#include "minibidi.h"

/************************************************************************
 * $Id: minibidi.c 6910 2006-11-18 15:10:48Z simon $
 *
 * ------------
 * Description:
 * ------------
 * This is an implemention of Unicode's Bidirectional Algorithm
 * (known as UAX #9).
 *
 *   http://www.unicode.org/reports/tr9/
 *
 * Author: Ahmad Khalifa
 *
 * -----------------
 * Revision Details:    (Updated by Revision Control System)
 * -----------------
 *  $Date: 2006-11-18 15:10:48 +0000 (Sat, 18 Nov 2006) $
 *  $Author: simon $
 *  $Revision: 6910 $
 *
 * (www.arabeyes.org - under MIT license)
 *
 ************************************************************************/

/*
 * TODO:
 * =====
 * - Explicit marks need to be handled (they are not 100% now)
 * - Ligatures
 */


#define LMASK	0x3F    /* Embedding Level mask */
#define OMASK	0xC0    /* Override mask */
#define OISL	0x80    /* Override is L */
#define OISR	0x40    /* Override is R */

/* Shaping Helpers */
#define STYPE(xh) ((((xh) >= SHAPE_FIRST) && ((xh) <= SHAPE_LAST)) ? \
shapetypes[(xh)-SHAPE_FIRST].type : SU) /*)) */
#define SISOLATED(xh) \
  (0xFE00 + (shapetypes[(xh)-SHAPE_FIRST].form_b ?: -0xFE00))
#define SFINAL(xh) ((xh)+1)
#define SINITIAL(xh) ((xh)+2)
#define SMEDIAL(ch) ((ch)+3)

#define leastGreaterOdd(x) ( ((x)+1) | 1 )
#define leastGreaterEven(x) ( ((x)+2) &~ 1 )

/* character types */
enum {
  L, LRE, LRO, R, AL, RLE, RLO, PDF, EN, ES, ET, AN, CS, NSM, BN, B, S, WS, ON
};

/* Shaping Types */
enum {
  SL,   /* Left-Joining, doesnt exist in U+0600 - U+06FF */
  SR,   /* Right-Joining, ie has Isolated, Final */
  SD,   /* Dual-Joining, ie has Isolated, Final, Initial, Medial */
  SU,   /* Non-Joining */
  SC    /* Join-Causing, like U+0640 (TATWEEL) */
};

typedef struct {
  uchar type;
  uchar form_b;
} shape_node;

/* Kept near the actual table, for verification. */
enum { SHAPE_FIRST = 0x621, SHAPE_LAST = 0x64A };

static const shape_node shapetypes[] = {
 /* index, Typ, Iso, Ligature Index */
 /* 621 */ {SU, 0x80},
 /* 622 */ {SR, 0x81},
 /* 623 */ {SR, 0x83},
 /* 624 */ {SR, 0x85},
 /* 625 */ {SR, 0x87},
 /* 626 */ {SD, 0x89},
 /* 627 */ {SR, 0x8D},
 /* 628 */ {SD, 0x8F},
 /* 629 */ {SR, 0x93},
 /* 62A */ {SD, 0x95},
 /* 62B */ {SD, 0x99},
 /* 62C */ {SD, 0x9D},
 /* 62D */ {SD, 0xA1},
 /* 62E */ {SD, 0xA5},
 /* 62F */ {SR, 0xA9},
 /* 630 */ {SR, 0xAB},
 /* 631 */ {SR, 0xAD},
 /* 632 */ {SR, 0xAF},
 /* 633 */ {SD, 0xB1},
 /* 634 */ {SD, 0xB5},
 /* 635 */ {SD, 0xB9},
 /* 636 */ {SD, 0xBD},
 /* 637 */ {SD, 0xC1},
 /* 638 */ {SD, 0xC5},
 /* 639 */ {SD, 0xC9},
 /* 63A */ {SD, 0xCD},
 /* 63B */ {SU, 0x0},
 /* 63C */ {SU, 0x0},
 /* 63D */ {SU, 0x0},
 /* 63E */ {SU, 0x0},
 /* 63F */ {SU, 0x0},
 /* 640 */ {SC, 0x0},
 /* 641 */ {SD, 0xD1},
 /* 642 */ {SD, 0xD5},
 /* 643 */ {SD, 0xD9},
 /* 644 */ {SD, 0xDD},
 /* 645 */ {SD, 0xE1},
 /* 646 */ {SD, 0xE5},
 /* 647 */ {SD, 0xE9},
 /* 648 */ {SR, 0xED},
 /* 649 */ {SR, 0xEF},
 /* 64A */ {SD, 0xF1}
};


/*
 * Finds the index of a run with level equals tlevel
 */
static int
findIndexOfRun(uchar * level, int start, int count, int tlevel)
{
  int i;
  for (i = start; i < count; i++) {
    if (tlevel == level[i]) {
      return i;
    }
  }
  return count;
}

/*
 * Flips the text buffer, according to max level, and
 * all higher levels
 *
 * Input:
 * from: text buffer, on which to apply flipping
 * level: resolved levels buffer
 * max: the maximum level found in this line (should be uchar)
 * count: line size in bidi_char
 */
static void
flipThisRun(bidi_char * from, uchar * level, int max, int count)
{
  int i, j, k, tlevel;
  bidi_char temp;

  j = i = 0;
  while (i < count && j < count) {

   /* find the start of the run of level=max */
    tlevel = max;
    i = j = findIndexOfRun(level, i, count, max);
   /* find the end of the run */
    while (i < count && tlevel <= level[i]) {
      i++;
    }
    for (k = i - 1; k > j; k--, j++) {
      temp = from[k];
      from[k] = from[j];
      from[j] = temp;
    }
  }
}

/*
 * Returns the bidi character type of ch.
 *
 * The data table in this function is constructed from the Unicode
 * Character Database, downloadable from unicode.org at the URL
 * 
 *     http://www.unicode.org/Public/UNIDATA/UnicodeData.txt
 * 
 * by the following fragment of Perl:
 
 perl -ne 'split ";"; $num = hex $_[0]; $type = $_[4];' \
 -e '$fl = ($_[1] =~ /First/ ? 1 : $_[1] =~ /Last/ ? 2 : 0);' \
 -e 'if ($type eq $runtype and ($runend == $num-1 or ' \
 -e '    ($fl==2 and $pfl==1))) {$runend = $num;} else { &reset; }' \
 -e '$pfl=$fl; END { &reset }; sub reset {' \
 -e 'printf"        {0x%04x, 0x%04x, %s},\n",$runstart,$runend,$runtype' \
 -e '  if defined $runstart and $runtype ne "ON";' \
 -e '$runstart=$runend=$num; $runtype=$type;}' \
 UnicodeData.txt
 
