8080-Emulator/emulator_shell.c

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h> // for the uintx_t's
#include <unistd.h> // for sleep
#include <gtk/gtk.h>

// gcc emulator_shell.c `pkg-config --cflags --libs gtk+-3.0` -o emulator

#define FREQUENCY 500
void keyDown(uint8_t key);
void keyUp(uint8_t key);

//===== GTK SETUP =====

static gboolean on_key_press(GtkWidget *widget, GdkEventKey *event, gpointer user_data)
{
    switch (event->keyval)
    {
        case GDK_KEY_Left:
            // Code to be executed when the left arrow key is pressed down
            g_print("Left arrow key pressed down\n");
            keyDown(1);
            break;
        case GDK_KEY_Right:
            // Code to be executed when the right arrow key is pressed down
            g_print("Right arrow key pressed down\n");
            keyDown(2);
            break;
        case GDK_KEY_space:
            // Code to be executed when the space bar is pressed down
            g_print("Space bar pressed down\n");
            keyDown(3);
            break;
        case GDK_KEY_c:
            // Code to be executed when the 'c' key is pressed down
            g_print("'c' key pressed down\n");
            keyDown(0);
            break;
        case GDK_KEY_s:
            // Code to be executed when the 's' key is pressed down
            g_print("'s' key pressed down\n");
            keyDown(4);
            break;
    }

    return FALSE;
}

static gboolean on_key_release(GtkWidget *widget, GdkEventKey *event, gpointer user_data)
{
    switch (event->keyval)
    {
        case GDK_KEY_Left:
            // Code to be executed when the left arrow key is released
            g_print("Left arrow key released\n");
            keyUp(1);
            break;
        case GDK_KEY_Right:
            // Code to be executed when the right arrow key is released
            g_print("Right arrow key released\n");
            keyUp(2);
            break;
        case GDK_KEY_space:
            // Code to be executed when the space bar is pressed down
            g_print("Space bar released\n");
            keyUp(3);
            break;
        case GDK_KEY_c:
            // Code to be executed when the 'c' key is pressed down
            g_print("'c' key released\n");
            keyUp(0);
            break;
        case GDK_KEY_s:
            // Code to be executed when the 's' key is pressed down
            g_print("'s' key released\n");
            keyUp(4);
            break;
    }
    return FALSE;
}

//===== EMULATOR SETUP =====

uint8_t in_port; //GLOBALLY DECLARED
char which_interrupt = 1; //GLOBALLY DECLARED

typedef struct ConditionCodes {
    //bitfields for condition codes
    //the number following the variables sets the number of bits    
    uint8_t    z:1;    
    uint8_t    s:1;    
    uint8_t    p:1;    
    uint8_t    cy:1;    
    uint8_t    ac:1;    
    uint8_t    pad:3;    
} ConditionCodes;


typedef struct State8080 {    
    uint8_t    a;    
    uint8_t    b;    
    uint8_t    c;    
    uint8_t    d;    
    uint8_t    e;    
    uint8_t    h;    
    uint8_t    l;    
    uint16_t    sp;    
    uint16_t    pc;    
    uint8_t     *memory;    
    ConditionCodes      cc;    
    uint8_t     int_enable;  
    uint8_t shift_offset;
    uint8_t shift0;
    uint8_t shift1;  
} State8080;

unsigned char cycles8080[] = {
	4, 10, 7, 5, 5, 5, 7, 4, 4, 10, 7, 5, 5, 5, 7, 4, //0x00..0x0f
	4, 10, 7, 5, 5, 5, 7, 4, 4, 10, 7, 5, 5, 5, 7, 4, //0x10..0x1f
	4, 10, 16, 5, 5, 5, 7, 4, 4, 10, 16, 5, 5, 5, 7, 4, //etc
	4, 10, 13, 5, 10, 10, 10, 4, 4, 10, 13, 5, 5, 5, 7, 4,
	
	5, 5, 5, 5, 5, 5, 7, 5, 5, 5, 5, 5, 5, 5, 7, 5, //0x40..0x4f
	5, 5, 5, 5, 5, 5, 7, 5, 5, 5, 5, 5, 5, 5, 7, 5,
	5, 5, 5, 5, 5, 5, 7, 5, 5, 5, 5, 5, 5, 5, 7, 5,
	7, 7, 7, 7, 7, 7, 7, 7, 5, 5, 5, 5, 5, 5, 7, 5,
	
