'use strict';
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var GetIntrinsic = require('get-intrinsic');
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var callBound = require('call-bind/callBound');
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var $pow = GetIntrinsic('%Math.pow%');
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var $RangeError = GetIntrinsic('%RangeError%');
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var $TypeError = GetIntrinsic('%TypeError%');
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var $charAt = callBound('String.prototype.charAt');
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var $reverse = callBound('Array.prototype.reverse');
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var $slice = callBound('Array.prototype.slice');
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var hasOwnProperty = require('./HasOwnProperty');
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var IsArray = require('./IsArray');
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var Type = require('./Type');
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var every = require('../helpers/every');
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var isByteValue = require('../helpers/isByteValue');
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var keys = require('object-keys');
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// https://262.ecma-international.org/8.0/#table-50
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var TypeToSizes = {
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__proto__: null,
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Int8: 1,
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Uint8: 1,
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Uint8C: 1,
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Int16: 2,
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Uint16: 2,
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Int32: 4,
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Uint32: 4,
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Float32: 4,
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Float64: 8
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};
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// https://262.ecma-international.org/8.0/#sec-rawbytestonumber
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module.exports = function RawBytesToNumber(type, rawBytes, isLittleEndian) {
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if (typeof type !== 'string' || !hasOwnProperty(TypeToSizes, type)) {
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throw new $TypeError('Assertion failed: `type` must be a TypedArray element type: ' + keys(TypeToSizes));
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}
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if (!IsArray(rawBytes) || !every(rawBytes, isByteValue)) {
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throw new $TypeError('Assertion failed: `rawBytes` must be an Array of bytes');
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}
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if (Type(isLittleEndian) !== 'Boolean') {
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throw new $TypeError('Assertion failed: `isLittleEndian` must be a Boolean');
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}
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var elementSize = TypeToSizes[type]; // step 1
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if (rawBytes.length !== elementSize) {
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// this assertion is not in the spec, but it'd be an editorial error if it were ever violated
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throw new $RangeError('Assertion failed: `rawBytes` must have a length of ' + elementSize + ' for type ' + type);
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}
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// eslint-disable-next-line no-param-reassign
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rawBytes = $slice(rawBytes, 0, elementSize);
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if (!isLittleEndian) {
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// eslint-disable-next-line no-param-reassign
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rawBytes = $reverse(rawBytes); // step 2
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}
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/* eslint no-redeclare: 1 */
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if (type === 'Float32') { // step 3
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/*
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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.
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If value is an IEEE 754-2008 binary32 NaN value, return the NaN Number value.
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Return the Number value that corresponds to value.
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*/
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var sign = (rawBytes[3] & 0x80) >> 7; // first bit
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var exponent = ((rawBytes[3] & 0x7F) << 1) // 7 bits from index 3
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| ((rawBytes[2] & 0x80) >> 7); // 1 bit from index 2
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var mantissa = ((rawBytes[2] & 0x7F) << 16) // 7 bits from index 2
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| (rawBytes[1] << 8) // 8 bits from index 1
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| rawBytes[0]; // 8 bits from index 0
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if (exponent === 0 && mantissa === 0) {
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return sign === 0 ? 0 : -0;
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}
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if (exponent === 0xFF && mantissa === 0) {
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return sign === 0 ? Infinity : -Infinity;
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}
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if (exponent === 0xFF && mantissa !== 0) {
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return NaN;
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}
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exponent -= 127; // subtract the bias
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// return $pow(-1, sign) * mantissa / $pow(2, 23) * $pow(2, exponent);
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// return $pow(-1, sign) * (mantissa + 0x1000000) * $pow(2, exponent - 23);
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return $pow(-1, sign) * (1 + (mantissa / $pow(2, 23))) * $pow(2, exponent);
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}
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if (type === 'Float64') { // step 4
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/*
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Let value be the byte elements of rawBytes concatenated and interpreted as a little-endian bit string encoding of an IEEE 754-2008 binary64 value.
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If value is an IEEE 754-2008 binary64 NaN value, return the NaN Number value.
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Return the Number value that corresponds to value.
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*/
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var sign = rawBytes[7] & 0x80 ? -1 : 1; // first bit
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var exponent = ((rawBytes[7] & 0x7F) << 4) // 7 bits from index 7
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| ((rawBytes[6] & 0xF0) >> 4); // 4 bits from index 6
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var mantissa = ((rawBytes[6] & 0x0F) * 0x1000000000000) // 4 bits from index 6
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+ (rawBytes[5] * 0x10000000000) // 8 bits from index 5
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+ (rawBytes[4] * 0x100000000) // 8 bits from index 4
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+ (rawBytes[3] * 0x1000000) // 8 bits from index 3
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+ (rawBytes[2] * 0x10000) // 8 bits from index 2
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+ (rawBytes[1] * 0x100) // 8 bits from index 1
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+ rawBytes[0]; // 8 bits from index 0
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if (exponent === 0 && mantissa === 0) {
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return sign * 0;
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}
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if (exponent === 0x7FF && mantissa !== 0) {
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return NaN;
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}
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if (exponent === 0x7FF && mantissa === 0) {
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return sign * Infinity;
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}
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exponent -= 1023; // subtract the bias
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return sign * (mantissa + 0x10000000000000) * $pow(2, exponent - 52);
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}
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// this is common to both branches
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var intValue = 0;
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for (var i = 0; i < rawBytes.length; i++) {
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intValue |= rawBytes[i] << (8 * i);
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}
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/*
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Let intValue be the byte elements of rawBytes concatenated and interpreted as a bit string encoding of an unsigned little-endian binary number.
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*/
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if ($charAt(type, 0) !== 'U') { // 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 (bitLength < 32) {
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intValue = (intValue << (32 - bitLength)) >> (32 - 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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