 */
static uchar
getType(wchar ch)
{
  static const struct {
    wchar first, last;
    uchar type;
  } lookup[] = {
    {0x0000, 0x0008, BN},  {0x0009, 0x0009, S},
    {0x000a, 0x000a, B},   {0x000b, 0x000b, S},
    {0x000c, 0x000c, WS},  {0x000d, 0x000d, B},
    {0x000e, 0x001b, BN},  {0x001c, 0x001e, B},
    {0x001f, 0x001f, S},   {0x0020, 0x0020, WS},
    {0x0023, 0x0025, ET},  {0x002b, 0x002b, ES},
    {0x002c, 0x002c, CS},  {0x002d, 0x002d, ES},
    {0x002e, 0x002f, CS},  {0x0030, 0x0039, EN},
    {0x003a, 0x003a, CS},  {0x0041, 0x005a, L},
    {0x0061, 0x007a, L},   {0x007f, 0x0084, BN},
    {0x0085, 0x0085, B},   {0x0086, 0x009f, BN},
    {0x00a0, 0x00a0, CS},  {0x00a2, 0x00a5, ET},
    {0x00aa, 0x00aa, L},   {0x00ad, 0x00ad, BN},
    {0x00b0, 0x00b1, ET},  {0x00b2, 0x00b3, EN},
    {0x00b5, 0x00b5, L},   {0x00b9, 0x00b9, EN},
    {0x00ba, 0x00ba, L},   {0x00c0, 0x00d6, L},
    {0x00d8, 0x00f6, L},   {0x00f8, 0x0236, L},
    {0x0250, 0x02b8, L},   {0x02bb, 0x02c1, L},
    {0x02d0, 0x02d1, L},   {0x02e0, 0x02e4, L},
    {0x02ee, 0x02ee, L},   {0x0300, 0x0357, NSM},
    {0x035d, 0x036f, NSM}, {0x037a, 0x037a, L},
    {0x0386, 0x0386, L},   {0x0388, 0x038a, L},
    {0x038c, 0x038c, L},   {0x038e, 0x03a1, L},
    {0x03a3, 0x03ce, L},   {0x03d0, 0x03f5, L},
    {0x03f7, 0x03fb, L},   {0x0400, 0x0482, L},
    {0x0483, 0x0486, NSM}, {0x0488, 0x0489, NSM},
    {0x048a, 0x04ce, L},   {0x04d0, 0x04f5, L},
    {0x04f8, 0x04f9, L},   {0x0500, 0x050f, L},
    {0x0531, 0x0556, L},   {0x0559, 0x055f, L},
    {0x0561, 0x0587, L},   {0x0589, 0x0589, L},
    {0x0591, 0x05a1, NSM}, {0x05a3, 0x05b9, NSM},
    {0x05bb, 0x05bd, NSM}, {0x05be, 0x05be, R},
    {0x05bf, 0x05bf, NSM}, {0x05c0, 0x05c0, R},
    {0x05c1, 0x05c2, NSM}, {0x05c3, 0x05c3, R},
    {0x05c4, 0x05c4, NSM}, {0x05d0, 0x05ea, R},
    {0x05f0, 0x05f4, R},   {0x0600, 0x0603, AL},
    {0x060c, 0x060c, CS},  {0x060d, 0x060d, AL},
    {0x0610, 0x0615, NSM}, {0x061b, 0x061b, AL},
    {0x061f, 0x061f, AL},  {0x0621, 0x063a, AL},
    {0x0640, 0x064a, AL},  {0x064b, 0x0658, NSM},
    {0x0660, 0x0669, AN},  {0x066a, 0x066a, ET},
    {0x066b, 0x066c, AN},  {0x066d, 0x066f, AL},
    {0x0670, 0x0670, NSM}, {0x0671, 0x06d5, AL},
    {0x06d6, 0x06dc, NSM}, {0x06dd, 0x06dd, AL},
    {0x06de, 0x06e4, NSM}, {0x06e5, 0x06e6, AL},
    {0x06e7, 0x06e8, NSM}, {0x06ea, 0x06ed, NSM},
    {0x06ee, 0x06ef, AL},  {0x06f0, 0x06f9, EN},
    {0x06fa, 0x070d, AL},  {0x070f, 0x070f, BN},
    {0x0710, 0x0710, AL},  {0x0711, 0x0711, NSM},
    {0x0712, 0x072f, AL},  {0x0730, 0x074a, NSM},
    {0x074d, 0x074f, AL},  {0x0780, 0x07a5, AL},
    {0x07a6, 0x07b0, NSM}, {0x07b1, 0x07b1, AL},
    {0x0901, 0x0902, NSM}, {0x0903, 0x0939, L},
    {0x093c, 0x093c, NSM}, {0x093d, 0x0940, L},
    {0x0941, 0x0948, NSM}, {0x0949, 0x094c, L},
    {0x094d, 0x094d, NSM}, {0x0950, 0x0950, L},
    {0x0951, 0x0954, NSM}, {0x0958, 0x0961, L},
    {0x0962, 0x0963, NSM}, {0x0964, 0x0970, L},
    {0x0981, 0x0981, NSM}, {0x0982, 0x0983, L},
    {0x0985, 0x098c, L},   {0x098f, 0x0990, L},
    {0x0993, 0x09a8, L},   {0x09aa, 0x09b0, L},
    {0x09b2, 0x09b2, L},   {0x09b6, 0x09b9, L},
    {0x09bc, 0x09bc, NSM}, {0x09bd, 0x09c0, L},
    {0x09c1, 0x09c4, NSM}, {0x09c7, 0x09c8, L},
    {0x09cb, 0x09cc, L},   {0x09cd, 0x09cd, NSM},
    {0x09d7, 0x09d7, L},   {0x09dc, 0x09dd, L},
    {0x09df, 0x09e1, L},   {0x09e2, 0x09e3, NSM},
    {0x09e6, 0x09f1, L},   {0x09f2, 0x09f3, ET},
    {0x09f4, 0x09fa, L},   {0x0a01, 0x0a02, NSM},
    {0x0a03, 0x0a03, L},   {0x0a05, 0x0a0a, L},
    {0x0a0f, 0x0a10, L},   {0x0a13, 0x0a28, L},
    {0x0a2a, 0x0a30, L},   {0x0a32, 0x0a33, L},
    {0x0a35, 0x0a36, L},   {0x0a38, 0x0a39, L},
    {0x0a3c, 0x0a3c, NSM}, {0x0a3e, 0x0a40, L},
    {0x0a41, 0x0a42, NSM}, {0x0a47, 0x0a48, NSM},
    {0x0a4b, 0x0a4d, NSM}, {0x0a59, 0x0a5c, L},
    {0x0a5e, 0x0a5e, L},   {0x0a66, 0x0a6f, L},
    {0x0a70, 0x0a71, NSM}, {0x0a72, 0x0a74, L},
    {0x0a81, 0x0a82, NSM}, {0x0a83, 0x0a83, L},
    {0x0a85, 0x0a8d, L},   {0x0a8f, 0x0a91, L},
    {0x0a93, 0x0aa8, L},   {0x0aaa, 0x0ab0, L},
    {0x0ab2, 0x0ab3, L},   {0x0ab5, 0x0ab9, L},
    {0x0abc, 0x0abc, NSM}, {0x0abd, 0x0ac0, L},
    {0x0ac1, 0x0ac5, NSM}, {0x0ac7, 0x0ac8, NSM},
    {0x0ac9, 0x0ac9, L},   {0x0acb, 0x0acc, L},
    {0x0acd, 0x0acd, NSM}, {0x0ad0, 0x0ad0, L},
    {0x0ae0, 0x0ae1, L},   {0x0ae2, 0x0ae3, NSM},
    {0x0ae6, 0x0aef, L},   {0x0af1, 0x0af1, ET},
    {0x0b01, 0x0b01, NSM}, {0x0b02, 0x0b03, L},
    {0x0b05, 0x0b0c, L},   {0x0b0f, 0x0b10, L},
    {0x0b13, 0x0b28, L},   {0x0b2a, 0x0b30, L},
    {0x0b32, 0x0b33, L},   {0x0b35, 0x0b39, L},
    {0x0b3c, 0x0b3c, NSM}, {0x0b3d, 0x0b3e, L},
    {0x0b3f, 0x0b3f, NSM}, {0x0b40, 0x0b40, L},
    {0x0b41, 0x0b43, NSM}, {0x0b47, 0x0b48, L},
    {0x0b4b, 0x0b4c, L},   {0x0b4d, 0x0b4d, NSM},
    {0x0b56, 0x0b56, NSM}, {0x0b57, 0x0b57, L},
    {0x0b5c, 0x0b5d, L},   {0x0b5f, 0x0b61, L},
    {0x0b66, 0x0b71, L},   {0x0b82, 0x0b82, NSM},
    {0x0b83, 0x0b83, L},   {0x0b85, 0x0b8a, L},
    {0x0b8e, 0x0b90, L},   {0x0b92, 0x0b95, L},
    {0x0b99, 0x0b9a, L},   {0x0b9c, 0x0b9c, L},
