39 lines
1.2 KiB
JavaScript
39 lines
1.2 KiB
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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module.exports = function bytesAsFloat32(rawBytes) {
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// return new $Float32Array(new $Uint8Array(rawBytes).buffer)[0];
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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 ? -1 : 1; // Check the sign bit
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var exponent = ((rawBytes[3] & 0x7F) << 1)
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| (rawBytes[2] >> 7); // Combine bits for exponent
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var mantissa = ((rawBytes[2] & 0x7F) << 16)
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| (rawBytes[1] << 8)
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| rawBytes[0]; // Combine bits for mantissa
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if (exponent === 0 && mantissa === 0) {
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return sign === 1 ? 0 : -0;
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}
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if (exponent === 0xFF && mantissa === 0) {
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return sign === 1 ? 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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if (exponent === -127) {
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return sign * mantissa * $pow(2, -126 - 23);
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}
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return sign * (1 + (mantissa * $pow(2, -23))) * $pow(2, exponent);
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};
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