nese/v1/src/input.c

#include "nes.h"


static uint8_t read_controller_bit(nes_controller* controller) {
    uint8_t state = 1;
    if (controller->shift < 0) {
        state = (controller->buttons >> Button_A) & 1;
    } else if (controller->shift < nes_controller_num_buttons) {
        state = (controller->buttons >> controller->shift) & 1;
        controller->shift++;
    }
    return state;
}

uint8_t nes_input_read(nes_input* input, uint16_t addr) {
    nes_controller* controller =
            &input->controllers[(nes_input_2_reg == addr)];
    return ((addr >> 8) & nes_controller_bus_mask) |
           read_controller_bit(controller);
}

void nes_input_write(nes_input* input, uint16_t addr, uint8_t val) {
    if (val & 1) {
        input->controllers[0].shift = -1;
        input->controllers[1].shift = -1;
    } else {
        input->controllers[0].shift = 0;
        input->controllers[1].shift = 0;
    }
}