firebase-token-generator/js/src/utf8.js

A utility to generate signed Firebase Authentication Tokens

goog.provide('fb.tokengenerator.utf8');

// Code originally came from goog.crypt.stringToUtf8ByteArray, but for some reason they
// automatically replaced '\r\n' with '\n', and they didn't handle surrogate pairs,
// so it's been modified.
fb.tokengenerator.utf8.stringToByteArray = function(str) {
  var out = [], p = 0;
  for (var i = 0; i < str.length; i++) {
    var c = str.charCodeAt(i);

    // Is this the lead surrogate in a surrogate pair?
    if (c >= 0xd800 && c <= 0xdbff) {
      var high = c - 0xd800; // the high 10 bits.
      i++;
      fb.core.util.assert(i < str.length, 'Surrogate pair missing trail surrogate.');
      var low = str.charCodeAt(i) - 0xdc00; // the low 10 bits.
      c = 0x10000 + (high << 10) + low;
    }

    if (c < 128) {
      out[p++] = c;
    } else if (c < 2048) {
      out[p++] = (c >> 6) | 192;
      out[p++] = (c & 63) | 128;
    } else if (c < 65536) {
      out[p++] = (c >> 12) | 224;
      out[p++] = ((c >> 6) & 63) | 128;
      out[p++] = (c & 63) | 128;
    } else {
      out[p++] = (c >> 18) | 240;
      out[p++] = ((c >> 12) & 63) | 128;
      out[p++] = ((c >> 6) & 63) | 128;
      out[p++] = (c & 63) | 128;
    }
  }
  return out;
};

// Calculate length without actually converting; useful for doing cheaper validation.
fb.tokengenerator.utf8.stringLength = function(str) {
  var p = 0;
  for (var i = 0; i < str.length; i++) {
    var c = str.charCodeAt(i);
    if (c < 128) {
      p++;
    } else if (c < 2048) {
      p += 2;
    } else if (c >= 0xd800 && c <= 0xdbff) {
      // Lead surrogate of a surrogate pair.  The pair together will take 4 bytes to represent.
      p += 4;
      i++; // skip trail surrogate.
    } else {
      p += 3;
    }
  }
  return p;
};