From 21c97f509d0d61179b49238ffe82899d01b72261 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nicol=C3=A1s=20Ortega=20Froysa?=
 <nortega@themusicinnoise.net>
Date: Sat, 24 Feb 2018 10:04:41 +0100
Subject: [PATCH] Incomplete screen driver.

---
 drivers/screen.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 drivers/screen.h | 13 +++++++++++++
 2 files changed, 59 insertions(+)
 create mode 100644 drivers/screen.c
 create mode 100644 drivers/screen.h

diff --git a/drivers/screen.c b/drivers/screen.c
new file mode 100644
index 0000000..bbd07ef
--- /dev/null
+++ b/drivers/screen.c
@@ -0,0 +1,46 @@
+#include "screen.h"
+
+#include "../kernel/ports.h"
+
+void print_char(char c, int col, int row, char attr_byte) {
+	unsigned char *vidmem = (unsigned char*) VIDEO_ADDRESS;
+
+	if(!attr_byte)
+		attr_byte = WHITE_ON_BLACK;
+
+	/* get the offset of the screen location specified */
+	int offset;
+	/*
+	 * if row & col are non-negative then they can be used
+	 * as an offset
+	 */
+	if(col >= 0 && row >= 0)
+	{
+		offset = get_screen_offset(col, row);
+	}
+	/* otherwise use the cursor's current location */
+	else
+	{
+		offset = get_cursor();
+	}
+
+	/* handle a newline */
+	if(c == '\n')
+	{
+		int rows = offset / (2 * MAX_COLS);
+		offset = get_screen_offset(79,rows);
+	}
+	/* else set the character */
+	else
+	{
+		vidmem[offset] = c;
+		vidmem[offset+1] = attr_byte;
+	}
+
+	/* update the offset to the next cell */
+	offset += 2;
+	/* set scrolling adjustment */
+	offset = handle_scrolling(offset);
+	/* update the cursor position */
+	set_cursor(offset);
+}
diff --git a/drivers/screen.h b/drivers/screen.h
new file mode 100644
index 0000000..d07f2cb
--- /dev/null
+++ b/drivers/screen.h
@@ -0,0 +1,13 @@
+#pragma once
+
+#define VIDEO_ADDRESS   0xb8000
+#define MAX_ROWS        25
+#define MAX_COLS        80
+
+#define WHITE_ON_BLACK  0x0f
+
+#define REG_SCREEN_CTRL 0x3d4
+#define REG_SCREEN_DATA 0x3d5
+
+void print_char(char c, int col, int row, char attr_byte);
+int get_screen_offset(int col, int row);