1 // IEEE754 conversions based on https://github.com/feross/ieee754
2 var global = require('../internals/global');
4 var Array = global.Array;
7 var floor = Math.floor;
11 var pack = function (number, mantissaLength, bytes) {
12 var buffer = Array(bytes);
13 var exponentLength = bytes * 8 - mantissaLength - 1;
14 var eMax = (1 << exponentLength) - 1;
15 var eBias = eMax >> 1;
16 var rt = mantissaLength === 23 ? pow(2, -24) - pow(2, -77) : 0;
17 var sign = number < 0 || number === 0 && 1 / number < 0 ? 1 : 0;
19 var exponent, mantissa, c;
21 // eslint-disable-next-line no-self-compare -- NaN check
22 if (number != number || number === Infinity) {
23 // eslint-disable-next-line no-self-compare -- NaN check
24 mantissa = number != number ? 1 : 0;
27 exponent = floor(log(number) / LN2);
28 c = pow(2, -exponent);
33 if (exponent + eBias >= 1) {
36 number += rt * pow(2, 1 - eBias);
38 if (number * c >= 2) {
42 if (exponent + eBias >= eMax) {
45 } else if (exponent + eBias >= 1) {
46 mantissa = (number * c - 1) * pow(2, mantissaLength);
47 exponent = exponent + eBias;
49 mantissa = number * pow(2, eBias - 1) * pow(2, mantissaLength);
53 while (mantissaLength >= 8) {
54 buffer[index++] = mantissa & 255;
58 exponent = exponent << mantissaLength | mantissa;
59 exponentLength += mantissaLength;
60 while (exponentLength > 0) {
61 buffer[index++] = exponent & 255;
65 buffer[--index] |= sign * 128;
69 var unpack = function (buffer, mantissaLength) {
70 var bytes = buffer.length;
71 var exponentLength = bytes * 8 - mantissaLength - 1;
72 var eMax = (1 << exponentLength) - 1;
73 var eBias = eMax >> 1;
74 var nBits = exponentLength - 7;
75 var index = bytes - 1;
76 var sign = buffer[index--];
77 var exponent = sign & 127;
81 exponent = exponent * 256 + buffer[index--];
84 mantissa = exponent & (1 << -nBits) - 1;
86 nBits += mantissaLength;
88 mantissa = mantissa * 256 + buffer[index--];
93 } else if (exponent === eMax) {
94 return mantissa ? NaN : sign ? -Infinity : Infinity;
96 mantissa = mantissa + pow(2, mantissaLength);
97 exponent = exponent - eBias;
98 } return (sign ? -1 : 1) * mantissa * pow(2, exponent - mantissaLength);