	4, 4, 4, 4, 4, 4, 7, 4, 4, 4, 4, 4, 4, 4, 7, 4, //0x80..8x4f
	4, 4, 4, 4, 4, 4, 7, 4, 4, 4, 4, 4, 4, 4, 7, 4,
	4, 4, 4, 4, 4, 4, 7, 4, 4, 4, 4, 4, 4, 4, 7, 4,
	4, 4, 4, 4, 4, 4, 7, 4, 4, 4, 4, 4, 4, 4, 7, 4,
	
	11, 10, 10, 10, 17, 11, 7, 11, 11, 10, 10, 10, 10, 17, 7, 11, //0xc0..0xcf
	11, 10, 10, 10, 17, 11, 7, 11, 11, 10, 10, 10, 10, 17, 7, 11, 
	11, 10, 10, 18, 17, 11, 7, 11, 11, 5, 10, 5, 17, 17, 7, 11, 
	11, 10, 10, 4, 17, 11, 7, 11, 11, 5, 10, 4, 17, 17, 7, 11, 
};

//===== EMULATOR FUNCTIONS =====

int disassemble8080(unsigned char* code) {
    int opbytes = 1;
    switch (*code) {
        case 0x00: printf("NOP"); break;

        case 0x01: printf("LXI B,#$%02x%02x", code[2], code[1]); opbytes = 3; break;
        case 0x02: printf("STAX B"); break;
        case 0x03: printf("INX B"); break;
        case 0x04: printf("INR B"); break;
        case 0x05: printf("DCR B"); break;
        case 0x06: printf("MVI B,#$%02x", code[1]); opbytes = 2; break;
        case 0x07: printf("RLC"); break;
        case 0x08: printf("NOP"); break;

        case 0x09: printf("DAD B"); break;
        case 0x0a: printf("LDAX B"); break; 
        case 0x0b: printf("DCX B"); break;
        case 0x0c: printf("INR C"); break;
        case 0x0d: printf("DCR C"); break;
        case 0x0e: printf("MVI C,#$%02x", code[1]); opbytes = 2; break;
        case 0x0f: printf("RRC"); break;
        case 0x10: printf("NOP"); break;

        case 0x11: printf("LXI D,#$%02x%02x", code[2], code[1]); opbytes = 3; break;
        case 0x12: printf("STAX D"); break;
        case 0x13: printf("INX D"); break;
        case 0x14: printf("INR D"); break;
        case 0x15: printf("DCR D"); break;
        case 0x16: printf("MVI D,#$%02x", code[1]); opbytes = 2; break;
        case 0x17: printf("RAL"); break;
        case 0x18: printf("NOP"); break;

        case 0x19: printf("DAD D"); break;
        case 0x1a: printf("LDAX D"); break;
        case 0x1b: printf("DCX D"); break;
        case 0x1c: printf("INR E"); break;
        case 0x1d: printf("DCR E"); break;
        case 0x1e: printf("MVI E,#$%02x", code[1]); opbytes = 2; break;
        case 0x1f: printf("RAR"); break;
        case 0x20: printf("NOP"); break;

        case 0x21: printf("LXI H,#$%02x%02x", code[2], code[1]); opbytes = 3; break;
        case 0x22: printf("SHLD $%02x%02x", code[2], code[1]); opbytes = 3; break;
        case 0x23: printf("INX H"); break;
        case 0x24: printf("INR H"); break;
        case 0x25: printf("DCR H"); break;
        case 0x26: printf("MVI H,#$%02x", code[1]); opbytes = 2; break;
        case 0x27: printf("DAA"); break;
        case 0x28: printf("NOP"); break;

        case 0x29: printf("DAD H"); break;
        case 0x2a: printf("LHLD $%02x%02x", code[2], code[1]); opbytes = 3; break;
        case 0x2b: printf("DCX H"); break;
        case 0x2c: printf("INR L"); break;
        case 0x2d: printf("DCR L"); break;
        case 0x2e: printf("MVI L,#$%02x", code[1]); opbytes = 2; break;
        case 0x2f: printf("CMA"); break;
        case 0x30: printf("NOP"); break;

        case 0x31: printf("LXI SP,#$%02x%02x", code[2], code[1]); opbytes = 3; break;
        case 0x32: printf("STA $%02x%02x", code[2], code[1]); opbytes = 3; break;
        case 0x33: printf("INX SP"); break;
        case 0x34: printf("INR M"); break;
        case 0x35: printf("DCR M"); break;
        case 0x36: printf("MVI M,#$%02x", code[1]); opbytes = 2; break;
        case 0x37: printf("STC"); break;
        case 0x38: printf("NOP"); break;

