1 files changed, 112 insertions, 0 deletions
diff --git a/src/vga.c b/src/vga.c
new file mode 100644
index 0000000..150af9b
--- /dev/null
+++ b/src/vga.c
@@ -0,0 +1,112 @@
+#include <nrvn.h>
+#include <vga.h>
+
+static size_t vga_x, vga_y;
+static uint8_t vga_color;
+static uint16_t *vga_buffer;
+
+void vga_init(void) {
+	vga_x = vga_y = 0;
+	vga_set_color(VGA_LIGHT_MAGENTA, VGA_BLACK);
+	vga_buffer = (uint16_t *)0xB8000;
+	for (size_t y = 0; y < VGA_HEIGHT; y++)
+		for (size_t x = 0; x < VGA_WIDTH; x++)
+			vga_buffer[y * VGA_WIDTH + x] = ' ' | (vga_color << 8);
+}
+
+void vga_scroll() {
+	if (vga_y < VGA_HEIGHT)
+		return;
+
+	for (size_t y = 0; y < VGA_HEIGHT - 1; y++) {
+		for (size_t x = 0; x < VGA_WIDTH; x++) {
+			const size_t from = (y + 1) * VGA_WIDTH + x;
+			const size_t to = y * VGA_WIDTH + x;
+			vga_buffer[to] = vga_buffer[from];
+		}
+	}
+	vga_y = VGA_HEIGHT - 1;
+	for (size_t x = 0; x < VGA_HEIGHT; x++) {
+		vga_buffer[vga_y * VGA_WIDTH + x] = ' ' | (vga_color << 8);
+	}
+}
+
+void vga_update_cursor(void) {
+	size_t index = vga_y * VGA_WIDTH + vga_x;
+
+	outb(0x3D4, 14);
+	outb(0x3D5, index >> 8);
+	outb(0x3D4, 15);
+	outb(0x3D5, index);
+}
+
+void vga_putn(const size_t number) {
+	char digits[32] = { 0 };
+	size_t num = number, count = 0;
+	do {
+		digits[count] = (num % 10) + '0';
+		count++;
+	} while ((num /= 10) > 0);
+
+	do {
+		vga_putc(digits[count]);
+	} while (count-- > 0);
+}
+
+void vga_putx(const size_t hex) {
+	char digits[32] = { 0 };
+	size_t num = hex, count = 0;
+	do {
+		digits[count] = "0123456789abcdef"[num % 16];
+		count++;
+	} while ((num /= 16) > 0);
+
+	vga_puts("0x");
+	do {
+		vga_putc(digits[count]);
+	} while (count-- > 0);
+}
+
+void vga_putc(const char c) {
+	switch (c) {
+		case '\n':
+			vga_x = 0;
+			vga_y++;
+			break;
+		case '\b':
+			if (vga_x > 0)
+				vga_x--;
+			break;
+		case '\r':
+			vga_x = 0;
+			break;
+		case '\t':
+			break;
+		default:
+			// Any character greater than and including a space, is a printable character
+			if (c >= ' ')
+				vga_buffer[vga_y * VGA_WIDTH + vga_x++] = (uint16_t) c | ((uint16_t) vga_color << 8);
+	}
+
+	if (vga_x >= VGA_WIDTH) {
+		vga_x = 0;
+		vga_y++;
+	}
+
+	vga_scroll();
+	vga_update_cursor();
+}
+
+void vga_puts(const char *s) {
+	while (*s)
+		vga_putc(*s++);
+}
+
+void vga_putsn(const char *s, const size_t len) {
+	for (size_t i = 0; i < len; i++)
+		vga_putc(s[i]);
+}
+
+void vga_set_color(const uint8_t fg, const uint8_t bg) {
+	vga_color = fg | bg << 4;
+}