pcvideo.c

nucleus 文件系统,内核和彩色图形系统,在小系统上非常好用

#include <dos.h>
#include <bios.h>

/* PCVIDEO.C -
    This file has two routines.
    1. _screen_say()
    2. screen_clear()

    They write characters to and clear the screen. All other io is portable
    except the keyboard functions. in looping(); */
    

#define ATTRIB 15
unsigned char far *video = 0;

unsigned char far *video_address()
{
union REGS regs;

    if (video)
        return(video);

    /* Write chars using bios. Read them back via pointer to find the video 
       address */

    /* Assume mono to start */
    video =  (unsigned char far *) 0xB0000000L;
    /* Put the cursor at 0, 0 */
    regs.h.ah = 2;regs.h.dh = 0;regs.h.dl = 0;regs.h.bh = 0;int86(0x10,&regs,&regs);
    /* Write '~' */
    regs.h.ah = 0x0a; regs.h.al = '~';
    regs.h.bh = 0;regs.h.bl = 0;
    regs.x.cx = 1;int86(0x10,&regs,&regs);
    if (*video == (unsigned char) '~')
    {    /* Write 'X' */
        regs.h.ah = 0x0a; regs.h.al = 'X';
        regs.h.bh = 0;regs.h.bl = 0;
        regs.x.cx = 1;int86(0x10,&regs,&regs);
        if (*video ==  (unsigned char) 'X')
            return(video);
    }
    video =  (unsigned char far *) 0xB8000000L;  /* Must be color */
    return(video);
}

void _screen_say(int length, int x, int y, unsigned char *p)
{
	unsigned char far *v;
    int i;
    v = video_address() + (y*160)+x*2;
    for (i = 0; i < length; i++)
    {
        if (*p)
            *v++ = *p++;
        else
            *v++ = ' ';
        *v++ = (unsigned char) ATTRIB;
    }
}

void screen_clear()
{
	unsigned char far *v;
    int i;

    v = video_address();
    for (i = 0; i < 80*25; i++)
    {
       *v++ = ' ';
       *v++ = (unsigned char) ATTRIB;
    }
}