1 files changed, 105 insertions, 0 deletions
diff --git a/kernel/drivers/tty.c b/kernel/drivers/tty.c
new file mode 100644
index 0000000..74715a2
--- /dev/null
+++ b/kernel/drivers/tty.c
@@ -0,0 +1,105 @@
+#include <lib.h>
+#include <comus/drivers/tty.h>
+#include <comus/asm.h>
+#include <comus/memory.h>
+#include <stdint.h>
+#include <stdio.h>
+
+#define VGA_ADDR 0xB8000
+
+static const uint8_t width = 80;
+static const uint8_t height = 25;
+static volatile uint16_t *buffer = NULL;
+
+// position
+static uint32_t x, y;
+
+// color
+static uint8_t fg, bg;
+
+// blank color
+const uint16_t blank = (uint16_t) 0 | 0 << 12 | 15 << 8;
+
+static void term_clear_line(int line) {
+	if (line < 0 || line >= height)
+		return;
+	for (uint8_t x = 0; x < width; x++) {
+		const size_t index = line * width + x;
+		buffer[index] = blank;
+	}
+}
+
+static void term_clear(void) {
+    for (uint8_t y = 0; y < height; y++)
+        term_clear_line(y);
+}
+
+static void term_scroll(int lines) {
+	cli();
+	y -= lines;
+	if (!lines) return;
+	if (lines >= height || lines <= -height) {
+		term_clear();
+	} else if (lines > 0) {
+		memmovev(buffer, buffer + lines * width, 2 * (height - lines) * width);
+		term_clear_line(height - lines);
+	} else {
+		memmovev(buffer + lines * width, buffer + lines, (height + lines) * width);
+	}
+	sti();
+}
+
+void tty_init(void)
+{
+	buffer = mapaddr((void*)VGA_ADDR, width * height * sizeof(uint16_t));
+	x = 0;
+	y = 0;
+	fg = 15;
+	bg = 0;
+}
+
+void tty_out(char c)
+{
+	if (buffer == NULL)
+		return;
+
+	// handle special chars
+	switch (c) {
+	case '\n':
+		x = 0;
+		y++;
+		break;
+	case '\t':
+		x += 4;
+		break;
+	case '\v':
+	case '\f':
+		y++;
+		break;
+	case '\r':
+		x = 0;
+		break;
+	default: {
+		const size_t index = y * width + x;
+		buffer[index] = c | bg << 12 | fg << 8;
+		x++;
+	}
+	}
+
+	// wrap cursor if needed
+	if (x >= width) {
+		x = 0;
+		y++;
+	}
+	if (y >= height) {
+		term_scroll(y - (height - 1));
+		y = height - 1;
+	}
+
+	// set cursor position on screen
+	const uint16_t pos = y * width + x;
+	outb(0x3D4, 0x0F);
+	outb(0x3D5, (uint8_t) (pos & 0xFF));
+	outb(0x3D4, 0x0E);
+	outb(0x3D5, (uint8_t) ((pos >> 8) & 0xFF));
+}