XerzTerm: A serial terminal for controlling an Arduino (Uno)

XerzTerm.ino

/*
    XerzTerm - A serial terminal for controlling an Arduino (Uno)

    Written in 2018 by Francisco Gómez García <espectalll@kydara.com>

    To the extent possible under law, the author(s) have dedicated all copyright
    and related and neighboring rights to this software to the public domain
    worldwide. This software is distributed without any warranty.

    You should have received a copy of the CC0 Public Domain Dedication along
    with this software. If not, see
    <http://creativecommons.org/publicdomain/zero/1.0/>. 
*/

String input = "";
bool inputDone = false;
int INPUT_LEN = 128;

void setup() {
  Serial.begin(9600);
  input.reserve(INPUT_LEN);
  Serial.print("# ");
}

void loop() {
  if (inputDone) {
    String args[INPUT_LEN / 2] = {};
    int argsLen;
    
    parse(input, args, argsLen);
    exec(args, argsLen);
    
    input = "";
    inputDone = false;
    Serial.print("# ");
  }
}

void serialEvent() {
  while (Serial.available()) {
    char inputChar = (char)Serial.read();
    
    input += inputChar;
    
    if (inputChar == '\n') {
      inputDone = true;
    }
  }
}

void parse(String &text, String vars[], int &n) {
  int pos[INPUT_LEN / 2] = {};
  n = 0;
  
  text.trim();
  for (int i = text.indexOf(' ', 0);
        i != -1; i = text.indexOf(' ', ++i))
  {
    pos[n] = i;
    n++;
  }
  for (int i = 0; i <= n; i++)
  	vars[i] = text.substring(
  	    i > 0 ? pos[i - 1] + 1 : 0,
  	    i < n ? pos[i] : text.length());
  n++;
}

void exec(String vars[], int items) {
    vars[0].toLowerCase();
    int PIN = vars[1].toInt();
    
    if (items >= 1 && vars[0] == "echo") {
        for (int i = 1; i < items; i++) Serial.print(vars[i] + " ");
        Serial.println();
    }
    
    if (items >= 3 && vars[0] == "pinmode" &&
            PIN > 0 && PIN <= 13)
        pinMode(PIN, vars[2] == "output" ? OUTPUT : INPUT);
    
    if (items >= 2 && vars[0] == "on" &&
            PIN > 0 && PIN <= 13)
        digitalWrite(PIN, HIGH);
    
    if (items >= 2 && vars[0] == "off" &&
            PIN > 0 && PIN <= 13)
        digitalWrite(PIN, LOW);
}