dos33fsprogs/gr-sim/hgr/random16.c
2018-09-10 15:04:57 -04:00

153 lines
2.2 KiB
C

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include "6502_emulate.h"
#include "gr-sim.h"
#define SEEDL 0x4e
#define SEEDH 0x4f
#define MAGIC "vW" // $7657
static int cycles=0;
static int path=0;
#define PATH_R16 1
#define PATH_LNZ 2
#define PATH_LOZ 4
#define PATH_NEO 8
#define PATH_DEO 16
#define PATH_CEO 32
#define PATH_CEP 64
/* based on Linear feedback shift register type of PRNG by White Flame */
/* http://codebase64.org/doku.php?id=base:small_fast_16-bit_prng */
unsigned short random16(void) {
path=0;
path|=PATH_R16;
lda(SEEDL); cycles+=3;
if (a==0) {
cycles+=3;
goto low_zero;
}
cycles+=2;
//lownz:
path|=PATH_LNZ;
asl_mem(SEEDL); cycles+=5;
lda(SEEDH); cycles+=3;
rol(); cycles+=2;
if (c==1) {
cycles+=3;
goto five_cycle_do_eor;
}
cycles+=2;
if (c==0) {
cycles+=3;
goto two_cycle_no_eor;
}
fprintf(stderr,"CAN'T HAPPEN\n");
eleven_cycle_do_eor:
cycles+=6;
five_cycle_do_eor:
cycles+=2;
three_cycle_do_eor:
sta(SEEDH); cycles+=3;
//do_eor:
path|=PATH_DEO;
a=a^0x76; cycles+=2;
sta(SEEDH); cycles+=3;
lda(SEEDL); cycles+=3;
a=a^0x57; cycles+=2;
sta(SEEDL); cycles+=3;
eor_rts:
cycles+=6;
return ((ram[SEEDH]<<8)|ram[SEEDL]);
six_cycles_no_eor:
cycles+=2;
four_cycle_no_eor:
cycles+=2;
two_cycle_no_eor:
cycles+=2;
//no_eor:
cycles+=2;
path|=PATH_NEO;
cycles+=6;
sta(SEEDH); cycles+=3;
cycles+=3;
goto eor_rts;
low_zero:
path|=PATH_LOZ;
lda(SEEDH); cycles+=3;
if (a==0) {
cycles+=3;
goto eleven_cycle_do_eor;
}
cycles+=2;
//ceo:
path|=PATH_CEO;
asl(); cycles+=2;
if (a==0) {
cycles+=3;
goto six_cycles_no_eor;
}
cycles+=2;
//cep:
path|=PATH_CEP;
if (c==0) {
cycles+=3;
goto four_cycle_no_eor;
}
cycles+=2;
if (c==1) {
cycles+=3;
goto three_cycle_do_eor;
}
cycles+=2;
return 0;
}
static int results[65536];
int main(int argc, char **argv) {
int i,x;
int errors=0;
memset(results,0,65536*sizeof(int));
for(i=0;i<65536*2;i++) {
cycles=0;
x=random16();
results[x]++;
if (cycles!=42) {
fprintf(stderr,"Error! Cycles=%d Path=%x\n",
cycles,path);
errors++;
}
}
for(i=0;i<65536;i++) {
if (results[i]!=2) printf("%d: %d\n",i,results[i]);
}
printf("Errors: %d\n",errors);
return 0;
}