33 lines
1000 B
JavaScript
33 lines
1000 B
JavaScript
'use strict';
|
||
|
||
var GetIntrinsic = require('get-intrinsic');
|
||
|
||
var $pow = require('math-intrinsics/pow');
|
||
|
||
var $Number = GetIntrinsic('%Number%');
|
||
var $BigInt = GetIntrinsic('%BigInt%', true);
|
||
|
||
module.exports = function bytesAsInteger(rawBytes, elementSize, isUnsigned, isBigInt) {
|
||
var Z = isBigInt ? $BigInt : $Number;
|
||
|
||
// this is common to both branches
|
||
var intValue = Z(0);
|
||
for (var i = 0; i < rawBytes.length; i++) {
|
||
intValue += Z(rawBytes[i] * $pow(2, 8 * i));
|
||
}
|
||
/*
|
||
Let intValue be the byte elements of rawBytes concatenated and interpreted as a bit string encoding of an unsigned little-endian binary number.
|
||
*/
|
||
|
||
if (!isUnsigned) { // steps 5-6
|
||
// Let intValue be the byte elements of rawBytes concatenated and interpreted as a bit string encoding of a binary little-endian 2's complement number of bit length elementSize × 8.
|
||
var bitLength = elementSize * 8;
|
||
|
||
if (rawBytes[elementSize - 1] & 0x80) {
|
||
intValue -= Z($pow(2, bitLength));
|
||
}
|
||
}
|
||
|
||
return intValue; // step 7
|
||
};
|