2 files changed, 74 insertions, 0 deletions
diff --git a/src/device/screen.c b/src/device/screen.c
new file mode 100755
index 0000000..6ad9a87
--- /dev/null
+++ b/src/device/screen.c
@@ -0,0 +1,52 @@
+#include <time.h>
+#include <stdlib.h>
+#include "screen.h"
+
+void draw_lines(struct display_status *status);
+void update_lines(struct display_status *status);
+char * get_line(struct display_status *status, size_t rline);
+
+void display_update_scroll(struct display_status *status)
+{
+	time_t crr_time = time(NULL);
+	if (status->last_scroll_time - crr_time > status->delta) {
+		status->last_scroll_time += status->delta;
+		status->line_cursor++;
+		update_lines(status);
+	}
+	draw_lines(status);
+}
+
+void draw_lines(struct display_status *status)
+{
+
+}
+
+void update_lines(struct display_status *status)
+{
+	status->first_line = get_line(status, status->line_cursor);
+	status->second_line = get_line(status, status->line_cursor + 1);
+}
+
+/**
+ * Returns a pointer to the first charachter of requested line. If line does not
+ * exist --- a null is returned.
+ */
+char * get_line(struct display_status *status, size_t rline)
+{
+	size_t i;
+	size_t line_idx = 0;
+
+	for (i = 0; i < status->message_len; i++) {
+		if (rline == line_idx) {
+			return status->message + i;
+		}
+		if (status->message[i] == '\0') {
+			line_idx++;
+		}
+	}
+	/* The fact that we are here means that end of the message was reached.
+	 * In that case --- return null;
+	 */
+	return NULL;
+}
+\ No newline at end of file
diff --git a/src/device/screen.h b/src/device/screen.h
new file mode 100755
index 0000000..ec30cd5
--- /dev/null
+++ b/src/device/screen.h
@@ -0,0 +1,22 @@
+#ifndef DEVICE_SCREEN_H
+#define DEVICE_SCREEN_H
+
+#include <time.h>
+
+/**
+ * Struct that keeps track of the lines on the screen.
+ */
+struct display_status {
+	time_t delta;			/* Seconds/Line */
+	time_t last_scroll_time;	/* Last second the line was scrolled */
+	char *message;			/* Entire message to be shown */
+	char *first_line;		/* First line on display */
+	char *second_line;		/* Second line on display */
+	size_t message_len;		/* Length of the message */
+	size_t line_cursor;		/* Index of the first line being displayed. */
+};
+
+void display_update_scroll(struct display_status *status);
+void display_status_init(struct display_status *status, char *msg);
+
+#endif /* DEVICE_SCREEN_H */
+\ No newline at end of file