for using rotary encoder on Arduino without library

Arduino_Rotary_Encoder.ino

#define ROT_PIN_A 2
#define ROT_PIN_B 3
uint8_t prev;
int16_t counter;

void funcInterruptA()
{
  Serial.print("A : ");
  funcInterrupt();  
}
void funcInterruptB()
{
  Serial.print("B : ");
  funcInterrupt();
}

int8_t checkStateRotaryEncoder(uint8_t status)
{
  int8_t result=0;
  static const uint8_t positive_array[4]={0b0010,0b1011,0b1101,0b0100};
  static const uint8_t negative_array[4]={0b0001,0b0111,0b1110,0b1000};
  for(int8_t i=0;i<4;i+=1)
  {
    if(status==positive_array[i])
    {
      result=1;
      break;
    }
    if(status==negative_array[i])
    {
      result=-1;
      break;
    }
  }
  return result;
}

void funcInterrupt()
{
  uint8_t current=0;
  uint8_t ca=(digitalRead(ROT_PIN_A));
  uint8_t cb=(digitalRead(ROT_PIN_B));
  current+=ca<<1;
  current+=cb;
  if(prev==current)
  {
    Serial.println();
    return;
  }
  current+=prev<<2;
  counter+=checkStateRotaryEncoder(current);
  Serial.println(counter);
//  current+=1<<4; //ゼロ埋めさせるためのダミー
//  Serial.println(current,BIN);
  prev=(ca<<1)+cb;
}

void setup() {
  Serial.begin(9600);
  pinMode(ROT_PIN_A,INPUT);
  pinMode(ROT_PIN_B,INPUT);
  attachInterrupt(digitalPinToInterrupt(ROT_PIN_A),funcInterruptA,CHANGE);
  attachInterrupt(digitalPinToInterrupt(ROT_PIN_B),funcInterruptB,CHANGE);
  prev=0;
  counter=0;
  Serial.println("START");
}

void loop() {
  delay(1000*1000*1000);
}