    {0x0b9e, 0x0b9f, L},   {0x0ba3, 0x0ba4, L},
    {0x0ba8, 0x0baa, L},   {0x0bae, 0x0bb5, L},
    {0x0bb7, 0x0bb9, L},   {0x0bbe, 0x0bbf, L},
    {0x0bc0, 0x0bc0, NSM}, {0x0bc1, 0x0bc2, L},
    {0x0bc6, 0x0bc8, L},   {0x0bca, 0x0bcc, L},
    {0x0bcd, 0x0bcd, NSM}, {0x0bd7, 0x0bd7, L},
    {0x0be7, 0x0bf2, L},   {0x0bf9, 0x0bf9, ET},
    {0x0c01, 0x0c03, L},   {0x0c05, 0x0c0c, L},
    {0x0c0e, 0x0c10, L},   {0x0c12, 0x0c28, L},
    {0x0c2a, 0x0c33, L},   {0x0c35, 0x0c39, L},
    {0x0c3e, 0x0c40, NSM}, {0x0c41, 0x0c44, L},
    {0x0c46, 0x0c48, NSM}, {0x0c4a, 0x0c4d, NSM},
    {0x0c55, 0x0c56, NSM}, {0x0c60, 0x0c61, L},
    {0x0c66, 0x0c6f, L},   {0x0c82, 0x0c83, L},
    {0x0c85, 0x0c8c, L},   {0x0c8e, 0x0c90, L},
    {0x0c92, 0x0ca8, L},   {0x0caa, 0x0cb3, L},
    {0x0cb5, 0x0cb9, L},   {0x0cbc, 0x0cbc, NSM},
    {0x0cbd, 0x0cc4, L},   {0x0cc6, 0x0cc8, L},
    {0x0cca, 0x0ccb, L},   {0x0ccc, 0x0ccd, NSM},
    {0x0cd5, 0x0cd6, L},   {0x0cde, 0x0cde, L},
    {0x0ce0, 0x0ce1, L},   {0x0ce6, 0x0cef, L},
    {0x0d02, 0x0d03, L},   {0x0d05, 0x0d0c, L},
    {0x0d0e, 0x0d10, L},   {0x0d12, 0x0d28, L},
    {0x0d2a, 0x0d39, L},   {0x0d3e, 0x0d40, L},
    {0x0d41, 0x0d43, NSM}, {0x0d46, 0x0d48, L},
    {0x0d4a, 0x0d4c, L},   {0x0d4d, 0x0d4d, NSM},
    {0x0d57, 0x0d57, L},   {0x0d60, 0x0d61, L},
    {0x0d66, 0x0d6f, L},   {0x0d82, 0x0d83, L},
    {0x0d85, 0x0d96, L},   {0x0d9a, 0x0db1, L},
    {0x0db3, 0x0dbb, L},   {0x0dbd, 0x0dbd, L},
    {0x0dc0, 0x0dc6, L},   {0x0dca, 0x0dca, NSM},
    {0x0dcf, 0x0dd1, L},   {0x0dd2, 0x0dd4, NSM},
    {0x0dd6, 0x0dd6, NSM}, {0x0dd8, 0x0ddf, L},
    {0x0df2, 0x0df4, L},   {0x0e01, 0x0e30, L},
    {0x0e31, 0x0e31, NSM}, {0x0e32, 0x0e33, L},
    {0x0e34, 0x0e3a, NSM}, {0x0e3f, 0x0e3f, ET},
    {0x0e40, 0x0e46, L},   {0x0e47, 0x0e4e, NSM},
    {0x0e4f, 0x0e5b, L},   {0x0e81, 0x0e82, L},
    {0x0e84, 0x0e84, L},   {0x0e87, 0x0e88, L},
    {0x0e8a, 0x0e8a, L},   {0x0e8d, 0x0e8d, L},
    {0x0e94, 0x0e97, L},   {0x0e99, 0x0e9f, L},
    {0x0ea1, 0x0ea3, L},   {0x0ea5, 0x0ea5, L},
    {0x0ea7, 0x0ea7, L},   {0x0eaa, 0x0eab, L},
    {0x0ead, 0x0eb0, L},   {0x0eb1, 0x0eb1, NSM},
    {0x0eb2, 0x0eb3, L},   {0x0eb4, 0x0eb9, NSM},
    {0x0ebb, 0x0ebc, NSM}, {0x0ebd, 0x0ebd, L},
    {0x0ec0, 0x0ec4, L},   {0x0ec6, 0x0ec6, L},
    {0x0ec8, 0x0ecd, NSM}, {0x0ed0, 0x0ed9, L},
    {0x0edc, 0x0edd, L},   {0x0f00, 0x0f17, L},
    {0x0f18, 0x0f19, NSM}, {0x0f1a, 0x0f34, L},
    {0x0f35, 0x0f35, NSM}, {0x0f36, 0x0f36, L},
    {0x0f37, 0x0f37, NSM}, {0x0f38, 0x0f38, L},
    {0x0f39, 0x0f39, NSM}, {0x0f3e, 0x0f47, L},
    {0x0f49, 0x0f6a, L},   {0x0f71, 0x0f7e, NSM},
    {0x0f7f, 0x0f7f, L},   {0x0f80, 0x0f84, NSM},
    {0x0f85, 0x0f85, L},   {0x0f86, 0x0f87, NSM},
    {0x0f88, 0x0f8b, L},   {0x0f90, 0x0f97, NSM},
    {0x0f99, 0x0fbc, NSM}, {0x0fbe, 0x0fc5, L},
    {0x0fc6, 0x0fc6, NSM}, {0x0fc7, 0x0fcc, L},
    {0x0fcf, 0x0fcf, L},   {0x1000, 0x1021, L},
    {0x1023, 0x1027, L},   {0x1029, 0x102a, L},
    {0x102c, 0x102c, L},   {0x102d, 0x1030, NSM},
    {0x1031, 0x1031, L},   {0x1032, 0x1032, NSM},
    {0x1036, 0x1037, NSM}, {0x1038, 0x1038, L},
    {0x1039, 0x1039, NSM}, {0x1040, 0x1057, L},
    {0x1058, 0x1059, NSM}, {0x10a0, 0x10c5, L},
    {0x10d0, 0x10f8, L},   {0x10fb, 0x10fb, L},
    {0x1100, 0x1159, L},   {0x115f, 0x11a2, L},
    {0x11a8, 0x11f9, L},   {0x1200, 0x1206, L},
    {0x1208, 0x1246, L},   {0x1248, 0x1248, L},
    {0x124a, 0x124d, L},   {0x1250, 0x1256, L},
    {0x1258, 0x1258, L},   {0x125a, 0x125d, L},
    {0x1260, 0x1286, L},   {0x1288, 0x1288, L},
    {0x128a, 0x128d, L},   {0x1290, 0x12ae, L},
    {0x12b0, 0x12b0, L},   {0x12b2, 0x12b5, L},
    {0x12b8, 0x12be, L},   {0x12c0, 0x12c0, L},
    {0x12c2, 0x12c5, L},   {0x12c8, 0x12ce, L},
    {0x12d0, 0x12d6, L},   {0x12d8, 0x12ee, L},
    {0x12f0, 0x130e, L},   {0x1310, 0x1310, L},
    {0x1312, 0x1315, L},   {0x1318, 0x131e, L},
    {0x1320, 0x1346, L},   {0x1348, 0x135a, L},
    {0x1361, 0x137c, L},   {0x13a0, 0x13f4, L},
    {0x1401, 0x1676, L},   {0x1680, 0x1680, WS},
    {0x1681, 0x169a, L},   {0x16a0, 0x16f0, L},
    {0x1700, 0x170c, L},   {0x170e, 0x1711, L},
    {0x1712, 0x1714, NSM}, {0x1720, 0x1731, L},
    {0x1732, 0x1734, NSM}, {0x1735, 0x1736, L},
    {0x1740, 0x1751, L},   {0x1752, 0x1753, NSM},
    {0x1760, 0x176c, L},   {0x176e, 0x1770, L},
    {0x1772, 0x1773, NSM}, {0x1780, 0x17b6, L},
    {0x17b7, 0x17bd, NSM}, {0x17be, 0x17c5, L},
    {0x17c6, 0x17c6, NSM}, {0x17c7, 0x17c8, L},
    {0x17c9, 0x17d3, NSM}, {0x17d4, 0x17da, L},
    {0x17db, 0x17db, ET},  {0x17dc, 0x17dc, L},
    {0x17dd, 0x17dd, NSM}, {0x17e0, 0x17e9, L},
    {0x180b, 0x180d, NSM}, {0x180e, 0x180e, WS},
    {0x1810, 0x1819, L},   {0x1820, 0x1877, L},
    {0x1880, 0x18a8, L},   {0x18a9, 0x18a9, NSM},
    {0x1900, 0x191c, L},   {0x1920, 0x1922, NSM},
    {0x1923, 0x1926, L},   {0x1927, 0x192b, NSM},
    {0x1930, 0x1931, L},   {0x1932, 0x1932, NSM},
    {0x1933, 0x1938, L},   {0x1939, 0x193b, NSM},
    {0x1946, 0x196d, L},   {0x1970, 0x1974, L},
    {0x1d00, 0x1d6b, L},   {0x1e00, 0x1e9b, L},
    {0x1ea0, 0x1ef9, L},   {0x1f00, 0x1f15, L},
