nesem/controller.c at main · KoNickss/nesem · GitHub

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#include "controller.h"
#include "common.h"
#include <stdio.h>

typedef struct{
	byte state;
	byte cur_bit_mask;
	bool is_polled;
}joypad_state_t;

static joypad_state_t jp[2] = {{0, 1, false}, {0, 1, false}};

#define JOYPAD_COUNT (sizeof(jp)/sizeof(joypad_state_t))

static inline void check_for_valid_jp(JOYPAD_t joypad_index){
	if(joypad_index >= JOYPAD_COUNT){
		fprintf(stderr, "ERR: Tried to read from joypad %d which does not exist!\n", joypad_index);
		abort();
	}
}


byte joypad_read_bit(JOYPAD_t joypad_index){
	check_for_valid_jp(joypad_index);

	if(jp[joypad_index].is_polled == false) return 0; //Dont do anything with the controller if we never recived a poll command

	bool read_bit = !!(jp[joypad_index].state & jp[joypad_index].cur_bit_mask);
	jp[joypad_index].cur_bit_mask <<= 1;
	//Check if wrap around happens
	if(jp[joypad_index].cur_bit_mask == 0){
		jp[joypad_index].cur_bit_mask = 1;
		jp[joypad_index].is_polled = false;
	}

	//Idk why but emulators always have 0x40 as well as the bit read
	return 0x40 | (byte)read_bit;
}

void joypad_zero_out(JOYPAD_t joypad_index){
	check_for_valid_jp(joypad_index);

	jp[joypad_index].state = 0;
	jp[joypad_index].cur_bit_mask = 1;
}

void joypad_prepare_read(void){
	for(int i = 0; i < JOYPAD_COUNT; i++){
		jp[i].cur_bit_mask = 0b1;
	}
}

//Fills the shift register and publishes the button states
void joypad_publish_state(void){
	for(int i = 0; i < JOYPAD_COUNT; i++){
		jp[i].is_polled = true;
	}
}


void joypad_set_button(JOYPAD_t joypad_index, BUTTON_t bit_index, bool button_state){
	check_for_valid_jp(joypad_index);

	if(bit_index >= 8){
		fprintf(stderr, "ERR: jpad bit index of %d is too high!\n", bit_index);
		abort();
	}

	#ifdef DEBUG
		if(button_state == true){
			fprintf(stderr, "Pressed ");
		}else{
			fprintf(stderr, "Released ");
		}
		switch(bit_index){
			case BUTTON_A:
				fprintf(stderr, "A Button\n");
			break;
			case BUTTON_B:
				fprintf(stderr, "B Button\n");
			break;
			case BUTTON_SELECT:
				fprintf(stderr, "Select Button\n");
			break;
			case BUTTON_START:
				fprintf(stderr, "Start Button\n");
			break;
			case BUTTON_UP:
				fprintf(stderr, "Up Button\n");
			break;
			case BUTTON_DOWN:
				fprintf(stderr, "Down Button\n");
			break;
			case BUTTON_LEFT:
				fprintf(stderr, "Left Button\n");
			break;
			case BUTTON_RIGHT:
				fprintf(stderr, "Right Button\n");
			break;
		}

	#endif

	byte bval = ((byte)button_state) << bit_index;
	byte bmask = 1 << bit_index;
	jp[joypad_index].state &= ~bmask;
	jp[joypad_index].state |= bval;
}