#include <conio.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define ROWS 24
#define COLS 40

#define BASL      0x28
#define RD80VID 0xC01F
#define LOWSCR  0xC054
#define HISCR   0xC055

char* getscreen(void)
{
  char wide = *(signed char*)RD80VID < 0;
  unsigned char x = wherex();
  unsigned char y = wherey();
  unsigned char row;
  char* screen;
  char* buffer;

  screen = buffer = malloc(1 + ROWS * COLS * (1 + wide) + 2);
  *screen++ = wide;

  for (row = 0; row < ROWS; ++row)
  {
    gotoy(row);
    memcpy(screen, *(char**)BASL, COLS);
    screen += COLS;
    if (wide)
    {
      *(char*)HISCR = 0;
      memcpy(screen, *(char**)BASL, COLS);
      screen += COLS;
      *(char*)LOWSCR = 0;
    }
  }
  *screen++ = y;
  *screen   = x;

  gotoy(y);
  return buffer;
}

void putscreen(char* screen)
{
  char wide = *screen++;
  unsigned char row;

  for (row = 0; row < ROWS; ++row)
  {
    gotoy(row);
    memcpy(*(char**)BASL, screen, COLS);
    screen += COLS;
    if (wide)
    {
      *(char*)HISCR = 0;
      memcpy(*(char**)BASL, screen, COLS);
      screen += COLS;
      *(char*)LOWSCR = 0;
    }
  }
  gotoy(*screen++);
  gotox(*screen);
}

void main(void)
{
  void* screen;

  printf("Init...\n");
  screen = getscreen();

  cgetc();
  clrscr();
  printf("Hello, World\n");  

  cgetc();
  putscreen(screen);
  printf("Exit...\n");

  free(screen);
}