    {0x1f18, 0x1f1d, L},   {0x1f20, 0x1f45, L},
    {0x1f48, 0x1f4d, L},   {0x1f50, 0x1f57, L},
    {0x1f59, 0x1f59, L},   {0x1f5b, 0x1f5b, L},
    {0x1f5d, 0x1f5d, L},   {0x1f5f, 0x1f7d, L},
    {0x1f80, 0x1fb4, L},   {0x1fb6, 0x1fbc, L},
    {0x1fbe, 0x1fbe, L},   {0x1fc2, 0x1fc4, L},
    {0x1fc6, 0x1fcc, L},   {0x1fd0, 0x1fd3, L},
    {0x1fd6, 0x1fdb, L},   {0x1fe0, 0x1fec, L},
    {0x1ff2, 0x1ff4, L},   {0x1ff6, 0x1ffc, L},
    {0x2000, 0x200a, WS},  {0x200b, 0x200d, BN},
    {0x200e, 0x200e, L},   {0x200f, 0x200f, R},
    {0x2028, 0x2028, WS},  {0x2029, 0x2029, B},
    {0x202a, 0x202a, LRE}, {0x202b, 0x202b, RLE},
    {0x202c, 0x202c, PDF}, {0x202d, 0x202d, LRO},
    {0x202e, 0x202e, RLO}, {0x202f, 0x202f, WS},
    {0x2030, 0x2034, ET},  {0x2044, 0x2044, CS},
    {0x205f, 0x205f, WS},  {0x2060, 0x2063, BN},
    {0x206a, 0x206f, BN},  {0x2070, 0x2070, EN},
    {0x2071, 0x2071, L},   {0x2074, 0x2079, EN},
    {0x207a, 0x207b, ET},  {0x207f, 0x207f, L},
    {0x2080, 0x2089, EN},  {0x208a, 0x208b, ET},
    {0x20a0, 0x20b1, ET},  {0x20d0, 0x20ea, NSM},
    {0x2102, 0x2102, L},   {0x2107, 0x2107, L},
    {0x210a, 0x2113, L},   {0x2115, 0x2115, L},
    {0x2119, 0x211d, L},   {0x2124, 0x2124, L},
    {0x2126, 0x2126, L},   {0x2128, 0x2128, L},
    {0x212a, 0x212d, L},   {0x212e, 0x212e, ET},
    {0x212f, 0x2131, L},   {0x2133, 0x2139, L},
    {0x213d, 0x213f, L},   {0x2145, 0x2149, L},
    {0x2160, 0x2183, L},   {0x2212, 0x2213, ET},
    {0x2336, 0x237a, L},   {0x2395, 0x2395, L},
    {0x2488, 0x249b, EN},  {0x249c, 0x24e9, L},
    {0x2800, 0x28ff, L},   {0x3000, 0x3000, WS},
    {0x3005, 0x3007, L},   {0x3021, 0x3029, L},
    {0x302a, 0x302f, NSM}, {0x3031, 0x3035, L},
    {0x3038, 0x303c, L},   {0x3041, 0x3096, L},
    {0x3099, 0x309a, NSM}, {0x309d, 0x309f, L},
    {0x30a1, 0x30fa, L},   {0x30fc, 0x30ff, L},
    {0x3105, 0x312c, L},   {0x3131, 0x318e, L},
    {0x3190, 0x31b7, L},   {0x31f0, 0x321c, L},
    {0x3220, 0x3243, L},   {0x3260, 0x327b, L},
    {0x327f, 0x32b0, L},   {0x32c0, 0x32cb, L},
    {0x32d0, 0x32fe, L},   {0x3300, 0x3376, L},
    {0x337b, 0x33dd, L},   {0x33e0, 0x33fe, L},
    {0x3400, 0x4db5, L},   {0x4e00, 0x9fa5, L},
    {0xa000, 0xa48c, L},   {0xac00, 0xd7a3, L},
    {0xd800, 0xfa2d, L},   {0xfa30, 0xfa6a, L},
    {0xfb00, 0xfb06, L},   {0xfb13, 0xfb17, L},
    {0xfb1d, 0xfb1d, R},   {0xfb1e, 0xfb1e, NSM},
    {0xfb1f, 0xfb28, R},   {0xfb29, 0xfb29, ET},
    {0xfb2a, 0xfb36, R},   {0xfb38, 0xfb3c, R},
    {0xfb3e, 0xfb3e, R},   {0xfb40, 0xfb41, R},
    {0xfb43, 0xfb44, R},   {0xfb46, 0xfb4f, R},
    {0xfb50, 0xfbb1, AL},  {0xfbd3, 0xfd3d, AL},
    {0xfd50, 0xfd8f, AL},  {0xfd92, 0xfdc7, AL},
    {0xfdf0, 0xfdfc, AL},  {0xfe00, 0xfe0f, NSM},
    {0xfe20, 0xfe23, NSM}, {0xfe50, 0xfe50, CS},
    {0xfe52, 0xfe52, CS},  {0xfe55, 0xfe55, CS},
    {0xfe5f, 0xfe5f, ET},  {0xfe62, 0xfe63, ET},
    {0xfe69, 0xfe6a, ET},  {0xfe70, 0xfe74, AL},
    {0xfe76, 0xfefc, AL},  {0xfeff, 0xfeff, BN},
    {0xff03, 0xff05, ET},  {0xff0b, 0xff0b, ET},
    {0xff0c, 0xff0c, CS},  {0xff0d, 0xff0d, ET},
    {0xff0e, 0xff0e, CS},  {0xff0f, 0xff0f, ES},
    {0xff10, 0xff19, EN},  {0xff1a, 0xff1a, CS},
    {0xff21, 0xff3a, L},   {0xff41, 0xff5a, L},
    {0xff66, 0xffbe, L},   {0xffc2, 0xffc7, L},
    {0xffca, 0xffcf, L},   {0xffd2, 0xffd7, L},
    {0xffda, 0xffdc, L},   {0xffe0, 0xffe1, ET},
    {0xffe5, 0xffe6, ET}
    /*
    {0x10000, 0x1000b, L},   {0x1000d, 0x10026, L},
    {0x10028, 0x1003a, L},   {0x1003c, 0x1003d, L},
    {0x1003f, 0x1004d, L},   {0x10050, 0x1005d, L},
    {0x10080, 0x100fa, L},   {0x10100, 0x10100, L},
    {0x10102, 0x10102, L},   {0x10107, 0x10133, L},
    {0x10137, 0x1013f, L},   {0x10300, 0x1031e, L},
    {0x10320, 0x10323, L},   {0x10330, 0x1034a, L},
    {0x10380, 0x1039d, L},   {0x1039f, 0x1039f, L},
    {0x10400, 0x1049d, L},   {0x104a0, 0x104a9, L},
    {0x10800, 0x10805, R},   {0x10808, 0x10808, R},
    {0x1080a, 0x10835, R},   {0x10837, 0x10838, R},
    {0x1083c, 0x1083c, R},   {0x1083f, 0x1083f, R},
    {0x1d000, 0x1d0f5, L},   {0x1d100, 0x1d126, L},
    {0x1d12a, 0x1d166, L},   {0x1d167, 0x1d169, NSM},
    {0x1d16a, 0x1d172, L},   {0x1d173, 0x1d17a, BN},
    {0x1d17b, 0x1d182, NSM}, {0x1d183, 0x1d184, L},
    {0x1d185, 0x1d18b, NSM}, {0x1d18c, 0x1d1a9, L},
    {0x1d1aa, 0x1d1ad, NSM}, {0x1d1ae, 0x1d1dd, L},
    {0x1d400, 0x1d454, L},   {0x1d456, 0x1d49c, L},
    {0x1d49e, 0x1d49f, L},   {0x1d4a2, 0x1d4a2, L},
    {0x1d4a5, 0x1d4a6, L},   {0x1d4a9, 0x1d4ac, L},
    {0x1d4ae, 0x1d4b9, L},   {0x1d4bb, 0x1d4bb, L},
    {0x1d4bd, 0x1d4c3, L},   {0x1d4c5, 0x1d505, L},
    {0x1d507, 0x1d50a, L},   {0x1d50d, 0x1d514, L},
    {0x1d516, 0x1d51c, L},   {0x1d51e, 0x1d539, L},
    {0x1d53b, 0x1d53e, L},   {0x1d540, 0x1d544, L},
    {0x1d546, 0x1d546, L},   {0x1d54a, 0x1d550, L},
    {0x1d552, 0x1d6a3, L},   {0x1d6a8, 0x1d7c9, L},
    {0x1d7ce, 0x1d7ff, EN},  {0x20000, 0x2a6d6, L},
    {0x2f800, 0x2fa1d, L},   {0xe0001, 0xe0001, BN},
    {0xe0020, 0xe007f, BN},  {0xe0100, 0xe01ef, NSM},
    {0xf0000, 0xffffd, L},   {0x100000, 0x10fffd, L}
*/
  };

