kernel/kernel.c at main · Buryyy/kernel · GitHub

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#include "kernel.h"

/*
16 bit video buffer elements(register ax)
8 bits(ah) higher :
  lower 4 bits - forec olor
  higher 4 bits - back color

8 bits(al) lower :
  8 bits : ASCII character to print
*/
uint16 vga_entry(unsigned char ch, uint8 fore_color, uint8 back_color)
{
  uint16 ax = 0;
  uint8 ah = 0, al = 0;

  ah = back_color;
  ah <<= 4;
  ah |= fore_color;
  ax = ah;
  ax <<= 8;
  al = ch;
  ax |= al;

  return ax;
}

//clear video buffer array
void clear_vga_buffer(uint16 **buffer, uint8 fore_color, uint8 back_color)
{
  uint32 i;
  for(i = 0; i < BUFSIZE; i++){
    (*buffer)[i] = vga_entry(NULL, fore_color, back_color);
  }
}

//initialize vga buffer
void init_vga(uint8 fore_color, uint8 back_color)
{
  vga_buffer = (uint16*)VGA_ADDRESS;  //point vga_buffer pointer to VGA_ADDRESS
  clear_vga_buffer(&vga_buffer, fore_color, back_color);
}

void kernel_entry()
{
  init_vga(WHITE, BLACK);

  vga_buffer[0] = vga_entry('H', WHITE, BLACK);
  vga_buffer[1] = vga_entry('e', WHITE, BLACK);
  vga_buffer[2] = vga_entry('l', WHITE, BLACK);
  vga_buffer[3] = vga_entry('l', WHITE, BLACK);
  vga_buffer[4] = vga_entry('o', WHITE, BLACK);
  vga_buffer[5] = vga_entry(' ', WHITE, BLACK);
  vga_buffer[6] = vga_entry('W', WHITE, BLACK);
  vga_buffer[7] = vga_entry('o', WHITE, BLACK);
  vga_buffer[8] = vga_entry('r', WHITE, BLACK);
  vga_buffer[9] = vga_entry('l', WHITE, BLACK);
  vga_buffer[10] = vga_entry('d', WHITE, BLACK);
}