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#define _DEFAULT_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <time.h>
#include <stdarg.h>
#include <endian.h>
#include "bits.c"
#include "fnt.c"
#include "log.c"
#define C8_RESET_VECTOR 0x200
#define C8_CYCLES_PER_FRAME 1000
typedef struct
{
u16 pc;
u8 sp;
u16 i;
u16 keys;
u64 cycles;
/* timers: */
u8 dt; /* - delay */
u8 st; /* - sound */
bool running;
union
{
struct
{
u8 v[16];
u64 disp[32];
u8 font[sizeof(fnt)];
u16 stack[16];
} sys;
u8 ram[4*KB];
} mem;
} chip8;
#define V mem.sys.v
#define STACK mem.sys.stack
#define DISPLAY mem.sys.disp
#define FONT mem.sys.font
#define RAM mem.ram
#include "instr.c"
void c8_reset(chip8* c8)
{
assert(c8);
assert(sizeof(c8->mem) > sizeof(fnt));
assert(sizeof(c8->mem) >= 4*KB);
memcpy(c8->FONT, fnt, sizeof(fnt));
c8->pc = C8_RESET_VECTOR;
c8->running = true;
}
void c8_dump_state(chip8* c8, bool stack)
{
int i = 0;
for(i = 0; i < (int)sizeof(c8->V); i += 4)
{
printf(" V%x: %02X (%-3d) ", i+0, c8->V[i+0], c8->V[i+0]);
printf("V%x: %02X (%-3d) ", i+1, c8->V[i+1], c8->V[i+1]);
printf("V%x: %02X (%-3d) ", i+2, c8->V[i+2], c8->V[i+2]);
printf("V%x: %02X (%-3d)\n", i+3, c8->V[i+3], c8->V[i+3]);
}
printf(" I:%04X SP: %02X DT: %02X ST: %02X\n", c8->i, c8->sp, c8->dt, c8->st);
if(stack)
{
printf("stack:\n");
for(i = 0; i < (int)sizeof(c8->STACK); i += 2)
{
printf(" %-2d: %04X ", i+0, c8->STACK[i+0]);
printf("%-2d: %04X\n", i+1, c8->STACK[i+1]);
}
}
}
int main(int argc, char** argv)
{
u64 sz = 0;
FILE* f = NULL;
chip8 c8 = {0};
srand(time(NULL));
c8_reset(&c8);
if(argc > 1)
{
u64 got = 0;
f = fopen(argv[1], "r");
if(!f) return 1;
fseek(f, 0, SEEK_END);
sz = (u64)ftell(f);
rewind(f);
if(sz >= (sizeof(c8.RAM) - 512)) return 2;
got = fread(c8.RAM + C8_RESET_VECTOR, 1, sz, f);
if(got != sz) return 3;
fclose(f);
}
else
{
c8.RAM[C8_RESET_VECTOR + iota] = 0x60;
c8.RAM[C8_RESET_VECTOR + iota] = 0x04;
c8.RAM[C8_RESET_VECTOR + iota] = 0x61;
c8.RAM[C8_RESET_VECTOR + iota] = 0x03;
c8.RAM[C8_RESET_VECTOR + iota] = 0x72;
c8.RAM[C8_RESET_VECTOR + iota] = 0x01;
c8.RAM[C8_RESET_VECTOR + iota] = 0x80;
c8.RAM[C8_RESET_VECTOR + iota] = 0x14;
c8.RAM[C8_RESET_VECTOR + iota] = 0x30;
c8.RAM[C8_RESET_VECTOR + iota] = 0x10;
c8.RAM[C8_RESET_VECTOR + iota] = 0x12;
c8.RAM[C8_RESET_VECTOR + iota] = 0x04;
sz = iota;
}
printf("Disasm:\n");
{
u64 i;
char buf[512] = {0};
for(i = 0; i < sz; i += 2)
{
u16 pc = C8_RESET_VECTOR + i;
c8_disasm(c8.RAM, pc, buf);
printf("%04X: %s\n", pc, buf);
}
}
printf("\nExec:\n");
while(c8.running)
{
char buf[512] = {0};
if(c8.pc >= sizeof(c8.mem))
{
report(ERR, "PC Overflow!\n");
c8.running = false;
}
if(c8.pc & 0x0001)
{
report(ERR, "PC is not aligned!\n");
c8.running = false;
}
c8_disasm(c8.RAM, c8.pc, buf);
printf("%04X: %s\n", c8.pc, buf);
c8_exec(c8.RAM, c8.pc, &c8);
c8_dump_state(&c8, false);
c8.cycles++;
if((c8.cycles % C8_CYCLES_PER_FRAME) == 0)
{
if(c8.dt) c8.dt--;
if(c8.st) c8.st--;
}
c8.pc += 2;
}
return 0;
}
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