  int i, j, k;

  i = -1;
  j = lengthof(lookup);

  while (j - i > 1) {
    k = (i + j) / 2;
    if (ch < lookup[k].first)
      j = k;
    else if (ch > lookup[k].last)
      i = k;
    else
      return lookup[k].type;
  }

 /*
  * If we reach here, the character was not in any of the
  * intervals listed in the lookup table. This means we return
  * ON (`Other Neutrals'). This is the appropriate code for any
  * character genuinely not listed in the Unicode table, and
  * also the table above has deliberately left out any
  * characters _explicitly_ listed as ON (to save space!).
  */
  return ON;
}

/*
 * Function exported to front ends to allow them to identify
 * bidi-active characters (in case, for example, the platform's
 * text display function can't conveniently be prevented from doing
 * its own bidi and so special treatment is required for characters
 * that would cause the bidi algorithm to activate).
 * 
 * This function is passed a single Unicode code point, and returns
 * nonzero if the presence of this code point can possibly cause
 * the bidi algorithm to do any reordering. Thus, any string
 * composed entirely of characters for which is_rtl() returns zero
 * should be safe to pass to a bidi-active platform display
 * function without fear.
 * 
 * (is_rtl() must therefore also return true for any character
 * which would be affected by Arabic shaping, but this isn't
 * important because all such characters are right-to-left so it
 * would have flagged them anyway.)
 */
bool
is_rtl(wchar c)
{
 /*
  * After careful reading of the Unicode bidi algorithm (URL as
  * given at the top of this file) I believe that the only
  * character classes which can possibly cause trouble are R,
  * AL, RLE and RLO. I think that any string containing no
  * character in any of those classes will be displayed
  * uniformly left-to-right by the Unicode bidi algorithm.
  */
  const int mask = (1 << R) | (1 << AL) | (1 << RLE) | (1 << RLO);

  return mask & (1 << (getType(c)));
}

/*
 * The most significant 2 bits of each level are used to store
 * Override status of each character
 * This function sets the override bits of level according
 * to the value in override, and reurns the new byte.
 */
static uchar
setOverrideBits(uchar level, uchar override)
{
  if (override == ON)
    return level;
  else if (override == R)
    return level | OISR;
  else if (override == L)
    return level | OISL;
  return level;
}

/*
 * Find the most recent run of the same value in `level', and
 * return the value _before_ it. Used to process U+202C POP
 * DIRECTIONAL FORMATTING.
 */
static int
getPreviousLevel(uchar * level, int from)
{
  if (from > 0) {
    uchar current = level[--from];

    while (from >= 0 && level[from] == current)
      from--;

    if (from >= 0)
      return level[from];

    return -1;
  }
  else
    return -1;
}

/* The Main shaping function, and the only one to be used
 * by the outside world.
 *
 * line: buffer to apply shaping to. this must be passed by doBidi() first
 * to: output buffer for the shaped data
 * count: number of characters in line
 */
int
do_shape(bidi_char * line, bidi_char * to, int count)
{
  int i, tempShape, ligFlag;

  for (ligFlag = i = 0; i < count; i++) {
    to[i] = line[i];
    tempShape = STYPE(line[i].wc);
    switch (tempShape) {
      when SR:
        tempShape = (i + 1 < count ? STYPE(line[i + 1].wc) : SU);
        if ((tempShape == SL) || (tempShape == SD) || (tempShape == SC))
          to[i].wc = SFINAL((SISOLATED(line[i].wc)));
        else
          to[i].wc = SISOLATED(line[i].wc);
      when SD: {
       /* Make Ligatures */
        tempShape = (i + 1 < count ? STYPE(line[i + 1].wc) : SU);
        if (line[i].wc == 0x644) {
          if (i > 0)
            switch (line[i - 1].wc) {
              when 0x622:
                ligFlag = 1;
                if ((tempShape == SL) || (tempShape == SD) || (tempShape == SC))
                  to[i].wc = 0xFEF6;
                else
                  to[i].wc = 0xFEF5;
              when 0x623:
                ligFlag = 1;
                if ((tempShape == SL) || (tempShape == SD) || (tempShape == SC))
                  to[i].wc = 0xFEF8;
                else
                  to[i].wc = 0xFEF7;
              when 0x625:
                ligFlag = 1;
                if ((tempShape == SL) || (tempShape == SD) || (tempShape == SC))
                  to[i].wc = 0xFEFA;
                else
                  to[i].wc = 0xFEF9;
              when 0x627:
                ligFlag = 1;
                if ((tempShape == SL) || (tempShape == SD) || (tempShape == SC))
                  to[i].wc = 0xFEFC;
                else
                  to[i].wc = 0xFEFB;
            }
          if (ligFlag) {
            to[i - 1].wc = 0x20;
            ligFlag = 0;
            break;
          }
        }

        if ((tempShape == SL) || (tempShape == SD) || (tempShape == SC)) {
          tempShape = (i > 0 ? STYPE(line[i - 1].wc) : SU);
          if ((tempShape == SR) || (tempShape == SD) || (tempShape == SC))
            to[i].wc = SMEDIAL((SISOLATED(line[i].wc)));
          else
            to[i].wc = SFINAL((SISOLATED(line[i].wc)));
          break;
        }

        tempShape = (i > 0 ? STYPE(line[i - 1].wc) : SU);
        if ((tempShape == SR) || (tempShape == SD) || (tempShape == SC))
          to[i].wc = SINITIAL((SISOLATED(line[i].wc)));
        else
          to[i].wc = SISOLATED(line[i].wc);
      }
    }
  }
  return 1;
}

