void cpu_execute(struct cpu* cpu) {
cpu->pc += 2;
uint8_t vx = cpu->v[cpu->opcode.x];
uint8_t vy = cpu->v[cpu->opcode.y];
switch (cpu->opcode.op) {
case 0x0:
switch (cpu->opcode.n) {
case 0x0: return cpu_clear(cpu);
case 0xE: return cpu_jump(cpu, cpu->stack[--cpu->sp]);
default: return cpu_error(cpu);
}
case 0x1: return cpu_jump(cpu, cpu->opcode.addr);
case 0x2: return cpu_call(cpu, cpu->opcode.addr);
case 0x3: return cpu_skip(cpu, vx == cpu->opcode.kk);
case 0x4: return cpu_skip(cpu, vx != cpu->opcode.kk);
case 0x5: return cpu_skip(cpu, vx == vy);
case 0x6: return cpu_assign_register(cpu, cpu->opcode.x, cpu->opcode.kk);
case 0x7: return cpu_assign_register(cpu, cpu->opcode.x, vx + cpu->opcode.kk);
case 0x8:
switch (cpu->opcode.n) {
case 0x0: return cpu_assign_register(cpu, cpu->opcode.x, vy);
case 0x1: return cpu_assign_register(cpu, cpu->opcode.x, vx | vy);
case 0x2: return cpu_assign_register(cpu, cpu->opcode.x, vx & vy);
case 0x3: return cpu_assign_register(cpu, cpu->opcode.x, vx ^ vy);
case 0x4: return cpu_add_carry(cpu, vx, vy);
case 0x5: return cpu_subtract_borrow(cpu, vx, vy);
case 0x6: return cpu_shift_right(cpu);
case 0x7: return cpu_subtract_borrow(cpu, vy, vx);
case 0xE: return cpu_shift_left(cpu);
default: return cpu_error(cpu);
}
case 0x9: return cpu_skip(cpu, vx != vy);
case 0xA: return cpu_assign_i(cpu, cpu->opcode.addr);
case 0xB: return cpu_jump(cpu, cpu->opcode.addr + cpu->v[0]);
case 0xC: return cpu_random(cpu);
case 0xD: return cpu_draw(cpu);
case 0xE:
switch (cpu->opcode.kk) {
case 0x9E: return cpu_skip(cpu, SDL_GetKeyboardState(NULL)[key_map[vx]]);
case 0xA1: return cpu_skip(cpu, !SDL_GetKeyboardState(NULL)[key_map[vx]]);
default: return cpu_error(cpu);
}
case 0xF:
switch (cpu->opcode.kk) {
case 0x07: return cpu_assign_register(cpu, cpu->opcode.x, cpu->delay_timer);
case 0x0A: return cpu_wait_key_press(cpu);
case 0x15: return cpu_assign_delay_timer(cpu, vx);
case 0x18: return cpu_assign_sound_timer(cpu, vx);
case 0x1E: return cpu_assign_i(cpu, cpu->i + vx);
case 0x29: return cpu_assign_i(cpu, vx * 5);
case 0x33: return cpu_store_bcd(cpu);
case 0x55: return cpu_copy_to_memory(cpu);
case 0x65: return cpu_copy_from_memory(cpu);
default: return cpu_error(cpu);
}
}
return cpu_error(cpu);
}
void cpu_call(cpu_state_t *state, reg16_t addr)
{
reg16_t jump = addr;
cpu_push(state, state->pc);
cpu_jump(state, jump);
}
