// RANDOM.C
// From: Nico E de Vries <nevries@cc.ruu.nl>
// Date: Wed, 27 Jan 93 11:13:32 MET
// (C) 1993 AIP, all rights reserved
// AIP is not responsible for any damages resulting from use of this program.
//
// Use of this source or derivates of this source is allowed only
// * for non commercial use (no fee asked)
// * if this copyright is not changed in any way
// * if the name AIP is not used in the executable or its docs
// (use of the name Nico de Vries is allowed if he agrees)
// * and if AIP is notified of its use in a specific program
// No permision is needed. Notification is sufficient.
//
// (Notifications can be sent to Nico de Vries or directly to AIP)
//
// Notes:
// This routine only works in MS-DOS real mode. Not under Windows,
// DesqView, OS/2 etc.


#include <dos.h>
#include <stdlib.h>

// onld interrupt handler
static void interrupt (*vivOld)(void);

// needed to make clock run OK
static int iIntCtr;

// storage for temporary information
static volatile int iActive;
static volatile unsigned uCtr;
static int iPtr;
static unsigned puArray[32];

static void interrupt Handler (void){
// 0.86 ms timeslice
outportb (0x43,0x36);
outportb (0x40,0x0);
outportb (0x40,0x4);

if (iActive){
if (iPtr==32){
iActive=0;
iPtr=0;
} else {
puArray[iPtr] = uCtr;
iPtr++;
}
}

if (++iIntCtr==64){
(*vivOld)(); // 18.2 times per second call
iIntCtr=0;
}else
outportb (0x20, 0x20);
}

// remove handler
void RemHan (void){
disable();
setvect (0x08, vivOld);
enable();

// set timer to 18.2 times/second
outportb (0x43,0x36);
outportb (0x40,0);
outportb (0x40,0);
}

// install handler
void InstHan (void){
disable();
vivOld = getvect (0x08); // timer
setvect (0x08, Handler);
enable();
}

// generate true random number
unsigned long Random (void){
int i,j;
unsigned long res=0;
unsigned long tmp;
InstHan();
// to be on the safe side we intialize uCtr with the timer
uCtr = peek(0x40,0x6c) & 0xFF;

// repeat 8 times to change random "bursts" into random numbers
for (j=0;j<8;j++){
iActive=1;
while (iActive){
while (uCtr) uCtr--;
uCtr = 0xFF;
}
for (i=0;i<32;i++)
tmp = (tmp<<1) ^ (puArray[i] & 1);
res^=tmp;
}
RemHan();
return res;
}

#if 0 // TEST SOFTWARE

void main (void){
int i,j;
unsigned long r;
printf ("RANDOM [1.0] 'generates 16 true random numbers'\n");
printf ("(C) Copyright 1992, All rights reserved, AIP.\n");
printf ("'AS IS' use allowed for non commercial use only.\n");
printf ("AIP is not responsible for any damages resulting from use of this program.\n\n");
for (i=0;i<16;i++){
r = Random();
printf ("%08lX ",r);
for (j=0;j<32;j++){
printf ("%d",(r&(1L<<(31-j)))!=0);
}
printf ("\n");
}
}
#endif

#if 1 // TEST SOFTWARE #2, graphical investigation

// Can be used for testing AIP random generator.
// At least hercules, EGA or VGA needed.
// Source uses Borland BGI.

#include <graphics.h>

static int ctr[256];

// update histogram
void upd (int i){
ctr[i]++;
line (i+266,255-ctr[i],i+266,255-ctr[i]);
}

void main (void){
int i,j;
unsigned long r;

// INITIALIZE GRAPHICS
int gdriver = DETECT, gmode, errorcode;
initgraph(&gdriver, &gmode, "");
errorcode = graphresult();
if (errorcode != grOk){exit(1);}


for (;;){
// get 4 values in the range 0..255
unsigned long r = Random();
int x1 = r&255;
int x2 = (r>>8)&255;
int y1 = (r>>16)&255;
int y2 = (r>>24)&255;

// update histogram
upd (x1); upd (x2); upd (y1); upd (y2);

// update 2D image
line (x1,y1,x1,y1);
line (x2,y2,x2,y2);

if (kbhit()) break;
}

closegraph();
}
#endif