static wchar
mirror(wchar c)
{
  static const struct { wchar from, to; } pairs[] = {
    {0x0028, 0x0029}, {0x0029, 0x0028}, {0x003C, 0x003E}, {0x003E, 0x003C},
    {0x005B, 0x005D}, {0x005D, 0x005B}, {0x007B, 0x007D}, {0x007D, 0x007B},
    {0x00AB, 0x00BB}, {0x00BB, 0x00AB}, {0x2039, 0x203A}, {0x203A, 0x2039},
    {0x2045, 0x2046}, {0x2046, 0x2045}, {0x207D, 0x207E}, {0x207E, 0x207D},
    {0x208D, 0x208E}, {0x208E, 0x208D}, {0x2208, 0x220B}, {0x2209, 0x220C},
    {0x220A, 0x220D}, {0x220B, 0x2208}, {0x220C, 0x2209}, {0x220D, 0x220A},
    {0x2215, 0x29F5}, {0x223C, 0x223D}, {0x223D, 0x223C}, {0x2243, 0x22CD},
    {0x2252, 0x2253}, {0x2253, 0x2252}, {0x2254, 0x2255}, {0x2255, 0x2254},
    {0x2264, 0x2265}, {0x2265, 0x2264}, {0x2266, 0x2267}, {0x2267, 0x2266},
    {0x2268, 0x2269}, {0x2269, 0x2268}, {0x226A, 0x226B}, {0x226B, 0x226A},
    {0x226E, 0x226F}, {0x226F, 0x226E}, {0x2270, 0x2271}, {0x2271, 0x2270},
    {0x2272, 0x2273}, {0x2273, 0x2272}, {0x2274, 0x2275}, {0x2275, 0x2274},
    {0x2276, 0x2277}, {0x2277, 0x2276}, {0x2278, 0x2279}, {0x2279, 0x2278},
    {0x227A, 0x227B}, {0x227B, 0x227A}, {0x227C, 0x227D}, {0x227D, 0x227C},
    {0x227E, 0x227F}, {0x227F, 0x227E}, {0x2280, 0x2281}, {0x2281, 0x2280},
    {0x2282, 0x2283}, {0x2283, 0x2282}, {0x2284, 0x2285}, {0x2285, 0x2284},
    {0x2286, 0x2287}, {0x2287, 0x2286}, {0x2288, 0x2289}, {0x2289, 0x2288},
    {0x228A, 0x228B}, {0x228B, 0x228A}, {0x228F, 0x2290}, {0x2290, 0x228F},
    {0x2291, 0x2292}, {0x2292, 0x2291}, {0x2298, 0x29B8}, {0x22A2, 0x22A3},
    {0x22A3, 0x22A2}, {0x22A6, 0x2ADE}, {0x22A8, 0x2AE4}, {0x22A9, 0x2AE3},
    {0x22AB, 0x2AE5}, {0x22B0, 0x22B1}, {0x22B1, 0x22B0}, {0x22B2, 0x22B3},
    {0x22B3, 0x22B2}, {0x22B4, 0x22B5}, {0x22B5, 0x22B4}, {0x22B6, 0x22B7},
    {0x22B7, 0x22B6}, {0x22C9, 0x22CA}, {0x22CA, 0x22C9}, {0x22CB, 0x22CC},
    {0x22CC, 0x22CB}, {0x22CD, 0x2243}, {0x22D0, 0x22D1}, {0x22D1, 0x22D0},
    {0x22D6, 0x22D7}, {0x22D7, 0x22D6}, {0x22D8, 0x22D9}, {0x22D9, 0x22D8},
    {0x22DA, 0x22DB}, {0x22DB, 0x22DA}, {0x22DC, 0x22DD}, {0x22DD, 0x22DC},
    {0x22DE, 0x22DF}, {0x22DF, 0x22DE}, {0x22E0, 0x22E1}, {0x22E1, 0x22E0},
    {0x22E2, 0x22E3}, {0x22E3, 0x22E2}, {0x22E4, 0x22E5}, {0x22E5, 0x22E4},
    {0x22E6, 0x22E7}, {0x22E7, 0x22E6}, {0x22E8, 0x22E9}, {0x22E9, 0x22E8},
    {0x22EA, 0x22EB}, {0x22EB, 0x22EA}, {0x22EC, 0x22ED}, {0x22ED, 0x22EC},
    {0x22F0, 0x22F1}, {0x22F1, 0x22F0}, {0x22F2, 0x22FA}, {0x22F3, 0x22FB},
    {0x22F4, 0x22FC}, {0x22F6, 0x22FD}, {0x22F7, 0x22FE}, {0x22FA, 0x22F2},
    {0x22FB, 0x22F3}, {0x22FC, 0x22F4}, {0x22FD, 0x22F6}, {0x22FE, 0x22F7},
    {0x2308, 0x2309}, {0x2309, 0x2308}, {0x230A, 0x230B}, {0x230B, 0x230A},
    {0x2329, 0x232A}, {0x232A, 0x2329}, {0x2768, 0x2769}, {0x2769, 0x2768},
    {0x276A, 0x276B}, {0x276B, 0x276A}, {0x276C, 0x276D}, {0x276D, 0x276C},
    {0x276E, 0x276F}, {0x276F, 0x276E}, {0x2770, 0x2771}, {0x2771, 0x2770},
    {0x2772, 0x2773}, {0x2773, 0x2772}, {0x2774, 0x2775}, {0x2775, 0x2774},
    {0x27D5, 0x27D6}, {0x27D6, 0x27D5}, {0x27DD, 0x27DE}, {0x27DE, 0x27DD},
    {0x27E2, 0x27E3}, {0x27E3, 0x27E2}, {0x27E4, 0x27E5}, {0x27E5, 0x27E4},
    {0x27E6, 0x27E7}, {0x27E7, 0x27E6}, {0x27E8, 0x27E9}, {0x27E9, 0x27E8},
    {0x27EA, 0x27EB}, {0x27EB, 0x27EA}, {0x2983, 0x2984}, {0x2984, 0x2983},
    {0x2985, 0x2986}, {0x2986, 0x2985}, {0x2987, 0x2988}, {0x2988, 0x2987},
    {0x2989, 0x298A}, {0x298A, 0x2989}, {0x298B, 0x298C}, {0x298C, 0x298B},
    {0x298D, 0x2990}, {0x298E, 0x298F}, {0x298F, 0x298E}, {0x2990, 0x298D},
    {0x2991, 0x2992}, {0x2992, 0x2991}, {0x2993, 0x2994}, {0x2994, 0x2993},
    {0x2995, 0x2996}, {0x2996, 0x2995}, {0x2997, 0x2998}, {0x2998, 0x2997},
    {0x29B8, 0x2298}, {0x29C0, 0x29C1}, {0x29C1, 0x29C0}, {0x29C4, 0x29C5},
    {0x29C5, 0x29C4}, {0x29CF, 0x29D0}, {0x29D0, 0x29CF}, {0x29D1, 0x29D2},
    {0x29D2, 0x29D1}, {0x29D4, 0x29D5}, {0x29D5, 0x29D4}, {0x29D8, 0x29D9},
    {0x29D9, 0x29D8}, {0x29DA, 0x29DB}, {0x29DB, 0x29DA}, {0x29F5, 0x2215},
    {0x29F8, 0x29F9}, {0x29F9, 0x29F8}, {0x29FC, 0x29FD}, {0x29FD, 0x29FC},
    {0x2A2B, 0x2A2C}, {0x2A2C, 0x2A2B}, {0x2A2D, 0x2A2C}, {0x2A2E, 0x2A2D},
    {0x2A34, 0x2A35}, {0x2A35, 0x2A34}, {0x2A3C, 0x2A3D}, {0x2A3D, 0x2A3C},
    {0x2A64, 0x2A65}, {0x2A65, 0x2A64}, {0x2A79, 0x2A7A}, {0x2A7A, 0x2A79},
    {0x2A7D, 0x2A7E}, {0x2A7E, 0x2A7D}, {0x2A7F, 0x2A80}, {0x2A80, 0x2A7F},
    {0x2A81, 0x2A82}, {0x2A82, 0x2A81}, {0x2A83, 0x2A84}, {0x2A84, 0x2A83},
    {0x2A8B, 0x2A8C}, {0x2A8C, 0x2A8B}, {0x2A91, 0x2A92}, {0x2A92, 0x2A91},
    {0x2A93, 0x2A94}, {0x2A94, 0x2A93}, {0x2A95, 0x2A96}, {0x2A96, 0x2A95},
    {0x2A97, 0x2A98}, {0x2A98, 0x2A97}, {0x2A99, 0x2A9A}, {0x2A9A, 0x2A99},
    {0x2A9B, 0x2A9C}, {0x2A9C, 0x2A9B}, {0x2AA1, 0x2AA2}, {0x2AA2, 0x2AA1},
    {0x2AA6, 0x2AA7}, {0x2AA7, 0x2AA6}, {0x2AA8, 0x2AA9}, {0x2AA9, 0x2AA8},
    {0x2AAA, 0x2AAB}, {0x2AAB, 0x2AAA}, {0x2AAC, 0x2AAD}, {0x2AAD, 0x2AAC},
    {0x2AAF, 0x2AB0}, {0x2AB0, 0x2AAF}, {0x2AB3, 0x2AB4}, {0x2AB4, 0x2AB3},
    {0x2ABB, 0x2ABC}, {0x2ABC, 0x2ABB}, {0x2ABD, 0x2ABE}, {0x2ABE, 0x2ABD},
    {0x2ABF, 0x2AC0}, {0x2AC0, 0x2ABF}, {0x2AC1, 0x2AC2}, {0x2AC2, 0x2AC1},
    {0x2AC3, 0x2AC4}, {0x2AC4, 0x2AC3}, {0x2AC5, 0x2AC6}, {0x2AC6, 0x2AC5},
    {0x2ACD, 0x2ACE}, {0x2ACE, 0x2ACD}, {0x2ACF, 0x2AD0}, {0x2AD0, 0x2ACF},
    {0x2AD1, 0x2AD2}, {0x2AD2, 0x2AD1}, {0x2AD3, 0x2AD4}, {0x2AD4, 0x2AD3},
    {0x2AD5, 0x2AD6}, {0x2AD6, 0x2AD5}, {0x2ADE, 0x22A6}, {0x2AE3, 0x22A9},
    {0x2AE4, 0x22A8}, {0x2AE5, 0x22AB}, {0x2AEC, 0x2AED}, {0x2AED, 0x2AEC},
    {0x2AF7, 0x2AF8}, {0x2AF8, 0x2AF7}, {0x2AF9, 0x2AFA}, {0x2AFA, 0x2AF9},
    {0x3008, 0x3009}, {0x3009, 0x3008}, {0x300A, 0x300B}, {0x300B, 0x300A},
    {0x300C, 0x300D}, {0x300D, 0x300C}, {0x300E, 0x300F}, {0x300F, 0x300E},
    {0x3010, 0x3011}, {0x3011, 0x3010}, {0x3014, 0x3015}, {0x3015, 0x3014},
    {0x3016, 0x3017}, {0x3017, 0x3016}, {0x3018, 0x3019}, {0x3019, 0x3018},
    {0x301A, 0x301B}, {0x301B, 0x301A}, {0xFF08, 0xFF09}, {0xFF09, 0xFF08},
    {0xFF1C, 0xFF1E}, {0xFF1E, 0xFF1C}, {0xFF3B, 0xFF3D}, {0xFF3D, 0xFF3B},
    {0xFF5B, 0xFF5D}, {0xFF5D, 0xFF5B}, {0xFF5F, 0xFF60}, {0xFF60, 0xFF5F},
    {0xFF62, 0xFF63}, {0xFF63, 0xFF62}
  };
  int i = 0;
  int j = lengthof(pairs);
  while (j - i > 1) {
    int k = (i + j) / 2;
    if (c == pairs[k].from)
      return pairs[k].to;
    if (c < pairs[k].from)
      j = k;
    else
      i = k;
  }
  return c;
}

