fwin

commit 3e37b20fd2c4a1b1a75838bf4ab81b52ff1c2226
parent 1f86a7bb32b059c0d115ecd196f3aa3beb06b53f
Author: kocotian <kocotian@kocotian.pl>
Date:   Fri, 15 Jan 2021 21:35:10 +0100

locking skelet

Diffstat:
M
fwin.c
 | 
8
++++++++
M
include/flib.h
 | 
3
+++
M
lib/flib.c
 | 
31
+++++++++++++++++++++++++++++++

3 files changed, 42 insertions(+), 0 deletions(-)
diff --git a/fwin.c b/fwin.c
@@ -10,9 +10,13 @@
 #include <flib.h>
 #include "getch.h"
 
+#define LOCKFILE "/tmp/.F0.lock"
+
 int
 main(void)
 {
+	int err;
+
 	FbDrawable fbdev, buffer;
 	/* fbdev is actual framebuffer device, buffer is only temporary
 	   buffer for making operations and its content is copied to fbdev.
@@ -24,6 +28,9 @@ main(void)
 	if ((fbdev.fbdesc = fbopen(DEFAULT_FRAMEBUFFER)) < 0)
 		exit(fbdev.fbdesc);
 
+	if ((err = fblock(LOCKFILE)) < 0)
+		exit(err);
+
 	/* Getting resolution from fbdev */
 	fbdev.res[0] =  getres(fbdev.fbdesc);
 	fbdev.res[1] = getvres(fbdev.fbdesc);
@@ -66,4 +73,5 @@ main(void)
 	/* Unmapping and closing fbdev */
 	fbunmap(&fbdev.mappoint, fbdev.len);
 	fbclose(fbdev.fbdesc);
+	fbunlock(LOCKFILE);
 }
diff --git a/include/flib.h b/include/flib.h
@@ -41,6 +41,9 @@ void fbunmap(char **mappoint, int64_t len);
 int fbgetinfo(int fbdesc, struct fb_var_screeninfo *info);
 int fbsetinfo(int fbdesc, struct fb_var_screeninfo *info);
 
+int fblock(const char *lockfile);
+int fbunlock(const char *lockfile);
+
 int64_t getres(int fbdesc);
 int64_t getvres(int fbdesc);
 
diff --git a/lib/flib.c b/lib/flib.c
@@ -10,6 +10,7 @@
 #include <sys/types.h>
 
 #include <fcntl.h>
+#include <stdio.h>
 #include <unistd.h>
 
 #include <flib.h>
@@ -92,6 +93,36 @@ fbsetinfo(int fbdesc, struct fb_var_screeninfo *info)
 	return ioctl(fbdesc, FBIOPUT_VSCREENINFO, info);
 }
 
+/* --- typical server function --- */
+
+int
+fblock(const char *lockfile)
+{
+	int fd, bc;
+	char pidstr[8];
+
+	if (!access(lockfile, F_OK))
+		return -1;
+
+	if ((fd = open(lockfile, O_RDWR | O_CREAT)) < 0)
+		return -2;
+
+	bc = snprintf(pidstr, 8, "%d", getpid());
+	if (write(fd, pidstr, bc) < 0)
+		return -3;
+
+	if (close(fd) < 0)
+		return -4;
+
+	return 0;
+}
+
+int
+fbunlock(const char *lockfile)
+{
+	return unlink(lockfile);
+}
+
 int64_t /* first 32 bits are x, second 32 bits are y */
 getres(int fbdesc)
 {