48 lines
1.2 KiB
Plaintext
48 lines
1.2 KiB
Plaintext
'use strict';
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var $pow = require('math-intrinsics/pow');
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module.exports = function bytesAsFloat32(rawBytes) {
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// return new $Float16Array(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 754-2019 binary16 value.
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If value is a NaN, return NaN.
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Return the Number value that corresponds to value.
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*/
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var bits = (rawBytes[1] << 8) | rawBytes[0];
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// extract sign, exponent, mantissa
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var sign = bits & 0x8000 ? -1 : 1;
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var exponent = (bits & 0x7C00) >> 10;
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var mantissa = bits & 0x03FF;
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// zero (±0)
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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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// infinities
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if (exponent === 0x1F && mantissa === 0) {
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return sign === 1 ? Infinity : -Infinity;
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}
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// NaN
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if (exponent === 0x1F && mantissa !== 0) {
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return NaN;
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}
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// remove bias (15)
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exponent -= 15;
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// subnormals
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if (exponent === -15) {
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// value = sign * (mantissa) * 2^(1-bias-10) = mantissa * 2^(-14-10)
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return sign * mantissa * $pow(2, -24);
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}
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// normals
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// value = sign * (1 + mantissa/2^10) * 2^exponent
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return sign * (1 + (mantissa * $pow(2, -10))) * $pow(2, exponent);
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};
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