utf16.js

   1 if (typeof define !== 'function') { var define = require('amdefine')(module) }
   2
   3 define(function(require) {
   4
   5 var decode = function(string, points) {
   6     if (typeof points === "undefined")
   7         points = [];
   8
   9     for (var i = 0, e = string.length; i != e; ++i) {
  10         var unit = string.charCodeAt(i);
  11         var part = unit & 0xfc00;
  12         if (part == 0xdc00)
  13             return null;
  14         else if (part != 0xd800)
  15             points.push(unit);
  16         else if (++i == e)
  17             return null;
  18         else {
  19             var next = string.charCodeAt(i);
  20             if ((next & 0xfc00) != 0xdc00)
  21                 return null;
  22             points.push(0x10000 | (unit & 0x03ff) << 10 | next & 0x03ff);
  23         }
  24     }
  25
  26     return points;
  27 };
  28
  29 var encode = function(points) {
  30     var units = [];
  31     for (var i = 0, e = points.length; i != e; ++i) {
  32         var point = points[i];
  33         if (point < 0x10000)
  34             units.push(point);
  35         else {
  36             point -= 0x10000;
  37             units.push(0xd800 | (0xffc00 & point) >> 10, 0xdc00 | 0x03ff & point);
  38         }
  39     } return String.fromCharCode.apply(String, units);
  40 };
  41
  42 var adjust = function(mode, string, after) {
  43     var before = after.slice();
  44     var offset = 0, index = 0;
  45
  46     var check = function() {
  47         var from = mode ? index : offset;
  48         var to = mode ? offset : index;
  49
  50         for (var o = 0, l = after.length; o != l; ++o)
  51             if (before[o] == from) {
  52                 before[o] = null;
  53                 after[o] = to;
  54             }
  55     };
  56
  57     for (var e = string.length; index != e; ++index) {
  58         check();
  59
  60         var unit = string.charCodeAt(index);
  61         var part = unit & 0xfc00;
  62
  63         if (part == 0xdc00)
  64             return null;
  65         else if (part != 0xd800);
  66         else if (++index == e)
  67             return null;
  68         else {
  69             var next = string.charCodeAt(index);
  70             if ((next & 0xfc00) != 0xdc00)
  71                 return null;
  72         }
  73
  74         ++offset;
  75     }
  76
  77     check();
  78     return after;
  79 };
  80
  81 var point2unit = function(string, offsets) {
  82     return adjust(false, string, offsets);
  83 };
  84
  85 var unit2point = function(string, offsets) {
  86     return adjust(true, string, offsets);
  87 };
  88
  89 var charAt = function(string, offset) {
  90     return substring(string, offset, offset + 1);
  91 };
  92
  93 var length = function(string) {
  94     return unit2point(string, [string.length])[0];
  95 };
  96
  97 var substr = function(string, start, length) {
  98     var stop;
  99     if (typeof length !== "undefined")
 100         stop = start + length;
 101     return substring(string, start, stop);
 102 };
 103
 104 var substring = function(string, start, stop) {
 105     var range = point2unit(string, [start, stop]);
 106     return string.substring(range[0], range[1]);
 107 };
 108
 109 return {
 110     decode: decode,
 111     encode: encode,
 112
 113     point2unit: point2unit,
 114     unit2point: unit2point,
 115
 116     charAt: charAt,
 117     length: length,
 118     substr: substr,
 119     substring: substring,
 120 };
 121
 122 });