util: Import screen_width() developed for the SMCRoute project

This patch introduces the screen_width() method from the SMCRoute
project.  The code is hereby also available under MIT/X11.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

src/util.c

@@ -21,10 +21,17 @@
  * THE SOFTWARE.
  */
 
+#include "config.h"
 #include <ctype.h>		/* isprint() */
 #include <string.h>
 #include <unistd.h>
 
+#ifdef HAVE_TERMIOS_H		/* for screen_width() */
+#include <poll.h>
+#include <stdio.h>
+#include <termios.h>
+#endif
+
 char *prognm = NULL;
 
 char *progname(char *arg0)
@@ -69,6 +76,36 @@ char *sanitize(char *arg, size_t len)
 	return NULL;
 }
 
+#define ESC "\033"
+int screen_width(void)
+{
+	int ret = 80;
+#ifdef HAVE_TERMIOS_H
+	char buf[42];
+	struct termios tc, saved;
+	struct pollfd fd = { STDIN_FILENO, POLLIN, 0 };
+
+	memset(buf, 0, sizeof(buf));
+	tcgetattr(STDERR_FILENO, &tc);
+	saved = tc;
+	tc.c_cflag |= (CLOCAL | CREAD);
+	tc.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
+	tcsetattr(STDERR_FILENO, TCSANOW, &tc);
+	fprintf(stderr, ESC "7" ESC "[r" ESC "[999;999H" ESC "[6n");
+
+	if (poll(&fd, 1, 300) > 0) {
+		int row, col;
+
+		if (scanf(ESC "[%d;%dR", &row, &col) == 2)
+			ret = col;
+	}
+
+	fprintf(stderr, ESC "8");
+	tcsetattr(STDERR_FILENO, TCSANOW, &saved);
+#endif
+	return ret;
+}
+
 /**
  * Local Variables:
  *  indent-tabs-mode: t

src/util.h

@@ -1,6 +1,6 @@
 /* Misc. shared utility functions for initctl, reboot and finit
  *
- * Copyright (c) 2016  Joachim Nilsson <troglobit@gmail.com>
+ * Copyright (c) 2016-2017  Joachim Nilsson <troglobit@gmail.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -26,9 +26,10 @@
 
 extern char *prognm;
 
-char *progname(char *arg0);
+char *progname     (char *arg0);
-void  do_sleep(unsigned int sec);
+void  do_sleep     (unsigned int sec);
-char *sanitize(char *arg, size_t len);
+char *sanitize     (char *arg, size_t len);
+int   screen_width (void);
 
 #endif /* FINIT_UTIL_H_ */