39 lines
1.2 KiB
JavaScript
39 lines
1.2 KiB
JavaScript
'use strict';
|
|
|
|
var GetIntrinsic = require('get-intrinsic');
|
|
|
|
var $pow = GetIntrinsic('%Math.pow%');
|
|
|
|
module.exports = function bytesAsFloat32(rawBytes) {
|
|
// return new $Float32Array(new $Uint8Array(rawBytes).buffer)[0];
|
|
|
|
/*
|
|
Let value be the byte elements of rawBytes concatenated and interpreted as a little-endian bit string encoding of an IEEE 754-2008 binary32 value.
|
|
If value is an IEEE 754-2008 binary32 NaN value, return the NaN Number value.
|
|
Return the Number value that corresponds to value.
|
|
*/
|
|
var sign = rawBytes[3] & 0x80 ? -1 : 1; // Check the sign bit
|
|
var exponent = ((rawBytes[3] & 0x7F) << 1)
|
|
| (rawBytes[2] >> 7); // Combine bits for exponent
|
|
var mantissa = ((rawBytes[2] & 0x7F) << 16)
|
|
| (rawBytes[1] << 8)
|
|
| rawBytes[0]; // Combine bits for mantissa
|
|
|
|
if (exponent === 0 && mantissa === 0) {
|
|
return sign === 1 ? 0 : -0;
|
|
}
|
|
if (exponent === 0xFF && mantissa === 0) {
|
|
return sign === 1 ? Infinity : -Infinity;
|
|
}
|
|
if (exponent === 0xFF && mantissa !== 0) {
|
|
return NaN;
|
|
}
|
|
|
|
exponent -= 127; // subtract the bias
|
|
|
|
if (exponent === -127) {
|
|
return sign * mantissa * $pow(2, -126 - 23);
|
|
}
|
|
return sign * (1 + (mantissa * $pow(2, -23))) * $pow(2, exponent);
|
|
};
|