        case 0x39: printf("DAD SP"); break;
        case 0x3a: printf("LDA $%02x%02x", code[2], code[1]); opbytes = 3; break;
        case 0x3b: printf("DCX SP"); break;
        case 0x3c: printf("INR A"); break;
        case 0x3d: printf("DCR A"); break;
        case 0x3e: printf("MVI A,#$%02x", code[1]); opbytes = 2; break;
        case 0x3f: printf("CMC"); break;

        case 0x40: printf("MOV B,B"); break;
        case 0x41: printf("MOV B,C"); break;
        case 0x42: printf("MOV B,D"); break;
        case 0x43: printf("MOV B,E"); break;
        case 0x44: printf("MOV B,H"); break;
        case 0x45: printf("MOV B,L"); break;
        case 0x46: printf("MOV B,M"); break;
        case 0x47: printf("MOV B,A"); break;

        case 0x48: printf("MOV C,B"); break;
        case 0x49: printf("MOV C,C"); break;
        case 0x4a: printf("MOV C,D"); break;
        case 0x4b: printf("MOV C,E"); break;
        case 0x4c: printf("MOV C,H"); break;
        case 0x4d: printf("MOV C,L"); break;
        case 0x4e: printf("MOV C,M"); break;
        case 0x4f: printf("MOV C,A"); break;

        case 0x50: printf("MOV D,B"); break;
        case 0x51: printf("MOV D,C"); break;
        case 0x52: printf("MOV D,D"); break;
        case 0x53: printf("MOV D,E"); break;
        case 0x54: printf("MOV D,H"); break;
        case 0x55: printf("MOV D,L"); break;
        case 0x56: printf("MOV D,M"); break;
        case 0x57: printf("MOV D,A"); break;

        case 0x58: printf("MOV E,B"); break;
        case 0x59: printf("MOV E,C"); break;
        case 0x5a: printf("MOV E,D"); break;
        case 0x5b: printf("MOV E,E"); break;
        case 0x5c: printf("MOV E,H"); break;
        case 0x5d: printf("MOV E,L"); break;
        case 0x5e: printf("MOV E,M"); break;
        case 0x5f: printf("MOV E,A"); break;

        case 0x60: printf("MOV H,B"); break;
        case 0x61: printf("MOV H,C"); break;
        case 0x62: printf("MOV H,D"); break;
        case 0x63: printf("MOV H,E"); break;
        case 0x64: printf("MOV H,H"); break;
        case 0x65: printf("MOV H,L"); break;
        case 0x66: printf("MOV H,M"); break;
        case 0x67: printf("MOV H,A"); break;

        case 0x68: printf("MOV L,B"); break;
        case 0x69: printf("MOV L,C"); break;
        case 0x6a: printf("MOV L,D"); break;
        case 0x6b: printf("MOV L,E"); break;
        case 0x6c: printf("MOV L,H"); break;
        case 0x6d: printf("MOV L,L"); break;
        case 0x6e: printf("MOV L,M"); break;
        case 0x6f: printf("MOV L,A"); break;

        case 0x70: printf("MOV M,B"); break;
        case 0x71: printf("MOV M,C"); break;
        case 0x72: printf("MOV M,D"); break;
        case 0x73: printf("MOV M,E"); break;
        case 0x74: printf("MOV M,H"); break;
        case 0x75: printf("MOV M,L"); break;
        case 0x76: printf("HLT"); break;
        case 0x77: printf("MOV M,A"); break;

        case 0x78: printf("MOV A,B"); break;
        case 0x79: printf("MOV A,C"); break;
        case 0x7a: printf("MOV A,D"); break;
        case 0x7b: printf("MOV A,E"); break;
        case 0x7c: printf("MOV A,H"); break;
        case 0x7d: printf("MOV A,L"); break;
        case 0x7e: printf("MOV A,M"); break;
        case 0x7f: printf("MOV A,A"); break;

        case 0x80: printf("ADD B"); break;
        case 0x81: printf("ADD C"); break;
        case 0x82: printf("ADD D"); break;
        case 0x83: printf("ADD E"); break;
        case 0x84: printf("ADD H"); break;
        case 0x85: printf("ADD L"); break;
        case 0x86: printf("ADD M"); break;
        case 0x87: printf("ADD A"); break;

        case 0x88: printf("ADC B"); break;
        case 0x89: printf("ADC C"); break;
        case 0x8a: printf("ADC D"); break;
        case 0x8b: printf("ADC E"); break;
        case 0x8c: printf("ADC H"); break;
        case 0x8d: printf("ADC L"); break;
        case 0x8e: printf("ADC M"); break;
        case 0x8f: printf("ADC A"); break;