/*
 * The Main Bidi Function, and the only function that should
 * be used by the outside world.
 *
 * line: a buffer of size count containing text to apply
 * the Bidirectional algorithm to.
 */

int
do_bidi(bidi_char * line, int count)
{
  uchar paragraphLevel;
  uchar currentEmbedding;
  uchar currentOverride;
  uchar tempType;
  int i, j, imax, yes, bover;

 /* Check the presence of R or AL types as optimization */
  yes = 0;
  for (i = 0; i < count; i++) {
    int type = getType(line[i].wc);
    if (type == R || type == AL) {
      yes = 1;
      break;
    }
  }
  if (yes == 0)
    return L;

 /* Initialize types, levels */
  uchar types[count];
  uchar levels[count];

 /* Rule (P1)  NOT IMPLEMENTED
  * P1. Split the text into separate paragraphs. A paragraph separator is
  * kept with the previous paragraph. Within each paragraph, apply all the
  * other rules of this algorithm.
  */

 /* Rule (P2), (P3)
  * P2. In each paragraph, find the first character of type L, AL, or R.
  * P3. If a character is found in P2 and it is of type AL or R, then set
  * the paragraph embedding level to one; otherwise, set it to zero.
  */
  paragraphLevel = 0;
  for (i = 0; i < count; i++) {
    int type = getType(line[i].wc);
    if (type == R || type == AL) {
      paragraphLevel = 1;
      break;
    }
    else if (type == L)
      break;
  }

 /* Rule (X1)
  * X1. Begin by setting the current embedding level to the paragraph
  * embedding level. Set the directional override status to neutral.
  */
  currentEmbedding = paragraphLevel;
  currentOverride = ON;

 /* Rule (X2), (X3), (X4), (X5), (X6), (X7), (X8)
  * X2. With each RLE, compute the least greater odd embedding level.
  * X3. With each LRE, compute the least greater even embedding level.
  * X4. With each RLO, compute the least greater odd embedding level.
  * X5. With each LRO, compute the least greater even embedding level.
  * X6. For all types besides RLE, LRE, RLO, LRO, and PDF:
  *          a. Set the level of the current character to the current
  *              embedding level.
  *          b.  Whenever the directional override status is not neutral,
  *               reset the current character type to the directional
  *               override status.
  * X7. With each PDF, determine the matching embedding or override code.
  * If there was a valid matching code, restore (pop) the last
  * remembered (pushed) embedding level and directional override.
  * X8. All explicit directional embeddings and overrides are completely
  * terminated at the end of each paragraph. Paragraph separators are not
  * included in the embedding. (Useless here) NOT IMPLEMENTED
  */
  bover = 0;
  for (i = 0; i < count; i++) {
    tempType = getType(line[i].wc);
    switch (tempType) {
      when RLE:
        currentEmbedding = levels[i] = leastGreaterOdd(currentEmbedding);
        levels[i] = setOverrideBits(levels[i], currentOverride);
        currentOverride = ON;
      when LRE:
        currentEmbedding = levels[i] = leastGreaterEven(currentEmbedding);
        levels[i] = setOverrideBits(levels[i], currentOverride);
        currentOverride = ON;
      when RLO:
        currentEmbedding = levels[i] = leastGreaterOdd(currentEmbedding);
        tempType = currentOverride = R;
        bover = 1;
      when LRO:
        currentEmbedding = levels[i] = leastGreaterEven(currentEmbedding);
        tempType = currentOverride = L;
        bover = 1;
      when PDF:
        if (getPreviousLevel(levels, i) == -1) {
          currentEmbedding = paragraphLevel;
          currentOverride = ON;
        }
        else {
          currentOverride = currentEmbedding & OMASK;
          currentEmbedding = currentEmbedding & ~OMASK;
        }
        levels[i] = currentEmbedding;
       /* Whitespace is treated as neutral for now */
      when WS or S:
        levels[i] = currentEmbedding;
        tempType = ON;
        if (currentOverride != ON)
          tempType = currentOverride;
      otherwise:
        levels[i] = currentEmbedding;
        if (currentOverride != ON)
          tempType = currentOverride;
    }
    types[i] = tempType;
  }
 /* this clears out all overrides, so we can use levels safely... */
 /* checks bover first */
  if (bover)
    for (i = 0; i < count; i++)
      levels[i] = levels[i] & LMASK;

