mojo/public/js/unicode.js

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 /**
   6  * Defines functions for translating between JavaScript strings and UTF8 strings
   7  * stored in ArrayBuffers. There is much room for optimization in this code if
   8  * it proves necessary.
   9  */
  10 define("mojo/public/js/unicode", function() {
  11   /**
  12    * Decodes the UTF8 string from the given buffer.
  13    * @param {ArrayBufferView} buffer The buffer containing UTF8 string data.
  14    * @return {string} The corresponding JavaScript string.
  15    */
  16   function decodeUtf8String(buffer) {
  17     return decodeURIComponent(escape(String.fromCharCode.apply(null, buffer)));
  18   }
  19
  20   /**
  21    * Encodes the given JavaScript string into UTF8.
  22    * @param {string} str The string to encode.
  23    * @param {ArrayBufferView} outputBuffer The buffer to contain the result.
  24    * Should be pre-allocated to hold enough space. Use |utf8Length| to determine
  25    * how much space is required.
  26    * @return {number} The number of bytes written to |outputBuffer|.
  27    */
  28   function encodeUtf8String(str, outputBuffer) {
  29     var utf8String = unescape(encodeURIComponent(str));
  30     if (outputBuffer.length < utf8String.length)
  31       throw new Error("Buffer too small for encodeUtf8String");
  32     for (var i = 0; i < outputBuffer.length && i < utf8String.length; i++)
  33       outputBuffer[i] = utf8String.charCodeAt(i);
  34     return i;
  35   }
  36
  37   /**
  38    * Returns the number of bytes that a UTF8 encoding of the JavaScript string
  39    * |str| would occupy.
  40    */
  41   function utf8Length(str) {
  42     var utf8String = unescape(encodeURIComponent(str));
  43     return utf8String.length;
  44   }
  45
  46   var exports = {};
  47   exports.decodeUtf8String = decodeUtf8String;
  48   exports.encodeUtf8String = encodeUtf8String;
  49   exports.utf8Length = utf8Length;
  50   return exports;
  51 });