kernel.cpp

#include "types.h"
#include "gdt.h"
#include "interrupts.h"
#include "keyboard.h"

// void printf(char* str)
// {
//     // anything written at this address will be printed on screen
//     // each byte in between are used for colour information
//     // 4 high bits + 4 low bits, foreground and background of char
//     // on start up these are already at a kind of default (white text on black) so it's not needed to set manually
//     // note to change for future when doing bg art
//     // Video memory address for VGA text mode
//     static uint16_t* VideoMemory = (uint16_t*)0xb8000;

//     // might need to update later if compiler issues with inconsistent int sizes
//     // Constants for screen dimensions
//     static uint8_t screenWidth = 80,  screenHeight = 25;

//     // Calculate the center position
//     static uint8_t centerRow = screenHeight / 2, centerCol = (screenWidth - 13) / 2;

//     // Loop through each character in the input string
//     for (int i = 0; str[i] != '\0'; ++i) {
//         // Calculate the position in the video memory
//         int position = (centerRow * screenWidth) + centerCol + i;

//         // Set the ASCII art character at the center of the screen
//         VideoMemory[position] = (VideoMemory[position] & 0xFF00) | str[i];

//         // Set the colour (alternating between shades of red and white)
//         // colours: 0x04 (dark red), 0x0C (light red), 0x07 (white)
//         uint16_t colour = ((i % 3) == 0 ? 0x0400 : ((i % 3) == 1 ? 0x0C00 : 0x0700));
//         VideoMemory[position] |= colour;
//     }
// } 

void printf(char* str)
{
    static uint16_t* VideoMemory = (uint16_t*)0xb8000;

    static uint8_t x=0,y=0;

    for(int i = 0; str[i] != '\0'; ++i)
    {
        switch(str[i])
        {
            case '\n':
                x = 0;
                y++;
                break;
            default:
                VideoMemory[80*y+x] = (VideoMemory[80*y+x] & 0xFF00) | str[i];
                x++;
                break;
        }

        if(x >= 80)
        {
            x = 0;
            y++;
        }

        if(y >= 25)
        {
            for(y = 0; y < 25; y++)
                for(x = 0; x < 80; x++)
                    VideoMemory[80*y+x] = (VideoMemory[80*y+x] & 0xFF00) | ' ';
            x = 0;
            y = 0;
        }
    }
}

typedef void (*constructor)();
extern "C" constructor start_ctors;
extern "C" constructor end_ctors;
extern "C" void callConstructors()
{
  for (constructor* i = &start_ctors; i != &end_ctors; i++)  
    (*i)();
}



// magic number could be used for error checking
extern "C" void kernelMain(const void* multiboot_structure, uint32_t /*magic_number*/)
{

    printf("A C H T U N G");

    GlobalDescriptorTable gdt;
    // instantiate table --> hardware
    InterruptManager interrupts(&gdt);
    
    //instantiate hardware before activate but after interrupt
    KeyboardDriver keyboard(&interrupts);

    interrupts.Activate();
    while(1);
}