pdf.js/src/bidi.js

var baseTypes = [
  "BN", "BN", "BN", "BN", "BN", "BN", "BN", "BN", "BN", "S", "B", "S", "WS",
  "B", "BN", "BN", /*U+000*/
  "BN", "BN", "BN", "BN", "BN", "BN", "BN", "BN", "BN", "BN", "BN", "BN", "B",
  "B", "B", "S", /*U+001*/
  "WS", "ON", "ON", "ET", "ET", "ET", "ON", "ON", "ON", "ON", "ON", "ON", "CS",
  "ON", "CS", "ON", /*U+002*/
  "EN", "EN", "EN", "EN", "EN", "EN", "EN", "EN", "EN", "EN", "ON", "ON", "ON",
  "ON", "ON", "ON", /*U+003*/
  "ON", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L",
  "L", /*U+004*/
  "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "ON", "ON", "ON", "ON",
  "ON", /*U+005*/
  "ON", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L",
  "L", /*U+006*/
  "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "ON", "ON", "ON", "ON",
  "BN", /*U+007*/
  "BN", "BN", "BN", "BN", "BN", "B", "BN", "BN", "BN", "BN", "BN", "BN", "BN",
  "BN", "BN", "BN", /*U+008*/
  "BN", "BN", "BN", "BN", "BN", "BN", "BN", "BN", "BN", "BN", "BN", "BN", "BN",
  "BN", "BN", "BN", /*U+009*/
  "CS", "ON", "ET", "ET", "ET", "ET", "ON", "ON", "ON", "ON", "L", "ON", "ON",
  "ON", "ON", "ON", /*U+00a*/
  "ET", "ET", "EN", "EN", "ON", "L", "ON", "ON", "ON", "EN", "L", "ON", "ON",
  "ON", "ON", "ON", /*U+00b*/
  "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L",
  "L", /*U+00c*/
  "L", "L", "L", "L", "L", "L", "L", "ON", "L", "L", "L", "L", "L", "L", "L",
  "L", /*U+00d*/
  "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L", "L",
  "L", /*U+00e*/
  "L", "L", "L", "L", "L", "L", "L", "ON", "L", "L", "L", "L", "L", "L", "L",
  "L"   /*U+00f*/
];

var arabicTypes = [
  "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "CS",
  "AL", "ON", "ON", //60
  "NSM", "NSM", "NSM", "NSM", "NSM", "NSM", "AL", "AL", "AL", "AL", "AL", "AL",
  "AL", "AL", "AL", "AL", //61
  "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL",
  "AL", "AL", "AL", //62
  "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL",
  "AL", "AL", "AL", //63
  "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "NSM",
  "NSM", "NSM", "NSM", "NSM", //64
  "NSM", "NSM", "NSM", "NSM", "NSM", "NSM", "NSM", "NSM", "NSM", "AL", "AL",
  "AL", "AL", "AL", "AL", "AL", //65
  "AN", "AN", "AN", "AN", "AN", "AN", "AN", "AN", "AN", "AN", "ET", "AN", "AN",
  "AL", "AL", "AL", //66
  "NSM", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL",
  "AL", "AL", "AL", //67
  "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL",
  "AL", "AL", "AL", //68
  "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL",
  "AL", "AL", "AL", //69
  "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL",
  "AL", "AL", "AL", //6a
  "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL",
  "AL", "AL", "AL", //6b
  "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL",
  "AL", "AL", "AL", //6c
  "AL", "AL", "AL", "AL", "AL", "AL", "NSM", "NSM", "NSM", "NSM", "NSM", "NSM",
  "NSM", "NSM", "NSM", "NSM", //6d
  "NSM", "NSM", "NSM", "NSM", "NSM", "NSM", "NSM", "NSM", "NSM", "ON", "NSM",
  "NSM", "NSM", "NSM", "AL", "AL", //6e
  "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL",
  "AL", "AL", "AL"  //6f
];

function bidi(text, startLevel) {
  var str = text.str;
  var strLength = str.length;
  if (strLength == 0) return str;