        case 0x90: printf("SUB B"); break;
        case 0x91: printf("SUB C"); break;
        case 0x92: printf("SUB D"); break;
        case 0x93: printf("SUB E"); break;
        case 0x94: printf("SUB H"); break;
        case 0x95: printf("SUB L"); break;
        case 0x96: printf("SUB M"); break;
        case 0x97: printf("SUB A"); break;

        case 0x98: printf("SBB B"); break;
        case 0x99: printf("SBB C"); break;
        case 0x9a: printf("SBB D"); break;
        case 0x9b: printf("SBB E"); break;
        case 0x9c: printf("SBB H"); break;
        case 0x9d: printf("SBB L"); break;
        case 0x9e: printf("SBB M"); break;
        case 0x9f: printf("SBB A"); break;

        case 0xa0: printf("ANA B"); break;
        case 0xa1: printf("ANA C"); break;
        case 0xa2: printf("ANA D"); break;
        case 0xa3: printf("ANA E"); break;
        case 0xa4: printf("ANA H"); break;
        case 0xa5: printf("ANA L"); break;
        case 0xa6: printf("ANA M"); break;
        case 0xa7: printf("ANA A"); break;

        case 0xa8: printf("XRA B"); break;
        case 0xa9: printf("XRA C"); break;
        case 0xaa: printf("XRA D"); break;
        case 0xab: printf("XRA E"); break;
        case 0xac: printf("XRA H"); break;
        case 0xad: printf("XRA L"); break;
        case 0xae: printf("XRA M"); break;
        case 0xaf: printf("XRA A"); break;

        case 0xb0: printf("ORA B"); break;
        case 0xb1: printf("ORA C"); break;
        case 0xb2: printf("ORA D"); break;
        case 0xb3: printf("ORA E"); break;
        case 0xb4: printf("ORA H"); break;
        case 0xb5: printf("ORA L"); break;
        case 0xb6: printf("ORA M"); break;
        case 0xb7: printf("ORA A"); break;

        case 0xb8: printf("CMP B"); break;
        case 0xb9: printf("CMP C"); break;
        case 0xba: printf("CMP D"); break;
        case 0xbb: printf("CMP E"); break;
        case 0xbc: printf("CMP H"); break;
        case 0xbd: printf("CMP L"); break;
        case 0xbe: printf("CMP M"); break;
        case 0xbf: printf("CMP A"); break;

        case 0xc0: printf("RNZ"); break;
        case 0xc1: printf("POP B"); break;
        case 0xc2: printf("JNZ $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xc3: printf("JMP $%02x%02x",code[2],code[1]); opbytes = 3; break; 
        case 0xc4: printf("CNZ $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xc5: printf("PUSH B"); break;
        case 0xc6: printf("ADI,#$%02x", code[1]); opbytes = 2; break;
        case 0xc7: printf("RST 0"); break;

        case 0xc8: printf("RZ"); break;
        case 0xc9: printf("RET"); break;
        case 0xca: printf("JZ $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xcb: printf("NOP"); break;
        case 0xcc: printf("CZ $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xcd: printf("CALL $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xce: printf("ACI,#$%02x", code[1]); opbytes = 2; break;
        case 0xcf: printf("RST 1"); break;

        case 0xd0: printf("RNC"); break;
        case 0xd1: printf("POP D"); break;
        case 0xd2: printf("JNC $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xd3: printf("OUT #$%02x", code[1]); opbytes = 2; break;
        case 0xd4: printf("CNC $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xd5: printf("PUSH D"); break;
        case 0xd6: printf("SUI,#$%02x", code[1]); opbytes = 2; break;
        case 0xd7: printf("RST 2"); break;

        case 0xd8: printf("RC"); break;
        case 0xd9: printf("NOP"); break;
        case 0xda: printf("JC $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xdb: printf("IN #$%02x", code[1]); opbytes = 2; break;
        case 0xdc: printf("CC $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xdd: printf("NOP"); break;
        case 0xde: printf("SBI,#$%02x", code[1]); opbytes = 2; break;
        case 0xdf: printf("RST 3"); break;

        case 0xe0: printf("RPO"); break;
        case 0xe1: printf("POP H"); break;
        case 0xe2: printf("JPO $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xe3: printf("XTHL"); break;
        case 0xe4: printf("CPO $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xe5: printf("PUSH H"); break;
        case 0xe6: printf("ANI,#$%02x", code[1]); opbytes = 2; break;
        case 0xe7: printf("RST 4"); break;

        case 0xe8: printf("RPE"); break;
        case 0xe9: printf("PCHL"); break;
        case 0xea: printf("JPE $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xeb: printf("XCHG"); break;
        case 0xec: printf("CPE $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xed: printf("NOP"); break;
        case 0xee: printf("XRI,#$%02x", code[1]); opbytes = 2; break;
        case 0xef: printf("RST 5"); break;