 /* Rule (X9)
  * X9. Remove all RLE, LRE, RLO, LRO, PDF, and BN codes.
  * Here, they're converted to BN.
  */
  for (i = 0; i < count; i++) {
    switch (types[i]) {
      when RLE or LRE or RLO or LRO or PDF:
        types[i] = BN;
    }
  }

 /* Rule (W1)
  * 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.
  */
  if (types[0] == NSM)
    types[0] = paragraphLevel;

  for (i = 1; i < count; i++) {
    if (types[i] == NSM)
      types[i] = types[i - 1];
   /* Is this a safe assumption?
    * I assumed the previous, IS a character.
    */
  }

 /* Rule (W2)
  * 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.
  */
  for (i = 0; i < count; i++) {
    if (types[i] == EN) {
      j = i;
      while (j >= 0) {
        if (types[j] == AL) {
          types[i] = AN;
          break;
        }
        else if (types[j] == R || types[j] == L) {
          break;
        }
        j--;
      }
    }
  }

 /* Rule (W3)
  * W3. Change all ALs to R.
  *
  * Optimization: on Rule Xn, we might set a flag on AL type
  * to prevent this loop in L R lines only...
  */
  for (i = 0; i < count; i++) {
    if (types[i] == AL)
      types[i] = R;
  }

 /* Rule (W4)
  * 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 (i = 1; i < (count - 1); i++) {
    if (types[i] == ES) {
      if (types[i - 1] == EN && types[i + 1] == EN)
        types[i] = EN;
    }
    else if (types[i] == CS) {
      if (types[i - 1] == EN && types[i + 1] == EN)
        types[i] = EN;
      else if (types[i - 1] == AN && types[i + 1] == AN)
        types[i] = AN;
    }
  }

 /* Rule (W5)
  * W5. A sequence of European terminators adjacent to European numbers
  * changes to all European numbers.
  *
  * Optimization: lots here... else ifs need rearrangement
  */
  for (i = 0; i < count; i++) {
    if (types[i] == ET) {
      if (i > 0 && types[i - 1] == EN) {
        types[i] = EN;
        continue;
      }
      else if (i < count - 1 && types[i + 1] == EN) {
        types[i] = EN;
        continue;
      }
      else if (i < count - 1 && types[i + 1] == ET) {
        j = i;
        while (j < count && types[j] == ET) {
          j++;
        }
        if (types[j] == EN)
          types[i] = EN;
      }
    }
  }

 /* Rule (W6)
  * W6. Otherwise, separators and terminators change to Other Neutral:
  */
  for (i = 0; i < count; i++) {
    switch (types[i]) {
      when ES or ET or CS:
        types[i] = ON;
    }
  }

 /* Rule (W7)
  * 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.
  */
  for (i = 0; i < count; i++) {
    if (types[i] == EN) {
      j = i;
      while (j >= 0) {
        if (types[j] == L) {
          types[i] = L;
          break;
        }
        else if (types[j] == R || types[j] == AL) {
          break;
        }
        j--;
      }
    }
  }

 /* Rule (N1)
  * 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.
  */
  if (count >= 2 && types[0] == ON) {
    if ((types[1] == R) || (types[1] == EN) || (types[1] == AN))
      types[0] = R;
    else if (types[1] == L)
      types[0] = L;
  }
  for (i = 1; i < (count - 1); i++) {
    if (types[i] == ON) {
      if (types[i - 1] == L) {
        j = i;
        while (j < (count - 1) && types[j] == ON) {
          j++;
        }
        if (types[j] == L) {
          while (i < j) {
            types[i] = L;
            i++;
          }
        }

      }
      else if ((types[i - 1] == R) || (types[i - 1] == EN) ||
               (types[i - 1] == AN)) {
        j = i;
        while (j < (count - 1) && types[j] == ON) {
          j++;
        }
        if ((types[j] == R) || (types[j] == EN) || (types[j] == AN)) {
          while (i < j) {
            types[i] = R;
            i++;
          }
        }
      }
    }
  }
  if (count >= 2 && types[count - 1] == ON) {
    if (types[count - 2] == R || types[count - 2] == EN ||
        types[count - 2] == AN)
      types[count - 1] = R;
    else if (types[count - 2] == L)
      types[count - 1] = L;
  }

 /* Rule (N2)
  * N2. Any remaining neutrals take the embedding direction.
  */
  for (i = 0; i < count; i++) {
    if (types[i] == ON) {
      if ((levels[i] % 2) == 0)
        types[i] = L;
      else
        types[i] = R;
    }
  }

 /* Rule (I1)
  * 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.
  */
  for (i = 0; i < count; i++) {
    if ((levels[i] % 2) == 0) {
      if (types[i] == R)
        levels[i] += 1;
      else if (types[i] == AN || types[i] == EN)
        levels[i] += 2;
    }
  }

 /* Rule (I2)
  * I2. For all characters with an odd (right-to-left) embedding direction,
  * those of type L, EN or AN go up one level.
  */
  for (i = 0; i < count; i++) {
    if ((levels[i] % 2) == 1) {
      if (types[i] == L || types[i] == EN || types[i] == AN)
        levels[i] += 1;
    }
  }

 /* Rule (L1)
  * L1. On each line, reset the embedding level of the following characters
  * to the paragraph embedding level:
  *          (1)segment separators, (2)paragraph separators,
  *           (3)any sequence of whitespace characters preceding
  *           a segment separator or paragraph separator,
  *           (4)and any sequence of white space characters
  *           at the end of the line.
  * The types of characters used here are the original types, not those
  * modified by the previous phase.
  */
  j = count - 1;
  while (j > 0 && (getType(line[j].wc) == WS)) {
    j--;
  }
  if (j < (count - 1)) {
    for (j++; j < count; j++)
      levels[j] = paragraphLevel;
  }
  for (i = 0; i < count; i++) {
    tempType = getType(line[i].wc);
    if (tempType == WS) {
      j = i;
      while (j < count && (getType(line[j].wc) == WS)) {
        j++;
      }
      if (j == count || getType(line[j].wc) == B || getType(line[j].wc) == S) {
        for (j--; j >= i; j--) {
          levels[j] = paragraphLevel;
        }
      }
    }
    else if (tempType == B || tempType == S) {
      levels[i] = paragraphLevel;
    }
  }

 /* Rule (L4) NOT IMPLEMENTED
  * 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.
  */
 /* Note: this is implemented before L2 for efficiency */
  for (i = 0; i < count; i++)
    if ((levels[i] % 2) == 1)
      line[i].wc = mirror(line[i].wc);

 /* Rule (L2)
  * L2. From the highest level found in the text to the lowest odd level on
  * each line, including intermediate levels not actually present in the
  * text, reverse any contiguous sequence of characters that are at that
  * level or higher
  */
 /* we flip the character string and leave the level array */
  imax = 0;
  i = 0;
  tempType = levels[0];
  while (i < count) {
    if (levels[i] > tempType) {
      tempType = levels[i];
      imax = i;
    }
    i++;
  }
 /* maximum level in tempType, its index in imax. */
  while (tempType > 0) {        /* loop from highest level to the least odd, */
   /* which i assume is 1 */
    flipThisRun(line, levels, tempType, count);
    tempType--;
  }

 /* Rule (L3) NOT IMPLEMENTED
  * 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.
  */
  return R;
}
