ -0,0 +1,55 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * process.h - Process object
+ */
+#ifndef __LIBCAMERA_PROCESS_H__
+#define __LIBCAMERA_PROCESS_H__
+
+#include <string>
+#include <vector>
+
+#include <libcamera/event_notifier.h>
+
+namespace libcamera {
+
+class Process final
+{
+public:
+	enum ExitStatus {
+		NotExited,
+		NormalExit,
+		SignalExit,
+	};
+
+	Process();
+	~Process();
+
+	int start(const std::string &path,
+		  const std::vector<std::string> &args = std::vector<std::string>(),
+		  const std::vector<int> &fds = std::vector<int>());
+
+	ExitStatus exitStatus() const { return exitStatus_; }
+	int exitCode() const { return exitCode_; }
+
+	void kill();
+
+	Signal<Process *, enum ExitStatus, int> finished;
+
+private:
+	void closeAllFdsExcept(const std::vector<int> &fds);
+	int isolate();
+	void died(int wstatus);
+
+	pid_t pid_;
+	bool running_;
+	enum ExitStatus exitStatus_;
+	int exitCode_;
+
+	friend class ProcessManager;
+};
+
+} /* namespace libcamera */
+
+#endif /* __LIBCAMERA_PROCESS_H__ */