kernel/arch/x86/tty/tty.c

   1 #define VGA_WIDTH 80
   2 #define VGA_HEIGHT 25
   3
   4 volatile char *video_memory = (char *) 0xB8000; /* VGA VRAM starts at 0xB8000 */
   5
   6 static int cursor_x = 0;
   7 static int cursor_y = 0;
   8
   9 void screen_clear(void)
  10 {
  11         int x, y;
  12         for ( y = 0; y < VGA_HEIGHT; y++ ) {
  13                 for ( x = 0; x < VGA_WIDTH; x++ ) {
  14                         video_memory[(y * VGA_WIDTH + x) * 2 + 1] = 0x07;
  15                         video_memory[(y * VGA_WIDTH + x) * 2] = ' ';
  16                 }
  17         }
  18
  19         cursor_x = 0;
  20         cursor_y = 0;
  21 }
  22
  23 void scroll_up(void)
  24 {
  25         int x, y;
  26         for ( y = 1; y < VGA_HEIGHT; y++ ) {
  27                 for ( x = 0; x < VGA_WIDTH; x++ ) {
  28                         video_memory[((y - 1) * VGA_WIDTH + x) * 2] = video_memory[(y * VGA_WIDTH + x) * 2];
  29                 }
  30         }
  31         for ( x = 0; x < VGA_WIDTH; x++ ) {
  32                 video_memory[((VGA_HEIGHT - 1) * VGA_WIDTH + x) * 2] = ' ';
  33         }
  34         cursor_y = VGA_HEIGHT - 1;
  35 }
  36
  37 void kprint(const char *string)
  38 {
  39         char next_char;
  40         next_char = *string;
  41
  42         while ( next_char != 0 ) {
  43                 if ( next_char == '\n') { cursor_x = 0; cursor_y++; }
  44                 else { video_memory[(cursor_y * VGA_WIDTH + cursor_x++) * 2] = next_char; }
  45                 if ( cursor_x >= VGA_WIDTH ) { cursor_x = 0; cursor_y++; }
  46                 if ( cursor_y >= VGA_HEIGHT ) { scroll_up(); }
  47                 next_char = *++string;
  48         }
  49 }