/files/phpjs/0.1/misc/pack.js

function pack (format) {
  // http://kevin.vanzonneveld.net
  // +   original by: Tim de Koning (http://www.kingsquare.nl)
  // +      parts by: Jonas Raoni Soares Silva (http://www.jsfromhell.com)
  // +   bugfixed by: Tim de Koning (http://www.kingsquare.nl)
  // %        note 1: Float encoding by: Jonas Raoni Soares Silva
  // %        note 2: Home: http://www.kingsquare.nl/blog/12-12-2009/13507444
  // %        note 3: Feedback: phpjs-pack@kingsquare.nl
  // %        note 4: 'machine dependent byte order and size' aren't
  // %        note 4: applicable for JavaScript; pack works as on a 32bit,
  // %        note 4: little endian machine
  // *     example 1: pack('nvc*', 0x1234, 0x5678, 65, 66);
  // *     returns 1: '4xVAB'
  var formatPointer = 0,
    argumentPointer = 1,
    result = '',
    argument = '',
    i = 0,
    r = [],
    instruction, quantifier, word, precisionBits, exponentBits, extraNullCount;

  // vars used by float encoding
  var bias, minExp, maxExp, minUnnormExp, status, exp, len, bin, signal, n, intPart, floatPart, lastBit, rounded, j, k, tmpResult;

  while (formatPointer < format.length) {
    instruction = format.charAt(formatPointer);
    quantifier = '';
    formatPointer++;
    while ((formatPointer < format.length) && (format.charAt(formatPointer).match(/[\d\*]/) !== null)) {
      quantifier += format.charAt(formatPointer);
      formatPointer++;
    }
    if (quantifier === '') {
      quantifier = '1';
    }

    // Now pack variables: 'quantifier' times 'instruction'
    switch (instruction) {
    case 'a':
      // NUL-padded string
    case 'A':
      // SPACE-padded string
      if (typeof arguments[argumentPointer] === 'undefined') {
        throw new Error('Warning:  pack() Type ' + instruction + ': not enough arguments');
      } else {
        argument = String(arguments[argumentPointer]);
      }
      if (quantifier === '*') {
        quantifier = argument.length;
      }
      for (i = 0; i < quantifier; i++) {
        if (typeof argument[i] === 'undefined') {
          if (instruction === 'a') {
            result += String.fromCharCode(0);
          } else {
            result += ' ';
          }
        } else {
          result += argument[i];
        }
      }
      argumentPointer++;
      break;
    case 'h':
      // Hex string, low nibble first
    case 'H':
      // Hex string, high nibble first
      if (typeof arguments[argumentPointer] === 'undefined') {
        throw new Error('Warning: pack() Type ' + instruction + ': not enough arguments');
      } else {
        argument = arguments[argumentPointer];
      }
      if (quantifier === '*') {
        quantifier = argument.length;
      }
      if (quantifier > argument.length) {
        throw new Error('Warning: pack() Type ' + instruction + ': not enough characters in string');
      }
      for (i = 0; i < quantifier; i += 2) {
        // Always get per 2 bytes...
        word = argument[i];
        if (((i + 1) >= quantifier) || typeof argument[i + 1] === 'undefined') {
          word += '0';
        } else {
          word += argument[i + 1];
        }
        // The fastest way to reverse?
        if (instruction === 'h') {
          word = word[1] + word[0];
        }
        result += String.fromCharCode(parseInt(word, 16));
      }
      argumentPointer++;
      break;

    case 'c':
      // signed char
    case 'C':
      // unsigned char
      // c and C is the same in pack
      if (quantifier === '*') {
        quantifier = arguments.length - argumentPointer;
      }
      if (quantifier > (arguments.length - argumentPointer)) {
        throw new Error('Warning:  pack() Type ' + instruction + ': too few arguments');
      }

      for (i = 0; i < quantifier; i++) {
        result += String.fromCharCode(arguments[argumentPointer]);
        argumentPointer++;
      }
      break;

