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