12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576777879808182 |
- // 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;
- };
|