        case 0xf0: printf("RP"); break;
        case 0xf1: printf("POP PSW"); break;
        case 0xf2: printf("JP $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xf3: printf("DI"); break;
        case 0xf4: printf("CP $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xf5: printf("PUSH PSW"); break;
        case 0xf6: printf("ORI,#$%02x", code[1]); opbytes = 2; break;
        case 0xf7: printf("RST 6"); break;

        case 0xf8: printf("RM"); break;
        case 0xf9: printf("SPHL"); break;
        case 0xfa: printf("JM $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xfb: printf("EI"); break;
        case 0xfc: printf("CM $%02x%02x",code[2],code[1]); opbytes = 3; break;
        case 0xfd: printf("NOP"); break;
        case 0xfe: printf("CPI,#$%02x", code[1]); opbytes = 2; break;
        case 0xff: printf("RST 7"); break;

    }
    printf("\n");
    return opbytes;
}


void unknownInstruction(State8080* state) {
    printf("Error: Unknown instruction");
    return exit(1);
}

int parity(int x, int size)
{
	int i;
	int p = 0;
	x = (x & ((1<<size)-1));
	for (i=0; i<size; i++)
	{
		if (x & 0x1) p++;
		x = x >> 1;
	}
	return (0 == (p & 0x1));
}

void printState(State8080* state) {
    printf("\tC=%d,P=%d,S=%d,Z=%d\n", state->cc.cy, state->cc.p,    
        state->cc.s, state->cc.z);    
    printf("\tA $%02x B $%02x C $%02x D $%02x E $%02x H $%02x L $%02x SP %04x\n",    
        state->a, state->b, state->c, state->d,    
        state->e, state->h, state->l, state->sp); 
}

uint8_t machineIn(State8080* state, uint8_t port) {
    uint8_t a;
    switch(port) {
        case 0:
            a = 1;
            break;
        case 2:
            a = in_port;
            break;
        case 3:
        {
            uint16_t v = (state->shift1<<8) | (state->shift0);
            a = ((v >> (8-state->shift_offset)) & 0xff);
        }
            break;
    }
    return a;
}

void machineOut(State8080* state, uint8_t port, uint8_t value) {
    switch(port) {
        case 2:
        {
            state->shift_offset = value & 0x7;
        } break;
        case 4:
        {   
            state->shift0 = state->shift1;
            state->shift1 = value;
            break;
        }
    }
}


int emulate8080(State8080* state) {
    unsigned char *opcode = &(state->memory[state->pc]);

    printf("%04x ", state->pc);

    disassemble8080(opcode);
    state->pc++;

    switch(*opcode) {
        case 0x00: break;       // NOP does nothing
        case 0x01:              // LXI B, word
            state->c = opcode[1];
            state->b = opcode[2];
            state->pc += 2;
            break;
        case 0x05:              // DCR B
            {
            uint8_t res = state->b - 1;
            state->b = res;
            state->cc.z = (res == 0);
            state->cc.s = (0x80 == (res & 0x80));
            state->cc.p = parity(res, 8);
            }
            break;
        case 0x06:              // MVI B, byte
            state->b = opcode[1];
            state->pc += 1;
            break;
        case 0x09:              // DAD B
            {
            uint32_t h1 = (state->h << 8) | state->l;
            uint32_t bc = (state->b << 8) | state->c;
            uint32_t result = h1 + bc;
            state->h = (result & 0xff00) >> 8;
            state->l = result & 0xff;
            state->cc.cy = ((result & 0xffff0000) != 0);
            }
            break;
        
        case 0x0d:              // DCR C
            {
            uint8_t res = state->c - 1;
            state->c = res;
            state->cc.z = (res == 0);
            state->cc.s = ((res & 0x80) == 0x80);
            state->cc.p = parity(res, 8);
            }
            break;
        case 0x0e:              // MVI C, byte
            state->c = opcode[1];
            state->pc++;
            break;
        case 0x0f:              // RRC
            {
            uint8_t x = state->a;
            state->a = ((x & 1) << 7) | (x >> 1);
            state->cc.cy = (1 == (x & 1));
            }
            break;
        case 0x11:              // LXI D, word
            {
            state->d = opcode[2];
            state->e = opcode[1];
            state->pc += 2;
            }
            break;
        case 0x13:              // INX D
            {
            state->e++;
            if (state->e == 0) {
                state->d++;
            }}
            break;
        case 0x19:              // DAD D
            {
            uint32_t h1 = (state->h << 8) | state->l;
            uint32_t de = (state->d << 8) | state->e;
            uint32_t result = h1 + de;
            state->h = (result & 0xff00) >> 8;
            state->l = result & 0xff;
            state->cc.cy = ((result & 0xffff0000) != 0);
            }
            break;
        case 0x1a:              // LDAX D
            {
            uint16_t de = (state->d << 8) | state->e;
            state->a = state->memory[de];
            }
            break;