  // get types, fill arrays

  var chars = new Array(strLength);
  var types = new Array(strLength);
  var oldtypes = new Array(strLength);
  var numBidi = 0;

  for (var i = 0; i < strLength; ++i) {
    var c = str.charAt(i);
    chars[i] = c;

    var t = "L";
    if (c <= '\u00ff')
      t = baseTypes[c.charCodeAt(0)];
    else if ('\u0590' <= c && c <= '\u05f4')
      t = "R";
    else if ('\u0600' <= c && c <= '\u06ff')
      t = arabicTypes[c.charCodeAt(0) & 0xff];
    else if ('\u0700' <= c && c <= '\u08AC')
      t = "AL";

    if (t == "R" || t == "AL" || t == "AN")
      numBidi++;

    oldtypes[i] = types[i] = t;
  }

  // detect the bidi method
  //  if there are no rtl characters then no bidi needed
  //  if less than 30% chars are rtl then string is primarily ltr
  //  if more than 30% chars are rtl then string is primarily rtl
  if (numBidi == 0) {
    text.direction = 'ltr';
    return str;
  }
  else if (startLevel == -1) {
    if ((strLength / numBidi) < 0.3) {
      text.direction = 'ltr';
      startLevel = 0;
    } else {
      text.direction = 'rtl';
      startLevel = 1;
    }
  }

  var levels = new Array(strLength);

  for (var i = 0; i < strLength; ++i) {
    levels[i] = startLevel;
  }

  var diffChars = new Array(strLength);
  var diffLevels = new Array(strLength);
  var diffTypes = new Array(strLength);

  /*
   X1-X10: skip most of this, since we are NOT doing the embeddings.
   */

  var e = isOdd(startLevel) ? "R" : "L";
  var sor = e;
  var eor = sor;

  /*
   W1. Examine each non-spacing mark (NSM) in the level run, and change the type
   of the NSM to the type of the previous character. If the NSM is at the start
   of the level run, it will get the type of sor.
   */

  var lastType = sor;
  for (var i = 0; i < strLength; ++i) {
    if (types[i] == "NSM") types[i] = lastType;
    else lastType = types[i];
  }

  /*
   W2. Search backwards from each instance of a European number until the first
   strong type (R, L, AL, or sor) is found.  If an AL is found, change the type
   of the European number to Arabic number.
   */

  var lastType = sor;
  for (var i = 0; i < strLength; ++i) {
    var t = types[i];
    if (t == "EN")
      types[i] = (lastType == "AL") ? "AN" : "EN";
    else if (t == "R" || t == "L" || t == "AL")
      lastType = t;
  }

  /*
   W3. Change all ALs to R.
   */

  for (var i = 0; i < strLength; ++i) {
    var t = types[i];
    if (t == "AL") types[i] = "R";
  }

  /*
   W4. A single European separator between two European numbers changes to a
   European number. A single common separator between two numbers of the same
   type changes to that type:
   */

  for (var i = 1; i < strLength - 1; ++i) {
    if (types[i] == "ES" && types[i - 1] == "EN" && types[i + 1] == "EN")
      types[i] = "EN";
    if (types[i] == "CS" && (types[i - 1] == "EN" || types[i - 1] == "AN") &&
        types[i + 1] == types[i - 1])
      types[i] = types[i - 1];
  }

  /*
   W5. A sequence of European terminators adjacent to European numbers changes
   to all European numbers:
   */

  for (var i = 0; i < strLength; ++i) {
    if (types[i] == "EN") {
      // do before
      for (j = i - 1; j >= 0; --j) {
        if (types[j] == "ET")
          types[j] = "EN";
        else break;
      }
      // do after
      for (j = i + 1; j < strLength; --j) {
        if (types[j] == "ET")
          types[j] = "EN";
        else break;
      }
    }
  }

  /*
   W6. Otherwise, separators and terminators change to Other Neutral:
   */

  for (var i = 0; i < strLength; ++i) {
    var t = types[i];
    if (t == "WS" || t == "ES" || t == "ET" || t == "CS")
      types[i] = "ON";
  }

  /*
   W7. Search backwards from each instance of a European number until the first
   strong type (R, L, or sor) is found. If an L is found,  then change the type
   of the European number to L.
   */

  var lastType = sor;
  for (var i = 0; i < strLength; ++i) {
    var t = types[i];
    if (t == "EN")
      types[i] = (lastType == "L") ? "L" : "EN";
    else if (t == "R" || t == "L")
      lastType = t;
  }

  /*
   N1. A sequence of neutrals takes the direction of the surrounding strong text
   if the text on both sides has the same direction. European and Arabic numbers
   are treated as though they were R. Start-of-level-run (sor) and
   end-of-level-run (eor) are used at level run boundaries.
   */

  for (var i = 0; i < strLength; ++i) {
    if (types[i] == "ON") {
      var end = findUnequal(types, i + 1, "ON");
      var before = sor;
      if (i > 0)
        before = types[i - 1];
      var after = eor;
      if (end + 1 < strLength)
        after = types[end + 1];
      if (before != "L")
        before = "R";
      if (after != "L")
        after = "R";
      if (before == after)
        setValues(types, i, end, before);
      i = end - 1; // reset to end (-1 so next iteration is ok)
    }
  }

