RockOS/kernel/drivers/vga/vga_stream_writer.c

#include <stddef.h>
#include <stdint.h>

#include <lib/stream.h>

#define VGA_WIDTH   80
#define VGA_HEIGHT  25
#define VGA_MEMORY  (0xB8000 + 0xC0000000)

enum vga_color {
	VGA_COLOR_BLACK = 0,
	VGA_COLOR_BLUE = 1,
	VGA_COLOR_GREEN = 2,
	VGA_COLOR_CYAN = 3,
	VGA_COLOR_RED = 4,
	VGA_COLOR_MAGENTA = 5,
	VGA_COLOR_BROWN = 6,
	VGA_COLOR_LIGHT_GREY = 7,
	VGA_COLOR_DARK_GREY = 8,
	VGA_COLOR_LIGHT_BLUE = 9,
	VGA_COLOR_LIGHT_GREEN = 10,
	VGA_COLOR_LIGHT_CYAN = 11,
	VGA_COLOR_LIGHT_RED = 12,
	VGA_COLOR_LIGHT_MAGENTA = 13,
	VGA_COLOR_LIGHT_BROWN = 14,
	VGA_COLOR_WHITE = 15,
};

size_t terminal_row;
size_t terminal_column;
uint8_t terminal_color;
uint16_t* terminal_buffer = (uint16_t*)VGA_MEMORY;

static inline uint8_t vga_entry_color(enum vga_color fg, enum vga_color bg) 
{
	return fg | bg << 4;
}

static inline uint16_t vga_entry(unsigned char uc, uint8_t color) 
{
	return (uint16_t) uc | (uint16_t) color << 8;
}

void vga_initialize() 
{
	terminal_row = 0;
	terminal_column = 0;
	terminal_color = vga_entry_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK);
	
	for (size_t y = 0; y < VGA_HEIGHT; y++) {
		for (size_t x = 0; x < VGA_WIDTH; x++) {
			const size_t index = y * VGA_WIDTH + x;
			terminal_buffer[index] = vga_entry(' ', terminal_color);
		}
	}
}

void vga_putchar(char c) 
{
	if (c == '\n') {
		terminal_row++;
		terminal_column = 0;
		return;
	}

	if (c == '\t') {
		for (int i = 0; i < 4; i++) {
			vga_putchar(' ');
		}
		return;
	}

    const size_t index = terminal_row * VGA_WIDTH + terminal_column;
    terminal_buffer[index] = vga_entry(c, terminal_color);
	if (++terminal_column == VGA_WIDTH) {
		terminal_column = 0;
		if (++terminal_row == VGA_HEIGHT)
			terminal_row = 0;
	}
}

print_stream_t vga_print_stream = {
    .putchar = vga_putchar,
    .trunc = vga_initialize,
};