        case 0x21:              // LXI H, word
            {
            state->h = opcode[2];
            state->l = opcode[1];
            state->pc += 2;
            break;
            }
        case 0x23:              // INX H
            {
            state->l++;
            if (state->l == 0) {
                state->h++;
            }}
            break;
        case 0x26:              // MVI H, byte
            {
            state->h = opcode[1];
            state->pc++;
            }
            break;
        case 0x27:              // DAA
            {
            if ((state->a & 0x0f) > 9) {
                state->a += 6;
            } else if ((state->a & 0xf0) > 0x90) {
                uint16_t res = (uint16_t) state->a + 0x60;
                state->a = res & 0xff;
                state->cc.cy = (res > 0xff);
                state->cc.z = ((res & 0xff) == 0);
                state->cc.s = (0x80 == (res & 0x80));
                state->cc.p = parity((res & 0xff), 8);
            }
            }
        case 0x29:              // DAD H
            {
            uint32_t hl = (state->h << 8) | state->l;
            uint32_t result = hl + hl;
            state->h = (result & 0xff00) >> 8;
            state->l = result & 0xff;
            state->cc.cy = ((result & 0xffff0000) != 0);
            }
            break;
        case 0x31:              // LXI SP, word
            state->sp = ((opcode[2] << 8) | opcode[1]);
            state->pc += 2;
            break;
        case 0x32:              // STA adress
            {
            uint16_t adress = (opcode[2]<<8) | (opcode[1]);
            state->memory[adress] = state->a;
            state->pc += 2;
            }
            break;

        case 0x36:              // MVI M, byte
            {
            uint16_t adress = (state->h <<8) | (state->l);
            state->memory[adress] = opcode[1];
            state->pc++;
            }
            break;

        case 0x3a:              // LDA adress
            {
            uint16_t adress = (opcode[2]<<8) | (opcode[1]);
            state->a = state->memory[adress];
            state->pc += 2;
            }
            break;
        case 0x3e:              // MVI A, byte
            state->a = opcode[1];
            state->pc++;
            break;
        case 0x41:              // MOV B, C
            state->b = state->c; 
            break;
        case 0x42:              // MOV B, D
            state->b = state->d; 
            break;
        case 0x43:              // MOV B, E
            state->b = state->e; 
            break;
        case 0x56:              // MOV D, M
            {
            uint16_t adress = (state->h<<8) | (state->l);
            state->d = state->memory[adress];
            }
            break;
        case 0x5e:              // MOV E, M
            {
            uint16_t adress = (state->h<<8) | (state->l);
            state->e = state->memory[adress];
            }
            break;
        case 0x66:              // MOV H, M
            {
            uint16_t adress = (state->h<<8) | (state->l);
            state->h = state->memory[adress];
            }
            break;
        case 0x6f:              // MOV L, A
            state->l = state->a;
            break;
        case 0x77:              // MOV M, A
            {
            uint16_t adress = (state->h<<8) | (state->l);
            state->memory[adress] = state->a;
            }
            break;
        case 0x7a:              // MOV A, D
            state->a = state->d;
            break;
        case 0x7b:              // MOV A, E
            state->a = state->e;
            break;
        case 0x7c:              // MOV A, H
            state->a = state->h;
            break;
        case 0x7e:              // MOV A, M
            {
            uint16_t adress = (state->h<<8) | (state->l);
            state->a = state->memory[adress];
            }
            break;
        case 0x80:              // ADD B
            {
            uint16_t answer = (uint16_t) state->a + (uint16_t) state->b;
            state->cc.z = ((answer & 0xff) == 0);
            state->cc.s = ((answer & 0x80) != 0);
            state->cc.cy = (answer > 0xff);
            state->cc.p = parity(answer & 0xff, 8);
            state->a = answer & 0xff;
            }
            break;

        case 0x86:              // ADD M
            {
            uint16_t offset = (state->h<<8) | (state->l);
            uint16_t answer = (uint16_t) state->a + state->memory[offset];
            state->cc.z = ((answer & 0xff) == 0);
            state->cc.s = ((answer & 0x80) != 0);
            state->cc.cy = (answer > 0xff);
            state->cc.p = parity(answer & 0xff, 8);
            state->a = answer & 0xff;
            }
            break;
        case 0x1f:              // RAR
            {
            uint8_t x = state->a;
            state->a = (state->cc.cy << 7) | (x >> 1);
            state->cc.cy = (1 == (x & 1));
            }
            break;

