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

   1 // Credit: https://github.com/paulmillr/es6-shim/
   2
   3 'use strict';
   4
   5 var abs = Math.abs, floor = Math.floor, log = Math.log, min = Math.min
   6   , pow = Math.pow, LN2 = Math.LN2
   7   , roundToEven;
   8
   9 roundToEven = function (n) {
  10         var w = floor(n), f = n - w;
  11         if (f < 0.5) return w;
  12         if (f > 0.5) return w + 1;
  13         return w % 2 ? w + 1 : w;
  14 };
  15
  16 module.exports = function (v, ebits, fbits) {
  17         var bias = (1 << (ebits - 1)) - 1, s, e, f, i, bits, str, bytes;
  18
  19         // Compute sign, exponent, fraction
  20         if (isNaN(v)) {
  21                 // NaN
  22                 // http://dev.w3.org/2006/webapi/WebIDL/#es-type-mapping
  23                 e = (1 << ebits) - 1;
  24                 f = pow(2, fbits - 1);
  25                 s = 0;
  26         } else if (v === Infinity || v === -Infinity) {
  27                 e = (1 << ebits) - 1;
  28                 f = 0;
  29                 s = (v < 0) ? 1 : 0;
  30         } else if (v === 0) {
  31                 e = 0;
  32                 f = 0;
  33                 s = (1 / v === -Infinity) ? 1 : 0;
  34         } else {
  35                 s = v < 0;
  36                 v = abs(v);
  37
  38                 if (v >= pow(2, 1 - bias)) {
  39                         e = min(floor(log(v) / LN2), 1023);
  40                         f = roundToEven(v / pow(2, e) * pow(2, fbits));
  41                         if (f / pow(2, fbits) >= 2) {
  42                                 e = e + 1;
  43                                 f = 1;
  44                         }
  45                         if (e > bias) {
  46                                 // Overflow
  47                                 e = (1 << ebits) - 1;
  48                                 f = 0;
  49                         } else {
  50                                 // Normal
  51                                 e = e + bias;
  52                                 f = f - pow(2, fbits);
  53                         }
  54                 } else {
  55                         // Subnormal
  56                         e = 0;
  57                         f = roundToEven(v / pow(2, 1 - bias - fbits));
  58                 }
  59         }
  60
  61         // Pack sign, exponent, fraction
  62         bits = [];
  63         for (i = fbits; i; i -= 1) {
  64                 bits.push(f % 2 ? 1 : 0);
  65                 f = floor(f / 2);
  66         }
  67         for (i = ebits; i; i -= 1) {
  68                 bits.push(e % 2 ? 1 : 0);
  69                 e = floor(e / 2);
  70         }
  71         bits.push(s ? 1 : 0);
  72         bits.reverse();
  73         str = bits.join('');
  74
  75         // Bits to bytes
  76         bytes = [];
  77         while (str.length) {
  78                 bytes.push(parseInt(str.substring(0, 8), 2));
  79                 str = str.substring(8);
  80         }
  81         return bytes;
  82 };