tty.cpp

#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>

#include <tty.h>

#include "vga.h"

namespace
{
    constexpr size_t VGA_WIDTH = 80;
    constexpr size_t VGA_HEIGHT = 25;
    uint16_t* constexpr VGA_MEMORY = reinterpret_cast<uint16_t*>(0xB8000);

    size_t terminal_row;
    size_t terminal_column;
    uint8_t terminal_color;
    uint16_t* terminal_buffer;
}

void terminal_initialize(void)
{
    terminal_row = 0;
    terminal_column = 0;
    terminal_color = vga_entry_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK);
    terminal_buffer = VGA_MEMORY;
    for(size_t y = 0; y < VGA_HEIGHT; ++y)
        for(size_t x = 0; x < VGA_WIDTH; ++x)
        {
            const size_t index = y * VGA_WIDTH + x;
            terminal_buffer[index] = vga_entry(' ', terminal_color);
        }
}

void terminal_setcolor(uint8_t color)
{
    terminal_color = color;
}

void terminal_putentryat(unsigned char c, uint8_t color, size_t x, size_t y)
{
    const size_t index = y * VGA_WIDTH + x;
    terminal_buffer[index] = vga_entry(c, color);
}

void terminal_putchar(char c)
{
    unsigned char uc = c;
    terminal_putentryat(uc, terminal_color, terminal_column, terminal_row);
    if(++terminal_column == VGA_WIDTH)
    {
        terminal_column = 0;
        if(++terminal_row == VGA_HEIGHT)
            terminal_row = 0;
    }
}

void terminal_write(const char* data, size_t size)
{
    for(size_t i = 0; i < size; ++i)
        terminal_putchar(data[i])
}

void terminal_writestring(const char* data)
{
    terminal_write(data, strlen(data));
}