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/*
* con.c
*
* Basic VGA text console. Implements printk().
*/
#include <asm/io.h>
#include <stdarg.h>
#include <stdint.h>
#include <stdio.h>
#define COLS 80
#define ROWS 25
static uint8_t *vram = (uint8_t*) 0xB8000;
static int pos;
static inline void cursorpos(int pos) {
outb(0x3D4, 0x0E);
outb(0x3D5, (uint8_t) ((pos >> 9) & 0xFF));
outb(0x3D4, 0x0F);
outb(0x3D5, (uint8_t) ((pos >> 1) & 0xFF));
}
/* scrolls the console up one line */
static void scroll_up(void) {
int n = (COLS * (ROWS - 1)) << 1;
uint8_t *p = vram;
while(n--) {
*p = p[COLS << 1];
p++;
}
p = (uint8_t*) (vram + (COLS * (ROWS - 1) << 1));
n = COLS;
while(n--) {
*p = ' ';
p += 2;
}
pos -= COLS << 1;
cursorpos(pos);
}
/* clear the console and reset the cursor to the starting position */
void con_clear(void) {
int n = COLS * ROWS;
uint8_t *p = vram;
while(n--) {
*(p++) = 0x20;
*(p++) = 0x07;
}
pos = 0;
cursorpos(0);
}
/* must be called before any console output */
void con_init(void) {
/* clear the console */
con_clear();
}
/* write a zero-terminated string to console */
static int con_puts(char *s) {
uint8_t *p = &vram[pos];
while(*s) {
if(*s == '\n') {
pos = (int) (p - vram);
pos = ((pos / (COLS << 1)) + 1) * (COLS << 1);
p = &vram[pos];
s++;
} else {
*p = *(s++);
p += 2;
}
pos = (int) (p - vram);
if(pos >= (COLS * ROWS) << 1)
scroll_up();
}
/* update the cursor position */
cursorpos(pos);
/* this always succeeds */
return 0;
}
int printk(char *fmt, ...) {
int ret;
char buf[1024];
va_list ap;
va_start(ap, fmt);
ret = vsprintf(buf, fmt, ap);
va_end(ap);
con_puts(buf);
return ret;
}
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