refactor: Break proc API functions out of the main daemon source

Signed-off-by: Kai Krakow <kai@kaishome.de>

daemon/gamemode-proc.c

@@ -0,0 +1,61 @@
+/*
+
+Copyright (c) 2017-2018, Feral Interactive
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+ * Redistributions of source code must retain the above copyright notice,
+   this list of conditions and the following disclaimer.
+ * Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions and the following disclaimer in the
+   documentation and/or other materials provided with the distribution.
+ * Neither the name of Feral Interactive nor the names of its contributors
+   may be used to endorse or promote products derived from this software
+   without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.
+
+ */
+
+#define _GNU_SOURCE
+
+#include "gamemode.h"
+#include "helpers.h"
+
+#include <fcntl.h>
+#include <linux/limits.h>
+#include <unistd.h>
+
+/**
+ * Opens the process environment for a specific PID and returns
+ * a file descriptor to the directory /proc/PID. Doing it that way prevents
+ * the directory going MIA when a process exits while we are looking at it
+ * and allows us to handle fewer error cases.
+ */
+procfd_t game_mode_open_proc(const pid_t pid)
+{
+	char buffer[PATH_MAX];
+	const char *proc_path = buffered_snprintf(buffer, "/proc/%d", pid);
+
+	return proc_path ? open(proc_path, O_RDONLY | O_CLOEXEC) : INVALID_PROCFD;
+}
+
+/**
+ * Closes the process environment.
+ */
+int game_mode_close_proc(const procfd_t procfd)
+{
+	return close(procfd);
+}