        case 0xa7:              // ANA A
            state->a &= state->a;
            state->cc.z = (state->a == 0);
            state->cc.s = (0x80 == (state->a & 0x80));
            state->cc.p = parity(state->a, 8);
            state->cc.cy = 0;
            state->cc.ac = 0;
            break;
        case 0xaf:              // XRA A
            state->a ^= state->a;
            state->cc.z = (state->a == 0);
            state->cc.s = (0x80 == (state->a & 0x80));
            state->cc.p = parity(state->a, 8);
            state->cc.cy = 0;
            state->cc.ac = 0;
            break;
        case 0xc1:              // POP B
            state->c = state->memory[state->sp];
            state->b = state->memory[state->sp+1];
            state->sp += 2;
            break;

        case 0xc2:              // JNZ adress
            if (0 == state-> cc.z) {
                state->pc = (opcode[2] << 8) | opcode[1];
            } else {
                state->pc += 2;
            }
            break;
        
        case 0xc3:              // JMP adress
            state->pc = (opcode[2] << 8) | opcode[1];
            break;

        case 0xc5:              // PUSH B
            state->memory[state->sp-1] = state->b;
            state->memory[state->sp-2] = state->c;
            state->sp -= 2;
            break;
        case 0xc6:              // ADI byte
            {
            uint16_t answer = (uint16_t) state->a + (uint16_t) opcode[1];
            state->cc.z = ((state->a & 0xff) == 0);
            state->cc.s = ((state->a & 0x80) == 0x80);
            state->cc.cy = (state->a > 0xff);
            state->cc.p = parity(state->a & 0xff, 8);
            state->pc++;
            }
            break;
        case 0xc9:              // RET
            state->pc = (state->memory[state->sp+1] << 8) | state->memory[state->sp];
            state->sp += 2;
            break;
        case 0xcd:              // CALL adress
            {
            uint16_t ret = state -> pc+2;
            state->memory[state->sp-1] = (ret >> 8) & 0xff;
            state->memory[state->sp-2] = (ret & 0xff);
            state->sp -= 2;
            state->pc = (opcode[2] << 8) | opcode[1];
            }
            break;
        case 0xd1:              // POP D
            state->e = state->memory[state->sp];
            state->d = state->memory[state->sp+1];
            state->sp += 2;
            break;
        case 0xd3:              // OUT byte
            {
            uint8_t port = opcode[1];
            machineOut(state, port, 0x00); // PROBLEM: We need to pass a value to machineOUT
            state->pc++;
            }
            break;
        case 0xd5:              // PUSH D
            state->memory[state->sp-1] = state->d;
            state->memory[state->sp-2] = state->e;
            state->sp -= 2;
            break;
        case 0xdb:              // IN byte
            {
            uint8_t port = opcode[1];
            state->a = machineIn(state, port);
            state->pc++;
            }
            break;
        case 0xe1:              // POP H
            state->l = state->memory[state->sp];
            state->h = state->memory[state->sp+1];
            state->sp += 2;
            break;
        case 0xe5:              // PUSH H
            state->memory[state->sp-1] = state->h;
            state->memory[state->sp-2] = state->l;
            state->sp -= 2;
            break;

        case 0x2f:              // CMA (NOT)
            state->a = ~state->a;
            break; 
        case 0xe6:              // ANI byte
            {
            uint8_t x = state->a & opcode[1];
            state->cc.z = (x == 0);
            state->cc.s = (0x80 == (x & 0x80));
            state->cc.cy = 0;
            state->cc.p = parity(x, 8);
            state->pc++;
            }
            break;
        
        case 0xeb:              // XCHG
            {
            uint8_t tmp = state->h;
            state->h = state->d;
            state->d = tmp;
            tmp = state->l;
            state->l = state->e;
            state->e = tmp;
            }
            break;

        case 0xf1:              // POP PSW
            {
            state->a = state->memory[state->sp+1];
            uint8_t psw = state->memory[state->sp];
            state->cc.z = (0x01 == (psw & 0x01));
            state->cc.s = (0x02 == (psw & 0x02));
            state->cc.p = (0x04 == (psw & 0x04));
            state->cc.cy = (0x08 == (psw & 0x08));
            state->cc.ac = (0x10 == (psw & 0x10));
            state->sp += 2;
            }
            break;
        
        case 0xf5:              // PUSH PSW
            state->memory[state->sp-1] = state->a;
            state->memory[state->sp-2] = (state->cc.z | (state->cc.s << 1) | (state->cc.p << 2) | (state->cc.cy << 3) | (state->cc.ac << 4));
            state->sp -= 2;
            break;