    case 's':
      // signed short (always 16 bit, machine byte order)
    case 'S':
      // unsigned short (always 16 bit, machine byte order)
    case 'v':
      // s and S is the same in pack
      if (quantifier === '*') {
        quantifier = arguments.length - argumentPointer;
      }
      if (quantifier > (arguments.length - argumentPointer)) {
        throw new Error('Warning:  pack() Type ' + instruction + ': too few arguments');
      }

      for (i = 0; i < quantifier; i++) {
        result += String.fromCharCode(arguments[argumentPointer] & 0xFF);
        result += String.fromCharCode(arguments[argumentPointer] >> 8 & 0xFF);
        argumentPointer++;
      }
      break;

    case 'n':
      // unsigned short (always 16 bit, big endian byte order)
      if (quantifier === '*') {
        quantifier = arguments.length - argumentPointer;
      }
      if (quantifier > (arguments.length - argumentPointer)) {
        throw new Error('Warning:  pack() Type ' + instruction + ': too few arguments');
      }

      for (i = 0; i < quantifier; i++) {
        result += String.fromCharCode(arguments[argumentPointer] >> 8 & 0xFF);
        result += String.fromCharCode(arguments[argumentPointer] & 0xFF);
        argumentPointer++;
      }
      break;

    case 'i':
      // signed integer (machine dependent size and byte order)
    case 'I':
      // unsigned integer (machine dependent size and byte order)
    case 'l':
      // signed long (always 32 bit, machine byte order)
    case 'L':
      // unsigned long (always 32 bit, machine byte order)
    case 'V':
      // unsigned long (always 32 bit, little endian byte order)
      if (quantifier === '*') {
        quantifier = arguments.length - argumentPointer;
      }
      if (quantifier > (arguments.length - argumentPointer)) {
        throw new Error('Warning:  pack() Type ' + instruction + ': too few arguments');
      }

      for (i = 0; i < quantifier; i++) {
        result += String.fromCharCode(arguments[argumentPointer] & 0xFF);
        result += String.fromCharCode(arguments[argumentPointer] >> 8 & 0xFF);
        result += String.fromCharCode(arguments[argumentPointer] >> 16 & 0xFF);
        result += String.fromCharCode(arguments[argumentPointer] >> 24 & 0xFF);
        argumentPointer++;
      }

      break;
    case 'N':
      // unsigned long (always 32 bit, big endian byte order)
      if (quantifier === '*') {
        quantifier = arguments.length - argumentPointer;
      }
      if (quantifier > (arguments.length - argumentPointer)) {
        throw new Error('Warning:  pack() Type ' + instruction + ': too few arguments');
      }

      for (i = 0; i < quantifier; i++) {
        result += String.fromCharCode(arguments[argumentPointer] >> 24 & 0xFF);
        result += String.fromCharCode(arguments[argumentPointer] >> 16 & 0xFF);
        result += String.fromCharCode(arguments[argumentPointer] >> 8 & 0xFF);
        result += String.fromCharCode(arguments[argumentPointer] & 0xFF);
        argumentPointer++;
      }
      break;

    case 'f':
      // float (machine dependent size and representation)
    case 'd':
      // double (machine dependent size and representation)
      // version based on IEEE754
      precisionBits = 23;
      exponentBits = 8;
      if (instruction === 'd') {
        precisionBits = 52;
        exponentBits = 11;
      }

      if (quantifier === '*') {
        quantifier = arguments.length - argumentPointer;
      }
      if (quantifier > (arguments.length - argumentPointer)) {
        throw new Error('Warning:  pack() Type ' + instruction + ': too few arguments');
      }
      for (i = 0; i < quantifier; i++) {
        argument = arguments[argumentPointer];
        bias = Math.pow(2, exponentBits - 1) - 1;
        minExp = -bias + 1;
        maxExp = bias;
        minUnnormExp = minExp - precisionBits;
        status = isNaN(n = parseFloat(argument)) || n === -Infinity || n === +Infinity ? n : 0;
        exp = 0;
        len = 2 * bias + 1 + precisionBits + 3;
        bin = new Array(len);
        signal = (n = status !== 0 ? 0 : n) < 0;
        n = Math.abs(n);
        intPart = Math.floor(n);
        floatPart = n - intPart;

