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#include "vga.h"
#include <stdint.h>
#include <sys/io.h>
const uint16_t cga_idx_port = 0x3d4;
const uint16_t cga_dat_port = 0x3d5;
const uint8_t cursor_start = 0xa;
const uint8_t cursor_end = 0xb;
const uint8_t cursor_addr_h = 0xe;
const uint8_t cursor_addr_l = 0xf;
const uint8_t cursor_hide = 0x20;
struct __attribute__((packed)) VGAEntry {
unsigned char text;
uint8_t foreground : 4;
uint8_t background : 4;
};
_Static_assert(sizeof(struct VGAEntry) == 2, "sizeof VGAEntry");
const int width = 80;
const int height = 25;
struct VGAEntry *buffer;
int col = 0;
int row = 0;
// *** Cursor ***
void
vga_enable_cursor(unsigned char start, unsigned char end)
{
outb(cga_idx_port, cursor_start);
outb(cga_dat_port, (inb(cga_dat_port) & 0xc0) | start);
outb(cga_idx_port, cursor_end);
outb(cga_dat_port, (inb(cga_dat_port) & 0xe0) | end);
}
void
vga_disable_cursor()
{
outb(cga_idx_port, cursor_start);
outb(cga_dat_port, cursor_hide);
}
void
vga_update_cursor()
{
const uint16_t pos = row * width + col;
outb(cga_idx_port, cursor_addr_l);
outb(cga_dat_port, pos & 0xff);
outb(cga_idx_port, cursor_addr_h);
outb(cga_dat_port, (pos >> 8) & 0xff);
}
// *** Text Mode ***
void
vga_init()
{
buffer = (struct VGAEntry *)0xc03ff000;
vga_enable_cursor(0, 15);
vga_clear(VGA_COLOR_LIGHT_BLUE, VGA_COLOR_LIGHT_GREY);
}
void
vga_clear(enum vga_color foreground, enum vga_color background)
{
for (int y = 0; y < height; ++y)
for (int x = 0; x < width; ++x) {
const int index = y * width + x;
buffer[index].text = ' ';
buffer[index].foreground = foreground;
buffer[index].background = background;
}
col = row = 0;
vga_update_cursor();
}
void
vga_putc(char a)
{
switch (a) {
case '\n':
col = 0;
++row;
break;
case '\r':
col = 0;
break;
case '\b':
--col;
if (col < 0) col = 0;
break;
default:
buffer[row * width + col].text = a;
++col;
}
if (col == width) {
col = 0;
++row;
}
if (row == height) {
// scroll up
for (int y = 1; y < height; ++y)
for (int x = 0; x < width; ++x) {
const int prev = (y - 1) * width + x;
const int curr = y * width + x;
buffer[prev] = buffer[curr];
}
// blank out last row
for (int i = (height - 1) * width; i < height * width; ++i) buffer[i].text = ' ';
--row;
}
}
void
vga_puts(const char *string, int len)
{
if (len == -1)
while (*string != '\0') {
vga_putc(*string);
++string;
}
else
for (int i = 0; i < len; ++i) { vga_putc(string[i]); }
}
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