        case 0xfb:              // EI
            state->int_enable = 1;  break;	
            break;

        case 0xfe:              // CPI byte
            {
            uint8_t x = state->a - opcode[1];
            state->cc.z = (x == 0);
            state->cc.s = (0x80 == (x & 0x80));
            state->cc.cy = (state->a < opcode[1]);
            state->cc.p = parity(x, 8);
            state->pc++;
            }
            break;

        default: unknownInstruction(state); break;
    }
    printState(state);
    return cycles8080[*opcode];
}

   void generateInterrupt(State8080* state, int interrupt_num)    
   {    
        //perform "PUSH PC"
        state->memory[state->sp-1] = ((state->pc & 0xFF00) >> 8);
        state->memory[state->sp-2] = (state->pc & 0xff);
        state->sp -= 2; 

        //Set the PC to the low memory vector.    
  
        state->pc = 8 * interrupt_num;
        state->int_enable = 0;    
   }    


void read_Space_Invaders_ROM(State8080* state, const char* filename, int offset) {
    //Works exclusively with the memory system of Space Invaders
    FILE* file = fopen(filename, "rb");
    if (file == NULL) {
        printf("Issue opening the file.\n");
        exit(1);
    }
    //Get the file size and read it into a memory buffer    
    fseek(file, 0L, SEEK_END);    
    int fsize = ftell(file);    
    fseek(file, 0L, SEEK_SET);

    uint8_t *buffer = &state->memory[offset];    

    fread(buffer, fsize, 1, file);    
    fclose(file);    
}

void keyDown(uint8_t key)
{
    switch(key) {
        case 0: // COIN
            in_port |= 0x1;
            break;
        case 1: // LEFT
            in_port |= 0x20;
            break;
        case 2: // RIGHT
            in_port |= 0x40;
            break;
        case 3: // FIRE
            in_port |= 0x10;
            break;
        case 4: // START
            in_port |= 0x04;
            break;
    }
}

void keyUp( uint8_t key)
{
    switch(key) {
        case 0: // COIN
            in_port &= ~0x1;
            break;
        case 1: // LEFT
            in_port &= ~0x20;
            break;
        case 2: // RIGHT
            in_port &= ~0x40;
            break;
        case 3: // FIRE
            in_port &= ~0x10;
            break;
        case 4: // START
            in_port &= ~0x04;
            break;
    }
}

void simulateNanoseconds(unsigned int numNanoseconds)
{
    struct timespec sleepTime;
    sleepTime.tv_sec = 0;
    sleepTime.tv_nsec = numNanoseconds;

    // Pause the program execution for the specified duration
    nanosleep(&sleepTime, NULL);
}


int main (int argc, char *argv[])  {

    // GTK INIT
    gtk_init(&argc, &argv);
    GtkWidget *window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    g_print("Test\n");
    g_signal_connect(window, "key-press-event", G_CALLBACK(on_key_press), NULL);
    g_signal_connect(window, "key-release-event", G_CALLBACK(on_key_release), NULL);
    gtk_widget_show(window);
    

    // EMULATOR INIT

    State8080 *state = (State8080*) calloc(1, sizeof(State8080)); //memset obsolte with calloc
    state->cc.z = 1;
    state->cc.s = 1;
    state->cc.p = 1;
    state->cc.cy = 0;
    state->cc.ac = 1;    
    state->pc = 0;
    state->memory = malloc(0x10000);

    read_Space_Invaders_ROM(state, "ROM/invaders.h", 0);
    read_Space_Invaders_ROM(state, "ROM/invaders.g", 0x800);
    read_Space_Invaders_ROM(state, "ROM/invaders.f", 0x1000);
    read_Space_Invaders_ROM(state, "ROM/invaders.e", 0x1800);
    gtk_main();



    int i = 0;
    char done = 0;
    int counter;
    int total_count = 0;

    while (!done) {
        counter = emulate8080(state);
        total_count += counter;

        i++;
        simulateNanoseconds(FREQUENCY * counter); // EMULATION OF THE PROCESSOR ŠPEED
        if ((total_count  > 16000000) && (state->int_enable))  //1/60 second has elapsed    
        {     
            // draw_screen(state);
            if (which_interrupt == 2) {
                generateInterrupt(state, 2);    //interrupt 2  
                total_count = 0;
                which_interrupt = 1;
            } else {
                generateInterrupt(state, 1);    //interrupt 0
                total_count = 0;
                which_interrupt = 2;
            }
        }    
    }

    free(state->memory);
    free(state);
    return 0;

}