chip8.c

#include "chip8.h"
#include "ops.h"
#include <string.h>
#include <time.h>
#include <stdlib.h>
#include <stdio.h>

#define ZERO_INITIALIZE_ARR(arr, len) for (int i = 0; i < len; i++) arr[i] = 0;

const unsigned int START_ADDRESS = 0x200;
const unsigned int FONTSET_SIZE = 80;
const unsigned int FONTSET_START_ADDRESS = 0x50;

size_t rom_size = 0;

uint8_t fontset[FONTSET_SIZE] =
{
	0xF0, 0x90, 0x90, 0x90, 0xF0, // 0
	0x20, 0x60, 0x20, 0x20, 0x70, // 1
	0xF0, 0x10, 0xF0, 0x80, 0xF0, // 2
	0xF0, 0x10, 0xF0, 0x10, 0xF0, // 3
	0x90, 0x90, 0xF0, 0x10, 0x10, // 4
	0xF0, 0x80, 0xF0, 0x10, 0xF0, // 5
	0xF0, 0x80, 0xF0, 0x90, 0xF0, // 6
	0xF0, 0x10, 0x20, 0x40, 0x40, // 7
	0xF0, 0x90, 0xF0, 0x90, 0xF0, // 8
	0xF0, 0x90, 0xF0, 0x10, 0xF0, // 9
	0xF0, 0x90, 0xF0, 0x90, 0x90, // A
	0xE0, 0x90, 0xE0, 0x90, 0xE0, // B
	0xF0, 0x80, 0x80, 0x80, 0xF0, // C
	0xE0, 0x90, 0x90, 0x90, 0xE0, // D
	0xF0, 0x80, 0xF0, 0x80, 0xF0, // E
	0xF0, 0x80, 0xF0, 0x80, 0x80  // F
};

void ch_initialize(chip_8* proc) {
	ZERO_INITIALIZE_ARR(proc->registers, NUM_REGISTERS);
	ZERO_INITIALIZE_ARR(proc->memory, MEM_SIZE);
	ZERO_INITIALIZE_ARR(proc->stack, STACK_SIZE);
	ZERO_INITIALIZE_ARR(proc->keypad, KEYPAD_SIZE);
	ZERO_INITIALIZE_ARR(proc->video, VIDEO_SIZE);

	proc->index = 0;
	proc->sp = 0;
	proc->delayTimer = 0;
	proc->soundTimer = 0;
	proc->pc = START_ADDRESS;
	memcpy(proc->memory + FONTSET_START_ADDRESS, fontset, FONTSET_SIZE);	

	srand(time(NULL));
	initialize_optable();
}

unsigned char getRandomByte() {
	return (unsigned char)(rand() & 0xFF);
}

void ch_loadRom(chip_8* proc, char const* filename) {
	FILE* rom = fopen(filename, "rb");
	long startPos, endPos;
	if (!feof(rom)) {
		startPos = ftell(rom);
		if (startPos == -1) {
			printf("Processing error\n");
			exit(1);
		}

		fread(proc->memory + START_ADDRESS, MEM_SIZE - START_ADDRESS, 1, rom);

		endPos = ftell(rom);

		if (endPos == -1) {
			printf("Processing error\n");
			exit(1);
		}

		rom_size = endPos - startPos;
	}

	fclose(rom);


}

void ch_cycle(chip_8* proc) {
	proc->opcode = (proc->memory[proc->pc] << 8u) | (proc->memory[proc->pc + 1]);
	proc->pc += 2;
	decxec(proc);

	if (proc->delayTimer > 0) --proc->delayTimer;

	if (proc->soundTimer > 0) --proc->soundTimer;
}

size_t ch_numBytes() { return rom_size; }