  /*
   N2. Any remaining neutrals take the embedding direction.
   */

  for (var i = 0; i < strLength; ++i) {
    if (types[i] == "ON")
      types[i] = e;
  }

  /*
   I1. For all characters with an even (left-to-right) embedding direction,
   those of type R go up one level and those of type AN or EN go up two levels.
   I2. For all characters with an odd (right-to-left) embedding direction, those
   of type L, EN or AN go up one level.
   */

  for (var i = 0; i < strLength; ++i) {
    var t = types[i];
    if (isEven(levels[i])) {
      if (t == "R") {
        levels[i] += 1;
      }
      else if (t == "AN" || t == "EN") {
        levels[i] += 2;
      }
    }
    else { // isOdd, so
      if (t == "L" || t == "AN" || t == "EN") {
        levels[i] += 1;
      }
    }
  }

  /*
   L1. On each line, reset the embedding level of the following characters to
   the paragraph embedding level:

   segment separators,
   paragraph separators,
   any sequence of whitespace characters preceding a segment separator or
   paragraph separator, and any sequence of white space characters at the end
   of the line.
   */

  //dont bother as text is only single line

  /*
   L2. From the highest level found in the text to the lowest odd level on each
   line, reverse any contiguous sequence of characters that are at that level or
   higher.
   */

  // find highest level & lowest odd level

  var highestLevel = -1;
  var lowestOddLevel = 99;
  for (var i = 0; i < levels.length; ++i) {
    var level = levels[i];
    if (highestLevel < level)
      highestLevel = level;
    if (lowestOddLevel > level && isOdd(level))
      lowestOddLevel = level;
  }

  // now reverse between those limits

  for (var level = highestLevel; level >= lowestOddLevel; --level) {
    // find segments to reverse
    var start = -1;
    for (var i = 0; i < levels.length; ++i) {
      if (levels[i] < level) {
        if (start >= 0) {
          reverseValues(chars, start, i);
          start = -1;
        }
      }
      else if (start < 0) {
        start = i;
      }
    }
    if (start >= 0) {
      reverseValues(chars, start, levels.length);
    }
  }

  /*
   L3. Combining marks applied to a right-to-left base character will at this
   point precede their base character. If the rendering engine expects them to
   follow the base characters in the final display process, then the ordering of
   the marks and the base character must be reversed.
   */

  // don't bother for now

  /*
   L4. A character that possesses the mirrored property as specified by
   Section 4.7, Mirrored, must be depicted by a mirrored glyph if the resolved
   directionality of that character is R.
   */

  //dont mirror as this is already in the pdf

  // Finally, return string

  var result = "";
  for (var i = 0; i < chars.length; ++i) {
    var ch = chars[i];
    if (ch != '<' && ch != '>')
      result += ch;
  }
  return result;
}

// UTILITIES

function isOdd(i) {
  return (i & 1) != 0;
}

function isEven(i) {
  return (i & 1) == 0;
}

function findUnequal(arr, start, value) {
  var j;
  for (var j = start; j < arr.length; ++j) {
    if (arr[j] != value) return j;
  }
  return j;
}

function setValues(arr, start, end, value) {
  for (var j = start; j < end; ++j) {
    arr[j] = value;
  }
}

function reverseValues(arr, start, end) {
  for (var i = start, j = end - 1; i < j; ++i, --j) {
    var temp = arr[i];
    arr[i] = arr[j];
    arr[j] = temp;
  }
}

function mirrorGlyphs(c) {
  /*
   # BidiMirroring-1.txt
   0028; 0029 # LEFT PARENTHESIS
   0029; 0028 # RIGHT PARENTHESIS
   003C; 003E # LESS-THAN SIGN
   003E; 003C # GREATER-THAN SIGN
   005B; 005D # LEFT SQUARE BRACKET
   005D; 005B # RIGHT SQUARE BRACKET
   007B; 007D # LEFT CURLY BRACKET
   007D; 007B # RIGHT CURLY BRACKET
   00AB; 00BB # LEFT-POINTING DOUBLE ANGLE QUOTATION MARK
   00BB; 00AB # RIGHT-POINTING DOUBLE ANGLE QUOTATION MARK
   */
  switch (c) {
    case '(':
      return ')';
    case ')':
      return '(';
    case '<':
      return '>';
    case '>':
      return '<';
    case ']':
      return '[';
    case '[':
      return ']';
    case '}':
      return '{';
    case '{':
      return '}';
    case '<27>':
      return '<27>';
    case '<27>':
      return '<27>';
    default:
      return c;
  }
}