telebit.js/machine.js

'use strict';

var machine = {};
machine._version = 1;
machine.state = 0;
machine.states = { 0: 'version', 1: 'headerLength', 2: 'header', 3: 'data'/*, 4: 'error'*/ };
machine.states_length = Object.keys(machine.states).length;
machine.chunkIndex = 0;
machine.fns = {};

function debug(chunk, i, len) {
  i = i || 0;
  len = len || chunk.length - i;
  console.log(chunk.slice(i, len)[0]);
  console.log(chunk);
  console.log('state:', machine.states[machine.state]);
  console.log('statei:', machine.state);
  console.log('index:', machine.chunkIndex);
}

machine.fns.version = function (chunk) {
  //console.log('');
  //console.log('[version]');
  if ((255 - machine._version) !== chunk[machine.chunkIndex]) {
    console.error("not v" + machine._version + " (or data is corrupt)");
    // no idea how to fix this yet
  }
  machine.chunkIndex += 1;

  return true;
};


machine.headerLen = 0;
machine.fns.headerLength = function (chunk) {
  //console.log('');
  //console.log('[headerLength]');
  machine.headerLen = chunk[machine.chunkIndex];
  machine.chunkIndex += 1;

  return true;
};


machine.buf = null;
machine.bufIndex = 0;
//var buf = Buffer.alloc(4096);
machine.fns.header = function (chunk) {
  //console.log('');
  //console.log('[header]');
  var curSize = machine.bufIndex + (chunk.length - machine.chunkIndex);
  var partLen = 0;
  var str = '';
  var part;

  if (curSize < machine.headerLen) {
    // I still don't have the whole header,
    // so just create a large enough buffer,
    // write these bits, and wait for the next chunk.
    if (!machine.buf) {
      machine.buf = Buffer.alloc(machine.headerLen);
      //console.log('[1a] machine.headerLen:', machine.headerLen);
    }

    // partLen should be no more than the available size
    partLen = Math.min(machine.headerLen - machine.bufIndex, chunk.length - machine.chunkIndex);
    part = chunk.slice(machine.chunkIndex, machine.chunkIndex + partLen);
    chunk.copy(machine.buf, machine.bufIndex, machine.chunkIndex, machine.chunkIndex + partLen);
    machine.chunkIndex += partLen; // this MUST be chunk.length
    machine.bufIndex += partLen;

    return false;
  }
  else {
    // it's now ready to discover the whole header
    if (machine.buf) {
      str += machine.buf.slice(0, machine.bufIndex).toString();
    }

    partLen = machine.headerLen - str.length;
    part = chunk.slice(machine.chunkIndex, machine.chunkIndex + partLen);
    str += part.toString();

    machine.chunkIndex += partLen;
    machine.buf = null; // back to null
    machine.bufIndex = 0; // back to 0

    machine._headers = str.split(/,/g);

    machine.family = machine._headers[0];
    machine.address = machine._headers[1];
    machine.port = machine._headers[2];
    machine.bodyLen = parseInt(machine._headers[3], 10) || -1;

    return true;
  }
};

machine.fns.data = function (chunk) {
  //console.log('');
  //console.log('[data]');
  var curSize = machine.bufIndex + (chunk.length - machine.chunkIndex);
  //console.log('curSize:', curSize);
  //console.log('bodyLen:', machine.bodyLen, typeof machine.bodyLen);
  var partLen = 0;

  partLen = Math.min(machine.bodyLen - machine.bufIndex, chunk.length - machine.chunkIndex);

  if (curSize < machine.bodyLen) {
    //console.log('curSize < bodyLen');

    // I still don't have the whole header,
    // so just create a large enough buffer,
    // write these bits, and wait for the next chunk.
    if (!machine.buf) {
      machine.buf = Buffer.alloc(machine.bodyLen);
    }

    chunk.copy(machine.buf, machine.bufIndex, machine.chunkIndex, machine.chunkIndex + partLen);
    machine.chunkIndex += partLen; // this MUST be chunk.length
    machine.bufIndex += partLen;

    return false;
  }

  if (machine.buf) {
    // the completing remainder of the body is in the current slice
    chunk.copy(machine.buf, machine.bufIndex, machine.chunkIndex, machine.chunkIndex + partLen);
  }
  else {
    // the whole body is in the current slice
    machine.buf = chunk.slice(machine.chunkIndex, machine.chunkIndex + partLen);
  }

  machine.onMessage({
    family: machine.family
  , address: machine.address
  , port: machine.port
  , data: machine.buf
  });

  machine.chunkIndex += partLen;  // === chunk.length
  machine.buf = null;             // reset to null
  machine.bufIndex = 0;           // reset to 0

  return true;
};
machine.fns.addChunk = function (chunk) {
  //console.log('');
  //console.log('[addChunk]');
  machine.chunkIndex = 0;
  while (machine.chunkIndex < chunk.length) {
    //console.log('chunkIndex:', machine.chunkIndex, 'state:', machine.state);

    if (true === machine.fns[machine.states[machine.state]](chunk)) {
      machine.state += 1;
      machine.state %= machine.states_length;
    }
  }
};

module.exports = machine;

process.on('uncaughtException', function (err) {
  console.error(err);
  debug(Buffer.from([0]));
});