random16: have it validated for 42 cycles

gr-sim/hgr/Makefile

@@ -6,7 +6,7 @@ SDL_LIBS= `sdl-config --libs`
 SDL_INCLUDE= `sdl-config --cflags`
 GR_SIM = ../gr-sim.a
 
-all:	fireworks fw_purple lines image_load hgr_view seven
+all:	fireworks fw_purple lines image_load hgr_view seven random16
 
 ###
 
@@ -55,8 +55,16 @@ seven:	seven.o $(GR_SIM)
 seven.o:	seven.c
 	$(CC) $(CFLAGS) -c seven.c
 
+###
+
+random16:	random16.o $(GR_SIM)
+	$(CC) $(LFLAGS) $(SDL_LIBS) -o random16 random16.o $(GR_SIM)
+
+random16.o:	random16.c
+	$(CC) $(CFLAGS) -c random16.c
+
 ####
 
 
 clean:	
-	rm -f *~ *.o fireworks lines image_load hgr_view fw_purple seven
+	rm -f *~ *.o fireworks lines image_load hgr_view fw_purple seven random16

gr-sim/hgr/random16.c

@@ -0,0 +1,152 @@
+#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;
+}