ieee754.js
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// IEEE754 conversions based on https://github.com/feross/ieee754
// eslint-disable-next-line no-shadow-restricted-names
var Infinity = 1 / 0;
var abs = Math.abs;
var pow = Math.pow;
var floor = Math.floor;
var log = Math.log;
var LN2 = Math.LN2;
var pack = function (number, mantissaLength, bytes) {
var buffer = new Array(bytes);
var exponentLength = bytes * 8 - mantissaLength - 1;
var eMax = (1 << exponentLength) - 1;
var eBias = eMax >> 1;
var rt = mantissaLength === 23 ? pow(2, -24) - pow(2, -77) : 0;
var sign = number < 0 || number === 0 && 1 / number < 0 ? 1 : 0;
var index = 0;
var exponent, mantissa, c;
number = abs(number);
// eslint-disable-next-line no-self-compare
if (number != number || number === Infinity) {
// eslint-disable-next-line no-self-compare
mantissa = number != number ? 1 : 0;
exponent = eMax;
} else {
exponent = floor(log(number) / LN2);
if (number * (c = pow(2, -exponent)) < 1) {
exponent--;
c *= 2;
}
if (exponent + eBias >= 1) {
number += rt / c;
} else {
number += rt * pow(2, 1 - eBias);
}
if (number * c >= 2) {
exponent++;
c /= 2;
}
if (exponent + eBias >= eMax) {
mantissa = 0;
exponent = eMax;
} else if (exponent + eBias >= 1) {
mantissa = (number * c - 1) * pow(2, mantissaLength);
exponent = exponent + eBias;
} else {
mantissa = number * pow(2, eBias - 1) * pow(2, mantissaLength);
exponent = 0;
}
}
for (; mantissaLength >= 8; buffer[index++] = mantissa & 255, mantissa /= 256, mantissaLength -= 8);
exponent = exponent << mantissaLength | mantissa;
exponentLength += mantissaLength;
for (; exponentLength > 0; buffer[index++] = exponent & 255, exponent /= 256, exponentLength -= 8);
buffer[--index] |= sign * 128;
return buffer;
};
var unpack = function (buffer, mantissaLength) {
var bytes = buffer.length;
var exponentLength = bytes * 8 - mantissaLength - 1;
var eMax = (1 << exponentLength) - 1;
var eBias = eMax >> 1;
var nBits = exponentLength - 7;
var index = bytes - 1;
var sign = buffer[index--];
var exponent = sign & 127;
var mantissa;
sign >>= 7;
for (; nBits > 0; exponent = exponent * 256 + buffer[index], index--, nBits -= 8);
mantissa = exponent & (1 << -nBits) - 1;
exponent >>= -nBits;
nBits += mantissaLength;
for (; nBits > 0; mantissa = mantissa * 256 + buffer[index], index--, nBits -= 8);
if (exponent === 0) {
exponent = 1 - eBias;
} else if (exponent === eMax) {
return mantissa ? NaN : sign ? -Infinity : Infinity;
} else {
mantissa = mantissa + pow(2, mantissaLength);
exponent = exponent - eBias;
} return (sign ? -1 : 1) * mantissa * pow(2, exponent - mantissaLength);
};
module.exports = {
pack: pack,
unpack: unpack
};