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#include "vga.h"
#include <stdint.h>
#include <sys/io.h>
#define cga_idx_port 0x3d4
#define cga_dat_port 0x3d5
#define cursor_start 0x0a
#define cursor_end 0x0b
#define cursor_addr_h 0x0e
#define cursor_addr_l 0x0f
#define 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(cursor_start, cga_idx_port);
outb((inb(cga_dat_port) & 0xc0) | start, cga_dat_port);
outb(cursor_end, cga_idx_port);
outb((inb(cga_dat_port) & 0xe0) | end, cga_dat_port);
}
void
vga_disable_cursor()
{
outb(cursor_start, cga_idx_port);
outb(cursor_hide, cga_dat_port);
}
void
vga_update_cursor()
{
const uint16_t pos = row * width + col;
outb(cursor_addr_l, cga_idx_port);
outb(pos & 0xff, cga_dat_port);
outb(cursor_addr_h, cga_idx_port);
outb((pos >> 8) & 0xff, cga_dat_port);
}
// *** Text Mode Output ***
void
vga_putc(__attribute__((unused)) const FILE *self, 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;
}
}
int
vga_puts(const FILE *self, const char *string, int len)
{
int written = 0;
if (len == -1)
while (*string != '\0') {
vga_putc(self, *string);
++string;
++written;
}
else
for (int i = 0; i < len; ++i) {
vga_putc(self, string[i]);
++written;
}
return written;
}
void
vga_flush(__attribute__((unused)) const FILE *self)
{
vga_update_cursor();
}
// *** Text Mode ***
FILE vga_stream;
FILE *
vga_init()
{
buffer = (struct VGAEntry *)0xc03ff000;
vga_enable_cursor(14, 15);
vga_clear(VGA_COLOR_LIGHT_BLUE, VGA_COLOR_LIGHT_GREY);
vga_stream.id = 0;
vga_stream.putc = &vga_putc;
vga_stream.puts = &vga_puts;
vga_stream.flush = &vga_flush;
return &vga_stream;
}
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();
}
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