        for (k = len; k;) {
          bin[--k] = 0;
        }
        for (k = bias + 2; intPart && k;) {
          bin[--k] = intPart % 2;
          intPart = Math.floor(intPart / 2);
        }
        for (k = bias + 1; floatPart > 0 && k; --floatPart) {
          (bin[++k] = ((floatPart *= 2) >= 1) - 0);
        }
        for (k = -1; ++k < len && !bin[k];) {}

        if (bin[(lastBit = precisionBits - 1 + (k = (exp = bias + 1 - k) >= minExp && exp <= maxExp ? k + 1 : bias + 1 - (exp = minExp - 1))) + 1]) {
          if (!(rounded = bin[lastBit])) {
            for (j = lastBit + 2; !rounded && j < len; rounded = bin[j++]) {}
          }
          for (j = lastBit + 1; rounded && --j >= 0;
          (bin[j] = !bin[j] - 0) && (rounded = 0)) {}
        }

        for (k = k - 2 < 0 ? -1 : k - 3; ++k < len && !bin[k];) {}

        if ((exp = bias + 1 - k) >= minExp && exp <= maxExp) {
          ++k;
        } else {
          if (exp < minExp) {
            if (exp !== bias + 1 - len && exp < minUnnormExp) { /*"encodeFloat::float underflow" */
            }
            k = bias + 1 - (exp = minExp - 1);
          }
        }

        if (intPart || status !== 0) {
          exp = maxExp + 1;
          k = bias + 2;
          if (status === -Infinity) {
            signal = 1;
          } else if (isNaN(status)) {
            bin[k] = 1;
          }
        }

        n = Math.abs(exp + bias);
        tmpResult = '';

        for (j = exponentBits + 1; --j;) {
          tmpResult = (n % 2) + tmpResult;
          n = n >>= 1;
        }

        n = 0;
        j = 0;
        k = (tmpResult = (signal ? '1' : '0') + tmpResult + bin.slice(k, k + precisionBits).join('')).length;
        r = [];

        for (; k;) {
          n += (1 << j) * tmpResult.charAt(--k);
          if (j === 7) {
            r[r.length] = String.fromCharCode(n);
            n = 0;
          }
          j = (j + 1) % 8;
        }

        r[r.length] = n ? String.fromCharCode(n) : '';
        result += r.join('');
        argumentPointer++;
      }
      break;

    case 'x':
      // NUL byte
      if (quantifier === '*') {
        throw new Error('Warning: pack(): Type x: \'*\' ignored');
      }
      for (i = 0; i < quantifier; i++) {
        result += String.fromCharCode(0);
      }
      break;

    case 'X':
      // Back up one byte
      if (quantifier === '*') {
        throw new Error('Warning: pack(): Type X: \'*\' ignored');
      }
      for (i = 0; i < quantifier; i++) {
        if (result.length === 0) {
          throw new Error('Warning: pack(): Type X:' + ' outside of string');
        } else {
          result = result.substring(0, result.length - 1);
        }
      }
      break;

    case '@':
      // NUL-fill to absolute position
      if (quantifier === '*') {
        throw new Error('Warning: pack(): Type X: \'*\' ignored');
      }
      if (quantifier > result.length) {
        extraNullCount = quantifier - result.length;
        for (i = 0; i < extraNullCount; i++) {
          result += String.fromCharCode(0);
        }
      }
      if (quantifier < result.length) {
        result = result.substring(0, quantifier);
      }
      break;

    default:
      throw new Error('Warning:  pack() Type ' + instruction + ': unknown format code');
    }
  }
  if (argumentPointer < arguments.length) {
    throw new Error('Warning: pack(): ' + (arguments.length - argumentPointer) + ' arguments unused');
  }

  return result;
}