Chunk long PD (pen down) lines in hpgl into small blocks. This should help with plotters w/ little memory

chunk-hpgl.js

process.stdin.setEncoding('utf8');
let commands = [];
let current = '';

const flatten = (arr) => {
  return Array.prototype.concat(...arr);
}

const collectChunk = (chunk) => {
  current = current + chunk;
  if (current.indexOf(';') == -1) {
    return;
  }

  let x = current.split(';');
  current = x.pop();
  commands.push(x.map( (e) => e.trim() ));
  commands = flatten(commands);
}

process.stdin.on('readable', () => {
  const chunk = process.stdin.read();
  if (chunk !== null) {
    collectChunk(chunk);
  }
});

process.stdin.on('end', () => {
  const chunk = process.stdin.read();
  if (chunk !== null) {
    collectChunk(chunk);
  }

  run();
});

function run() {
  commands.forEach((cmd) => {
    // suppress Select Pen command
    if (cmd.indexOf('SP') > -1) return;

    if (cmd.length > 128) {
      let parts = cmd.split(',');
      if (parts[0][0] == 'P' && parts[0][1] == 'D') {
        parts[0] = parts[0].replace(/^PD/i, '');
        var chunk = 8;
        for (var i = 0, j = parts.length; i < j; i += chunk) {
          process.stdout.write('PD' + parts.slice(i, i+chunk).join(',') + ';');
        }
      }
    } else {
      process.stdout.write(cmd + ';');
    }
  });
}