| // Credit: https://github.com/paulmillr/es6-shim/ |
| |
| 'use strict'; |
| |
| var abs = Math.abs, floor = Math.floor, log = Math.log, min = Math.min |
| , pow = Math.pow, LN2 = Math.LN2 |
| , roundToEven; |
| |
| roundToEven = function (n) { |
| var w = floor(n), f = n - w; |
| if (f < 0.5) return w; |
| if (f > 0.5) return w + 1; |
| return w % 2 ? w + 1 : w; |
| }; |
| |
| module.exports = function (v, ebits, fbits) { |
| var bias = (1 << (ebits - 1)) - 1, s, e, f, i, bits, str, bytes; |
| |
| // Compute sign, exponent, fraction |
| if (isNaN(v)) { |
| // NaN |
| // http://dev.w3.org/2006/webapi/WebIDL/#es-type-mapping |
| e = (1 << ebits) - 1; |
| f = pow(2, fbits - 1); |
| s = 0; |
| } else if (v === Infinity || v === -Infinity) { |
| e = (1 << ebits) - 1; |
| f = 0; |
| s = (v < 0) ? 1 : 0; |
| } else if (v === 0) { |
| e = 0; |
| f = 0; |
| s = (1 / v === -Infinity) ? 1 : 0; |
| } else { |
| s = v < 0; |
| v = abs(v); |
| |
| if (v >= pow(2, 1 - bias)) { |
| e = min(floor(log(v) / LN2), 1023); |
| f = roundToEven(v / pow(2, e) * pow(2, fbits)); |
| if (f / pow(2, fbits) >= 2) { |
| e = e + 1; |
| f = 1; |
| } |
| if (e > bias) { |
| // Overflow |
| e = (1 << ebits) - 1; |
| f = 0; |
| } else { |
| // Normal |
| e = e + bias; |
| f = f - pow(2, fbits); |
| } |
| } else { |
| // Subnormal |
| e = 0; |
| f = roundToEven(v / pow(2, 1 - bias - fbits)); |
| } |
| } |
| |
| // Pack sign, exponent, fraction |
| bits = []; |
| for (i = fbits; i; i -= 1) { |
| bits.push(f % 2 ? 1 : 0); |
| f = floor(f / 2); |
| } |
| for (i = ebits; i; i -= 1) { |
| bits.push(e % 2 ? 1 : 0); |
| e = floor(e / 2); |
| } |
| bits.push(s ? 1 : 0); |
| bits.reverse(); |
| str = bits.join(''); |
| |
| // Bits to bytes |
| bytes = []; |
| while (str.length) { |
| bytes.push(parseInt(str.substring(0, 8), 2)); |
| str = str.substring(8); |
| } |
| return bytes; |
| }; |