git.r.bdr.sh - rbdr/dotfiles/blob

   1 // Credit: https://github.com/paulmillr/es6-shim/
   2
   3 'use strict';
   4
   5 var pow = Math.pow;
   6
   7 module.exports = function (bytes, ebits, fbits) {
   8         // Bytes to bits
   9         var bits = [], i, j, b, str,
  10         bias, s, e, f;
  11
  12         for (i = bytes.length; i; i -= 1) {
  13                 b = bytes[i - 1];
  14                 for (j = 8; j; j -= 1) {
  15                         bits.push(b % 2 ? 1 : 0);
  16                         b = b >> 1;
  17                 }
  18         }
  19         bits.reverse();
  20         str = bits.join('');
  21
  22         // Unpack sign, exponent, fraction
  23         bias = (1 << (ebits - 1)) - 1;
  24         s = parseInt(str.substring(0, 1), 2) ? -1 : 1;
  25         e = parseInt(str.substring(1, 1 + ebits), 2);
  26         f = parseInt(str.substring(1 + ebits), 2);
  27
  28         // Produce number
  29         if (e === (1 << ebits) - 1) return f !== 0 ? NaN : s * Infinity;
  30         if (e > 0) return s * pow(2, e - bias) * (1 + f / pow(2, fbits));
  31         if (f !== 0) return s * pow(2, -(bias - 1)) * (f / pow(2, fbits));
  32         return s < 0 ? -0 : 0;
  33 };