build.js

var fs = require('fs');

var inputFile = 'messages';
var language = 'en';

if(process.argv[2]) {
  language = process.argv[2];
}
inputFile += '_' + language + '.str';

console.log("Processing file " + inputFile);

fs.readFile(inputFile, {encoding: 'ascii'}, function(err, data) {
  if (err) {
    throw err;
  }

  var outputFile = 'progmemStrings.h';
  fs.writeFileSync(outputFile, 
    "// DO NOT EDIT THIS FILE. It was generated from " + inputFile 
    + " by running the command 'node build.js " + language + "'\n\n#include <avr/pgmspace.h>\n\n",
    {encoding: 'ascii'});

  var lines = data.split('\u000a');

  var messages = "const char* const messages[] PROGMEM = {\n  ";
  var array = "const char* const messages[] PROGMEM = {";
  lines.pop();
  var count = 0;
  for(var i = 0 ; i < lines.length; i++) {
    if (!lines[i].length || lines[i][0] === '#') {
      continue;
    }

    var elements = lines[i].split(' ');
    var name = elements.shift();
    var value = elements.join(' ');

    var varNameElements = name.toLowerCase().split('_');
    var varName = varNameElements.shift();
    while(varNameElements.length) {
      var next = varNameElements.shift();
      varName += next[0].toUpperCase() + next.substr(1);
    }
    // Bug in GSM module cuts messages at lowercase 'w'
    // Make sure we don't have any lowercase 'w'
    // http://forum.arduino.cc/index.php?topic=269661.0
    value = value.replace(/w/g, 'W');

    if (name != '') {
      fs.appendFileSync(outputFile, 
        "const char " + varName + "[] PROGMEM = {" + value + "};\n"
        + "#define " + name + " " + count + "\n",
      {encoding: 'ascii'});

      messages += varName;
      if (i < lines.length-1) {
         messages += ", ";
      }
      if ((count + 1)%5 == 0) {
        messages += "\n  ";
      }
      count ++;
    }
  }
  messages += "\n};";

  fs.appendFileSync(outputFile, 
    messages,
  {encoding: 'ascii'});

});